V. V. Petrunin

Structure and dynamics of the negative alkaline-earth ions

Recent progress in experimental and computational methods for the study of negative atomic ions has greatly improved the knowledge about the structural and dynamic properties of the negative alkaline-earth ions. This review deals in particular with the stable ground states in , , and and with the metastable quartet states (, , and ) observed in , , , and . Future perspectives are discussed.

State-selective stepwise two-photon detachment study of the ion

The presence of two metastable states in the negative beryllium ion, and , which are connected by an optical transition, offers a unique possibility for gaining new information about this ion. Utilizing resonant, two-photon detachment, combined with resonant-ionization detection of the resulting neutral atoms, we have obtained results yielding the lifetimes of the () and () levels, the fine-structure splittings of the levels, and an improved transition wavelength.

Excess-photon absorption via autodetaching states: potential for spectroscopy beyond the isolated core excitation method

We report the observation and study of the excess-photon absorption (EPA) phenomenon in the region of short-lived autodetaching states of negative ions at low intensities . A sensitive resonant-ionization-based technique is utilized here for the first time to investigate nonlinear processes in the continuum, including detailed studies of signal response to laser power. We demonstrate that the sensitivity of the new method is sufficient to obtain actual positions and widths of the states at the limit of low intensities. Higher intensities (i.e. above ) can lead to significant displacement of the EPA signals from the autodetaching state positions and, depending on the shape of the one-photon detachment cross section, to either broadening or narrowing of the signal peaks. The amplitude of the signal at these higher intensities typically displays a sublinear dependence on laser power.

Resonance ionization spectroscopy of negative ions

A new technique based on state-selective, resonant-ionization detection of atoms, produced by laser detachment or resonant excess-photon- detachment processes, has made it possible to obtain significant progress in the studies of structural and dynamic properties of negative ions and of nonlinear interaction of an autoionizing state with a near-resonant laser field. New methods are briefly described and illustrated by examples from stable and autoionizing negative ions formed by elements with a closed s-electron subshell: He−, Be−, Ca−, Sr−, Ba−.

Negative ion spectroscopy with stored H−ions

This paper reviews the results obtained in recent years from spectroscopic studies of the negative hydrogen ion at the ASTRID storage ring. The two lowest-lying members of the 1P0 dipole series of autodetaching resonances in H− located just below the H(n=2) threshold have been observed and characterised, using Doppler-tuned collinear laser spectroscopy. The resonance positions have been determined for both H− and D−, allowing also a critical test of the predicted isotope effects. Further studies are in progress based on electron cooling of the negative hydrogen ion beam.This paper reviews the results obtained in recent years from spectroscopic studies of the negative hydrogen ion at the ASTRID storage ring. The two lowest-lying members of the 1P0 dipole series of autodetaching resonances in H− located just below the H(n=2) threshold have been observed and characterised, using Doppler-tuned collinear laser spectroscopy. The resonance positions have been determined for both H− and D−, allowing also a critical test of the predicted isotope effects. Further studies are in progress based on electron cooling of the negative hydrogen ion beam.