PHYSICS

V. N. LEVKOVSKII

CROSS SECTIONS OF THE REACTIONS Cd(n,p)Ag AT A NEUTRON ENERGY OF 14 MeV

(Presented by Academician V. N. Kondrat’ev, 23 XI 1956)

The cross sections of the reactions Cd ((n,p)) Ag were calculated by comparing the β-yield of these reactions with the yield of the reaction Cd(^{112}) ((n,\alpha)) Pd(^{109}), whose cross section had previously been found to be ((1.35 \pm 0.27)\cdot 10^{-27}\ \text{cm}^2) ((^1)).

Fig. 1. Decay curve of radioactive silver separated from a cadmium target irradiated with 14-MeV neutrons

Cadmium nitrate samples were irradiated for 0.5–1 hour with 14-MeV neutrons, dissolved, and palladium was separated from the solution with a carrier by precipitation with dimethylglyoxime. In the filtrate, silver with a carrier was precipitated in the form of AgCl. The precipitate was reprecipitated from ammonia, and its activity was measured with a standard cylindrical Geiger counter ((44.5\ \text{mg}/\text{cm}^2)). The activity of the palladium precipitates was measured under identical geometrical conditions.

Figure 1 shows a typical decay curve of the activity of the silver precipitate; Fig. 2 gives the results of graphical analysis of the curve in Fig. 1. The half-lives obtained—24 min, 3.2 h, 5.3 h, and 7.5 days—are in good agreement with the literature values of the half-lives of Ag(^{106}), Ag(^{112}), Ag(^{113}), and Ag(^{111}).

Table 1 presents the absorption-measurement data for the β-radiations of Ag(^{106}), Ag(^{111}), Ag(^{112}), and Ag(^{113}), obtained as a result of measuring

the activity of silver separated from the cadmium target, through aluminum filters of different thicknesses, and subsequent graphical analysis of the complete decay curves. The table also gives absorption-measurement data for the radiation of ( \mathrm{Pd}^{109} ), which were used in calculating the reaction cross sections. In the third and fourth columns of the table are given the maximum energies of the investigated (\beta)-radiations, as accepted in the literature and as calculated from our absorption measurements from the empirical relation (E = 2.12 \cdot 10^{-2} d_{1/2} + 0.17) ((^{2})).

Fig. 2. Results of graphical analysis of Fig. 1

Table 1

As follows from the table, the values we measured for the maximum energies of the 24 min, 3.2 h, 5.3 h, and 7.3 day radiations agree well with the literature values for the (\beta)-radiations of (\mathrm{Ag}^{106}), (\mathrm{Ag}^{112}), (\mathrm{Ag}^{113}), and (\mathrm{Ag}^{111}).

In Table 2 the initial activities of (\mathrm{Ag}^{106}), (\mathrm{Ag}^{111}), (\mathrm{Ag}^{112}), and (\mathrm{Ag}^{113}), obtained in two independent experiments, are compared; in Table 3, the activities of (\mathrm{Ag}^{111}) and (\mathrm{Pd}^{109}), obtained in three parallel irradiations.

Table 2

| \multicolumn{4}{c}{Initial activities, allowing for decay during irradiation} | \multicolumn{4}{c}{Relative activities} |
|---:|---:|---:|---:|---:|---:|---:|---:|
| (\mathrm{Ag}^{106}) | (\mathrm{Ag}^{111}) | (\mathrm{Ag}^{112}) | (\mathrm{Ag}^{113}) | (\mathrm{Ag}^{106}) | (\mathrm{Ag}^{111}) | (\mathrm{Ag}^{112}) | (\mathrm{Ag}^{113}) |
| 37600 | 150 | 19500 | 3680 | 251.0 | 1.0 | 130.0 | 24.6 |
| 85000 | 376 | 49800 | 9350 | 226.0 | 1.0 | 133.0 | 24.9 |

The reaction cross sections were calculated from the data of Tables 1, 2, and 3, from the known half-lives of (\mathrm{Ag}^{106}), (\mathrm{Ag}^{111}), (\mathrm{Ag}^{112}), (\mathrm{Ag}^{113}), and from the percentage contents of (\mathrm{Cd}^{106}), (\mathrm{Cd}^{111}), (\mathrm{Cd}^{112}), (\mathrm{Cd}^{113}) in the natural mixture of cadmium isotopes.

According to the literature data ((^3)), (\mathrm{Ag}^{106}) has two isomers with (T = 24) min and 8.2 days. The isomer with (T = 8.2) days decays exclusively by electron capture; the isomer with (T = 24) min, according to the literature data ((^4))

Table 3

Table 4

decays by positron emission in 69%, and by electron capture in 31%. Our data make it possible to calculate the cross section only for the isomer with (T = 24) min.

The results of the cross-section calculation are presented in Table 4.

The author expresses gratitude to Yu. Lapitskii for his great assistance in the work.

Institute of Chemical Physics
Academy of Sciences of the USSR

Received
20 XI 1956

CITED LITERATURE

(^1) B. G. Dzantiev, V. N. Levkovskii, A. D. Malievskii, DAN, 113, No. 3 (1957).
(^2) E. Broda, Modern State of Radiochemistry, 1953, p. 22.
(^3) I. M. Hollander, I. Perlman, G. T. Seaborg, Rev. Mod. Phys., 25, No. 2, 469 (1953).
(^4) W. L. Bendel, F. I. Shore, H. N. Brown, R. A. Becker, Phys. Rev. 90, 888 (1953).