Magnetic dipole moments near 32Sn: new measurement on 135I by NMR/ON

On-line low temperature nuclear orientation (OLNO) experiments have been performed on the isotope 135I using the technique of nuclear magnetic resonance on oriented nuclei (NMR/ON). The magnetic moment of the 7/2 + ground state has been measured to b e / z ( 7 / 2 +135I) = 2.940(2)/XN, thereby extending the known data on these states in odd-A I isotopes up to the neutron shell closure at N = 82. Shell-model calculations have been performed for the magnetic moments of 7/2 + states in the N = 82 isotones using free-nucleon and effective g-factors. The effective gfactors are obtained from a perturbation calculation that includes corrections for core polarisation and meson-exchange currents. The proton number dependence of the magnetic moments in the sequence of N = 82 isotones 133Sb-139La is discussed in terms of blocking of the 0g9/2 to 0g7// core polarisation with increasing 0g7/2 occupancy. Systematics of all measured 7/2 + odd-proton moments for 74 ~< N ~< 82 are reviewed. (~) 1998 Elsevier Science B.V.