Charge-state dependence of binary-encounter-electron cross sections and peak energies

• Published in: Physical review. A, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 1993-12, Vol.48 (6), p.4421-4428
• Main Authors: HIDMI, H. I, RICHARD, P, SANDERS, J. M, SCHÖNE, H, GIESE, J. P, LEE, D. H, ZOUROS, T. J. M, VARGHESE, S. L
• Format: Article
• Language: English
• Subjects: 664300 - Atomic & Molecular Physics- Collision Phenomena- (1992-); Atomic and molecular collision processes and interactions; ATOMIC AND MOLECULAR PHYSICS; BINARY ENCOUNTER METHOD; CALCULATION METHODS; CARBON IONS; CATIONS; CHARGE STATES; Charge transfer; CHARGED PARTICLES; CHLORINE IONS; COLLISIONS; COPPER IONS; CORRELATIONS; CROSS SECTIONS; DIFFERENTIAL CROSS SECTIONS; ELECTRON LOSS; ELEMENTS; ENERGY RANGE; Exact sciences and technology; FLUORINE IONS; HYDROGEN; HYDROGEN IONS; HYDROGEN IONS 1 PLUS; IMPACT PARAMETER; ION COLLISIONS; ION-MOLECULE COLLISIONS; IONS; MEV RANGE; MEV RANGE 01-10; MOLECULE COLLISIONS; MULTICHARGED IONS; NITROGEN IONS; NONMETALS; OXYGEN IONS; Physics; SILICON IONS
• ISSN: 1050-2947; 1094-1622
• DOI: 10.1103/PhysRevA.48.4421

The charge-state dependence of the binary-encounter-electron (BEE) double-differential cross section (DDCS) at 0[degree] with respect to the beam direction resulting from collisions of 1 MeV/amu H[sup +], C[sup [ital q]+], N[sup [ital q]+], O[sup [ital q]+], F[sup [ital q]+], Si[sup [ital q]+], and Cl[sup [ital q]+], and 0.5 MeV/amu Cu[sup [ital q]+] with H[sub 2] is reported. The data show an enhancement in the BEE DDCS as the charge state of the projectile is decreased, in agreement with the data reported by Richard [ital et] [ital al]. [J. Phys. B 23, L213 (1990)]. The DDCS enhancement ratios observed for the three-electron isoelectronic sequence C[sup 3+]:C[sup 6+], N[sup 4+]:N[sup 7+], O[sup 5+]:O[sup 8+], and F[sup 6+]:F[sup 9+] are about 1.35, whereas a DDCS enhancement of 3.5 was observed for Cu[sup 4+]. The BEE enhancement with increasing electrons on the projectile has been shown by several authors to be due to the non-Coulomb static potential of the projectile and additionally to the [ital e]-[ital e] exchange interaction. An impulse-approximation (IA) model fits the shape of the BEE DDCS and predicts a [ital Z][sub [ital p]][sup 2] dependence for the bare-ion cross sections. The IA also predicts a binary peak energy that is independent of [ital q] and [ital Z][sub [ital p]] and below the classical value of 4[ital t], where [ital t] is the energy of electrons traveling with the projectile velocity. We observed a BEE energy shift [Delta][ital E] ([Delta][ital E]=4[ital t][minus][ital E][sub peak], where [ital E][sub peak] is the measured energy at the peak of the binary encounter electrons) that is approximately independent of [ital q] for the low-[ital Z][sub [ital p]] ions, whereas the measured [Delta][ital E] values for Si, Cl, and Cu were found to be [ital q] dependent.