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Unimolecular processes in diatomic carbon anions at high rotational excitation

Viviane C. Schmidt*

Roman Čurík

Milan Ončák

Klaus Blaum, Sebastian George, Jürgen Göck, Manfred Grieser, Florian Grussie, Robert von Hahn†, Claude Krantz, Holger Kreckel, Oldřich Novotný et al.

  • Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck, Technikerstraße 25/3, Innsbruck 6020, Austria

Kaija Spruck and Andreas Wolf

  • *Contact author: viviane.schmidt@mpi-hd.mpg.de
  • †Deceased.
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Phys. Rev. A 110, 042828 – Published 31 October, 2024

DOI: https://doi.org/10.1103/PhysRevA.110.042828

Abstract

On the millisecond to second time scale, stored beams of diatomic carbon anions C2− from a sputter ion source feature unimolecular decay of yet unexplained origin by electron emission and fragmentation. To account for the magnitude and time dependence of the experimental rates, levels with high rotational and vibrational excitation are modeled for the lowest electronic states of C2−, also including the lowest quartet potential. Energies, spontaneous radiative decay rates (including spin-forbidden quartet-level decay), and tunneling dissociation rates are determined for a large number of highly excited C2− levels and their population in sputter-type ion sources is considered. For the quartet levels, the stability against autodetachment is addressed and recently calculated rates of rotationally assisted autodetachment are applied. Nonadiabatic vibrational autodetachment rates of high vibrational levels in the doublet C2− ground potential are also calculated. The results are combined to model the experimental unimolecular decay signals. Comparison of the modeled to the experimental rates measured at the cryogenic storage ring facility CSR gives strong evidence that C2− ions in quasistable levels of the quartet electronic states are the so far unidentified source of unimolecular decay.

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synopsis

Ejected Electron Slows Molecule’s Rotation

Published 31 October, 2024

Sometimes a rotating molecule can transition to a new state only if an electron carries away some of the molecule’s angular momentum.

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Autodetachment of Diatomic Carbon Anions from Long-Lived High-Rotation Quartet States

Viviane C. Schmidt, Roman Čurík, Milan Ončák, Klaus Blaum, Sebastian George, Jürgen Göck, Manfred Grieser, Florian Grussie, Robert von Hahn, Claude Krantz, Holger Kreckel, Oldřich Novotný, Kaija Spruck, and Andreas Wolf
Phys. Rev. Lett. 133, 183001 (2024)

Article Text

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Phys. Rev. A 110, 042828– Published 31 October, 2024
  • Received 12 July 2024
  • Accepted 29 August 2024
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