Photoionization of the3s 2 3p 4 3 P and the 3s 2 3p 4 1 DPhotoionization 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.

Photoionization and autoionization of electronically excited atomic oxygen O(D1) are investigated in the energy range between 12 and 26eV using tunable laser-produced plasma radiation in combination with time-of-flight mass spectrometry. A broad, asymmetric, and intense feature is observed that is peaking at 20.53±0.05eV. It is assigned to the 2s22p4(D1)→2s12p5(P1) transition, which subsequently autoionizes by a Coster-Kronig transition, as predicted by the previous theoretical work [K. L. Bell et al., J. Phys. B 22, 3197 (1989)]. Specifically, the energy of the unperturbed transition occurs at 20.35±0.07eV. Its shape is described by a Fano profile revealing a q parameter of 4.25±0.8 and a width of γ=2.2±0.15eV. Absolute photoionization cross section σ is derived, yielding σ=22.5±2.3Mb at the maximum of the resonance. In addition, weak contributions to the O(D1) yield from dissociative ionization originating from molecular singlet oxygen [O2(Δg1)] are identified as well. Possible applications of the 2s22p4(D1)→2s12p5(P1) transition as a state-selective and sensitive probe of excited oxygen in combination with photoionization mass spectrometry are briefly discussed.

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