ABUNDANCE OF EXCITED IONS IN AN NO+ ION BEAM

A study of a beam of NO+ ions has been undertaken to determine the relative abundances of excited-state ions and ground-state ions. The experimental procedure involved the attenuation of the ion beam in a gasfilled reaction chamber where different states of the ion were attenuated at different rates. The ions were produced from NO by impact of electrons with energies of 25, 50, and 100 eV. The abundances were determined ~20 μusec after the ions were formed, so that only ions in long-lived states remained in the beam. Several gases, H2, N2, O2, H2O, and Ar, were employed in the attenuation chamber to assess the importance of de-excitation processes and to reduce the possibility of identical-loss cross sections for excited and ground states. It was found that high pressures in the ion source, as well as the electron energy, could influence the abundance of excited-state ions. A typical result was that, using 50-eV electrons and low source pressures, 42% of the ions in the beam were excited.