Accurate rovibrational energies for the first excited torsional state of methylamine

Abstract

The torsional fundamental band of methylamine has been reassigned in a high resolution IR spectrum in the region from 40 to 360cm−1. Over 11,700 transitions with a resolution of 0.00125cm−1 for 0⩽K⩽17 and K⩽J⩽40 have been assigned. A global fit of the infrared, and previously assigned pure rotational and microwave data has been carried out and the band centre was determined at 264.583143(12)cm−1. The combined data were fit to a single state model based on the group theoretical formalism of Hougen and Ohashi what resulted in the total standard deviation of 0.00079cm−1 (0.31MHz for the microwave spectrum). The set of 88 parameters allows for a reliable calculation of rovibrational levels for the first excited torsional state which will subsequently facilitate the analysis of numerous hot bands observed for methylamine.