SAMOP 2021 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 5: Miscellaneous

MO 5.3: Vortrag

Donnerstag, 23. September 2021, 11:15–11:30, H2

Optical Properties of Simple Diamondoid Cations and Their Astrochemical Relevance — •Parker B. Crandall, Robert G. Radloff, Jan Weißflog, Marko Förstel, and Otto Dopfer — Technische Universität Berlin, Berlin, Germany

Diamondoids are a class of highly stable, aliphatic cycloalkanes arranged into cage-like structures by sp³ hybridization of the carbon atoms. Similarities between the IR spectra of diamondoids and unidentified infrared emission bands seen in the spectra of young stars with circumstellar disks were found.[1,2] It is also suggested that the radical cations of these molecules, which are predicted to absorb in the IR-UV/VIS range,[3] might be responsible for features in the diffuse interstellar bands. However, the optical spectra of these cations have not been measured experimentally until recently. Here, we present the first optical spectrum of the diamantane radical cation in the gas phase at 5 K by trapping in a cryogenic 22-pole ion trap and compare it to the recently reported spectrum of the adamantane radical cation (C₁₀H₁₆⁺).[4] Both spectra reveal broad features in the gas phase, which is attributed to significant lifetime broadening and/or Franck-Condon congestion. Geometric changes due to Jahn-Teller distortion and the astrophysical implications of these ions will also be discussed.

[1] O. Guillois et al., Astrophys. J. 1999, 521, L133

[2] O. Pirali et al., Astrophys. J. 2007, 661, 919

[3] M. Steglich et al., Astrophys. J. 2011, 729, 91

[4] P. B. Crandall et al., 2020, ApJL, 900, L20