Novel approach to angular distributions in precompound reactions Does the Bohr hypothesis always work?

Abstraet. We modify the standard statistical model for precompound reactions (exciton model) by taking into account the correlations between fluctuating S-matrix elements with different J (total spin) values. This is done in the framework of the statistical approach to nuclear reactions. While angle-integrated cross-sections are not affected by our modification, differential cross-sections become asymmetric about 90 ~ c.m. This asymmetry weakens with time and with increasing complexity of the decaying nuclear system, but need not disappear even for the compound (thermalized) system. We present a comparison with data showing such an asymmetry.