THE 193 NM PHOTOLYSIS OF PHOSPHORUS TRICHLORIDE AND PHOSPHORUS TRIBROMIDE

The creation of electronically excited species by the 193 nm excimer laser photolysis of PCl3 and PBr3 has been studied. In addition to halogen and phosphorus atomic lines, emission is detected from highly excited states of Cl2 and Br2, respectively, formed by a two-photon process. We also observe previously unreported emission systems which we attribute to the A 2A1 --> X B-2(1) transitions of PCl2 and PBr2, which are formed by a single-photon process. The PCl2 and PBr2 A --> X emission spectra are broad and structureless, peaking at almost-equal-to 460 and 527 nm with short wavelength thresholds of almost-equal-to 370 and 510 nm, respectively. The A states of PCl2 and PBr2 have long radiative lifetimes (29 +/- 6-mu-s and 21 +/- 9-mu-s, respectively) and are very efficiently quenched by PCl3 or PBr3.