The measurement of the widths and pressure-induced shifts of microwave spectra lines

Abstract

A microwave spectrometer for the observation of the widths and shifts of spectral lines is described. Results are reported for the self-broadening of the (J, K)=(12, 12) line in the inversion spectrum of NH₃, for the J=2 to 3 rotational line of COS and for the J=1 to 2 rotational line of CH₃CN; in addition, results are given for the broadening of the NH₃ line by the foreign gases He, CO₂ and CH₃CN, and for the COS line by He and CH₃CN. No evidence for a shift of either the COS or the CH₃CN rotational line was found. However, when the ammonia line was broadened, the centre frequency increased by a Delta v, Delta v being the linewidth parameter, where a had the values 0.002+or-0.002, -0.165+or-0.01, -0.045+or-0.008 and -0.012+or-0.006 for broadening by NH₃, CH₃CN, CO₂ and He respectively.