Rotational energy distribution in a nozzle beam

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Abstract
The fraction of beam molecules in J = 0, J = 1, and J = 2 rotational states of OCS was measured as a function of pressure behind a nozzle beam source. The fractional populations were obtained from the intensities of microwave emission and absorption signals observed with a beam maser spectrometer. Total beam intensities were measured also. Large deviations from a Boltzmann rotational energy distribution were observed. The ``effective rotational excitation temperature'' obtained from fractional population was near 15°K for J = 0, 40°K for J = 1, and 170°K for J = 2 with 150 Torr nozzle pressure.