Measurements of d, pγ directional correlations in 20F

Abstract

The reaction 19F(d, pγ) 20F was used to measure the directional correlations of the proton groups in coincidence with subsequent gamma radiations produced in de-excitation of the 2.05, 1.31, 1.06, 0.99 and 0.65 MeV levels of 20F. The effective deutron energy was 0.448 Mev. For the 2.05 MeV level, the 1–2 correlation between the protons and the 1.40 MeV gamma transition to the first excited state was measured simultaneously with the 1–3 correlation between the same proton energy group and the 0.65 MeV gamma transition, with the intermediate 1.40 MeV gamma radiation unobserved. These correlations were measured in two configurations: one with the protons being detected at an average angle of 170° with the beam passing through a centre hole in an annular-shaped detector, and the other with a disc-shaped detector at 135° and the gamma detector moving in the plane of the reaction. A plane-wave analysis of these data gave essentially identical correlation coefficients for these two configurations. Directional correlations were also measured in the 170° configuration between the proton energy groups and the subsequent ground-state gamma transitions from the 1.31, 1.06, 0.99 and 0.65 and 0.65 MeV levels. A plane-wave analysis of these data is compared with a distorted-wave analysis of related data from a previous experiment. A thorough computational comparison between all of these data and the predicted correlations, based on a plane-wave analysis using postulated spin values which are consistent with the proton angular distribution data, did not yield a unique spin value for any of these levels. It was possible in some cases, however, to put rather stringent conditions on the ratios of the angular-momentum matrix elements associated with the incoming and outgoing radiations which are compatible with the postulated spins.