Different laser induced diagnostics, originally developed for different purposes including material characterization and environmental monitoring, have been applied in the field of Cultural Inheritance preservation with the aim to facilitate successive conservation and restoration actions. In this paper results relevant to three different techniques are reviewed. The use of topologic laser and 3D sensor in checking small artifacts and large surfaces is discussed, the application of Speckle interferometry to defect analysis of ceramic artwork is represented, a demonstration of the capabilities of a time resolved LIF system in the characterization of surface composition of ancient ceramics and frescoes is finally given.

Three non destructive testing techniques x-ray fluorescence spectroscopy, laser induced fluorescence and fast luminescence imaging by an intensified charge coupled device have been applied to analyze a few most common painting materials, namely natural and synthetic pigments and resins. A comparison of the experimental results obtained shows the applicability of these three methods and to observe and study an entire oil painting by a mobile station for 'in situ' diagnostics for restoration and conservation.

Despite the long period of time since the first proposal of a laser approach to restoration of artworks, this technique is still under debate. The various material composition determines quite different results according to the laser interaction parameters, and their selection and optimization is the base to design laser instrumentation developed for this field of application. The principles of restoration followed by the Italian school of conversation provided quite selective criteria for the development of techniques and laser devices. In the following a description of the activity carried out by our group will be presented and discussed according to the application of new laser instrumentation for cleaning techniques of stones and metals.

After a general discussion about the optimum laser pulse duration for laser cleaning of stone artworks, we present a basic study aimed to state a methodological approach to optimize restoration interventions. As representative examples we investigated the cleaning problem of black crust removal from pliocene sandstone and marble of Siena. The trials were performed with a shot free running Nd:YAG on quarry samples, and on sample from historical buildings. Optical and thermal analyses, associated with petrological diagnostics of the irradiation effects, allowed to derive the damage thresholds and to understand the nature of any invasive phenomenon. The analysis of the experimental results provided the best irradiation conditions and the laser parameter ranges for a safe laser cleaning intervention of the lithotypes and degradation typologies here investigated.

A lidar system able to measure simultaneously different atmospheric parameters in the lower troposphere have been developed and used to monitor the air quality of an industrial area of Southern Italy. The system is based on a Nd:YAG laser pumping two dye lasers, and on two Newtonian telescopes, equipped with periscopes for 3D mapping. One telescope is devoted to DIAL and the other to the N₂ and H₂O Raman channels, and to the elastic channels at 1064 nm, 532 nm and 355 nm. Aerosol backscattering coefficients measurements have evidenced the presence of an aerosol layer. The laser has been characterized by measuring its temporal evolution and by correlating it with atmospheric transmissivity profiles measured at different zenithal angles. Preliminary results of atmospheric pollutants concentration measurements by UV DIAL technique are also reported.

Sensors developed within the Italian Antarctic Research Program will be presented. Application fields encompass researches in Astronomy, Astrophysics, Atmospheric Physics and Oceanography.

The ENEA mobile fluorosensor laboratory has participated to the XIII Italian Antarctic Mission operating in the oceanographic campaign. Sea water quality parameters have been remotely and in situ monitored during the cruise in the Ross sea and along the Southern Ocean transects up-to New Zealand. Georeferenced data have been collected and released on thematic maps. Algal blooms and temporal variations of the monitored quantities have been reported. Seawaters detailed spectroscopic analyses were carried out to distinguish among natural seawater components and to identify phytoplankton pigments.

A dial system based on CO₂ laser which can be used routinely having an high degrees of eye safety, has been implemented at the Department of PHysics of University of Calabria. Starting from this, a mobile dial unit has been realized under the project 'LIFE 95/IT/AII/IT/504/CAL' financial support of European Community. We describe the most important feature of the system.

A study of the transmissivity in the spectral UV range for two sites, with different pollutant content, has been performed. Results obtained from measurements covering a period of five years are shown and the variability of the transmissivity profile and its time evolution during a night has been correlated to the water vapor content at the lower height. The aerosol optical thickness has been retrieved from lidar measurements with an evident cloud extinction and the cloud lidar ratio has been estimated from the independent simultaneous measurements of the aerosol extinction and backscattering coefficients.

In this paper we present an intercomparison between ground based lidar, radiosonde and satellite atmospheric water vapor measurements. Comparisons expressed in terms of water vapor profiles, obtained by Raman lidar and simultaneous ballonborne radiosonde, are reported and discussed. The deviation between the two profiles is smaller than 10 percent up to an altitude of 5 km. Furthermore, the intercomparison between lidar and radiosonde data and between lidar and satellite data is performed also in terms of water vapor columnar content. The agreement between lidar and radiosonde columnar content is better than 4 percent. Water vapor contour map are showed in order to demonstrate the high spatial and temporal variability of water vapor in the lower atmosphere. Difficulties in comparing lidar and satellite water vapor columnar contents associated to H₂O spatial and temporal variability are discussed in the paper.

A lidar system capable to perform simultaneous measurements of atmospheric water vapor and aerosols have been developed in Tito Scalo, in the context of a cooperation between Universita della Baslicata and Istituo di Metodolgoie Avanzate di Analisis Ambientale. Aerosol observations by lidar in the nocturnal boundary laser (NBL) have been performed in the period 20 January- 20 February 1997, Radiosondes were launched during the measurement campaign simultaneously to lidar operation. Lidar observations have been sued to retrieve aerosol properties and dimensional characteristics. Aerosol sizes are determined by comparison measured and theoretical values of (beta) _A,723(z)/(beta) _A,355(z), with (beta) _A,723(z) and (beta) _A,355(z) being the aerosol backscattering coefficient at 723.37 and 355 nm, respectively. Furthermore, lidar and radiosonde data have been compared in order to study the NBL vertical structure and evolution. Lidar measurements of (beta) _A,723(z) are compared with simultaneous radiosonde data expressed in terms of potential temperature and relative humidity, with particular emphasis on the estimate of the residual layer height from both lidar and radiosonde data. Results from the present measurements campaign will be reported and discussed in this presentation.

High temporal and spatial resolution measurements by both space-borne and ground-based instruments are therefore necessary to monitor atmospheric water vapor for climate purposes. Lidar techniques can accomplish ground-based measurements of atmospheric water vapor with high space and time resolution. A lidar system capable to perform simultaneous measurements of atmospheric water vapor and aerosols has been developed in Potenza, Southern Italy, in the context of a cooperation between the Universita della Basilicata and Istituto di Metodologie Avanzate di Analisi Ambientale. An intensive measurement campaign was performed during 1997 in Potenza aimed to the simultaneous application of the Raman and DIAL techniques for water vapor ground- based lidar measurements. Raman and DIAL humidity measurements performed during 1997 in Potenza aimed to the simultaneous application of the Raman and DIAL techniques for water vapor ground-based lidar measurements. Raman and DIAL humidity measurements performed at night in the Planetary Boundary Layer have been compared with simultaneous radiosonde data obtained from both free and captive balloons. The agreement among Raman, DIAL and radiosonde data is found to be within 30 percent up to approximately 1.5 km. Results from this measurement campaign will be reported and discussed in this paper.

Recent results of sub-Doppler IR diode laser spectroscopy of freons in a supersonic jet are reported. The v₁ parallel band of CCl₃F has been recorded at a rotational temperature of about 20 K, in a supersonic slit jet expansion. A detailed rotational analysis has been performed yielding band origins and rotational constants for the three most abundant isotopomers C³⁵Cl₃F, C³⁵Cl₂ClF and C³⁵Cl³⁷Cl₂F. The CHF₂Cl molecule has two strong fundamental bands in the atmospheric window, v₃ at 1108.7278 cm^-1 and v₈ at 1127.2844 cm^-1. A preliminary analysis of the v₃ band of the CHF₂³⁷Cl isotopic species will be presented.

Recently we have developed a lidar fluorescence sensor system, consisting of a compact Nd:YAG laser with second and third harmonics generation, mounted on a Newtonian receiver coupled to a small monochromator with a ICCD detection unit. The laser radiation induces fluorescence on a remote target and fluorescence spectra are recorded. Substances like DOM, chlorophyll and other plants pigments, algae and phytoplankton, crude oil, etc. can be identified in this way. Preliminary laboratory work was done on various substances. The concentration of the trace compound in water is usually obtained by normalizing the integrated fluorescence intensity respect to the Raman peak of water at 402 nm. Preliminary results of laboratory calibration measurements on water pollution and vegetation will be presented.

Abstract not available.

The data on laboratory and field test of the versatile lidar based on a pulsed Nd:YAG laser for ecological monitoring of water bodies, ground vegetation, and soil are presented. The lidar was designed at the Wave Research of Russian Academy of Sciences. We report on the result of some experiments of 1997 and 1998, performed in Brazil. In particular, simultaneous measurement of soil, ground vegetation, and seawater fluorescence exited by the third laser harmonic at 355 nm has demonstrated the main spectral features of these objects. The new procedure of spectral processing gives us an opportunity to compare the vertical profiles of organic content in soil different Brazilian regions. The study has also shown the florescence characteristics of seawater samples kept inside a sealed box at fixed temperature to change dramatically during about two hours, which indicates the importance of water remote sensing in situ in comparison to the conventional microbiological analysis in vivo.

Lasing properties and photostability of 4,4'-CO₂C₄H₉ bis-substituted paraterphenyl and azacoumarin AClF emitting in the blue-green region of the spectrum in poly(methyl methacrylate) and ethanol pumped by a XeCl excimer laser and both pyrromethene 580 and phenalemine 512 pumped by a Cu laser emitting in the red region of the spectrum have been investigated.

We propose the original design of an active element of quantum unipolar semiconductor laser both for the optical pumping and current injection modes of operation. The peculiarities of the posed design are strongly asymmetric barriers surrounding a double-well active element. The suppression of intersubband transitions to the lower working subband can be readily achieved if the transformation point of electronic state dimensionality for lower subband occurs at small momentum. By this means the population inversion conditions in this system can be easily realized. The results of photoluminescence studies of the individual elements of the proposed structure are presented.

The maximum power range over which a laser resonator supports stable oscillation is mainly determined by the material constants of the active medium and by the cooling schemes. The power range for stable fundamental-mode operation can be shifted to higher powers with special cavity design and intra-cavity optics but the width of the stability range will be unaffected and can be enlarged only with adaptive optics. We present investigations on a multi- rod laser cavity and a high-power side-pumped laser system. In order to obtain constant beam parameters with varying power we prose a novel self-adaptive method to compensate for the power-dependent thermal lenses in high-power lasers.

The powerful CO₂-laser with power 1-50 kW, both continuous and pulse-periodical for use in different economics sectors were created in TRINITI. These lasers were used for laser welding, cutting and surface treatment of different materials. In the field of atomic industry the laser installations were used for solving some important problems.

Carbon nanoparticles, prepared by means of ns-laser ablation of carbon can be used for physical modeling of the interstellar dust. Different model for formation of interstellar dust were suggested for the last years, one assumes that carbon grains are generated by condensation in the expanding carbon-rich stellar plasma/vapor of cool red giants. Similar conditions for condensation can be reproduced in laser experiments. Calculations and experiments show that carbon particles produced by laser have the same size and extinction that can be seen in diffusive clouds of hydrogen-pure stars. The situation with hydrogen-rich stars is more complex: the most probable mechanism suggests that firstly the nanodiamonds are formed within these clouds which later transform to carbon onions due to annealing and graphitization.

The results of the experiments on the dynamics of laser produced vapor plumes show peculiarities in angular distribution of components, which lead to a change in stoichiometry of deposited films and to other effects, for example, a sharpening effect within the plumes produced by MALDI technique. A theoretical analysis of the MALDI plumes expansion is done on the basis of special solution of gas dynamic equations. This permits to explain experimental data and simulate many important characteristics, i.e. TOF spectra, film thickness profile of deposited material, etc.

Tissue ablation by mid-IR lasers is described using the linear mass loss model. The steady state equation, which relates the ablation depth to laser radiant exposure, can be transformed to characterize the dynamic crater formation. After the presentation of the steady state results obtained with the linear mass loss model,the basic equation is transformed into a time dependent equation. To calculate the focusability of laser beams, and hence the irradiance in the focal zone, the spot-size propagation for a Gaussian beam is taken into account. The model can be generalized for higher order modes by introducing the coefficient of beam quality (M²). The analytical solutions of the new equation gives valuable information on crater shape and dimensions on time evolution for crater formation and on time dependence of the ablation velocity. A comparison with experimental results proves usefulness of dynamic characterization of crater formation based on the time dependent linear mass loss model.

To analyze the chemical composition of the laser plume the techniques of the backward laser transfer and x-ray photo- electron spectroscopy have been applied. The films deposited from the plume at laser transfer in air have revealed a tendency of increase in oxidation degree and the change of their composition in comparison with the initial material.

Silicon nanopowders produced by CO₂-laser-induced decomposition of SiH₄ in a flow reactor have been investigated. The particles of these powders can be described as polycrystalline silicon grains surrounded by a Si-amorphous shells.

Recent advances in hard x-ray production from porous silicon targets have been reported. Experimental data on efficient hot electron generation in plasma, created by 200 fs laser pulses at intensity in excess of 10¹⁶ W/cm² are discussed. The assessment of the hot electron temperature in single laser shot was made using simple modification of the well known x-ray filter method. X-ray quanta with energy of approximately 80 keV were observed at the 'moderate' intensity of 2 X 10¹⁶ W/cm², revealing the existence of the second non-thermal electron component with the 'temperature' of 30-50 keV. Finally, we discuss the feasibility to design 2.5 MeV neutron source with peak flux of more than 10²⁰ neutrons using deuterium enriched nanowire metallic arrays.

We have designed and built an ultra high vacuum chamber which allows thin film depositions on large area flat substrates and on 3D substrates by the pulsed laser deposition and reactive pulsed laser deposition techniques. Heating of substrates during and after film deposition is possible by using either resistive heaters or a lamp array. Metal and metal nitride and carbide were deposited on Si wafers, 3D steel substrates, teflon plates and paper sheets.

We report on parametric studies of CN_x films deposited by excimer laser ablation of graphite targets in molecular nitrogen atmosphere as a function of gas pressure and laser fluence values. Substrates were Si single crystals at room temperature. Deposition rates decrease with increasing nitrogen pressure. The N/C atomic ratio generally increases with increasing nitrogen pressure and laser fluence, N atoms are mainly bonded to C atoms in the sp² and sp³ bonding states. At relatively high pressure and laser fluences about 40 percent of the C atoms and about 50 percent of the N atoms are bounded in the C-N single bonds, generally attributed to the (beta) -C₃N₄ compound.

We report on the investigation of XeF excimer laser ablation of YNi₂B₂C target by energy selective time-of-flight mass spectrometry (ES-TOFMS). ES-TOFMS allows laser plume investigation by providing a direct measurement of the ions kinetic energy and, through the TOF measurement, their simultaneous mass identification. In particular, the composition and the kinetic energy of the emitted ions has been accomplished by means of TOF technique coupled with a 160 degrees electrostatic energy analyzer. The analysis of the charged species composition and kinetic energy has been performed at different laser fluences and in high vacuum conditions.

We report on the investigation of XeF excimer laser ablation of YNi2B2C target by energy selective time-of-flight mass spectrometry (ES-TOFMS). ES-TOFMS allows laser plume investigation by providing a direct measurement of the ions kinetic energy and, through the TOF measurement, their simultaneous mass identification. In particular, the composition and the kinetic energy of the emitted ions has been accomplished by means of TOF technique coupled with a 1600 electrostatic energy analyzer. The analysis of the charged species composition and kinetic energy has been performed at different laser fluences and in high vacuum conditions.

A model of laser-solid-plasma interaction taking into account vapor ionization and absorption mechanisms and laser induced plasma kinetics was developed. The laser-solid interaction has been modeled by using a thermal approach, and inverse bremsstrahlung and direct photo-ionization from excited neutrals have been considered for the absorption of the laser light. The model shows that the plasma parameters, which are increasing function of the fluence at moderate laser intensities, approach a plateau regime at high laser fluences. Model provisions show a quite good agreement with the experimental findings suggesting that laser-plasma interaction processes and plasma kinetics are of great importance in nanosecond laser ablation of metallic targets for power densities of the order of approximately 10⁹ Wcm².

We report on prompt emission of fast electrons occurring during nanosecond excimer laser ablation of metallic targets in vacuum. Prompt electrons yield and most probable kinetic energy as a function of the laser pulse fluence have been obtained by charge collection and time of flight techniques. The experimental data show a strong dependence of the prompt electrons yield on laser fluence. In particular, the data follow a power law dependence with two distinct slopes, below and above approximately equals 5 Jcm^-2. Also the ion yield shows a similar behavior. The observed roll-off in the electron and ion dependence on the laser fluence has been discussed in terms of laser fluence has been discussed in terms of laser plasma shielding effects.

Pulsed laser ablation appears as a promising technique for depositing thin films. A large variety of successful experimental results were obtained in this field, including the growth of high-temperature superconducting films, ferroelectric films, oxides, semiconductors, diamonds, etc. One of the main advantages of this technology is the relative simplicity of the experimental set-up and the possibility to get good homogeneity, complex stoichiometry materials and well adhesive dense layers. The main drawback seems to be the production of macroparticles, their transfer to the growing film inducing inhomogeneity and roughness onto the surface, lowering the properties of the thin films. In a common configuration, the laser-generated flux is collected on a planar substrate positioned parallel to the irradiated surface. In order to improve the stoichiometry and the quality of the films, several modifications, like simultaneous generation of two plumes from different targets with different targets with different laser beams, were proposed. In this paper, we present some results concerning the production of cryolite thin films using the conventional pulsed laser deposition technique and the dual crossed beams pulsed laser deposition technique. Plasma plumes expanding in vacuum and interacting together are visualized. The different species ejected in the plumes are detected through narrow-band filters in order to determine their kinetic energies. The morphology and the composition of the films are compared with the thermal evaporation technique.

Carbon nitride films were deposited on Si substrates at room temperature by XeCl laser ablation of graphite targets in low pressure N₂ atmosphere at the fluence of 12 J/cm². The films have been submitted to x-ray diffraction and transmission electron microscopy investigations in order to study the structure of the films. Results showed that the samples are constituted of a continuous amorphous film inside which microcrystals are dispersed. A new CN_x phase has been identified. This new phase has a triclinic crystallographic cell with lattice parameters a equals b equals 0.384 nm, c equals 0.438 +/- 0.007 nm, (alpha) equals 110 +/- 1 degrees, (beta) equals 105 +/- 1 degrees, and (gamma) equals 120 degrees. It coherently grows on the Si plane with the following orientation relationships: (001)_CNx (parallel) (111)_Si; (100)_CNx (parallel) (1-10)_Si and (010)_CNx (parallel) (01-1)_Si.

The growth of aluminum nitride films by reactive laser ablation has been studied. The influence of process parameters such as laser energy density, nitrogen pressure on the composition, chemical nature and structure of the films has been investigated. Rutherford backscattering spectrometry, nuclear reaction analysis, x-ray diffraction were used to characterize the films. The main problem in AlN film growth was the oxygen incorporation. The origin of this contamination and the mechanisms of incorporation were studied, and the crucial parameter was found to be the residual pressure during ablation. Due to the difference in chemical reactivity between oxygen and nitrogen atomic species, it is necessary to increase the density of atomic nitrogen to obtain pure AlN films. Thus, ar radio-frequency discharge device was added allowing a better nitrogen molecule dissociation. Finally, despite 10 percent O composition deviations, the AlN phase was obtained in the laser deposited films.

Applications of photo-induced processes have over the years become essential technologies in several important industrial sectors. In this paper, the principles and properties of novel vacuum UV (VUV) and UV radiation generated by novel excimer sources are discussed. Compared with conventional sources, these excimers lamps offer narrow-band radiation at various wavelengths form 108-354 nm and over large areas. Since excimer complexes have no stable ground states self-absorption of the emitted radiation in the discharge is avoided. As a consequence, high efficiencies at high power densities can be achieved.

We analyze the conditions for the existence of LTE in LIBS plasmas. In particular we focus our attention to problems associated with nonequilibrium plasmas making use of a recent experimental study.

In this work a theoretical model to describe the expansion of the plume ablated from a monoxide titanium target is presented. The flow expansion has been studied by means of the Euler equations. Consideration of equilibrium and frozen conditions along the plume expansion allows the prediction of film composition on the substrate.

Silicon carbide ceramic seal rings are treated by KrF excimer laser irradiation. Surface characteristics, induced by laser treatment, depend upon laser fluence, the number of laser pulses, their energy and frequency, the rotation rate of the ring and the processing atmosphere. It was ascertained that silicon carbide has to be processed under an inert atmosphere to avoid surface oxidation. Microstructural analyses of surface and cross section of the laser processed samples showed that the SiC surface is covered by a scale due to the melting/resolidification processes. At high fluence there are no continuous scales on the surfaces; materials is removed by decomposition/vaporization and the ablation depth is linearly dependent on the number of pulses. Different surface morphologies are observed. The evolution of surface morphology and roughness is discussed with reference to compositions, microstructure and physical and optical properties of the ceramic material and to laser processing parameters. Preliminary results on tribological behavior of the treated seals are reported.

The results of spectroscopies studies of Me*NH₃)_n clusters formed in a supersonic beam from the laser ablated metal with gaseous ammonia are here reported. The ionization potentials of Cu(NH₃)_n 2 <EQ n <EQ 6 have been measured. The observed IPs are shifted to lower energies with respect to the bare Cu atom IP. They appear to decrease monotonically with increasing clusters size. The observed trend is consistent with a model in which the unpaired valence electron of the ground electronic state is delocalized in a well bound surface states. The data are confirmed by energetics and structure calculations performed by density functional method.

Polycrystalline pure and V-doped SnO₂ thin films have been prepare by pulsed laser deposition (PLD) on Si substrates, with a Si₃Ni₄ buffered layer. PLD technique, under proper conditions, has probed to produce nanocrystalline-structured materials, which are suitable for gas sensing. In this work we analyze the role of V doping in the structural properties and in the electrical conductivity of the films. The deposition temperature was fixed at 600 degrees C and the films were grown in oxygen atmosphere. The films resulted nanocrystalline with 50 to 120 nm average grain size connected by necks with high surface areas. The microstructural and electronic properties of all the films were analyzed using scanning-electron microscopy, x-ray diffraction and conversion electron Moessbauer spectroscopy. Electrical conductance in a dynamic regime in dry synthetic air has been evaluated as a function of temperature. Moessbauer spectra reveal the presence of 15 percent of Sn²⁺ in the 5at. percent V-doped films. At about 340 degrees C, a strong increase in the conductivity of the films occurs. Possible explanations are that thermal energy could excite electrons from the vanadium ions into the crystal's conduction band or promotes the diffusion of surface oxygen vacancies towards the bulk, increasing strongly the conductivity of the film.

Pulsed laser deposition method (PLD) is widely used nowadays to produce smooth, homogeneous thin films on solid surfaces for microelectronic's purpose. Different metal-nitride films as well as nitrides of W, V, Ta, Ni, Co, Pb have been produced in NH₃ and N₂ atmosphere of a few on Si surfaces with orientation. In the reaction chamber the pulses of excimer laser at fluence of 5.8 J/cm² were directed at angle of incidence of 45 degrees to the metallic sheet placed at distance 4.0 cm to the Si substrate. The metallic target was rotated at approximately 3 Hz. Different surface analyzing methods revealed that smooth, homogeneous thin films of the thickness of 20-100 nm were grown on the substrate surface. The chemical composition of the layers varied of metal-silicides to metal-nitrides. In some cases the appearance of carbon and oxygen consisting mixtures such as VNCO, N₁₃Si₉O_1.5C₆ and WN were observed. The film structures might be considered mostly amorphous according to the data of GR-XRD measurements.

Real-time Monte Carlo Molecular Dynamics (MC-MD) simulation techniques have been developed to model the nucleation, the initial stages of growth, and thin film growth, during InP Molecular Beam Epitaxy (MBE) on InP. The simulation mode includes tetrahedral lattice coordination, species-species interactions out to third-nearest neighbor, heterogeneous photolysis of precursors molecules on vacuum UV, adspecies migration on the lattice, nucleation on conventional and charge activated centers, and desorption dynamic effects. An InP homoepitaxy system, permits the simulator validation against MBE experimental results; although the model and the corresponding simulator are easily applied to a variety of other problems. The amount of InP epitaxy as a function of time is obtained over surface are of 50 X 50 atomic sites. The result of the simulations demonstrate that model treatment is accurate and encompasses several improvements over previous treatments. The agreement between experimental and simulated roughness serves to build confidence in the use of Mc-MD for MBE studies.

Laser cleaning has emerged as an effective cleaning technique for removing contaminants from solid surfaces. Dry laser cleaning and steam laser cleaning have been developed recently, relying on pulsed laser heating of the heating of the surface without and with the presence of a thin liquid coating. Two cleaning models for the viewpoint of force and energy for dry laser cleaning and a cleaning model for steam laser cleaning were established for removal of particles from solid surfaces by taking Van der Waals force, capillary force and cleaning force into account. The models not only explain the influence of laser fluence on cleaning efficiency, but also predict the cleaning thresholds. Laser- induced removal of film-type contaminants has been studied and the surface cleanliness has been studied and the surface cleanliness can be monitored in real time by acoustic and electric means.

Pulsed laser ablation is a very interesting method to deposit thin films of several materials and compounds as oxides, nitrides, insulators, semi- and super-conductors. Indium and In Oxide polycrystalline thin films have been gown on silicon substrates by reactive pulsed laser deposition from two metallic targets of indium and Tin by a multilayered deposition, both in presence of oxygen, using a frequency doubled Nd:YAG laser. These In₂O₃, SnO₂ thin films find valid application as antistatic coatings, transparent resistive heaters, electrical electrodes for flat panel display and electrochromic device.s A comparison has been performed, among Indium Oxide, Tin Oxide, and multilayers of Indium and Tin Oxides, to evaluate their use as gas sensor devices. The influence of the physical parameters such as the substrate temperature, the laser energy, and the oxygen pressure in the deposition chamber has been investigated. The plume has been monitored by fast photography. The characterization of the films has been performed by X-Ray Diffraction, showing a preferential orientation. A four-contact probe shows that our films exhibit an increase in resistivity when exposed to NO.

The XeCl laser facility Hercules, delivering a maximum energy of 8 J in 160 ns FWHM, has been used to irradiate amorphous silicon films on glass substrate. We designed an optical homogenizer to reshape the large cross-section of the laser beam (10 X 5) cm², in order to reach a fluence up to 0.5 J/cm² area. The beam resulted spatially homogeneous within 10 percent. We obtained poly- silicon films with grain size ranging from 0.1 to 2 micrometers , depending on the laser energy density. These preliminary results show that the grain size is critically fluence- dependent when the so-called super-lateral-growth regime is approached, with a maximum slope of the grain size vs. energy density greater than 0.5 micrometers /(mJ/cm²).

We report a numerical study of the main phenomena that are characteristic of the interaction between high-intensity UV laser pulses and solid targets in low-pressure ambient gas. The impact of laser radiation action on solid surface is described by solving the 1D heat conduction equation. The interaction between laser radiation and the plasma expanding in front of target is modeled by the gas-dynamics equations. The model includes laser irradiation absorption by target vapors through Inverse Bremsstrahlung and photoionization absorption. The transit of ablated material from target to collector is treated by a Monte Carlo method. The goal of our study is to determine the influence of the irradiation conditions and the ambient gas pressure upon the velocity, density and temperature of the ejected particles. The results of our analysis are in good concordance with experimental measurements obtained by reactive pulsed laser deposition from Ti and Al targets in low-pressure nitrogen atmosphere.

Write and erase (WE) thin film patterns obtained by in-situ consecutive photodeposition and photoablation cycles were investigated. The submicrometric structures of photodeposited and photoablated amorphous Selenium(a-Se) thin films were examined by high resolution scanning electron microscope (SEM). Magnification up to X100,000 was used to establish the morphology of the particles and islands on the substrate before and after the ablation cycle. The SEM micrographs show that the disintegration of the film during the ablation process leads to the creation of a variety of structures such as islands and particles in the nano to micrometer range. The findings indicate that similar to island film growth, viscoelastic phenomena are involved in the observed morphology in the ablation zones.

The optical properties of CdS_xSe(subscript 1-x/ alloy films, deposited on quartz substrate by means of pulsed laser ablation technique, have been investigated by absorption and photoluminescence measurements as a function of the temperature. The absorption measurements, analyzed according to the Elliot theory, permit to obtain the temperature and composition dependence of the band gap, which are in good agreement with well known phenomenological models. The photoluminescence efficiency persisting up to room temperature is very interesting for device applications, because of the capability of tuning the emission line in the spectral region from green to red, by varying the sulphur concentration x.

The joint effect of structural properties and electric field distribution on the laser damage threshold of HfO₂ thin films is investigated in this work. Hafnium dioxide thin films of different optical thicknesses and with different structural properties have been realized employing two different deposition techniques: ion-assisted electron beam evaporation and dual-ion-beam sputtering technique. Laser damage thresholds of the sample have been measured at 308 nm by the photoacoustic beam deflection technique. It will be shown that samples presenting lower packing densities and lower peak values of the electric field intensity have higher damage threshold.

Electron-phonon relaxation in metals following ultrashort- pulse optical excitation has been studied both in thin films and bulk metals by a number of investigators. Here we report recent experiments on ion emission from several different metals using a free-electron laser which delivers a train of subpicosecond micropulses in the mid-IR. The threshold intensities for the damage threshold together with the ion emission are used as markers for the onset of energy transfer to the lattice for ablation. Numerical calculations based on the Anisimov two-temperature model are used to evaluate the electron temperature T_e and the lattice temperature T_i from the incident fluence at the damage threshold and the ion-emission. The result will be discussed in terms of the Hertz-Knudsen equation for vaporization and of a model based on laser induced multiple electronic transitions.

TiO₂ film deposition by PAPLD with biased substrates is investigated into a wide range of laser fluence and oxygen pressure. It is established that plasma of the r.f. discharge excited inside PLD chamber strongly affects the films properties. TiO₂ films deposited by PAPLD were found better than those produced by the conventional PLD with regard to their morphology, optical properties, and uniformity. So, at the high values of Knudsen number (lambda) /L < 1 with an r.f. power of 70 Watt, PAPLD markedly improves the TiO₂ film stoichiometry for high laser fluence, and the deposition rate increases with it up to 2 A/s.

This paper presents the result of experiments on 1) rapid manufacture by a laser stereolithography of plastic copies of skull fragments on x-ray tomograms of patients obtained in St. Vladimir children's clinic; 2) UV laser initiated polymerization of mineral-polymeric composition, formation of implants of given shape from this photocurable composition and study of response of an osteal tissue on a material of an implant and examination the processes of its ostealintegration and ostealinduction; 3) creation of 3D microstructures by a photoinitiated laser polymerization.

The results of the theoretical analysis and computer simulations of the set of phenomena arising at high intensity subpicosecond laser pulse action on a solid target surface are presented. Surface damage processes are discussed including plasma creation, dynamics of the laser pulse interaction with the induced plasma layer, self- focusing and spatial instabilities of the laser beam. In particular a possibility of pulse energy density enhancement in plasma due to the self-focusing, self-organization and forging of dynamical structures and spatial instabilities are investigated. These structures are responsible for the creating of superstrong magnetic fields and appearance of ultrafast electrons with energy up to 50 MeV. Our researches are initiated by the latest experimental achievements and serve for the purposes of their theoretical support.

In a first experiment, different harmonics of the Nd:YLF laser, ranging from IR to UV wavelength region, were used for cleaning of Nb-gated silicon field emitter tips to improve the emission efficiency. An increase of the emission current by about 30 percent after laser irradiation was observed only in case of UV laser irradiation at (lambda) equals 349 nm, indicating contaminants were successfully removed from the tip surface and the cleaning process was strongly wavelength dependent. In a second set of experiments, the effect of ex-situ and in-situ deposition of diamond-like carbon (DLC) films on the field emitter arrays was studie. The thickness of the DLC film turns out to be a critical parameter for the improvement of the emission efficiency and stability. In a third set of experiments, maskless laser patterning of indium tin oxide films was studied. High process speeds in excess of 1 m/s could be achieved, making the process industrially viable. An essential requirement for residue-free patterning was found to be strong light absorption by the under-lying substrate.

The behavior of the protein macromolecules in the solution, which can absorb the metal ions on its surface, was considered. The newly found phenomenon consists in anomalies adsorption of heavy metal ions on the protein surface, connecting with a strong binding of its on the protein surface. In this case dipole-dipole interaction became the main interaction force, so when the protein macromolecules approach one to another, a macromolecule cluster can be formed. The light scattering method enables one to calculate the number of absorption centers on the protein surface.

Raman spectra (RS) of GaAs implanted with 140 keV Si⁺ ions, both before and after annealing, were obtained at room temperature, in x(yz)x backscattering geometry, using the 514.5 nm line of Ar laser. The implantation-induced amorphous bands and LO-line shape changes were observed with increasing fluences from 10¹³ to 5 10¹⁴ cm^-2. We explained the modifications of the spectra via disorder-induced selection rule breakdown and estimated nanocrystallite size for different fluences according to the mode of reduction of the spatial correlation length. For annealing studies implanted samples were caped with Si₃N₄ layer and annealed at 900 C for 20 min in hydrogen. After annealing, the amorphous bands have disappeared, and the new spectral features were observed. We explained the evolution of the spectra by the dopant activation, resulting in RS by phonon-plasmon coupled modes and RS by LO phonon, originating from the surface-depletion layer. We interpreted shifts of the coupled modes and LO intensity change as evidence of the carrier concentration variation with fluences. Experimental results were described by the Lindhard-Mermin dielectric function including the non-parabolicity of the conduction band, evaluated for the case, when Drude approximation is not available. From Raman line-shape analysis we have obtained that the value of carrier concentration were 10¹⁸ cm^-3 for ion fluences 10¹³-5 10¹⁴ cm^-2.

In this paper the use of Laser Induced Breakdown Spectroscopy as tool for quantitative elemental analysis of soils is considered. Namely the influence of plasma temperature on quantitative measurements is discussed and a single theoretical approach is used to model the plasma generation. It is shown that the estimation of temperature in the laser induced plasma and its inclusion in a model for line emissions allows for a substantial reduction of the matrix effect, formerly recognized as the main factor reducing the possibilities of quantitative applications. To illustrate the benefits of the proposed correction, some experimental results, obtained with the use some reference samples soils, are presented.

In the present investigation the properties and the structures of (R)-(+)-1-phenyl-1-propanol molecule (P_R), pure or clustered with chiral and non chiral molecules is reported. The studies have been accomplished in jet- cooled environment using mass selected R2PI excitation and ionization spectroscopy. It has been shown that this technique allows to study chiral molecules and to enantiodifferentiate the homo and heteroclusters. The different shift of the band origins of the molecular diasteroeomeric complexes relative to that of the bare P_R provides a means for spectroscopically discriminating the clusters. Measurements of threshold ionization and fragmentation spectra of the bare molecule and the clusters with chiral alcohols, n-butanol and H₂O allows to determine electronic ground state binding energy of these clusters and their ions. The analysis of the spectra, together with preliminary ab-initio calculations, gives information on the cluster structures. The calculations confirm that the difference in binding energy of these clusters depends on a balance between electrostatic and dispersive forces.

During the last years, the development of optical spectroscopic techniques have made possible measurements of weak IR absorption lines of many gases with biological, agricultural and environmental interest. An extracavity configuration for trace gas detection, based on CO₂ laser photoacoustic spectroscopy is discussed. We show the use of this system to determine the absorption spectra of ammonia and ethene for diluted absorber-nitrogen mixtures of 13 ppm at 54 different CO₂ laser wavelengths. Due to specific features of the experimental system, the result reported in literature present significant differences for some important spectral lines. The measurements were performed at room temperature and atmospheric pressure. In addition,the detection limits of C₂H₄NH₃ and O₃ were calculated.

The linear and non-linear optical properties of gold-coated nano-crystals embedded in glycerol have been investigated. The optical absorption spectra and the non-linear absorption of these nanostructures have been determined under various excitation conditions. The peak of the plasmon resonance like curve has been observed to be blue shifted compared to the plasmon peak of colloidal gold particles. The resonance behavior exhibited by the gold coated silicon nano-crystals is interpreted in terms of the third order non-linear susceptibility which is expressed as a saturation absorption behavior of the samples. The effect of the charged interface gold film, which covers the nanocrystals, on the electron band structure and on the linear and non-linear optical properties are discussed.

This article is presenting the revue of non-linear optical properties investigations of the silicon based nanostructures. The non-linear optical response of the silicon nanocrystal imbedded in to the glycerol matrix, as well as the silicon nanocrystals monolayer on the silver surface and the silicon nanocrystals covered by thin gold film were analyzed. For dressed particles the saturation absorption behavior was observed. The competition of the saturation absorption and third order non-linear optical absorption are realized for the undressed particles and nanocrystals monolayer. The huge nonlinear susceptibility 2 X 10^-3 cm/W was observed for silicon nanocrystal deposited on the silver surface. It has been established the effect of nanoparticles interface condition to the optical properties of ones by means of static electric field inside the nanoparticles. The internal static electric field origin and it influence on the linear and non-linear optical properties of the silicon based nanocomposite structures are discussing.

The huge non-linear optical response have been observed for the silicon nanocrystals monolayer on the silver surface in the normal back scattering configuration. The competition of non-linear saturation and absorption was observed. The value of the non-linear optical absorption coefficient is coming to the 2 X 10(superscript -3) cm/W. The structure of the monolayer was tested by atomic force microscope and average thickness have been estimated on the basis of the surface plasma waves resonance in Kretschmann configuration. It was observed the enhancing of non-linear susceptibility by effect of the surface of noble metal.