Microwave Spectrum of Methylamine

Microwave spectrum of methylamine molecule has been studied in the frequency range between 7 and 30 kMc/sec. More than two hundred lines and their Stark effects have been measured. These lines are divided into three kinds: (1) Δ J =0, Δ K =±1, (2) Δ J =±1, \ (K=1\), and (3) Δ J =0, Δ K =0. Lines of Δ J =0 and Δ K =±1 form seven well-defined series, p 1, p 2, q 1, q 2, r 1, r 2, and s 1. Among them, lines of p series show first-order Stark effects and the others show second-order Stark effects. With theoretical considerations we have assigned these series. From this assignment, the height of the potential barrier for the hindered internal rotation has been determined to be about 680 cm -1. Inversion doubling and its effect on the over-all and hindered rotations are studied. Lines belonging to the classes (2) and (3) are also analyzed. But the determination of molecular constants from the observed data is deferred to a forthcoming paper.