Neutron-proton pairing, Coulomb effects and shape coexistence in odd-odd N= Z(46)V

High-spin states up to the f(7/2)-shell band termination at J(pi) = 15(+) h ave been observed in the odd-odd N = Z = 23 nucleus V-46. A revised and sig nificantly extended level scheme contains two distinct structures correspon ding to spherical and prolate shapes. A band exhibiting rotational-like beh aviour in the latter structure has excellent correspondence with the yrast sequence in Ti-46 and is therefore assumed to be a T = 1 configuration. The difference between excited analogue states in the two nuclei is interprete d as a Coulomb effect and its variation with spin associated with np-pair a lignment effects in V-46. Shell-model calculations have been performed and are in good quantitative agreement with experimental level energies. The co mpetition between T = 1 and T = 0 structures is also reproduced. (C) 1999 E lsevier Science B.V. All rights reserved.