Non-dissociative and dissociative ionisation of H₂by 50-2000 keV antiprotons

Abstract

A beam of antiprotons with energies between 50 keV and 2 MeV has been used for measurements of non-dissociative and dissociative ionisation cross sections of H2. The results are compared with cross sections for equivelocity protons and electrons, and the role of interference effects in two-electron processes is discussed.

Collisions of low-energy antiprotons with molecular hydrogen: ionization, excitation and stopping power

“…data. The ionization cross sections [1] used as input for the analysis in [4] were, however, found to be erroneous for E < 200 keV [5,6]. On the other hand, the slope of the present curve for E > 100 keV is remarkably similar to that of the experimentalp curve but for E > 160 keV.…”

“…In the case of hydrogen also a number of contributions exist for atomic targets whereas the knowledge on low-energyp collisions with the simplest two-electron molecule H 2 is rather poor [1,5], especially, concerning theory [2,11]. Precise data onp + H 2 are, however, of great interest in many fields.…”

Stopping power of antiprotons in H,H2, and He targets

“…The shown S µr esults depend therefore also on additional data which were taken from literature. The experimentalp ionization cross sections σ ion [34] used in order to determine S µ¯, however, were later on found to be erroneous for E < 200 keV [2,35]. Due to these substantial uncertainties it is one aim of this work to discriminate with the help of the present findings between the different experimental results.…”

Close-coupling approach to antiproton-impact breakup of molecular hydrogen

“…For this reason and also because of natural abundance of the target the antiproton scattering on molecular hydrogen is the most studied system both experimentally and theoretically. The cross sections for single nondissociative ionization of molecular hydrogen have been measured on three occasions; presently the experimental data exist on a wide energy range from 2.4 keV to 1.6 MeV [8][9][10]. Available theoretical approaches to the problem [11][12][13][14][15] can be classified into two categories.…”