Some interesting effects of the angular localization of reaction sites caused by the damping of the incident and exit particle waves by the nuclear optical potential are described. Using the reactions and , as examples, we show that, due to the angular localization, the total reaction cross section is different for aligned than for unaligned target nuclei. For the target in or coupling the fractional change, , in the cross section for an incident energy of 6 BeV was given by , where is the fractional population of in the substates. At 140 MeV the value of the constant in the above expression was slightly but not significantly smaller. For the reaction the fractional change in the cross section is one half of and of the opposite sign of the value for the same amount of target alignment. Another result of angular localization of reaction sites in the nucleus is that product nuclear states will be oriented with respect to the incident beam. Using () and () reactions on and as examples, the amount of product nuclear state alignment was computed for the and excited hole states of , , and . The population ratios obtained for the substates in or were and for , . The angular anisotropies, , expected from gamma decay of these states were computed to be -0.125 assuming an transition for the or -states and 0.162 assuming an transition for the -state.
- Received 4 September 1962
- Published in the issue dated February 1963
© 1963 The American Physical Society