SAMOP 2023 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Electronic Spectroscopy

MO 5.6: Talk

Tuesday, March 7, 2023, 12:15–12:30, F142

Electronic Photodissociation Spectroscopy of Diamondoid Cations in a Cryogenic Trap — •Parker Crandall, Simone Stahl, Viktoria Lovasz, Marko Förstel, and Otto Dopfer — Technische Universität Berlin, Berlin, Germany

Similarities have been observed between the infrared spectra of diamondoids and unidentified IR emission bands seen in the spectra of young stars with circumstellar disks.^1,2 It is also suggested that their radical cations could contribute to features in the largely unassigned diffuse interstellar bands due to their low ionization energy and absorption in the visible range.³ However, the optical spectra of these cations have only recently begun to be measured experimentally, which is required for astronomical identification. Here, we present the optical spectra of the radical cations of adamantane (C₁₀H₁₆⁺)⁴, diamantane (C₁₄H₂₀⁺)⁵, and 1-cyanoadamantane (C₁₁H₁₅N⁺). These spectra were recorded by photodissociation of mass-selected ions in the gas phase at 5 K using a tandem mass spectrometer coupled to a cryogenic 22-pole ion trap. The experimental results are compared to photoelectron spectra and time-dependent DFT calculations for interpretation. All spectra reveal broad structures that are attributed to lifetime broadening and Franck-Condon congestion arising from geometric changes and/or Jahn-Teller distortion. The astrophysical implications of these ions will also be discussed.