Observation of high-lying weak autoionizing resonances of Ne, and Mg atoms by charge-separated photoion-yield method

Abstract

Photoabsorption and subsequent decay of Na and Mg atoms T Osawa, Y Tohyama, S Obara et al. 3pnp autoionizing resonance series of Ne atom as well as autoionizing resonances in the 2s region of Na and Mg atoms have been studied with monochromatized synchrotron radiation. Use of charge-separated photoion-yield method allowed us to detect these weak resonances in a clarified way in the yield curves of doubly-charged ions. The observed resonance states have been interpreted with the help of MCDF calculations, and the decay processes of these resonance states are discussed briefly. IntroductionAutoionizing resonances in photoabsorption of atoms have been a subject of extensive experimental and theoretical studies. Resonances in rare-gas atoms, which show typical Beutler-Fano profiles [1], have been precisely studied and have often been used for calibrating the photon energies. It is quite natural that the spectrum of inner-shell resonance-excitations or outer-shell resonant double excitation is superimposed on a strong valence ionization continuum. As the inner shell concerned becomes deeper, the resonance states in the spectrum are superimposed on two or more continua and result in not only singly charged ions but also multiply charged ions with respective probabilities. Excitation of such high-lying resonance states is generally quite weak, and we may face a difficulty in discriminating the excitations from the spectra of photoabsorption, total photoions, or photoelectrons, especially for metallic vapors which need high oven temperatures. In this respect, the chargeseparated photoion-yield method as used in this study is often advantageous because weaker resonances are observed in a clarified way in the double and even multiple ionization channels whose background levels are relatively low. In addition, from this kind of measurement, we may obtain information about the decay processes of observed resonance states, as well as the resonance energies and the associated configuration interaction comparing experiment with theoretical calculations.We have carried out an experiment of charge-separated photoion spectroscopy for Ne, Na, and Mg atoms in the region of 2s ionization and have observed weak high-lying autoionizing resonances. In this report, we present the experimental spectra, describe the results of assignment and profile analysis of the resonance features, and, for the Ne and Na cases, mention briefly the decay processes of the resonance states. The details of the assignment based on furthermore precise calculations will be given and discussed in a forthcoming paper. As far as we know, the resonance series observed in this study for Ne and Mg atoms have not been reported previously.

Photoabsorption and subsequent decay of Na and Mg atoms in the 2s–np autoionizing resonance region

“…The present work has been reported in part at HCI 2006 [13]. In this paper, we report detailed information about the 2s −1 np (n 3) resonances and 2s −1 2p −1 nln l high-lying shake-up resonances and their decay processes.…”