Degenerate four-wave mixing spectroscopy as a probe of photodissociation dynamics: nascent SH population distributions from the 266 nm photolysis of hydrogen sulfide

Degenerate four-wave mixing (DFWM) has been used to interrogate the nascent mercapto radicals (SH) emerging from photolysis of bulk-gas H2S samples at λdiss = 266 nm. These experiments reveal a ‘cold’ non-Boltzmann distribution of SH molecules formed exclusively in vibrationless levels of the X2Π ground electronic state, with a non-thermal population of spin-orbit states but no preference for lambda doublet components. Nearly all of the available energy appears as translational motion of the recoiling photofragments. Comparison with previous free-jet studies at λdiss = 193 nm shows the SH (ν = 0) rotational distribution to be relatively independent of photolysis wavelength and precursor rotational temperature.