A FEMTOSECOND-TIME-SCALE PHOTOLYSIS STUDY OF VAPOR-PHASE GACL

Time-resolved absorption spectra are recorded for Ga atoms produced by the photolytic action of 300 fs, 248.5 nm laser pulses on gas-phase GaCl molecules. Photodissociation of GaCl at 248.5 nm produces both ground-state (P-2(1/2)) and spin-orbit-excited (P-2(3/2)) Ga atoms, resulting in strong transient-absorption features at 403.3 and 417.2 nm, respectively. The experimental spectra are analyzed to obtain the kinetic energy of the photofragments, which is estimated to be congruent-to 0.08 eV for both channels. The analysis suggests that the dissociation limits are (1) Ga P-2(1/2) + Cl* P-2(1/2) for the 403.3 nm channel; and (2) Ga* P-2(3/2) + Cl P-2(3/2) for the 417.2 nm channel. From these results, a new estimate for the dissociation energy of GaCl is obtained: D0(0)=4.80+/-0.03 eV.