TUNABLE DIODE-LASER PROBE OF CHLORINE ATOMS PRODUCED FROM THE PHOTODISSOCIATION OF A NUMBER OF MOLECULAR PRECURSORS

Time-resolved diode laser absorption spectroscopy is used to probe Cl atoms produced from the photolysis of a number of molecular precursors at excimer laser wavelengths 193, 248 and 308 nm. The diode laser was tuned to the Cl atom fine structure transition, 2P3/2 --> 2P1/2. For 248 and 193 nm photolysis of S2Cl2, the translational energy of nascent Cl atoms is measured to be 7 +/- 1 and 10 +/- 3 kcal/mol, respectively, from the Doppler lineshape of the diode laser absorption. Only 17 +/- 2% and 15 +/- 4%, respectively, of the available energy appear as translational recoil energy of the photofragments produced at 248 and 193 nm. This result is generally consistent with a statistical model, suggesting a long-lived transition state complex. The relative yield, phi* = [Cl(2P1/2)]/{[Cl(2P1/2)] + [Cl(2P3/2)]}, for producing Cl(2P1/2) is 0.21 +/- 0.03 at 248 nm, 0.20 +/- 0.03 at 193 nm, and 0.48 +/- 0.06 at 308 nm, respectively. The relative yield for producing Cl(2P1/2) has also been measured for the photodissociation of various Cl precursors such as Cl2, HCl, ICl, NOCl, SCCl2, PCl3, and CCl4.