Hindered interband M1 transition in49V and the deformation of hole states

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Abstract
Positive-parity levels in 49V were studied using the 46Ti( alpha ,p gamma ) reaction of Ealpha =8 MeV. A gamma - gamma angular correlation measurement yielded the mixing ratio 1.4-0.8+10 for the transition between the 1646 keV level (1/21+) and the 748 keV level (3/21+). These levels were considered to be the band-heads of the 1/2(200) and 3/2(202) bands. The mean lifetime of the 1646 keV level was measured to be 9.5-1.1+1.5 ps by the recoil-distance method. A B(M1) value of (1.6-1.5+2.4)*10-5 e2 fm2 was deduced for the 1/21+ to 3/21+ transition from these data. Furthermore, a Doppler-shift attenuation experiment gives 0.7-0.2+0.3 ps as the mean lifetime of the 1995 keV (3/22+) level. The present results combined with previous data indicate that the B(M1) value for the 1/21+ to 3/21+ transition is 1/30-1/50 of those for other M1 transitions between the positive-parity levels in 49V. A strong-coupling model calculation with band mixing shows that this hindered M1 transition is the result of the cancellation of M1 matrix elements at beta approximately=0.2.