Nuclear spin orientation of 12,13B created in heavy ion collisions

The momentum dependences of the nuclear spin polarization P and alignment A of 12 B ( I π = 1 + , T 1 / 2 = 20.20 ms) [ 13 B ( I π = 3 / 2 − , T 1 / 2 = 17.36 ms)] produced in 100 A MeV 13 C [ 15 N] + Be collisions have been measured by detecting the β -ray asymmetry. Because both the P and A were significantly smaller than the prediction from a simple kinematical model, some depolarization mechanisms must be taken into account related with the collision process itself. Comparing the signs of the observed alignment of 12 B and 13 B, the sign of the quadrupole moment Q ( 13 B) was determined to be positive.