The atomic number of a composite sample is equal (Duvauchelle, Peix et al. 1999) with the sum of equation (6). It should be mentioned, however, that the theoretical determination of Zef does not always coincide with the experimental results (Manninen, Pitkanen et al. 1984; Duvauchelle, Peix et al. 1999).
Nr ~ = C1Zf / ^ Nr = C z
Nc~ ac C1Zf/Er Nc 3 ‘
where Cj, C2 and C3 coefficients which are not varied for the particular energy.
Fig. 2. Scattering Spectra for Fe obtained at scattering angle d=75°
determination of coefficients C3 in equation (26) is straightforward. It is known (Karellas, Leichter et al. 1983; Manninen and Koikkalainen 1984; Gigante, Pedraza et al. 1985; Leichter, Karellas et al. 1985; Perumallu, Rao et al. 1985; Duvauchelle, Peix et al. 1999), that the value of exponent n for large scattering angles is: n=3.
The determination of Zf from the ratio NR/NC depends on the separation of the spectrum lines of the coherently and incoherently scattered у-quanta. For the basic peaks of the spectrum lines of the coherent and incoherent scattering events, the variation of ratio NR / Nc appears mainly at the distribution maximum and does not significantly influence the shape of the spectrum lines (Plotnikov and Pschenicniji 1973). However, the separation of the peaks of the spectrum lines of Rayleigh and Compton scattering is not always possible (Fig. 2). It is common to observe an overlap of the peaks. For this reason, various methods are employed for the determination of the area under the peak. This complication imposes the use of detectors with high energy resolution.