Target dependence of postcollision interaction effects on fully differential ionization cross sections

Abstract

We have measured and calculated fully differential cross sections (FDCS) for ionization of helium by 75 keV proton impact. Ejected electron with a speed close to and above the projectile speed were investigated. This range of kinematics represents a largely unexplored regime. A high sensitivity of the FDCS to the details of the description of the few-body dynamics, reported earlier for ionization of H 2 , was confirmed. A new, so far unexplained peak structure was found in an electron angular range between the regions where the so-called binary-and recoil peaks are usually observed. The need for non-perturbative calculations using a two-center basis set is demonstrated.

Double differential cross sections for ionization of H by 75 keV proton impact: Assessing the role of correlated wave functions*

“…To analyze the different effects of each of the terms in the series (7), we have computed different DDCS p for ionization of hydrogen atom by 75-keV proton impact. The results are displayed in Fig.…”

“…. , 5, i.e., the individual DDCS p for m = 0, 1, • • • , 5 have been summed; each result represents the coherent sum of different orders in the transition matrix (7).…”

“…( 9) can be realized numerically by the Gauss-Legendre quadrature method for parameter t and the Gauss-Laguerre quadrature method for parameters s and τ. Convergence of the results has been tested by increasing the number of quadrate points to achieve an accuracy of 0.1%. It is necessary to sum only a few terms of the series (7).…”

“…Sec-ond, the wave functions of the hydrogen atom are completely accurate. In spite of the fundamental significance of the hydrogen atom as a target, due to the well-known difficulties of the fully differential cross section (FDCS) measurements for atomic hydrogen, the majority of the ionization experiments were carried out for the hydrogen molecule, [1][2][3] helium, [4][5][6][7] and other heavier atoms and molecules. Although protonhydrogen FDCS measurements are yet to be performed, experimental data on the double differential cross section (DDCS p ) are available.…”

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

“…Some of these shortcomings are circumvented in distorted wave approaches, e.g., [14][15][16]. However, recently, we demonstrated that in ionization of H 2 and He by intermediate energy proton impact even distorted wave calculations do not give satisfactory results if the electron is ejected with a velocity close to the projectile velocity [17,18].…”