J-Dependence of T2-Parameters for Rotational Transitions of SO2 and CH3OH in K-Band

With the help of a microwave Fourier transform spectrometer in the range from 18 GHz to 26 GHz, the coefficients ß for the linear pressure depedence of collisional dephasing rates 1/T2 have been determined by the transient emission technique for fourteen pure rotational transitions of SO2 with 5 ≦ J' ≦ 66 in the ground vibrational state, twelve transitions with 8 ≦ J' ≦ 62 in the first excited bending vibrational state, and twelve transitions of methanol with 2 ≦ J' ≦ 11, where J' is the rotational quantum number of the upper level of a transition. The T2-parameter ß for the transition J(K-, K+) - 49(4, 46 ) - 48(5, 43) of SO2 in the ground state shows an anomalous behaviour, whereas the values for all other transitions show a J-dependence in accordance with previous results. No significant variation of T2-parameters with J has been found for the rotational transitions of CH3OH.