Secondary ions produced from gaseous and frozen H2O under energetic (MeV/amu) Ar ion impact

摘要

Mass/charge spectra of secondary ions produced under energetic (sim;MeV/amu) Ar ion impact on gaseous and frozen H2O targets are measured using a magnethyphen;type mass spectrometer. The ion spectra are found to be quite different between these target phases. Multiply charged Oi+ions with charge statesi=2ndash;6, as well as fragmented H+, O+, and OH+ions, are clearly observed in the gas target, whereas the production of multiply charged ions is strongly suppressed in the frozen target. The most intense ion species is the parent H2O+ion in the gas target; the H3O+ion in the frozen target. The most outstanding feature in the frozen target is that the production of cluster ions of the type (H2O)nH+(n=1ndash;31), and their intensities, decreasing as the cluster sizenincreases, show anomalies betweenn=4 andn=5 and also aroundn=20, 21, and 22. Negatively charged cluster ions with formula (H2O)nOminus;and (H2O)nOHminus;are also efficiently produced in the frozen target.