The absolute photoionization cross section of the mercapto radical (SH) from threshold up to 15.0 eV

Abstract

We present the absolute photoionization cross-section of the mercapto radical, SH, recorded from its first ionization energy at 10.4 eV up to a photon energy of 15 eV. The absolute scale was calibrated at the fixed photon energy of 11.2 eV using the known values of H₂S and S as references. SH and S were produced in a microwave discharge flow-tube reactor by hydrogen abstraction of the H₂S precursor. The measured photoionization cross-section of SH dramatically differs from the one currently employed to model the presence of this species in a number of astronomical environments, where SH along with its ionic counterpart SH⁺ have been detected. The cation spectroscopy and fragmentation of H₂S, SH and S in the 9.2–15.0 eV energy range obtained using threshold photoelectron techniques is also presented and discussed in the context of existing literature.