Temperature of molecular vapor in laser ablation of CuCl

Optical emission spectra are studied from the vapor produced by irradiation of polycrystalline CuCl, under vacuum, by pulsed excimer laser radiation at 248 and 308 nm. For fluences φ≲0.4 J/cm2 (intensity I≲20 MW/cm2), well-resolved molecular CuCl emission bands and weak atomic Cu lines are observed. At higher fluences, the CuCl emission increases and develops into a broad continuum due to the broadening and overlap of the bands, whereas the Cu atomic line emission increases more rapidly. At even higher fluences (φ≳1 J/cm2, I≳50 MW/cm2), the Cu atomic emission dominates the entire spectrum. A thermal equilibrium model is used to calculate the vibrational-rotational temperature of the emitting CuCl molecules as a function of fluence by fitting the experimentally observed emission bands. Temperatures in the range 500<T<2000 K for fluences in the range 0.27<φ<0.4 J/cm2 were obtained.