Photoionization of the $3s^23p^4~ ^3P$ and the $3s^23p^4~^1D,~^1S$ states of sulfur: experiment and theory

TL;DR

This study combines high-resolution experimental measurements and advanced theoretical calculations to analyze the photoionization processes of atomic sulfur in various states, revealing detailed resonance structures and quantum defects.

Contribution

It provides the first detailed experimental and theoretical comparison of sulfur's photoionization cross sections and resonance features in the 9-30 eV energy range.

Findings

Identification of multiple autoionizing resonance series

Agreement between experimental data and Dirac Coulomb R-matrix calculations

Tabulated energies and quantum defects for resonance states

Abstract

Photoionization of neutral atomic sulfur in the ground and metastable states was studied experimentally at a photon energy resolution of 44 meV FWHM. Relative cross section measurements were recorded by using tunable vacuum ultraviolet (VUV) radiation in the energy range 9 -- 30 eV obtained from a laser-produced plasma and the atomic species were generated by photolysis of molecular precursors. Photoionization of this atom is characterized by multiple Rydberg series of autoionizing resonances superimposed on a direct photoionization continuum. A wealth of resonance features observed in the experimental spectra are spectroscopically assigned and their energies and quantum defects tabulated. The cross-section measurements are compared with state-of-the-art theoretical cross-section calculations obtained from the Dirac Coulomb R-matrix method. Resonances series in the spectra are identified and compared indicating similar features in both the theoretical and experimental spectra.