Possible evidence for the production of Ar metastable negative molecular ions in gaseous argon of two-phase detectors for dark matter searches

A. Buzulutskov; E. Frolov; E. Borisova; V. Nosov; V. Oleynikov; A. Sokolov

doi:10.1140/epjc/s10052-023-12088-4

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2023) 83: 899
https://doi.org/10.1140/epjc/s10052-023-12088-4

Letter

Possible evidence for the production of Ar $_{2}^{* -}$ $_2^{*-}$ metastable negative molecular ions in gaseous argon of two-phase detectors for dark matter searches

A. Buzulutskov¹^,2, E. Frolov¹^,2^b, E. Borisova¹^,2, V. Nosov¹^,2, V. Oleynikov¹^,2 and A. Sokolov¹^,2

¹ Budker Institute of Nuclear Physics SB RAS, Lavrentiev Avenue 11, 630090, Novosibirsk, Russia
² Novosibirsk State University, Pirogova Street 2, 630090, Novosibirsk, Russia

^b geffdroid@gmail.com

Received: 24 May 2023
Accepted: 28 September 2023
Published online: 6 October 2023

Abstract

Our recent studies of electroluminescence (EL) properties in two-phase argon detectors for dark matter searches have revealed the presence of unusual delayed pulses in the EL signal in the form of two slow components with time constants of about 5 and 50 $μ s$ $\upmu \text {s}$ . These components were shown to be present in the charge signal itself, which clearly indicates that drifting electrons are temporarily trapped on two states of metastable negative argon ions which have never been observed before. In this work, using the pressure dependence of the ratio of slow component contributions measured in experiment, it is deduced that these states are those of two types of metastable negative molecular ions, ${Ar}_{2}^{* -} (b^{4} Σ_{u}^{-})$ ${{\textrm{Ar}}}_2^{*-}(b \ ^4\varSigma _u^-)$ and ${Ar}_{2}^{* -} (a^{4} Σ_{g}^{+})$ ${{\textrm{Ar}}}_2^{*-}(a \ ^4\varSigma _g^+)$ for the higher and lower energy level respectively.

© The Author(s) 2023

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