Penning ionization electron spectroscopy of water molecules by metastable neon atoms

The Penning ionization electron spectra in metastable Ne∗(3P0,2) colliding with H2O molecules at 0.040, 0.075, 0.130, 0.200 and 0.300 eV collision energies have been measured and compared with the photoelectron spectrum with Ne(I) photons. The results show the formation of the ground X ̃ ( 2 B 1 ) and the first excited state A ̃ ( 2 A 1 ) of the H2O+ product ion, with a X ̃ / A ̃ branching ratio slightly increasing with the collision energy, and with an average value of 0.29 ± 0.03. The spectra have been analyzed in order to obtain some information and some basic features of the potential energy interaction between the two reacting particles.