Fully differential study of dissociative single capture and Coulomb explosion through double capture in p+H2 collisions

Abstract

We have measured fully differential cross sections for dissociative single capture and Coulomb explosion through double capture in 75 keV p + H 2 collisions. Data were analyzed for fixed kinetic energy releases and molecular orientations as a function of scattering angle. Two-center interference was identified for dissociative single capture. The interference pattern is not inconsistent with the symmetry of the dissociative electronic state affecting the phase angle of the interference term. No clear signatures of single-center interference were observed for either process. For double capture at most only a very weak two-center interference structure was found. This very small (or zero) visibility can probably be attributed to a convolution of two independent scatterings of the projectile with the two electrons yielding the measured scattering angle.

Differential Study of Projectile Coherence Effects on Double Capture Processes in p + Ar Collisions

“…Data were taken for two different coherence lengths and the interference term was extracted by analyzing the ratios between the cross sections for the larger and smaller coherence length. The data reveal less pronounced coherence effects than observed previously for single ionization [19] or single capture [20], but a more pronounced effect than in DC from a molecular target [28]. Furthermore, we analyzed the ratios between the DCI and DC cross sections and found some similarities to transfer-ionization to single capture cross section ratios measured earlier [41].…”

“…The much smaller value of α shows that here projectile coherence effects are much less pronounced. However, they are nevertheless more pronounced than in DC from H 2 , where they are essentially completely absent [28]. This suggests that indeed the phase is not unambiguously determined by the measured scattering angle due to multiple projectile scattering in two-electron processes (as argued in [28]).…”

“…However, they are nevertheless more pronounced than in DC from H 2 , where they are essentially completely absent [28]. This suggests that indeed the phase is not unambiguously determined by the measured scattering angle due to multiple projectile scattering in two-electron processes (as argued in [28]). For a molecular target, the single-center interference structure is further "washed out" by the presence of two-center interference.…”

“…Indeed, in the scattering angle dependence of measured double differential ionization cross sections for p + H 2 collisions, interference structures were observed for a coherent projectile beam, but were absent for an incoherent beam [19]. In numerous follow-up experiments, similar projectile coherence effects on the cross sections were observed [20][21][22][23][24][25][26][27][28][29][30] (for a review, see [31]). Furthermore, the interpretation of the experimental data was supported by several theoretical studies, e.g., [32][33][34][35][36].…”

“…In measured fully differential cross sections (FDCS) for dissociative capture leading to relatively large kinetic energy releases (KER) in p + H 2 collisions [28] such projectile coherence effects were found to be less pronounced than in single ionization or capture. In the case of Coulomb explosion following double capture, such effects were not discernable at all [28]. This was interpreted as a "washing out" of the phase due to multiple projectile scatterings leading to dissociative capture.…”