Level Crossing in CH4 Observed by Nonlinear Absorption

Abstract

Stark-tuned level crossing resonances in an excited vibration-rotation state of methane were detected through nonlinear optical absorption. The signal accurately follows a Lorentzian line shape with a 200-kHz minimum width. Pressure broadening studies yield the rotational relaxation in the excited vibrational state. © 1969 The American Physical Society.