Investigation of isomeric ratios in high-energy reactions
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EMENTARY PARTICLES AND FIELDS Theory
Investigation of Isomeric Ratios in High-Energy Reactions A. S. Danagulyan1) , G. H. Hovhannisyan1)* , A. R. Balabekyan1), N. A. Demekhina2), 3) , and V. G. Kalinnikov3) Received February 27, 2012; in final form, July 19, 2012
Abstract—Experimental data on the isomeric ratios of cross sections for products originating from the interaction of 12 C ions (E12 C = 26.4 GeV), protons (Ep = 3.65 GeV), and deuterons (Ed = 7.3 GeV) with targets enriched in the tin isotopes 112 Sn, 118 Sn, 120 Sn, and 124 Sn 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. DOI: 10.1134/S1063778813020099
INTRODUCTION Processes induced by nucleus–nucleus interactions lead to the formation of residual products whose nuclear states have different features, such as the excitation energy, spin, and parity. The inducedactivity method makes it possible to identify, in irradiated targets, radioactive products both in ground and in excited metastable states. The ratio of the cross sections for the production of high- and lowspin states is usually referred to in the literature as the isomeric ratio R = σ(Ih )/σ(Il ). Investigation of isomeric ratios is of interest as an additional source of information about the reaction mechanism and about the effect of the properties and structure of both nuclear products and intermediate nuclear systems on the character of the interaction. It is noteworthy that investigations of isomeric ratios were performed in reactions involving particles of different type [1–5]. In photonuclear reactions, experimental data on isomeric states were obtained both in the giant-resonance energy region (for an overview, see [1, 2]), and in the high-energy region extending up to 5 GeV [3–5]. Data on isomeric ratios in hadron–nucleus reactions are less abundant. In [6, 7], the values of R were obtained for various pairs of isomers (more than ten pairs) formed in reactions induced by protons of energy Ep = 0.66, 1, and 8.1 GeV in 112,118,120,124 Sn targets. In [8], 1)
Yerevan State University, Alex Manoogian str. 1, Yerevan, 375025 Armenia. 2) Yerevan Physics Institute, ul. Brat’ev Alikhanian 2, Yerevan, 375036 Armenia. 3) Joint Institute for Nuclear Research, Dubna, Moscow oblast, 141980 Russia. * E-mail: [email protected]
the ratios in question were measured for two pairs of isomers (99 Rh, 110 In) produced in 112,116,118,120,124 Sn targets irradiated with protons of energy 8.1 GeV and 12 С ions of energy 3.65 GeV per nucleon. However, the results reported in [8] and in [3–7] are not quite consistent. For example, a linear growth of R as a function of the number of emitted nucleons (ΔA) was obtained in [8]. Isomeric ratios were studied in [3– 7] for various isotopes, including 99 Rh and 110 In, and it was found there that the curve representing the dependence R(ΔA) rea
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