The ionization/recombination processes during the expansion of laser ablation products into a vacuum and into an ambient gas are investigated on the basis of gas dynamic model. The plasma is assumed to be heated immediately by laser irradiation up to the high temperature, and to reach the ionization equilibrium. The laser energy is estimated to be spent on the vaporization, dissociation and heating of an ablated material and on the ionization of evaporated particles. The plasma expansion is described in two-temperature approximation by the Euler equations. The model is used to analyze the laser ablation of YBaCuO superconductor in oxygen atmosphere under actual film deposition conditions. To understand the role of ionization, we compare the numerical results with one's computed ignoring the ionization processes and with the time-of-flight data. The computations show that only a small part of ionization energy goes away from the cloud with the radiation. The main part is converted into translation energy of expanding products at the initial stage of the expansion. As a result, the kinetic energy of the plasma is approximately doubled.

Date Published: 10 April 1995
PDF: 8 pages
Proc. SPIE 2403, Laser-Induced Thin Film Processing, (10 April 1995); doi: 10.1117/12.206264

Published in SPIE Proceedings Vol. 2403:
Laser-Induced Thin Film Processing
Jan J. Dubowski, Editor(s)