Irregularities in the differential and integral cross sections figures for ion-atom collisions in the plane-wave born approximation

Author(s):  
Masahiro Iwai ◽  
Isao Shimamura ◽  
Tsutomu Watanabe
1976 ◽  
Vol 54 (8) ◽  
pp. 870-888 ◽  
Author(s):  
Janusz W. Grabowski ◽  
Donald G. Fleming ◽  
Erich W. Vogt

Plane-wave Born approximation calculations have been carried out for the (p,d) reaction at intermediate beam energies with the purpose of elucidating the manner in which the various physical parameters of the problem determine the behaviour of the cross-sections. Analytical formulae for the differential cross section are derived for three choices of the bound state wave function: square well, Woods–Saxon, and truncated harmonic oscillator. The formulae can essentially be factored into two parts, one which oscillates rapidly with momentum transfer q(and is not physically important) and the other which varies smoothly with q and describes the 'envelope' of the calculated angular distribution. For the square well and truncated harmonic oscillator form factors, this envelope function varies as q−8 and q−10 respectively, but in the Woods–Saxon case it is given predominantly by an exponential q-dependence. To illustrate our main points, calculations are presented for the 208Pb(p,d) reaction, primarily at 200 MeV, as well as normalized fits to presently available data at 185 MeV on light and intermediate mass nuclei and at 700 MeV on 12C. The envelope dependence of the square well and Woods–Saxon form factors gives a reasonably good account of these data.


1995 ◽  
Vol 13 (2) ◽  
pp. 321-334 ◽  
Author(s):  
Eugene J. McGuire

In Chapter 14 of Atomic and Molecular Processes, Bates (1962) outlines a procedure for calculating ion-atom cross sections in the plane-wave Born approximation (pwBa). The procedure involves integration over the product of elastic scattering factors or generalized oscillator strengths for excitation or ionization from both projectile and target. We have programmed this procedure to use our large database of excitation and ionization generalized oscillator strengths (GOS). The program calculates both cross sections (CS) and stopping power (SP) on a subshell basis. The calculations are done in the center of mass system where the distinction between projectile and target is lost. Thus, the SP in the laboratory frames of both target and projectile are symmetrical in nuclear and net charges. The traditional simple modeling of SP, using scaled proton SP and an effective projectile charge, is unsymmetrical, and therefore dubious as a guide for extrapolating to ion-ion SP. At high projectile energy, the SP curves, as a function of increasing projectile charge, approach the scaled protonic result from above, indicating that lowering the average charge raises the SP, in contradiction to the traditional picture that the projectile SP increases with increasing effective charge (assuming there is an underlying physical reality relating the effective and average charge). Comparison with experimental SP data (mostly from 30 years ago) shows generally poor agreement for Li ion projectiles in the 1–10 MeV range.


1962 ◽  
Vol 15 (2) ◽  
pp. 135 ◽  
Author(s):  
LJ Tassie

The elastic and inelastic scattering of cx-particles by a vibrational nucleus is calculated using plane-wave Born approximation. The excitation of both single-phonon and twophonon states is considered. The effect of the diffuseness of the nuclear surface is included. The result for elastic scattering and the excitation of the single-phonon 2+ and 3- states is in good agreement with experiment for .oNi. The approximations used are discussed, and it is suggested that excitation of 0+, 1-, and 5- states should provide the best experimental test of the theory of two-phonon excitation of nuclei. The energies of the vibrational states are also considered.


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