G. H. Hovhannisyan

Formation of Light Isotopes by Protons and Deuterons of 3.65 GeV/nucleon on Separated Tin Isotopes

We measure cross sections for residual nuclide formation in the mass range 7 ≤ A ≤ 96 caused by bombardment with protons and deuterons of 3.65-GeV/nucleon energy of enriched tin isotopes (112,118,120,124Sn). The experimental data are compared with calculations by the codes FLUKA, LAHET, CEM03, and LAQGSM03. Scaling behavior is observed for the whole mass region of residual nuclei, showing a possible multifragmentation mechanism for the formation of light products (7 ≤ A ≤ 30). Our analysis of the isoscaling dependence also shows a possible contribution of multifragmentation to the production of heavier nuclides, in the mass region 40 ≤ A ≤ 80.

Formation of medical radioisotopes 111In, 117mSn, 124Sb, and 177Lu in photonuclear reactions

The possibility of the photonuclear production of radioisotopes 111In, 117mSn, 124Sb, and 177Lu is discussed. Reaction yields were measured by the gamma-activation method. The enriched tin isotopes 112, 118Sn and Te and HfO2 of natural isotopic composition were used as targets. The targets were irradiated at the linear electron accelerator of Alikhanian National Science Laboratory (Yerevan) at the energy of 40 MeV. The experimental results obtained in this way reveal that the yield and purity of radioisotopes 111In and 117mSn are acceptable for their production via photonuclear reactions. Reactions proceeding on targets from Te and HfO2 of natural isotopic composition and leading to the formation of 124Sb and 177Lu have small yields and are hardly appropriate for the photoproduction of these radioisotopes even in the case of enriched targets.

Photonuclear reactions on 112,118,124Sn, natTe, and natHf targets

The yields of products of photonuclear reactions on tin targets enriched in the isotopes 112,118,124Sn and on Te and HfO2 targets of natural isotopic composition were measured. The targets were irradiated at the linear electron accelerator of the A.I. Alikhanian National Science Laboratory (Yerevan Physics Institute) at the electron energy of Ee = 40 MeV. The dependence of the product yields on the nucleonic composition of the targets was discussed. The isomeric ratios were obtained for the 119m,gTe, 121m,gTe, 117m,gIn, and 123m,gSn products. The experimental data in question were compared with their theoretical counterparts calculated on the basis of the TALYS 1.4 code. The dependence of the isomeric ratios on the photon energy and on the mass number of the product is considered.

Special features of isomeric ratios in nuclear reactions induced by various projectile particles

Calculations for (p, n) and (α, p3n) reactions were performed with the aid of the TALYS-1.4 code. Reactions in which the mass numbers of target and product nuclei were identical were examined in the range of A = 44–124. Excitation functions were obtained for product nuclei in ground and isomeric states, and isomeric ratios were calculated. The calculated data reflect well the dependence of the isomeric ratios on the projectile type. A comparison of the calculated and experimental data reveals, that, for some nuclei in a high-spin state, the calculated data fall greatly short of their experimental counterparts. These discrepancies may be due to the presence of high-spin yrast states and rotational bands in these nuclei. Calculations involving various level-density models included in the TALYS-1.4 code with allowance for the enhancement of collective effects do not remove the discrepancies in the majority of cases.

Recoil studies in the reaction of 12C ions with the enriched isotope 118Sn

The recoil properties of the product nuclei from the interaction of 2.2 GeV/nucleon 12C ions from Nuclotron of the Laboratory of High Energies, Joint Institute for Nuclear Research at Dubna with a 118Sn target have been studied via catcher foils method. The experimental data were analyzed using the mathematical formalism of the standard two-step vector model. The results for 12C ions are compared with those for deuterons and protons. Three different Los Alamos versions of the Quark-Gluon String Model were used for comparison with our experimental data.

Analysis of isomeric ratios for medium-mass nuclei

Values of the isomeric ratios for product nuclei originating from simple charge-exchange reactions were analyzed. The cross sections for the formation of product nuclei in ground and isomeric states were calculated with the aid of the TALYS 1.4 and EMPIRE 3.2 codes. The calculated values of the isomeric ratios were compared with their experimental counterparts taken from the EXFOR database. For the 86,87Y, 94,95,96,99Tc, and 44Sc nuclei, the experimental values of the isomeric ratios exceed the respective calculated values. The nuclei in question feature weak deformations and have high-spin yrast lines and rotational bands. The possible reason behind the discrepancy between theoretical and experimental isomeric ratios is that the decay of yrast states leads with a high probability to the formation of isomeric states of detected product nuclei.

Investigation of isomeric ratios in high-energy reactions

Experimental data on the isomeric ratios of cross sections for products originating from the interaction of 12C ions (E12C = 26.4 GeV), protons (Ep = 3.65 GeV), and deuterons (Ed = 7.3 GeV) with targets enriched in the tin isotopes 112Sn, 118Sn, 120Sn, and 124Sn are presented. The dependence of the isomeric ratios on the interaction mechanism, projectile type and energy, and nuclear properties of the final-state nucleus are discussed. The dependence of the isomeric ratios on the degree of deformation of the product nucleus is also considered.

Interaction of 12C ions with nuclei of enriched tin isotopes at an energy of 2.2 GeV per nucleon

The formation cross sections for about 110 products of interaction between a 12C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes 112,118,120,124Sn were calculated. Massyield and charge distributions were obtained for 112,118,124Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Zp, are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions are compared for proton-, deuteron- and ion-nucleus reactions.

Formation of close-to-target products in reactions induced by 12C ions on tin isotopes at the energy of 2.2 GeV per nucleon

Cross sections for charge-exchange reactions induced by the interaction between 12C ions of energy