Electronic stopping cross sections of elements and compounds for swift Li ions

Abstract

Abstract. We report on experimental electronic stopping cross sections of elements and compounds for Li ions. They are measured with the Inverted Doppler Shift Attenuation (IDSA) method with an accuracy of the order of 1 }o-In cases where comparable data from other authors exist, agreement within the limits of error is obtained. Systematic and pronounced deviations up to about 30% from Lindhard's theory are found. It turns out that Bragg's rule is generally not valid for stopping cross sections in the velocity range 1.5.108 cm/sec to 4.8 -l0 s cm/sec.

On the invalidity of Bragg's rule in stopping cross sections of molecules for swift Li ions

“…In principle, it could be possible that one of the two AS belonging to a difference 6(AS) is zero or at least small but this is rather improbable as can be seen from the Cr-and Ta-borides and from the systematic general behaviour of the borides of the transition metals as will be discussed later. 4. A quantitative discussion of these data is not possible in a satisfactory manner at the moment.…”

“…More pronounced deviations from the additivity rule are to be expected at lower energies where the outer electrons predominantly contribute to the energy loss. Various investigations of Bragg's rule have been made with protons and alpha particles [4]. In most cases liquids or gases were used as targets.…”

Ranges of 7Li Produced in 10B(n,α)7*Li Reaction

“…Comparison of Dpir and DLSS gave excellent agreement for gaseous BF3 and elementary boron, while some disagreement was found for water. Neuwirth et al pointed out that the discrepancy occurring in the chemical Compounds should be put down to chemical bonding effects [9][10][11][12][13][14]. They have argued that Equation (14) be not strictly valid for chemical Compounds.…”

“…The correlation between Dpix and DLSS is illustrated in Fig. 3, where the degradation constants recalculated using the stopping cross sections measured for elementary boron and water by Neuwirth et al [9] are also shown. Comparison of Dpir and DLSS gave excellent agreement for gaseous BF3 and elementary boron, while some disagreement was found for water.…”

“…The optimal D values obtained on fitting, denoted by Dm, are listed in Table 1. The D values were estimated to be 2.19 and 0.98 X 10'^ s"' for elementary boron and water, respectively, by modification of the D values from the stopping cross sections at Bohr's velocity 5 (26.7 and 46.8 X 10"'^ eV • cm^/atom or molecule, respectively) reported by Neuwirth et al [9].…”