A. G. Belov

Excitation of the high-spin 180Hf isomerand de-excitation of the 180Ta isomer in(γ,γ') reactions

The reaction mechanism of excitation and de-excitation of the high-spin isomers 180Hf (J=8-) and 180Ta (J=9-) in inelastic gamma-quanta scattering was investigated. An anomalously large integral cross section and isomeric ratio for 180Ta in comparison to 180Hf were obtained. Level properties influencing these relations are discussed.

Excitation of isomeric 1h11/2 states in nuclear reactions induced by γ rays and neutrons and in beta decay

Isomeric ratios were measured for N=81 isotones (135Xe, 137Ba, 139Ce, 141Nd, 143Sm). In the experiment reported here, μν≤3±10−Jπ=11/2− isomers were excited in (n, γ) and (γ, n) reactions and in the β+ decay of 139Pr and 141Pm. In order to determine the reaction yields, use was made of the activation method involving measurement of the gamma-ray spectra of reaction products. It is found that, in the same reactions, isomeric ratios are different for isotones characterized by different atomic numbers Z. Isomeric ratios were calculated with the spectra of low-lying levels and radiative-transition probabilities established on the basis of the quasiparticle-phonon model. Good agreement between the experimental and calculated values of isomeric ratios is obtained for all isotopes invesigated here. The dependence of isomeric ratios on the atomic number Z of a nucleus is explained by the difference of reaction energies, which leads to different probabilities of excitation of activation levels through which the isomers being considered are populated.

Production of isotopes and isomers with irradiation of Z = 47–50 targets by 23-MeV bremsstrahlung

The irradiations of Ag to Sn targets by bremsstrahlung generated with 23-MeV electron beams are performed at the MT-25 microtron. Gamma spectra of the induced activities have been measured and the yields of all detected radionuclides and isomers are carefully measured and analyzed. A regular dependence of yields versus changed reaction threshold is confirmed. Many isomers are detected and the suppression of the production probability is observed with growing product spin. Special peculiarities for the isomer-to-ground state ratios were deduced for the 106mAg, 108mAg, 113mIn, 115mIn, and 123mSn isomers. The production of such nuclides as 108mAg, 115mIn, 117gIn, and 113mCd is of interest for applications, especially when economic methods are available.

Cross Sections and Yields for the Photo‐Fission Productions of 238U

The yields and reaction cross‐sections of 92Sr, 97Zr, 97Nb and 135I at the photofission of 238U were measured. These fission‐fragments have some peculiarities in nuclear structure or in practical using. The measurements were performed on the bremsstrahlung of FLNR JINR microtron, in the electron energy range 10–22 MeV. The activation method with Ge(Li)—detector was used in these measurements.