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

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$\nu$${}_3$ $\Leftarrow$ $\nu$${}_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 $\nu$${}_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.

References in corpus (4)

• Investigating the detectability of hydrocarbons in exoplanet atmospheres with JWST
• Sub-Doppler optical-optical double-resonance spectroscopy using a cavity-enhanced frequency comb probe
• Measurement and assignment of J = 5 to 9 rotational energy levels in the 9070-9370 cm${}^{-1}$ range of methane using optical frequency comb double-resonance spectroscopy
• Combined frequency comb and continuous wave cavity-enhanced optical-optical double-resonance spectrometer in the 1.7 $\mu$m range

Cited by in corpus (1)

• Theory of Lineshapes in Optical-Optical Double Resonance Spectroscopy