ON THE NEAR-ULTRAVIOLET PHOTODISSOCIATION OF HYDROGEN-SULFIDE

The near ultraviolet photolysis of H2S has been investigated further, at nine different excitation wavelengths in the range 244-198 nm and a t yet higher resolution than hitherto, using the technique of H (Rydbe rg) atom photofragment translational spectroscopy. Analyses of the tot al kinetic energy release spectra of the primary H + SH fragments has allowed further refinement of the parent bond dissociation energy, D-0 (0)(HS-H) = 31 440 +/- 20 cm(-1), and revealed a marked correlation be tween the wavelength dependence of [f(vib)], the fraction of the avail able energy partitioned into SH(X) product vibration, and the first of the diffuse vibronic structures evident in the UV absorption spectrum of the H2S parent. Secondary photolysis of the primary SH(X) fragment s has also been investigated further. 2 + 1 Resonance enhanced multiph oton ionization spectroscopy has been used to confirm that the S(P-3) atoms resulting from 218.2 nm photolysis of the primary SH(X) fragment s are formed in all three spin-orbit states, with a near statistical ( i.e. 2J'' + 1) population distribution. Such a finding is fully consis tent with our modelling of the shape of the structureless early time f eature in the H atom time-of-flight spectrum, which arises as a result of this secondary photolysis process. This modelling also serves to c onfirm the correctness of our previous determination of the S-H bond s trength in the mercapto radical: D-0(0)(S-H) = 29 300 +/- 100 cm(-1).