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Proceedings Paper

Photoexcitation and decay of weakly bound complexes: the Ar...Cl2 case
Author(s): Nadine Halberstadt; Kenneth C. Janda; Octavio Roncero
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Paper Abstract

Time-dependent and time-independent calculations are presented for the vibrational predissociation of Ar...Cl2 in the B excited electronic state: Ar...Cl2(B,v') yields Ar + Cl2(B,v < v', j). The potential energy surface used is a sum of pairwise Morse atom-atom interactions adjusted asymptotically to a C6/R6 + C8/R8 anisotropic van der Waals form. The results presented here correspond to excitation in the energy region of Ar...Cl2(B,v' equals 10 and 11). In agreement with the experimental findings, the final rotational distribution of Cl2 is found to be strongly dependent on the initial v' state being excited, as well as on the number of quanta lost in the vibrational predissociation process. The role of intramolecular vibrational redistribution (IVR) is examined. It is shown that the vibrational predissociation (VP) dynamics are dominated by the coupling of a zero-order `bright' state with a single `dark' state from the v' - 1 manifold of van der Waals vibrationally excited states which then decays to the continuum, and that the product state distribution is determined by the dissociation of the dark state. This is characteristic of the sparse limit for intramolecular vibrational redistribution. The corresponding time evolution is examined. Time-dependent calculations are performed for the Ar...Cl2 system frozen at its equilibrium angular configuration. It is found that the dissociation probability as a function of time exhibits oscillations due to interferences between IVR and dissociation. This result is general and simple models based on two bound zero-order levels (the `bright' and `dark' ones of the IVR process) are applied to generate the three- dimensional time-evolution of the system. This allowed us to analyze the effect of the rotation of the complex. It is shown that the oscillatory behavior of dissociation as a function of time can still be present. Moreover, the lifetime for the vibrational predissociation process is found to be dependent on the value of (Omega) , the quantum number for the projection of the overall rotation angular momentum onto the intermolecular axis.

Paper Details

Date Published: 22 April 1993
PDF: 12 pages
Proc. SPIE 1858, Laser Techniques for State-Selected and State-to-State Chemistry, (22 April 1993); doi: 10.1117/12.143095
Show Author Affiliations
Nadine Halberstadt, Univ. de Paris-Sud (France)
Kenneth C. Janda, Univ. of California/Irvine (United States)
Octavio Roncero, IFFM, CSIC-UCM (Spain)

Published in SPIE Proceedings Vol. 1858:
Laser Techniques for State-Selected and State-to-State Chemistry
Cheuk Yiu Ng, Editor(s)

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