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 Title: ROTATIONAL ACTION SPECTROSCOPY VIA STATE-SELECTIVE HELIUM ATTACHMENT Author(s): Schlemmer, Stephan Contributor(s): Asvany, Oskar; Brünken, Sandra; Stoffels, Alexander; Kluge, Lars Subject(s): Ions Abstract: Helium atoms can attach to molecular cations via ternary collision processes forming weakly bound ($approx 1$ kcal/mol) He-M$^+$ complexes. We developed a novel sensitive action spectroscopic scheme for molecular ions based on an observed rotational state dependency of the He attachment process [1]. A detailed account of the underlying kinetics will be presented on the example of the CD$^+$ ion, where our studies indicate a decrease of around 50% for the rotational state dependent ternary He attachment rate coefficient of the $J=1$ level with respect to the $J=0$ level. Experiments are performed on mass-selected ions stored in a temperature-variable ($Tgeq 3.9$~K) cryogenic rf 22-pole ion trap in the presence of a high number density of He ($approx 10^{15}$ cm$^{-3}$) [2]. Rotational spectra of the bare ions are recorded by measuring the change in the number of formed He-M$^+$ complexes after a certain storage time as a function of excitation wavelength. Here we will also present the first measurements of the rotational ground state transitions of CF$^+$ ($J=1-0$, hfs resolved) and NH$_3$D$^+$ ($J_K=1_0-0_0$), recorded in this way.\ noindent [1] Br\"{u}nken et al., ApJL {bf 783}, L4 (2014) \ noindent [2] Asvany et al., Applied Physics B {bf 114}, 203 (2014) Issue Date: 22-Jun-15 Publisher: International Symposium on Molecular Spectroscopy Citation Info: ACS Genre: CONFERENCE PAPER/PRESENTATION Type: Text Language: English URI: http://hdl.handle.net/2142/79364 Date Available in IDEALS: 2016-01-05
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