Pressure broadening of molecular lines in a Stark field

The collision broadening of Stark-resolved molecular lines is studied both experimentally and theoretically. Accurate measurements are performed on rotational transitions of ¹²CH₃F near 150 GHz and what may be the first experimental evidence of M-dependent pressure broadening of the lines is reported. A simple theoretical model is developed, in the framework of Anderson's theory, to estimate the broadening coefficients of the Stark-resolved components. The theory predicts that the linewidths may depend on M and their average may be different from the zero-field envelope. The calculated values are in good agreement with experimental results, proving that the theoretical approach described in this work is a useful tool to estimate the relevance of the effect in different cases.