Studies of Electron-Molecule Scattering at Microelectronvolt Energies Using Very-High-nRydberg Atoms

Atoms in very high Rydberg states, $100\lesssim n\lesssim 1100$, are used to investigate electron-molecule interactions at electron energies extending down to a few microelectronvolts. At such energies the cross section for electron capture by CC${\mathrm{l}}_4$ is observed to vary inversely with electron velocity, indicative of an $s$-wave process. Studies with the polar target C${\mathrm{H}}_3$Cl suggest that dipole-supported states may be important in inelastic electron-polar molecule scattering at very low electron energies.