Isomeric ratio of89Y(γ, 2n)87Y reaction yields

Abstract

There is a small amount of experimental data and no reliable computational methods for isomeric ratios of the cross sections (yields) of nuclear reactions at low excitation energy. This refers also to photonuclear reactions in which two nucleons emerge, including also the reaction 89y('y, 2n)87m,gy, the energy dependence of whose isomeric yield ratio was measured in the present work.Until recently, the isomeric yield ratios d = Ym/Yg for the reaction 89y('y, 2n)87y were determined in a small number of works. It is desirable to make a more systematic study of the energy dependence d(E) for the reaction 89y('y, 2n)87y, and we have done so in the present work. Targets consisting of chemically pure yttrium oxide with a mass from 2 to 10 g were activated in a bremsstrahlung beam from the B25/30/3etatron 20 cm from the radiator for a time t o = 4 h. After a pause of t n = 80 min, the -y-spectra of activated samples were recorded in a period t c = 4 h with a Ge(Li) detector using an AI-1024-95-17 pulse analyzer.The isomeric yield ratios were obtained by the method of Table 1.Our results agree, within the error limits, with the data of [I, 2, 5-7]. The results of [3] at 47 MeV are found to be too tow. The data in Table 1 are sufficient for representing analytically the energy dependence of the isomeric ratio of the reaction 89y('y, 2n)87y, including also for the region of the reaction threshold; this is especially convenient when the results are used in applied investigations. The energy dependence r(E) was approximated by the phenomenological ratio [9] ~ = ~/(v,. + Y,) = A th B (E -fro).where E 0 is the effective reaction threshold (3,, x)m; A is the value of r in the region of saturation (plateau); and, B characterizes the rate of emergence r onto the plateau. Our results and the data of [t, 2, 5-7] can be used to approximate r(E) up to 30 MeV.The following results were obtained for the parameters E o, A, and B by the least-squares method using n experimentally determined values of d(E) for energies ranging from E t to E2: As one can see, the values obtained for the parameters with n = 19 (results of our measurements) and n = 23 (all data taken together) agree. The effective reaction threshold E o is close to the expected value E n = 21.212 + 0.003 MeV, and the computed isomeric ratios on the plateau agree, within the limits of error, with the experimentally known values.

Measurement of isomeric yield ratios of 86m,g Y, 87m,g Y, and 89m,g Zr in the photonuclear reactions of 89 Y and nat Zr at the end-point bremsstrahlung energies of 45 and 55 MeV

“…However, the IR values of 87m,g Y from the nat Zr(c,pxn) reaction at the end-point bremsstrahlung energies of 45 and 55 MeV are the re-determined values and are found to be in agreement with the literature data [30]. The present results and literature data [1,5,8,[18][19][20][21][22][23][24][25][26][27][28][29][30] for the 87m,g Y and 86m,g Y isomeric pairs from the 89 Y(c,xn) reactions are shown in Figs. 3 and 4, respectively.…”

“…The measured values of IR together with the existing literature data [1,5,8,[18][19][20][21][22][23][24][25][26][27][28][29][30] are given in Table 2. The present results are the average values of isomeric yield ratios that calculated from different c-ray spectra.…”

“…Watson et al [21] measured the isomeric yield ratios of 87m,g Y in the 89 Y(c,2n) reactions with the end-point bremsstrahlung energies of 23-50 MeV. Davydov et al measured the isomeric yield ratios of 89m,g Zr in the 90 Zr(c,n) reaction and that for 87m,g Y in the 89 Y(c,2n) reaction with maximum photon energies from 21.5 to 24.5 MeV [22] and from 21.75 to 26.5 MeV [23,24], respectively. Luc et al measured the isomeric yield ratios of 89m,g Zr in the end-point bremsstrahlung energy of 15-20 MeV [25].…”