The ejected-electron spectra of highly excited autoionising levels of Li, Be, B and C have been studied by using the projectile electron spectroscopy method. Singly and doubly core-excited states are strongly populated in 100 to 500 keV Li+, Be+, B+ and C+ single collisions with He and CH4. High resolution is obtained by selecting a small observation angle (6.4 degrees ) with respect to the beam axis. Numerous states, previously not seen, have been resolved and identified by comparison with existing theoretical data. For a large number of core-excited states, absolute Auger transition and excitation energies are given. In particular, isoelectronic sequences for singly core-excited lithium-like (Z=2-16) and doubly core-excited helium-like (Z=1-14) autoionising states are studied.

High-resolution projectile Auger spectroscopy for Li, Be, B and C excited in single gas collisions. I. Line energies for prompt decays

The XUV spectra of free metal atoms obtained by absorption, photoion, photoelectron and two-photon spectroscopy are reviewed. The experimental results are discussed in comparison with the predictions of the different theoretical approaches. Emphasis is put on the basic excitation and de-excitation processes, the importance of electron correlation, on common features of groups and on trends along series.

https://iopscience.iop.org/article/10.1088/0034-4885/55/7/002/pdf

XUV spectroscopy of metal atoms

High resolution Auger spectroscopy in energetic ion atom collisions

Spectroscopic investigations of the structure of highly ionised atoms have undergone significant developments in recent years. The experimental progress is largely due to the introduction of several powerful light sources, such as laser-produced plasmas. Tokamaks and beams of fast, excited ions. The results obtained with these laboratory devices complement the data from astrophysical observations of the solar corona and solar flares. The experimental techniques are described in some detail. The results are discussed with respect to energy level studies along isoelectronic sequences, inner-shell excited levels, forbidden transitions, lifetimes and transition probabilities as well as the results of spectroscopic studies of quantum electrodynamics, QED. The experimental results are compared with theoretical predictions.

http://iopscience.iop.org/article/10.1088/0034-4885/52/2/002/pdf

The spectroscopy of highly ionised atoms

Using a dual laser plasma technique we have measured for the first time the photoabsorption spectrum of atomic lithium at energies corresponding to the simultaneous excitation of both 1s electrons. We have observed the main triply excited 1${\mathit{s}}^{2}$2s${(}^{2}$S)\ensuremath{\rightarrow}2${\mathit{s}}^{2}$p${(}^{2}$P) transition with Fano parameters ${\mathit{E}}_{0}$=142.32\ifmmode\pm\else\textpm\fi{}0.05 eV \ensuremath{\Gamma}=0.20\ifmmode\pm\else\textpm\fi{}0.04 eV, and q=-2.2\ifmmode\pm\else\textpm\fi{}0.6. Our experiment represents the first step in photoionization studies of this fundamental atomic system in which the motion of the three electrons in the field of the nucleus is so highly correlated.

/pdf/first-observation-of-a-photon-induced-triply-excited-state-2l4m3ln7rc.pdf

First observation of a photon-induced triply excited state in atomic lithium.

For pt.I see ibid., vol.9, no.9, p.1567 (1976). Z1+-Ar collisions, Z1=11-17 (except 14) are studied at impact energies of 10-100 keV by spectroscopy of L2,3-MM electrons from projectile Z1. Lines are resolved and identified using calculated energies and, in a few cases, photoabsorption data. Coster-Kronig structure, particularly pronounced for Z1=11, reveals formation of L1 vacancies. For Z1=15-17, low-energy lines in the L2,3 Auger group are due to the second transition in the Auger decay of double-vacancy states. Discussion of relative intensities based on previous charge-state and inner-shell excitation data indicates that: (i) in the initial double-vacancy state (after autoionization), the outer shell is in its ground state if the number of outer electrons is equal to or lower than the number of outer electrons on the incident ion; and (ii) with more outer electrons, a 3s vacancy is likely to be present. For the most probable double-vacancy states, the number of outer electrons is one higher than the number of electrons in the M shell of the incident ion.

https://iopscience.iop.org/article/10.1088/0022-3700/9/9/022/pdf

Auger spectroscopy on heavy-ion-atom collisions. II. Na+, Mg+, Al+, P+, S+, Cl+-Ar collisions

This is the first of a series of papers dealing with the spectroscopy of electrons from heavy-ion-atom collisions The paper presents a simple treatment of the Doppler effect comprising of not only line shift and broadening, but also of the effect on the angular distribution For line broadening, previous approximations are replaced by a more accurate, but still simple, expression The potential or Berry effect for fast autionization processes is discussed Owing to interaction with the Doppler effect, the Berry width vanishes under certain conditions The experimental conditions are outlined and illustrated by sample calculations

Auger spectroscopy on heavy-ion-atom collisions. I. Kinematic effects and apparatus

K-shell binding energies in free atoms for Be, B, and C have been obtained to within a few tenths of an eV by applying Auger spectroscopy to fast Be, B, and C ion beams being core-excited in single collisions with CH4 and He. The present values, which correspond to the lowest possible ionization energy, i.e., for B, BE1 S = E(1s2s22p)3P0 - E(1s22s22p)2 P0, are considerably higher than previous values derived from measurements where solid or molecular samples have been used, while good agreement is found with recent free-atom theoretical data.

https://iopscience.iop.org/article/10.1088/0031-8949/17/2/001/pdf

Measurement of Free-Atom K-Shell Binding Energies of Light Elements

Metastable, autoionizing high-spin states are studied using the ion-beam time-of-flight method in connection with single-collision excitation. High-resolution, time-delayed spectra are obtained from Li, Be, and B excited in 200-keV impact on CH/sub 4/. Evidence is found for the (1s2s2p/sup 2/)/sup 5/P state in B II. Excitation energies for the observed quartet and quintet states are given, and the branching ratio associated with the BII (1s2s2p/sup 2/)/sup 5/P decay is estimated.

M. Rødbro

Papers

High-resolution projectile Auger spectroscopy for Li, Be, B and C excited in single gas collisions. I. Line energies for prompt decays

Auger spectroscopy on heavy-ion-atom collisions. II. Na+, Mg+, Al+, P+, S+, Cl+-Ar collisions

Auger spectroscopy on heavy-ion-atom collisions. I. Kinematic effects and apparatus

Measurement of Free-Atom K-Shell Binding Energies of Light Elements

Time-Delayed Li, Be, and B Autoionization Spectra Excited in Low-Energy (200 keV) Single Gas Collisions