Determination of T2/T1 for inversion transitions in NH3 by analysis of power-broadened line shapes

A computer-coupled microwave spectrometer has been used to record the line shapes of 14 inversion transitions in 15NH3 at several pressures under conditions of low and moderate microwave powers. From the low-power line shapes, values of Δν/p= (2πpT2)−1 have been determined and used as input data for the analysis of the power-broadened line shapes from which values of T2/T1 have been obtained. The T2/T1 results generally increase with J and K and range from 1.11±0.06 for the (J,K) = (1,1) transition to 1.58±0.09 for the (5,5) transition. The data appear to imply that the ratio of the rate constant for adiabatic collisions to that for diabatic collisions is about 0.35 in NH3.