Inelastic electron--dipole-molecule scattering at sub-milli-electron-volt energies: HF and NH3

Studies of destruction of very-high-n (100<n<400) Rydberg atoms in collisions with the polar targets HF and NH3 are reported. Analysis of the data using the essentially-free-electron model suggests that, for ultralow electron energies (∼80 μeV--1.4 meV), the cross section σ(var-epsilon) for rotationally inelastic scattering of electrons by a polar target varies approximately as 1/var-epsilon, where var-epsilon is the electron energy