Anomalous q dependence of 0' binary encounter electron production in energetic collisions of F^q+(q=3-9) with He and H₂targets

Abstract

The projectile charge state dependence of binary encounter electron (BEe) production was studied at zero degrees with respect to the beam direction for collisions of 19 and 28.5 MeV F(3-9)+ with Hz and He targets. The measured double differential cross sections for BEe production were found to be increasingly enhanced with decreasing projectile charge state contrary to the usual screening behaviour. The relative enhancement of the BEe F8+ yields over the F9+ yields was found to be about 15% increasing to about 50% for F3+ projectiles. Plausible mechanisms are discussed; however, no theoretical explanation of this anomalous enhancement is established.

Angular distribution of δ electrons emitted in collisions of 1.0-MeV/uFq+(q=4,6,8,9) with molecular hydrogen

“…In summary, the angular distribution, as well as the energy distribution of b electrons produced in collisions of 1.0 MeV/u Fs+ (q=4, 6,8,9) ious with H2 has been studied from 0' to 70' with respect to the beam direction. Three prominent features of the electron spectra are discussed.…”

“…For non-bare-ion-atom collisions, Richard et al [6] reported that the double differential BEE cross section at Ol, = 0' in collisions of 1.0 and 1.5 MeV/u F +l with H2 and He targets increases with decreasing projectile charge state, which is in contradiction to the q -scaling law predicted by a erst Born approximation. This result was also confirmed in electron-projectile coincidence experiments [7,8], where the pure target ionization channel was selected.…”

Backward ejected electrons produced by 1-MeV/uOq+(q=3–8) projectile ions colliding with argon gas

“…We then calculate the DDCS for the production of the ELP at 180' with respect to the beam direction in the various OSA's using Eqs. (2), (3), and (4). If the projectile has more than one electron in the L shell, the contributions of each of the L-shell electrons are added to produce the total projectile electron-loss cross section at 180'.…”

“…This initial momentum distribution and the binding energy of the electron in the target must be taken into account by theoretical models, since prior to the collision the target electron is not actually free. Richard and co-workers [2] have investigated the yield and energy distribution of target BE electrons emitted near 0' with respect to the beam direction for bare and clothed projectiles. They conclude that for completely bare projectiles, an impulse approximation (IA) model to describe this process in which "quasifree" target electrons undergo Rutherford scattering in the projectile frame agrees well with the data [3].…”

“…But for collisions involving clothed projectiles, an anomalous projectile charge state (q) dependence of the yield of 0' binary-encounter electrons is found [2]. This behavior of the yield is a consequence of the non-Coulomb nature of the screened field of the projectile [4,5].…”