Microwave pressure broadening studies of some molecules

The line width of carbonyl sulphide (OCS) methyl cyanide (CH 3 CN) and formaldehyde (HCHO) molecules have been measured at room temperature by using a double modulation microwave spectrometer. Twenty cases of self-broadening and foreign gas broadening have been studied. The experimental results have been compared with the calculated results using impact theory of Anderson (1955) and collision broadening theory of Murphy and Boggs (1967-8). The experimental results are in good agreement with the theoretical values of line width parameter for linear molecules. In case of symmetric molecules the theoretical results are higher than the experimentally observed results. The quadrupole moments of OCS, CO 2 and N 2 are obtained from these measurements. The observed results agree better with Murphy and Boggs theory than with Anderson's theory.