ON THE ORIGIN OF ANOMALOUS RANGES OF 1.65 GEV XE-132 IONS IN MUSCOVITE MICA

Ranges of 1.65 GeV 132Xe ions in muscovite mica, determined using solid state nuclear track detector (SSNTD) techniques, are shown to vary strongly with angle of incidence to the basal plane. This is explained within the framework of the Chadderton-Koul-Biersack (CKB) model for latent track formation in real crystals. Not only are there clear bursts of electronic energy loss at individual molecular layers, as seen in intermittent tracks in the electron microscope, but the range variation can also be ascribed to a basic refractive effect of individual molecular layers on the particle trajectories. This, in turn. provides a strong nonlinear electronic stopping. The strong uniaxial anisotropy of muscovite mica imposes a new orbital motion, referred to as "ridging" (or "bridging" in the upper angular limit) on the swift xenon ions. which are almost completely stripped of electrons. Neither "channelling" nor "quasichannelling". which are determined by smaller critical angles, play any part in this specific aspect of anomalous range determination, which is entirely due to the smooth angular dependence of the "ridging" orbits on refracted pathways, and on the integrated stopping power sampled. The fact that incorporation of "ridging" and "bridging" into the broader picture now produces a complete angular set of classical positively charged particle orbits, encompassing all of real space in crystals. leads naturally to the construction of a new classical range (R) surface, quite analogous to the familiar Fermi surface of constant energy, described by conduction electron momentum vectors (k) in reciprocal space. © 1990.