Detection of vibrational overtone excitation in methane by laser‐induced grating spectroscopy

Laser‐induced grating spectroscopy is applied to measure weak overtone and combination bands of methane between 11 170 and 11 980 cm−1 at pressures ranging from 0.2 to 4 bar and ambient temperature. The background‐free method yields rotationally resolved spectra of transitions exhibiting cross‐sections as low as ≈ 10−26 cm2/molecule. The technique is suitable for clarifying the near‐infrared spectra of planetary objects and to provide data for the development and verification of new models describing the complex energy structure of highly vibrationally excited molecules.