Interacting asymmetric double Rydberg series: the Ba 8snl(l= 5) + 5f_jn′l′ case

Abstract

The 8snl double Rydberg states of barium with l = 5 and n = 12–15 are populated by employing an isolated core excitation (ICE) scheme in conjunction with the Stark switching technique. The recorded spectra show strong configuration interaction with three adjacent 5fjn′l′ series. One of the latter series is converging to the 5f5/2 ionization limit and the other two to the higher lying 5f7/2 one. A multichannel quantum defect theory (MQDT) analysis reveals the presence of low-lying members of double Rydberg series converging to higher ionization thresholds and determining the configuration mixing. At least two perturbers, affecting energy level positions, are identified while a comparison between experimental and fitted excitation profiles points towards the presence of a third one. Finally, theoretical calculations of the 8snl(l = 5) series members quantum defects demonstrate the onset of mutual penetration between the two excited electrons. Nevertheless, the most important quantum defect contributions stem from exchange and polarization effects and thus long-range interactions alone are insufficient for a proper description of the double Rydberg states involved.

Multichannel Quantum-Defect Study of q reversals in Overlapping Resonances in Systems involving 1 Open and 2 Closed Channels

“…Complex overlapping resonances caused by an interloper are observed routinely in autoionization spectra, such as in N2, 1 Ba, 2 Pb 3 and Yb. 4 Although configuration mixing theory (CM) was the first to study overlapping resonances in atomic and molecular systems, [5][6] there have been several difficulties in implementing it and only a few studies in this line of research have been carried out.…”

“…These widths can be obtained in Ueda's formula by expanding 2 ε% into the Taylor series around the resonance center, i.e., …”

“…5. As the cylinder moves toward the 2 q % axis, the magnitude of W q − % decreases hyperbolically whereas the upper root plane decreases linearly and the lower root plane remains constant. This means that from some point, W q − % no longer lies in between the two roots.…”

“…Fig. 7 shows the movement of the cylinder toward the 2 q % axis ( 3 q % = 0) as 13 K % increases in magnitude. Let W q − % lie between the two roots at first as in the case of the first spectra of Fig.…”

“…This means that from some point, W q − % no longer lies in between the two roots. One interesting question would be the possibility of another pattern change as the point moves further, beyond the double root point and toward the 2 q % axis. The pattern change in Fig.…”