Ionizaion of long-lived highly excited states of hydrogen and deuterium atoms by collision with water molecules

Abstract Long-lived highly excited Rydberg states of hydrogen (deuterium) atoms, H** or D**, were produced by impact of 80 eV electrons on H2O or D2O molecules. The ratio of the ionization cross sections forming protons and deuterons, σ(D**+D2O→D++D2O+e)/σ(H**+D2O→H++D2O+e), was estimated from the dependence of the ion intensities on the target gas pressures to be 1.35±0.15. This ratio is in close agreement with a theoretical estimate, 1.38, based on Matsuzawa's theory predicting the transfer of the rotational energy of a polar target to the Rydberg electron when the excited atom is ionized.