Radiative cooling of polyyne anions: C4H- and C6H-

Boxing Zhu, James N. Bull, Jose E. Navarro Navarrete, Alice Frederike Schmidt-May, Henrik Cederquist, Henning T. Schmidt, Henning Zettergren, Mark H. Stockett

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The time-dependent photodetachment action spectra of the linear hydrocarbon anions C4H- and C6H- are investigated using the cryogenic electrostatic ion storage ring DESIREE. Radiative cooling characteristics of the ions on the millisecond to second timescale are probed by monitoring changes in the spectra as the ions cool by spontaneous infrared (IR) emission. A simple harmonic cascade (SHC) model is used to model the cooling processes. The cooling rates, extracted using Non-negative Matrix Factorization (NMF), are fit with 1/e lifetimes of 19 {plus minus} 2 s and 3.0 {plus minus} 0.2 s for C4H- and C6H-, respectively. For C4H-, the adiabatic detachment energy is determined from the cold ions' photodetachment spectra to be 3.45 {plus minus} 0.02 eV. The photodetachment spectrum and the ultraslow radiative cooling dynamics interpreted in the present work provide important data for understanding the thermal cooling properties of linear hydrocarbon anions and for refining the formation and destruction processes of these anions in astrochemical models.
Original languageEnglish
Article number174308
JournalThe Journal of Chemical Physics
Issue number17
Early online date7 Oct 2022
Publication statusPublished - 1 Nov 2022

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