The millimeter wave spectrum of methyl cyanide and the l-type doubling

Abstract

The millimeter wave spectrum of methyl cyanide corresponding to the transitions J = 4 → 5 to J = 11 → 12 from 90 kMc/sec to 225 kMc/sec has been studied. Transitions corresponding to the molecules in the ground vibrational state as well as in the excited states v₈ = 1 and v₈ = 2 are observed. The B₀, D_J, and D_JK obtained for the ground vibrational state are 9198.899 Mc/sec, 3.81 kc, and 176.9 kc, respectively, and for the excited state v₈ = 1, 9226.444 Mc/sec, 3.9 kc, and 177.7 kc, respectively. The pattern for the excited state v₈ = 1 is qualitatively as expected according to Nielsen's theory, but it has been found that the theory is inadequate to give a quantitative fit.