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

Aleksandra Foltynowicz (1) , Lucile Rutkowski (2) , Isak Silander (1) , Alexandra C. Johansson (1) , Vinicius Silva de Oliveira (1) , Ove Axner (1) , Grzegorz Sobon (3) , Tadeusz Martynkien (3) , Pawel Mergo (4) , Kevin K. Lehmann (5)

1 Umeå University
2 IPR - Institut de Physique de Rennes
3 Wroclaw University of Science and Technology
4 UMCS - Maria Curie-Sklodowska University
5 University of Virginia

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 double-resonance transitions in methane measured using a 3.3-mu m continuous wave optical parametric oscillator as a pump and a 1.67-mu m 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 nine different transitions in the nu(3) fundamental band, we detected 36 ladder-type transitions to the 3 nu(3) overtone band region, and 18 V-type transitions to the 2 nu(3) 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.

Domaines: Physique [physics]

Aleksandra Foltynowicz, Lucile Rutkowski, Isak Silander, Alexandra C. Johansson, Vinicius Silva de Oliveira, et al.. Measurement and assignment of double-resonance transitions to the 8900-9100-cm(-1) levels of methane. Physical Review A, 2021, 103 (2), ⟨10.1103/PhysRevA.103.022810⟩. ⟨hal-03190289⟩