Ultraviolet photodissociation dynamics of D2S+: The S+-loss channel near the D-loss dissociation threshold

Abstract

Photodissociation dynamics of deuterium sulfide cations (D2S+) via the A2A1 state were investigated using the time-sliced velocity map ion imaging technique. High-resolution images of S+(4S) from the S+-loss channel, D2(X1Σg+) + S+(4S), were acquired at five wavelengths near 320 nm. From the high-resolution images, we derived the total product kinetic energy releases, angular distributions, and rovibrational-state populations of the D2(X1Σg+) co-products. The product angular distributions are nearly isotropic across all photolysis wavelengths studied. While the available energy distributions in internal and translational energy show only weak variations, the internal state populations of products exhibit clear wavelength dependence. Based on MRCI+Q/aug-cc-pV5Z calculations, the energy correlation diagram of D2S+ was constructed. The excitation photon energies employed in this study lie near the dissociation threshold of the SD+(3Σ−) + D(2S) channel. The results reveal rich photofragmentation dynamics arising from complex non-adiabatic couplings among several electronic states. Multiple dissociation pathways, including possible roaming mechanisms, contribute to the formation of D2(X1Σg+) + S+(4S) products at the excitation energy near the dissociation threshold of the SD+(3Σ−) + D(2S) channel.