Millimeter-wave spectroscopy of alpha-alanine

Millimeter-wave spectroscopy of of-alanine was carried out by using continuous molecular beam. The sample of alpha-alanine was heated up to 200-210 degrees C, and flowed with Ar buffer gas through a nozzle with a 0.4 mm diameter. Fifty-five lines of conformer 1 and 35 lines of conformer IIa of alpha-alanine were newly measured in 80-99 and 160-180 GHz regions. A least-squares analysis of the presently observed transitions combined with the previously observed millimeter-wave data below 72 GHz and Fourier transform microwave data gave a set of improved molecular constants which are useful for prediction of the transition frequencies in high frequency region. The rotational temperature of conformer I in the Continuous molecular beam was estimated to be 29.9 +/- 6.5 K. (C) 2008 Elsevier Inc. All rights reserved.