Related Experiment Video
Updated: Jan 15, 2026

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing
Published on: March 22, 2019
Assignment of collision-induced four-level double-resonance transitions in the 3ν3 ← ν3 spectral region of methane
Kevin K Lehmann1, Adrian Hjältén2, Isak Silander2
1Departments of Chemistry and Physics, University of Virginia, Charlottesville, Virginia 22904, USA.
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 3ν3 ← ν3 spectral region [Hjältén et al., J. Chem. Phys. 161, 124311 (2024)] when pumping from the J = (7, A2) 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 A1 symmetry state to other A1 and A2 symmetry (I = 2 meta nuclear spin) levels of the ν3 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. No collisional OODR transitions were observed to known final states starting from states in the ν1 fundamental band, nor from other symmetries of the ν3 fundamental band.
Related Concept Videos
UV–Vis Spectroscopy: Molecular Electronic Transitions
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied...
Mass Spectrum
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Inductive Effects on Chemical Shift: Overview

