Measurement and assignment of double-resonance transitions to the 8900--9100 cm-1 levels of methane

Authors:Foltynowicz, AleksandraUniversity of Umea Rutkowski, LucileUniversity of Rennes Silander, IsakUniversity of Umea Johansson, Alexandra C. University of Umea de Oliveira, Vinicius SilvaUniversity of Umea Axner, OveUniversity of Umea Soboń, GrzegorzWrocław University of Science and Technology Martynkien, TadeuszWrocław University of Science and Technology Lehmann, Kevin, AS-ChemistryUniversity of Virginia ORCID icon

Optical-optical double-resonance spectroscopy with a continuous wave pump and frequency comb probe allows measurement of sub-Doppler transitions to highly-excited molecular states over a wide spectral range with high frequency accuracy. We report on assessment and characterization of sub-Doppler doubleresonance transitions in methane measured using a 3.3 µm continuous wave optical parametric oscillator as a pump and a 1.67 µm frequency comb as a probe. The comb spectra were recorded using a Fourier transform spectrometer with comb-mode-limited resolution. With the pump tuned to 9 different transitions in the nu3 fundamental band, we detected 36 ladder-type transitions to the 3nu3 overtone band region, and 18 V-type transitions to the 2nu3 overtone band. We describe in detail the experimental approach and the pump stabilization scheme, which currently limits the frequency accuracy of the measurement. We present the data analysis procedure used to extract the frequencies and intensities of the probe transitions for parallel and perpendicular relative pump/probe polarization. We compare the center frequencies and relative intensities of the ladder-type transitions to theoretical predictions from the TheoReTS and ExoMol line lists, demonstrating good agreement with TheoReTS

Methane, Double-Resonance Spectroscopy, Frequency Combs
Source Citation:

Physical Review A 103, 022810 (2021).

American Physical Society
Published Date:
11 Feb. 2021
Sponsoring Agency:
Swedish Research Council (2016-03593,2 015-04374) The Knut and Alice Wallenberg Foundation (KAW 2015.0159)Foundation for Polish Science (POIR.04.04.00-00-434D/17-00).The Kempe Foundations (JCK 1317.1)

Final submitted version