High-resolution photoion yield measurements of 'hollow' atomic lithium

Abstract

Using monochromatized extreme-UV radiation from the undulator beamline BW3 at HASYLAB we have measured at high resolution (E/ Delta E approximately 7000) the Li+ photoion yield spectrum at excitation energies corresponding to transitions to double K-shell vacancy states. A number of such resonances including single-photon-three-electron excitations, e.g. 1s22s(2S) to 2p3(2p), have been observed for the first time. The spectrum is tentatively classified with the aid of Hartree-Fock calculations.

Autoionization of Triply Excited Rydberg Series

“…This observation applies particularly to doubly excited states while more systematic studies of triply excited states is of fairly recent origin [1][2][3][4][5]. Studies of nonradiative decays of triply excited states are still often limited to the lowest states, although recently the first observation of the Rydberg series associated with such states has been reported [6].…”

Experimental Observation and Theoretical Calculations of Rydberg Series in Hollow Lithium Atomic States

“…Simultaneous excitation of all three electrons can create hollow lithium states of the type nᐉn 0 ᐉ 0 n 00 ᐉ 00 with n $ 2 [1][2][3][4][5]. A calculation of some low-lying hollow lithium states in hyperspherical coordinates has been recently carried out [6] as a step towards the development of a classification scheme for triply excited states, analogous to the ͑K, T͒ A radial and angular correlation quantum numbers [7,8] used to describe the doubly excited states of helium [9].…”

“…The profiles of the cross section are predominantly symmetric and Lorentzian in the 2p 2 1 D channel, suggesting that the interference between the direct and resonant paths is weak in this channel. The relaxation processes leading to decay in these two channels (2p 2 1 D and 2s2p 1 P) are different; core relaxation is required for the decay to the 2s2p 1 P, whereas a coupling change suffices for decay to the 2p 2 We present in Tables I and II our measured values for the energies of the various terms of the ͓͑2s2p 3 P͒ns͔ 2 P and ͓͑2p 2 1 S͒np͔ 2 P Rydberg series, respectively, together with the results of our calculations. For the ͓͑2s2p 3 P͒ns͔ 2 P series the energies of the n 3 and n 4 terms were previously determined [5] from measurements into the 1s2p 1,3 P and 1s4ᐉ 1,3 L channels.…”

High Resolution Measurements of Partial Photoionization Cross Sections in Hollow Lithium: A Critical Comparison with Advanced Many-Body Calculations

“…Following the first photon-excited observation [1] of the lowest hollow atom resonance (1s 2 2s 2 S ! 2s 2 2p 2 P), two total ion yield photoion experiments at high [2] and medium [3] spectral resolution measured the autoionization of several hollow states in both the Li 1 and Li 21 decay channels. Photoelectron spectrometry [4] was also used with low resolution to study the decay of the hollow lithium 2s 2 2p state into the different continua of the Li 1 ion.…”

“…The previous photoion experiments [2,3] demonstrated a rich spectrum of multiply excited states in the 145-165 eV energy region. Because of cancellation effects particular resonances may sometimes be very weak in such experiments but be large if observed in a specific decay channel as in a photoelectron experiment; application of photoelectron spectroscopy to these higher lying resonances is therefore particularly advantageous.…”