J. M. Joyce

The electron capture cross section of 1.5–3 MeV protons from carbon☆

Abstract Since single collision conditions for electron capture processes cannot be obtained for solid carbon targets, gaseous carbon compounds (CH 4 , C 2 H 2 , C 2 H 4 , C 3 H 6 , C 3 H 6 , and C 4 H 8 ) were used as targets to determine the electron capture cross sections of protons from carbon. Although the statistical uncertainty of the measurement was less than 1%, the pressure determination limited our absolute accuracy to 10–15%. Within this uncertainty, the electron capture cross sections of protons from carbon was independent of the carbon compound used in the experiment. The measured cross sections were 8.6 × 10 −21 , 3.0 × 10 −21 7.4 × 10 −22 cm 2 /atom for proton enrgies 1.5, 2, and 3 MeV respectively.

Statistical scaling of C and O K-shell fluorescence yields

Abstract Relative C and O K-shell fluorescence yields, computed from statistically scaled radiative and nonradiative rates for various molecules, show good agreement with experimental fluorescence yields for CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , CO, CO 2 , and CF 4 (C-bearing), and O 2 , CO, CO 2 , H 2 O (O-bearing) gases.

Charge Transfer of 0.8 MeV/u H+, He+ in Various Hydrocarbon Gases

Systematic variations in total single electron capture cross sections, ¿10(CmHn), for 0.8 MeV/u H+ and He+ on various hydrocarbon gases are interpreted in terms of a model that incorporates intramolecular post-collision-interactions to estimate the reduction in the number of exiting neutral projectiles.

Reduction of the Electron Capture Cross-Section for Protons in Hydrocarbon Cases

The total electron capture cross section of 0.8 - 3.0 MeV protons in various hydrocarbon gases (CHn - C4H , n = 2 - 8) has been measured. We find that the electron capture cross section per carbon atom decreases as the number of carbon atoms per molecule is increased. This reduction amounts to ~7% for 3 MeV protons and is ~ 25% for 0.8 MeV protons. We find no significant change in the electron capture cross section for carbon as the number of hydrogen atoms per molecule is increased. The observed variations in the cross section can be reproduced by assuming that post-collision-interactions destroy the required velocity match between projectile and electron.

K X-Ray Yields from C-, O-, and F-Bearing Gases

The K x-ray yields induced by 2 MeV proton bombardment of various C-, O-, and F-bearing gases show variations that depend in a systematic way on the effective charge of the atom in the molecule.