INELASTIC ELECTRON DIPOLE-MOLECULE SCATTERING AT SUB-MILLI-ELECTRON-VOLT ENERGIES - CH3I AND CH2BR2

Studies of Rydberg-atom destruction in collisions with the polar targets CH3I and CH2Br2 for values of principal quantum number n in the range 100-400 are reported. Analysis of the data using the essentially-free-electron model suggests that, for ultralow electron energies (approximately 80 mueV to 1 meV), the cross section sigma(epsilon) for rotationally inelastic scattering of electrons by a polar target varies approximately as 1/epsilon, where epsilon is the electron energy. The Born approximation does not predict such behavior at very low collision energies, and possible reasons for this discrepancy are discussed.