Angular scattering in fast ion–atom electron transfer collisions: projectile wave diffraction and Thomas mechanisms

Abstract

We report experimental angular differential cross sections for double-electron capture in He2 + + He collisions and single-electron capture in H+ + He collisions for the 1.3–12.5 MeV kinetic energy range. In all cases, the total cross sections are dominated by forward scattering peaks in dσ/dΩ. The shapes and widths (but not the magnitudes) of these peaks are very similar for all energies and for capture of one or two electrons corresponding also to our measured linear increases in the transverse momentum transfers with increasing projectile velocities. These observations may be ascribed to diffraction limitations which are connected to electron transfer probabilities P(b) which are significant in limited regions of b only. For the H+ + He single-electron capture we observe two additional maxima in the angular differential cross sections. We conclude that while the secondary maxima at ∼0.5 mrad probably have large contributions from the Thomas proton–electron–nucleus scattering mechanism, the third maxima at ∼0.75 mrad are most likely mainly due to projectile de Broglie wave diffraction.

Fully Differential Study of Capture with Vibrational Dissociation in p+H2 Collisions

“…A similar analysis was performed for single capture in energetic p + He collisions [28]. The solid curve in the left panel of Fig.…”

Boundary-corrected four-body continuum-intermediate-state method: Single-electron capture from heliumlike atomic systems by fast nuclei

“…Decades later [12,14,15], also for the p-He collisions, the Thomas peak was recorded by multipass experiments that measure the momenta of recoiled ions. This was the COLTRIMS technique implemented within ion storage ring accelerators equipped with electron cooling.…”

“…The COLTRIMS technique has proven to be a powerful tool for revealing the details of the interactive dynamics of atomic collisions [9]. For example, within the past decade a number of experimental measurements [10][11][12][13][14][15][16][17][18] of differential cross sections for single charge exchange in p − He collision via the COLTRIMS technique have spurred renewed interest in theoretical calculations by means of a variety of methods [19][20][21][22][23][24][25][26][27][28][29][30].…”

Transfer excitation reactions in fast proton-helium collisions

“…Especially at higher impact energies E p > 100 keV/u, where the final electronic state determination in experiments is challenging or often impossible, the influence of excitation has not been investigated [20][21][22][23]. Projectile scattering angle distributions, which are final state selective, are rather rare [1,24,[26][27][28][29][30][31][32].…”