ملخص: A new expression for the collisional energy loss straggling of heavy ions valid below 100 MeV/u is derived within the .rst-order perturbation theory on the basis of the scattering of a Dirac particle o. an external .eld. The interaction potential is introduced via the stopping power function, thus conferring to this formula a semi-empirical character when average S?E? experimental data are used. The calculated straggling is compared to values obtained from other theories and with measured straggling data for 16O ions in Al. A discrepancy by at least a factor of 2 between theory and experiment shown by data taken at the Ganil accelerator even for fully stripped ions is fairly removed. An analytic formula for the charge-exchange straggling obtained by .tting the experimental data at low energy is also reported.

لغة: إنجليزية