Alignment of magnetic substates in double-electron-capture collisions.

Abstract

We have determined the magnetic-substate alignment produced in double-electron capture by the H-like projectiles C[sup 5+] and B[sup 4+] from He atoms by measuring the anisotropy of the Auger electron emission from the doubly excited 1[ital s]2[ital l]2[ital l][prime] [sup 2][ital L] projectile states formed in the collision. This work includes additional measurements and expands upon our previous short communication on the (C[sup 5+],He) system [Phys. Rev. A 43, 607 (1991)]. The measurements yield [ital M][sub [ital L]] substate population fractions which challenge theory at nearly the finest quantum state detail. We observe large differences between the results for B[sup 4+] and C[sup 5+] over the velocity range 0.25--0.50 a.u. for the substate and total 1[ital s]2[ital l]2[ital l][prime] [sup 2][ital L] relative cross sections. Substantial population of [ital M][sub [ital L]][gt]0 states shows the importance of rotational coupling in these slow collisions. The large anisotropies observed demonstrate that substantial errors can result from inferring cross sections'' from single-angle measurements and the assumption of isotropic electron emission.