Laser-induced grating spectroscopy of highly excited overtone and combination vibrational states of methane

• Published in: Journal of molecular spectroscopy 2013-09, Vol.291, p.23-32
• Main Authors: Kozlov, D.N., Sadovskii, D.A., Radi, P.P.
• Format: Article
• Language: English
• Subjects: CH4; Collisional deactivation processes; Four-wave mixing; Laser-induced gratings; Methane; Overtone spectroscopy; Vibrational polyads
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/j.jms.2013.04.005

[Display omitted] •High sensitivity laser-induced grating spectroscopy of weak transitions to vibrational polyads of CH4 between 891 and 618nm.•Doppler-limited rotationally-resolved spectra.•Collisional line broadening and shift coefficients evaluated for a certain prominent line in each of the bands.•Approach to a theoretical description and modeling of the rovibrational structure of highly excited spherical top polyads. Laser-induced grating spectroscopy is applied to investigate weak overtone and combination absorption bands of methane. The rotationally-resolved spectra of transitions to the polyads Pn, n=8–10, 12 recorded at pressures ranging from 0.2 to 4bar and temperatures 298K and 124–130K cover a broad interval between 891 and 618nm (11220–16180cm−1) and contain a significant amount of prominent narrow lines which correspond to stationary rovibrational states. The absorption cross sections of the weakest detected methane transitions are estimated to be as small as ≈10−26cm2molecule−1. The technique is suitable to provide data for the development and verification of new models describing the complex energy structure of highly vibrationally excited molecules.