Nuclear model calculations on proton and deuteron induced reactions on 122 Te and 120 Te with particular reference to the formation of the isomeric states 120m,g I S. SudaÂr a, b , A. Hohn a , S.M. Qaim a, * a Institut fu Èr Nuklearchemie, Forschungszentrum Ju Èlich GmbH, D-52425 Ju Èlich, Germany b Institute of Experimental Physics, Kossuth University, H-4001 Debrecen, Hungary Received 3 August 1999; accepted 2 September 1999 Abstract Nuclear model calculations were performed on (p,xn) reactions on 122 Te and 120 Te, and (d,xn) reactions on 120 Te. The computer code used (STAPRE) incorporates statistical and precompound models as well as nuclear structure eects. The total cross-sections of (p,xn) and (d,xn) processes leading to the formation of the radioisotopes 119 I, 120g I, 121 I and 122 I are described well by the calculations. The isomeric cross-section, however, is rather dicult to calculate. The yield of the high spin isomer ( 120m I) depends on the type of reaction involved and increases with the increasing projectile energy. From an analysis of the energy dependence of the isomeric cross-section ratio, the excitation energy of 120m I was deduced to be 550 2 50 keV and its spin and parity as 4 + . The experimental data reported earlier and the theoretical analysis presented in this work allow to de®ne the optimum conditions for the production of the medically important b + emitter 120g I with enhanced con®dence. 7 2000 Elsevier Science Ltd. All rights reserved. 1. Introduction In a series of papers published from JuÈlich during the last two years (cf. Hohn et al., 1998a,b; 1999, 2000) we described experimental studies on proton and deuteron induced reactions on highly enriched 122 Te and 120 Te, with particular reference to the production of 120g I. It has been established that this b + emitting radioisotope T 1 2  81 min is suitable for positron emission tomography (PET) and is thus of consider- able potential medical interest (cf. Hohn et al., 1999; Herzog et al., 1999). Since 120 I consists of a ground state 120g I and an iso- meric state 120m I T 1 2  53 min), it was of particular interest to study the isomeric cross-section ratio in var- ious nuclear processes. As is well known, a minimis- ation of the isomeric impurity is possible only through a comparative investigation of various possible reac- tions (cf. Qaim, 1994). Experimentally, excitation func- tions were measured for the formation of both the states in three nuclear reactions, viz. 123 Te(p,3n) 120m,g I, 120 Te(p,n) 120m,g I and 120 Te(d,2n) 120m,g I (cf. Hohn et al., 1998a,b; 1999, 2000). Now we consider the formation probabilities of the various products in terms of nuclear model calculations. This predictive investi- Applied Radiation and Isotopes 52 (2000) 937±941 0969-8043/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S0969-8043(99)00157-8 www.elsevier.com/locate/apradiso * Corresponding author. Tel.: +49-2461-613-282; fax: +49- 2461-612-535. E-mail address: s.m.qaim@fz-juelich.de (S.M. Qaim).