Ionic photofragmentation cross sections of the HS⁺, H₂S⁺ and HCl⁺ molecular ions near the 2p threshold

The absolute cross sections for the production of X²⁺ and X³⁺ ions following absorption of monochromatised SOLEIL synchrotron radiation by the HX⁺ hydride molecular ions (X = S, Cl) are presented as a function of photon energy in the region of the X_2p ionisation thresholds (∼180 eV and ∼220 eV for sulphur and chlorine, respectively). The experimental results are interpreted with the help of extensive <i>ab initio</i> density functional theory (DFT) and post-Hartree-Fock configuration interaction calculations including spin-orbit coupling to compute the absorption oscillator strengths of the X 2p core excitations to valence and Rydberg states. In order to account for all the experimental features, the calculations must include vibrational dynamics and spin-orbit coupling. Similar experimental data are also presented for the sulfaniumyl H₂S⁺ molecular ion.