Photoionization of the3s23p43Pand the3s2

Abstract

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 of Cl+from the 3s23p4 3P2,1,0and the 3s23p4 1D2,1S0states in the energy range 19–28 eV

“…The origin of such window resonances has already been discussed in our recent work on atomic sulphur (Barthel et al 2015). Suffice it is to say that in atomic sulphur, the 3s3p 4 4 P and 3s3p 4 2 P ionization states (occurring from a 3s vacancy state) are located at 19.056 eV and 22.105 eV, respectively, and two prominent Rydberg series of window resonances were found.…”

“…Singly ionized atomic chlorine is one such open-shell ion. In a similar manner to our previous work on atomic sulphur (Barthel et al 2015), to gauge the quality of our work we carried out large-scale close-coupling calculations and benchmarked the results with the experimental photoionisation cross section measurements (Hernández et al 2015). The target wavefunctions for our work were obtained using the GRASP code (Dyall et al 1989;Parpia et al 2006;Grant 2007), and the subsequent theoretical photoionisation cross sections were obtained with the DARC codes (Ballance 2015).…”

“…The corresponding series limits E∞ of Equation (2) for the window resonances converging to the 3s3p 4 4 P threshold is indicated by vertical lines. Müller et al 2014), 2p −1 inner-shell studies on Si + ions (Kennedy et al 2014), valence-shell studies on neutral sulphur (Barthel et al 2015), Tunsgten and its ions Müller et al 2015;McLaughlin et al 2016b) have been made using these DARC codes. We point out that suitable agreement of DARC photoionisation cross-sections calculations with the above high resolution measurements made at leading synchrotron light sources such as ALS, ASTRID, SOLEIL and PETRA III has been obtained.…”

“…Only the energies and quantum defects of the prominent 3s 2 3p 3 nd series were tabulated in the ALS experimental work (Hernández et al 2015) but were not spectroscopically assigned. A detailed discussion of such Rydberg series has already been given in our recent study on atomic sulphur (Barthel et al 2015) and will not be expanded upon here. Suffice it is to say that the dominant series is the 3s 2 3p 3 nd with the weaker series being the 3s 2 3p 3 ns.…”

Photoionization of the valence shells of the neutral tungsten atom

“…Recent modifications to the Dirac-Atomic-R-matrixCodes, as implemented for (DARC) [13,15,14] allowed high quality photoionization cross section calculations of Fe-peak elements and Mid-Z atoms of interest to astrophysics. Cross-section calculations for trans-Fe element single photoionization of Se + , Xe + , Xe 7+ , Kr + ions [14,15,16,17], Si + ions [18], and neutral Sulfur [19] have been made using the DARC code and have shown suitable agreement with high resolution measurements made at third generation light sources. In particular for the calculations presented here, the capacity to assign an arbitrary number of processors to the concurrent formation of every dipole matrix, mitigates the fact that matrix multiplications of eigenvector matrices over 60,000 by 60,000 in size require at least 2 × 10 14 operations each.…”