Experimental and Theoretical Considerations for Ionization of Simple Hydrocarbons, H2, D2, O2, H2O, and the Rare Gases by 2.2-MeV α Particles and by Electrons in a Mass Spectrometer

Abstract

The measurement of ionization cross sections and mass spectra produced by 2.2-MeV α particles is briefly discussed with emphasis on experimental details which lead to results which are more accurate than those of the previous study. Experimental techniques and apparatus have been developed and applied to these measurements for H2, D2, O2, H2O, CH4, C2H2, C2H4, C2H6, and the rare gases. The experimental results for H2 and He are compared with detailed calculations in the Börn—Bethe approximation and for Ar in the classical approximation. The ionization cross sections for the removal of one electron conform rather well to the predictions although the experimental results tend to be somewhat lower, than the theoretical values. Experimental values for He, Ar, H2, and N2 are in good agreement with extrapolated data of McDaniel and co-workers. The mass spectra produced by 2.2-MeV α particles show the same fragments as those produced by electrons with the same velocity, but the abundance of some fragment ions differ by a factor of four. Mass spectra produced by 75-eV electrons (the usual energy employed in conventional mass spectrometry) also show significantly more dissociative ionization than those produced by 2.2-MeV α particles.

Track structure of protons and other light ions in liquid water: Applications of the LIonTrack code at the nanometer scale

“…3 as a function of the ion's specific energy. The CDW-EIS TCSs are compared to the measurements reported by Rudolph and Melton, 57 Bolorizadeh and Rudd, 58 Ohsawa et al, 51 and Dal Cappello et al 53 There is very good agreement between theory and experiment for H + and He 2+ , especially for the latter, but the measured TCS of 6.0 MeV/u C 6+ ions is considerably lower than the prediction of the CDW-EIS. The origin of this discrepancy remains to be understood.…”

Classical treatment of ion-H2O collisions with a three-center model potential

“…8 with the experimental data of Refs. [52][53][54], as a function of the impact energy E. Good agreement is found for E 50 keV/amu, but discrepancies appear at lower E, where the underestimation of the experimental EP cross section can be attributed to the inaccurate computation, by means of the IEVM, of the many-electron probabilities that contribute to EP. On the other hand, the SI cross section, included in Fig.…”

“…Such improved initial conditions involve an electron energy distribution that spreads over the entire energy bin associated with the entry channel [57] and therefore allow us to mimic, to some extent, under-barrier [27]; purple dot-dashed line, [28]. Experimental results for EP: circles, [52]; triangles, [53]; squares, [54]. transitions, which are significant for projectile charges Z P = 1.…”

Theoretical investigations of electron emission after water vapour ionization by light ion impact

“…Total cross sections as a function of the incident projectile energy (in keV/ amu). The theoretical results are reported by solid line and compared to experimental data taken from different sources: [18] (open diamonds), [19] (open circles) and [20] (open triangles) for protons, [21] (solid down-triangles) for 3 He 2+ , [22] (solid circles) and [23] (solid up-triangle) for 4 He 2+ , [14] (solid circle) for C 6+ ions.…”