Spontaneous and photo-induced decay processes of WF₅^- and HfF₅^- molecular anions in a cryogenic storage ring

Author(s)

Hubert Gnaser, Martin Martschini, David Leimbach, Julia Karls, Dag Hanstorp, Suvasthika Indrajith, Mingchao Ji, Paul Martini, Ansgar Simonsson, Henning Zettergren, Henning T. Schmidt, Robin Golser

Abstract

Spontaneous and photo-induced decay processes of HfF5- and WF5- molecular anions were investigated in the Double ElectroStatic Ion Ring ExpEriment (DESIREE). The observation of these reactions over long time scales (several tens of ms) was possible due to the cryogenic temperatures (13 K) and the extremely low residual gas pressure (∼10-14 mbar) of DESIREE. For photo-induced reactions, laser wavelengths in the range 240 to 450 nm were employed. Both anion species were found to undergo spontaneous decay via electron detachment or fragmentation. After some ms, radiative cooling processes were observed to lower the probability for further decay through these processes. Photo-induced reactions indicate the existence of an energy threshold for WF5- anions at about 3.5 eV, above which the neutralization yield increases strongly. By contrast, HfF5- ions exhibit essentially no enhanced production of neutrals upon photon interaction, even for the highest photon energy used in this experiment (∼5.2 eV). This suppression will be highly beneficial for the efficient detection, in accelerator mass spectrometry, of the extremely rare isotope 182Hf using the 182HfF5- anion while effectively reducing the interfering stable isobar 182W in the analyte ion 182WF5-. The radionuclide 182Hf is of great relevance in astrophysical environments as it constitutes a potential candidate to study the events of nucleosynthesis that may have taken place in the vicinity of the solar system several million years ago.

Organisation(s)

Isotope Physics

External organisation(s)

University of Gothenburg, Stockholm University, University of Vienna

Journal

Journal of Chemical Physics

Volume

157

No. of pages

8

ISSN

0021-9606

DOI

https://doi.org/10.1063/5.0097896

Publication date

07-2022

Peer reviewed

Yes

Austrian Fields of Science 2012

103014 Nuclear physics, 103006 Chemical physics

Keywords

ASJC Scopus subject areas

General Physics and Astronomy, Physical and Theoretical Chemistry

Portal url

https://ucrisportal.univie.ac.at/en/publications/1f92bc3b-09b8-4409-aa44-4295f7e02116