Ultraviolet photodissociation dynamics of the SH radical

摘要

Ultraviolet(UV)photodissociation dynamics of jet-cooled SH radical(in ~2PI_(3/2),v"=0-2)is studied in the photolysis wavelength region of 216-232 nm using high-n Rydberg atom time-of-flight technique.In this wavelength region,anisotropy beta parameter of the H-atom product is ~-l,and spin-orbit branching fractions of the S(~3P_J)product are close to S(~3P_2):S(~3P_1):S(~3P_0)=0.51:0.36:0.13.The UV photolysis of SH is via a direct dissociation and is initiated on the repulsive ~2SIGMA~-potential-energy curve in the Franck-Condon region after the perpendicular transition ~2SIGMA~--X ~2PI.The S(~3P_J)product fine-structure state distribution approaches that in the sudden limit dissociation on the single repulsive ~2SIGMA~-state,but it is also affected by the nonadiabatic couplings among the repulsive ~4SIGMA~-,~2SIGMA~-,and ~4PI states,which redistribute the photodissociation flux from the initially excited ~2SIGMA~-state to the ~4SIGMA~-and ~4PI states.The bond dissociation energy D_0(S-H)=29 245(+-)25 cm~(-1)is obtained.