Ionization of phosphine and deuterated phosphine by electron impact from threshold up to 180 eV

Abstract

Electron impact ionization has been studied in PH3 and in a mixture of PH3 and PD3 as a function of electron energy up to 180 eV, with a double focusing mass spectrometer. Absolute partial ionization cross sections have been obtained in PH3 for the production of the parent ion PH+3, for the fragment ions PH+2, PH+, P+, H+2, and H+ and for the doubly charged ions PH++3, PH++2, PH++, and P++ by normalization against the Ar ionization cross section. From the measured partial ionization cross sections the total ionization cross section function of PH3 has been deduced. In addition, it has been possible to obtain the cross section ratios q (PD++3)/q (PD+3), q (PD++2)/q (PD+3), q (PD++)/q (PD+3), and q (P++)/q (PD+3) as a function of electron energy. The ion D++3, produced by the process PD3+e, has been found for the first time and an estimate of the ionization cross section is given. Using nth root extrapolation the following ionization and appearance potentials have been derived from the low energy cross section functions: I.P. (PH+3) =10.1±0.1 and 12.5±0.2 eV; I.P. (PD+3) =10.15±0.1 and 12.75±0.2 eV; A.P. (PH+2) =14.2±0.2 eV; A.P. (PD+2) =14.3±0.2 eV; A.P. (PH+) =13.0±0.2 eV; A.P. (PD+) =13.3±0.2 eV; A.P. (P+) from PH3=17.2±0.3, 18.8±0.3, and 23.5±0.3 eV; A.P. (P+) from PD3=17.7±0.3, 19.5±0.3, and 22.0±0.3 eV; A.P. (H+2) =14.8±0.2 and 24.8±0.5 eV; A.P. (D+2) =14.9±0.2 and 24.8±0.5 eV; A.P. (H+) =25.3±0.5 eV; A.P. (D+) =25.3±0.5 eV; I.P. (PH++3) =30.0±1.0 eV; I.P. (PD++3) =29.8±0.5 eV; A.P. (PH++2) =35.0±0.5 eV; A.P. (PD++2) =34.9±0.5 eV; A.P. (PH++) =33.0±1.0 eV; A.P. (PD++) =34.4±0.5 eV; A.P. (P++) from PH3=45.6±0.5 eV; and A.P. (P++) from PD3=46.7±0.5 eV. In all double ionization cases a square law has been found from threshold up to some 5–10 eV above threshold. The ionization and appearance potentials obtained are compared with previous results where available. It is possible to resolve a yet unexplained discrepancy of the ionization potentials of the doubly ionized ions of PH3.

Scattering of electrons from hydride molecules: PH3

“…). The electron spectrometer used in the present experiment consists of an electron source followed by an (1956); , Märk and Egger (1977).…”

“…Agreement of both TCSs in the overlapping intermediate energy range is quite good. For completeness, experimental electron-impact total ionization cross sections (Otvos andStevenson 1956, Märk andEgger 1977) are also presented.…”

“…So far much less is known about the absolute intensity of particular processes accompanying electron scattering from phosphine molecules. Electron-impact total ionization cross sections have been obtained (at 75 eV) by Otvos and Stevenson (1956) and (from the positive ion formation threshold to 180 eV) by Märk and Egger (1977). In swarm experiments, Cottrell et al (1968) and Millican and Walker (1987) measured the coefficients for electron transport in PH 3 .…”

“…Energy dependence of experimental cross sections for the electron-PH 3 scattering.Grand total cross section: •, present (error bars represent overall uncertainties, statistical plus systematical); ♦,Ariyasinghe et al (2003). Ionization total cross section: ,Otvos and Stevenson (1956); ,Märk and Egger (1977).…”

Synthesis of New Mixed-Metal Ammonium Vanadates: Cation Order versus Disorder, and Optical and Photocatalytic Properties

“…The quantitative analysis of H 2 O and NH 3 can be determined by the possibility of ionization (ionization cross section). At 40 eV, the major ionization product of H 2 O through electron impact are H 2 O + (mass 18) and OH + (mass 17) with a relative abundance of 1:0.251; the major ionization products of NH 3 through electron impact are NH 3 + (mass 17) and NH 2 + (mass 16) with a relative abundance of 0.675:1 . A control experiment on NH 4 VO 3 was performed.…”