6.0 MeV u-1 carbon ion (C6+ and C4+)-indiced secondary electron emission from water vapor

D. OHSAWA; H. TAWARA; F. SOGA; M. E. GALASSI; R. D. RIVAROLA

PHYSICA SCRIPTA - (Print)

IOP PUBLISHING LTD

Lugar: Londres; Año: 2013 vol. T p. 140391 - 140395

0031-8949

We have precisely measured absolute double differential cross sections (DDCSs) for secondary electron emission produced in collisions of 6.0MeVu−1 C6+ and C4+ ions with water vapor. Theoretical calculations of the DDCSs were made for C6+ ions using the continuum distorted wave-eikonal initial state model (CDW-EIS) in its straight-line version ofthe impact parameter approximation, showing general good agreement with experimental data, except in the intermediate- and high-energy region (>50 eV), particularly at the backward angles (>110). On the other hand, the single differential cross section (SDCS), which was obtained by integrating the measured DDCSs over the solid angle, showed fairly goodagreement with the CDW-EIS in the low-energy region (<200 eV), while a significant discrepancy between the observed SDCS and the Rudd-model scaling (×36) can be seen, suggesting that a simple Z2-scaling law (i.e. first Born approximation) is not applicable for high-Z bare projectiles such as C6+ ions. The SDCS of C4+ ions was observed to be smaller than that of C6+ ions by 50% in the low-energy region (<200 eV) due to the screening effect of its bound electrons in C4+ ions, which could be explained quantitatively by taking account of an effective projectile charge.