Ion-atom ionizing collisions: effective charges vs the rainbow effect

S. MARTINEZ, S. OTRANTO, C. R. GARIBOTTI, R. E. OLSON

Creta, Grecia

Simposio; XX International Symposium on Ion-Atom Collisions (ISIAC); 2007

In the last few years, the first fully differential cross sections (FDCS) were measured and presented for single ionization of He by ion impact in the low momentum transfer limit. Theoretical studies performed to reproduce the available data have so far been carried out by means of distorted wave quantum methods and the CTMC model [1-3]. In some cases, the Born-3C and CDW-EIS models have been used by assuming for the emitted-electron-target-core Coulomb-type interaction with an effective charge which was either set as Zeff  =1 (the asymptotic charge) or  Zeff =(n^2 åi)^0.5  (Belkic’s prescription). For low momentum transfers and low emission energies, FDCS obtained for He target by quantum models employing an effective charge Zeff  =1 are nearly identical to those obtained by using distorted waves which are generated as solutions of parameterized central potentials like those provided by Garvey or Hermann-Skillman. In this work, we present calculations of FDCS in the low momentum transfer limit and for low emission energies for targets other than He. We show that when considering multi-electronic targets, the use of effective charges leads to results that deviate from those obtained by solving a Garvey potential, and that these differences could be attributed to the rainbow effect studied by Ford and Wheeler in the late 1950s [4]. References [1] D. H. Madison et al., J. Phys. B 35 (2002) 3297. [2] J. Fiol and Olson, Nucl. Instr. Methods B 205 (2003) 474. [3] R. E. Olson and J. Fiol, J. Phys. B 36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259.35 (2002) 3297. [2] J. Fiol and Olson, Nucl. Instr. Methods B 205 (2003) 474. [3] R. E. Olson and J. Fiol, J. Phys. B 36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259.36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259. Zeff =(n^2 åi)^0.5  (Belkic’s prescription). For low momentum transfers and low emission energies, FDCS obtained for He target by quantum models employing an effective charge Zeff  =1 are nearly identical to those obtained by using distorted waves which are generated as solutions of parameterized central potentials like those provided by Garvey or Hermann-Skillman. In this work, we present calculations of FDCS in the low momentum transfer limit and for low emission energies for targets other than He. We show that when considering multi-electronic targets, the use of effective charges leads to results that deviate from those obtained by solving a Garvey potential, and that these differences could be attributed to the rainbow effect studied by Ford and Wheeler in the late 1950s [4]. References [1] D. H. Madison et al., J. Phys. B 35 (2002) 3297. [2] J. Fiol and Olson, Nucl. Instr. Methods B 205 (2003) 474. [3] R. E. Olson and J. Fiol, J. Phys. B 36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259.35 (2002) 3297. [2] J. Fiol and Olson, Nucl. Instr. Methods B 205 (2003) 474. [3] R. E. Olson and J. Fiol, J. Phys. B 36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259.36 (2003) L365. [4] K. W. Ford and J. A. Wheeler, Ann. Phys. (NY) 7 (1959) 259.7 (1959) 259.