Abstract
The total cross section has been measured in detail from threshold to 2.5-Mev proton energy. Between 1.88 and 1.92 Mev the cross section follows the equation for a very broad resonance and for -wave particles: , where at 50 kev above threshold. The remainder of the cross section up to 2.35 Mev is fitted by this level and the level at 2.25 Mev. The neutron reduced width exceeds that of the proton by a factor of about five for both the and levels; this is surprising for the self-mirror nucleus . A small dip is observed just above neutron threshold in the yield of 478-kev gamma rays from . The shape of these data support the assumption of the broad neutron producing resonance with Mev. No anomaly is observed in the yield of Li capture gamma rays at neutron threshold; the 2.10-Mev resonance in this reaction (which probably is due to a level) yields mainly 16-Mev gamma rays leading to the 2.9-Mev level in . The ratio of 16 to 19 Mev gamma rays is at both 1.7- and 2.5-Mev proton energy. The behavior of the extrapolated threshold was calculated as a function of target thickness and proton energy spread; shifts in the extrapolated thresholds and the distances between them and true threshold were less than one kev. The extrapolated threshold of a ½-kev target taken with a proton energy spread of 1 kev was observed to be ½ kev lower in proton energy than a thick-target threshold.
- Received 5 August 1957
DOI:https://doi.org/10.1103/PhysRev.108.1294
©1957 American Physical Society