Measurements of the 48Ca({\gamma},n) Reaction

TL;DR

This study measured the 48Ca({b3},n) reaction cross section using high-resolution gamma-ray beams, revealing resonance structures and providing new data on nuclear excitations relevant to nuclear physics models.

Contribution

First direct measurement of 48Ca({b3},n) cross sections with low energy spread gamma-ray beams, observing resonance structures and comparing results with ERPA calculations.

Findings

Measured cross sections at 34 gamma-ray energies.

Observed resonance at 10.23 MeV with B(M1)=6.8 b1 0.5 bcN^2.

Detected structures consistent with ERPA predictions.

Abstract

The 48Ca({\gamma},n) cross section was measured using {\gamma}-ray beams of energies between 9.5 and 15.3 MeV generated at the Triangle Universities Nuclear Laboratory (TUNL) high-intensity {\gamma}-ray source (HI{\gamma}S). Prior to this experiment, no direct measurements had been made with {\gamma}-ray beams of sufficiently low energy spread to observe structure in this energy range. The cross sections were measured at thirty-four different {\gamma}-ray energies with an enriched 48Ca target. Neutron emission is the dominant decay mechanism in the measured energy range that spans from threshold, across the previously identified M1 strength, and up the low-energy edge of the E1 giant dipole resonance (GDR). This work found B(M 1) = 6.8 \pm 0.5 {\mu}N2 for the 10.23 MeV resonance, a value greater than previously measured. Structures in the cross section commensurate with extended random-phase approximation (ERPA) calculations have also been observed whose magnitudes are in agreement with existing data.