Valence and L-shell photoionization of Cl-like argon using R-matrix techniques

Abstract

Photoionization cross sections are obtained using the relativistic Dirac Atomic Rmatrix Codes (darc) for all valence and L-shell energy ranges between 27-270eV. A total of 557 levels arising from the dominant configurations 3s 2 3p 4 , 3s3p 5 , 3p 6 , 3s 2 3p 3 [3d, 4s, 4p], 3p 5 3d, 3s 2 3p 2 3d 2 , 3s3p 4 3d, 3s3p 3 3d 2 and 2s 2 2p 5 3s 2 3p 5 have been included in the target wavefunction representation of the Ar iii ion, including up to 4p in the orbital basis. We also performed a smaller Breit-Pauli (bp) calculation containing the lowest 124 levels. Direct comparisons are made with previous theoretical and experimental work for both valence shell and L-shell photoionization. Excellent agreement was found for transitions involving the 2 P o initial state to all allowed final states for both calculations across a range of photon energies. A number of resonant states have been identified to help analyze and explain the nature of the spectra at photon energies between 250 and 270eV.

Benchmarking Current Capabilities for the Generation of Excitation and Photoionisation Atomic Data

“…In this publication, three sets of data are presented: the experimental measurements, the absolute measurements at the resonance-free regions, and a theoretical Breit-Pauli calculation. All three are presented in Figure 4 for completeness and compared with the results of [12]. Excellent agreement was found at all photon energies considered, with particularly good conformity in the low-energy region close to threshold, and in the vicinity of the Cooper minimum around 45 eV.…”

“…In Figures 3 and 4 we present some examples of the quality of the photoionisation cross sections that can now be produced and the level of agreement that can be achieved when compared with experiment. Figure 3 shows partial cross sections for the photoionisation of O-like S IX from the 2s 2 2p 4 3 P 2 ground state to the four lowest final target levels, 2s 2 2p 3 , 4 In Figure 4a we present the total photoionisation cross section from the initial 3s 2 3p 5 2 P o ground state of Cl-like Ar II from Tyndall et al [12] (Figure 2 in their paper). Two Breit-Pauli calculations as well as a large fully relativistic DARC calculation are shown in the figure and compared with absolute cross sections obtained from the merged beam apparatus at the Advanced Light Source (ALS) at an energy resolution of 10 meV [13].…”

“…(a) Total photoionisation cross section for the ground 2 P o state of Cl-like Ar II: yellow circles and green circles with error bars are respectively the experimental measurements and absolute measurements at resonance-free regions of [13], solid cyan are theoretical predictions of [13], solid purple are DARC evaluations of [12], dashed orange are the Breit-Pauli calculation of [12]; (b) Total photoionisation cross section for the ground 2 P o state of Cl-like Ar II between 27.8-29.2 eV just above threshold. The solid black line is the DARC calculation of [12], and the yellow circles are the experimental values of [13]. ALS: Advanced Light Source; BP: Breit-Pauli.…”

Photoionization of Co+and electron-impact excitation of Co2 +using the DiracR-matrix method

“…Validity of these methods between the outlined theoretical approaches are always important, and enhance the robustness of the techniques carried out as seen in Tyndall et al (2016) for Ar + and Fernández-Menchero et al (2015) for Al 9+ . Therefore, it is possible to benchmark sophisticated experimental techniques against theory (Müller et al 2009;Gharaibeh et al 2011).…”

Cooper minimum in singly ionized and neutral argon

“…HHG spectra are determined from the time-dependent expectation value of the dipole operator as extracted from calculations using the RMT code [43,44] while photoionization cross sections (PICS) for Ar + are extracted from calculations using the Dirac Atomic R-matrix Code (DARC) [45][46][47]. Calculation of the PICS for neutral argon is performed with the Breit-Pauli (BP) R-matrix codes [47,48].…”