Assignment of collision-induced four-level double-resonance transitions in the 3$ν$${_3}$ ${\Leftarrow}$ $ν$${_3}$ spectral region of methane

Kevin K. Lehmann; Isak Silander; Adrian Hjältén; Michael Rey; Aleksandra Foltynowicz

doi:10.1063/5.0285618

paper

Assignment of collision-induced four-level double-resonance transitions in the 3 $ν$ $_{3}$ $\Leftarrow$ $ν$ $_{3}$ spectral region of methane

arXiv:2506.13644 · doi:10.1063/5.0285618

Abstract

Optical-optical double-resonance (OODR) spectroscopy using a narrow-linewidth pump and a frequency comb probe has previously been used to measure and assign sub-Doppler transitions in the 3 $ν$ $_{3}$ $\Leftarrow$ $ν$ $_{3}$ spectral region [J. Chem. Phys. 161, 124311 (2024)] when pumping from the J = (7, A $_{2}$ ) ground state. Doppler-broadened double-resonance transitions were also observed in those OODR spectra. In this paper, 68 of these Doppler-broadened transitions are assigned to four-level double-resonance transitions involving collisional transfer from the pumped A $_{1}$ symmetry state to other A $_{1}$ and A $_{2}$ symmetry (I = 2 meta nuclear spin) levels of the $ν$ $_{3}$ fundamental state. Assignments are made using combination differences and comparison with the term values and intensities of lines predicted by a new effective Hamiltonian, the accuracy of which has been validated by the sub-Doppler transitions.

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Theory of Lineshapes in Optical-Optical Double Resonance Spectroscopy

Assignment of collision-induced four-level double-resonance transitions in the 3ν3​ ⇐ ν3​ spectral region of methane

Abstract

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Assignment of collision-induced four-level double-resonance transitions in the 3 $ν$ $_{3}$ $\Leftarrow$ $ν$ $_{3}$ spectral region of methane