Molecular beam maser measurements of relaxation cross sections in NH3

Direct measurements of scattering cross sections for NH₃ in well-defined quantum states are made using a molecular beam maser spectrometer. Cross sections are compared for a pure inversion state with those for a coherent superposition state for scattering gases He, Ar, N₂, N₂O, NH₃, CH₃H and CH₃CN. The cross sections are significantly larger for scattering of the pure inversion state by NH₃, CF₃H and CH₃CN than for scattering of the superposition state. The scattering is the same for both states on non-polar gases. These cross sections are related to relaxation parameters describing transitions between rotation and inversion states.