Experimental and theoretical investigation of odd 5p⁵_1/2<i>nl</i> autoionizing resonances in xenon atoms: energy dependence of the reduced widths

Abstract

Using two different experimental set-ups involving optogalvanic spectroscopy and atomic beam spectroscopy with mass spectrometric ion detection, respectively, we have measured the 5p5(2P1/2) nd' [K' = 3/2]J=2 and [K' = 5/2]J=2,3 (7 ≤ n ≤ 9) autoionizing resonances of xenon by means of two-step resonant laser excitation from the metastable Xe(J = 2, 0) levels. By selecting particular intermediate 6p' [1/2]1 and 6p' [3/2]1,2 levels, autoionizing resonances with specified K' and J values were addressed. Level energies and resonance widths have been derived by a Fano-type lineshape analysis, thus yielding reduced resonance widths which significantly decrease with rising n. With the aim to obtain a theoretical understanding of these and previous findings for the widths of odd Xe resonances, extended calculations for the Xe(ns' J = 0, 1), Xe(nd' J = 1, 2, 3) and Xe(ng' J = 3) autoionizing series have been carried out. They are based on the Pauli–Fock approach and include core polarization and electron correlation effects at a high level; in all cases, they reveal a substantial energy dependence of the reduced widths. Using this energy dependence and parameters of multichannel quantum defect theory (MQDT) determined in the discrete region, the MQDT widths of autoionizing resonances were derived. These values are in good agreement with recommended experimental values.