RotationalPredisscociation Double Resonance Spectroscopy of the HeHCO complex

Rotational-Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex Thomas Salomon, Matthias Töpfer, Phillip Schreier, Stephan Schlemmer, and Oskar Asvany I. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany Hiroshi Kohguchi Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama 1 -3 -1, Higashi-Hiroshima 739 -8526, Japan Leonid Surin Molecular Spectroscopy Department , Institute of Spectroscopy RAS, Fizicheskaya 5, 142190 Troitsk, Moscow, Russia

Content § Relevance of He-HCO+ § The 22 -pole Ion Trap Experiment Coltrap § Production of HCO+ complexes @ Coltrap § Preliminary Infrared Spectra of He-HCO+ § Rotational-Predissociation Double Resonance Spectroscopy § § § Rotational Spectra of He-HCO+ § § Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 § Technical Requirements Double Resonance Scheme Observed Rotational Transitions Phenomena of the weakly bound Helium complex Outlook

Relevance of He-HCO+ § For complexes consisting of molecular ions and H 2 or He very little is known about their bound states § elucidation of intermolecular forces -> high resolution spectroscopy of van der Waals complexes § Microwave measurements -> intermolecular dynamics § He-HCO+ particularly prominent test system, as it is linear and has a 1Σ ground state. Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex Y. Ohshima, Y. Sumiyoshi, and Y. Endo, The Journal of Chemical Physics 106, 2977 (1997). June 22, 2018 K. Seki, Y. Sumiyoshi, and Y. Endo, Chemical Physics Letters 331, 184 (2000).

COLTRAP & FELion: Experimental Setup quadrupole bender ion source mass filter 1 4 K coldhead 22 -pole trap Typical values: mass filter 2 He number density: 1014 – 1015 cm-3 Rotational. Predisscociation Trap temperature: Double Resonance Spectroscopy oftime: Trapping + the He-HCO complex # parent ions: June 22, 2018 4 – 12 K 0. 1 – 2 s 2000 - 20000 Daly type ion detector

Production of HCO+ complexes @ Coltrap k HCO++2 He → HCO+-He + He 3 Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex Experimental Parameters: Source pressure: Length of ion pulse: June 22, 2018 trap temperature: p. Source~10 -5 mbar 40~ms 4 K 1: 2: 3 mixture of CO, H 2 and He. estimated peak number density: n[He]~1015 cm-3 estimated ternary rate coefficient: k 3~10 -29 cm 6 s-1

Infrared Photodissociation Spectra of the He-HCO+ complex Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 § Goal: rotational predictions better than 30~MHz Ø re-investigated the ν 1 C-H stretching mode § 22 ro-vibrational transitions are observed between 3070 and 3083 cm-1. § some infrared transitions appear to be perturbed § Constant shift of roughly 0. 02 cm-1 with respect to Nizkorodov et al. [1] § Combination difference fit to predict rotational ground state [1] Nizkorodov et al, J. Chem. Phys. 103, 1297 (1995)

Rotational-Predisscociation Double Resonance Spectroscopy T=4 K mirror Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex mm-wave source § tunable narrow-bandwidth (sub)mm-wave source (83 -1100 GHz) § narrow bandwidth CW optical parametric oscillator. § elliptical mirror containing a 3~mm hole § 20 mm aperture diamond vacuum window. June 22, 2018

Rotational-Predisscociation Double Resonance Spectroscopy 14 ν 1=1 A 16 ν 1=0 Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 B 15 A 14 § High resolution at TTrap=4 K § Rotational temperature Trot=12 K § 11 rotational transitions measured B

Pure Rotational transitions of the He-HCO+ complex Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex K. Seki, Y. Sumiyoshi, and Y. Endo, Chemical Physics Letters 331, 184 (2000). June 22, 2018 Y. Ohshima, Y. Sumiyoshi, and Y. Endo, The Journal of Chemical Physics 106, 2977 (1997).

obs. -calc. / MHz Black model: § fit: νJ‘↔J‘‘=2 B(J‘‘+1) § obs. -calc. plotted with B from fit Red model: § fit: νJ‘↔J‘‘=2 B(J‘‘+1) - 4 D(J‘‘+1)³ § obs. -calc. plotted with B from fit upper state J § values for CO are normalized to the rotational constant of Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 Relative obs. -calc. / MHz (Δν=ΔνCO / BCO * BHe-HCO+ ). upper state J He-HCO+

Relative obs. -calc. / MHz HCO+ CO x 100 CO June 22, 2018 Relative obs. -calc. / MHz upper state J Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex He-HCO+ § obs. -calc. plotted according fits Ø implementing B, D, H, L, M Ø implementing B, D, H, L, M, N upper state J § fit: νJ‘↔J‘‘=2 B(J‘‘+1) - 4 D(J‘‘+1)³ § obs. -calc. values multiplied by 100

Outlook H 2 He+ Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 • fundamental 3 -electron system • strongly bound • early universe molecule • no high-resolution data yet • first preliminary vibrational spectra from FELion • Other molecules: He-H 3+ …

Cologne spectroscopy group Leonid Surin Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex Stephan Schlemmer Thomas Salomon Oskar Asvany Matthias Töpfer Hiroshi Kohguchi June 22, 2018 Funding: DFG via SFB 956 project B 2 and AS 319/2 -2

Preliminary Infrared Spectra of the He-HCO+ complex [1] Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018 [1] Nizkorodov et al, J. Chem. Phys. 103, 1297 (1995)

Pure Rotational transitions of the He-HCO+ complex Rotational. Predisscociation Double Resonance Spectroscopy of the He-HCO+ complex June 22, 2018