Far-infrared self-broadening in methylcyanide: Absorber-perturber resonance

Abstract

Using tunable far-infrared spectrometers with high-frequency stability and accuracy, we have measured the self-pressure broadening and shift of ${\mathrm{CH}}_3$CN. We obtained clear evidence of absorber-perturber resonance effects on the collisional line shape. This tests the theoretical model and its possible improvements and also allows us to make broadening and shift predictions for a large class of molecules. Moreover, the resonance effect produces a theoretical temperature dependence of self-broadening that is very different from what is commonly assumed.