Excitation function and isomeric ratio of Tc-isotopes from the 93Nb(α, xn) reaction

The excitation functions of Tc94-96 isotopes and independent isomeric ratios of (93m,) Tc-g, Tc-94m,Tc- g, and Tc-95m,Tc- g from the Nb-93(alpha, xn) reaction within the energy range below 40 MeV have been determined by using a stacked-foil activation and an off-line gamma-ray spectrometric technique at the Variable Energy Cyclotron Center, Kolkota, India. The excitation function of Tc94-96 in the Nb-93(alpha, xn) reaction was also calculated by using the computer code TALYS 1.6. The present data are found to be in general agreement with the literature data but have similar trend with some deviation from calculated data of the TALYS 1.6 code. The isomeric ratios of Tc-93m,Tc- g, Tc-94m,Tc- g, and Tc-95m,Tc- g in the Nb-93(alpha, xn) reactions from the present work and literature data were compared with similar data in the Nb-93(He-3, xn) and Mo-96(p, xn) reactions. In all the three reactions, the isomeric ratios increase with the increasing excitation energy. However, at all excitation energies, the isomeric ratios of Tc-93m,Tc- g, Tc-94m,Tc- g, and Tc-95m,Tc- g in the Nb-93(alpha, xn) and Nb-93(He-3, xn) reactions are higher than those in the Mo-96(p, xn) reactions, which indicate the role of input angular momentum besides excitation energy. Above the excitation energy of 35-55 MeV, the isomeric ratios of Tc-95m,Tc- g, Tc-94m,Tc- g, and Tc-93m,Tc- g decrease in all the Nb-93(alpha, xn), Nb-93(He-3, xn) and Mo-96(p, xn) reactions. This decreasing trend at higher excitation energy indicates the starting of pre-equilibrium reaction, which depends on the target, projectile, and type of reaction products. (C) 2015 Elsevier B.V. All rights reserved.