Amino Wagging and Inversion in Methylamines

Abstract

Fine structures have been observed of the amino‐wagging bands at 780 cm^—1 of CH₃¹⁴NH₂, at 776 cm^—1 of CH₃¹⁵NH₂, at 625 cm^—1 of CH₃¹⁴ND₂, and at 689 cm^—1 of CH₃¹⁴NHD. For each vibration—rotation line an appreciable inversion splitting is observed. There is a marked coupling found between the inversion and the internal rotation; and the amount of the inversion splitting of each absorption line depends greatly upon the internal rotation quantum number σ (=0, +1, or —1) and the over‐all rotation quantum number K of the state in question. A hypothetical inversion splitting when the coupling were absent is estimated to be 31.6 cm^—1 for the first excited state of the amino‐wagging vibration of CH₃¹⁴NH₂.