Absolute photoionization cross sections of the Ba ground state in the autoionization region: II. 221-209 nm

Abstract

Absolute photoionization cross sections of Ba in the autoionization region of 209-221 nm have been measured with a bandwidth of 0.0014 nm. The measured cross sections are compared with those obtained from R-matrix calculations combined with multichannel quantum defect theory (MQDT) techniques. The variations of the experimental lineshape parameters for the 5d(2D3/2)np[½] and 5d(2D5/2)np[3/2] series are analysed with empirical three-channel MQDT models. From the calculation of partial density of states in 6pns channels, the perturber of the 5d(2D3/2)np[½] series is confirmed to be the 6p7s 3P1 level and that of the 5d(2D5/2)np[3/2] series is identified as the 6p7s 1P1 level.

Inter-Series Interactions on the Atomic Photoionization Spectra Studied by the Phase-Shifted Multichannel-Quantum Defect Theory

“…The theory describes the barium system composed of two interacting 6pnp 1/2 and 6pnp 3/2 autoionizing series perturbed by an interloper series 6pnf spectrum obtained by de Graaff et al with just one parameter [38]. The merged case was found when the channel coupling of the two autoionizing series with the remaining channels was limited to equal strength and was applied to the analysis of the spectrum reported by Kalyar et al [39].…”

“…Contribution of interference terms among resonance eigenchannels may not be neglected in general and should be addressed in the analysis of degenerate autoionization spectra. The form (23) is different from the usual fitting form of ∑ k∈Q σ ak (ε k + q k ) 2 / 1 + ε 2 k + σ b [8,[38][39][40] of autoionizing spectra in that all the Beutler-Fano term has the same weight. The absence of σ b in (23) is due to the restriction of the number of open channels to one.…”

“…There were three directions in the previous research for this degenerate system. One approach is to use a phase-shifted MQDT formula based on the neglect of direct and indirect closed channel coupling [8,[38][39][40]. The other approach is to use Shore's formula, which is based on Feshbach's resonance theory [41][42][43][44].…”

Relations between Resonance Structures in Photoionization Spectra in Three-Channel-Systems Studied by Multichannel Quantum Defect Theory

“…In this limit interval, experimental data are routinely fitted to the form (9) and are represented with energy-insensitive QDT parameters ξ r , I 3 , μ c and D ri (i = 1, 2, 3). 24 On the other hand, different QDT parameters K 12 , K 13 and K 23 , I i , μ i (i = 2, 3) and D i (i = 1, 2, 3) are used to fit the experimental data in limit interval 2.…”

Multichannel photoelectron phase lag across atomic barium autoionizing resonances

“…relative to the double escape threshold. Barium photoionization spectra in this energy range have been previously measured [1,2,[25][26][27] in the laser wavelength range λ ω = 684.83 − 686.30 nm.…”