R. Jeppesen

The (n, p) reaction as a probe of Gamow-Teller strength

Abstract The ground state differential cross sections for the (n, p) reaction at 0° on 6 Li, 12 C and 13 C have been measured for 198 MeV neutrons with a precision of about 4% relative to the corresponding value for the H(n, p) reaction. These data, together with the accurately known ft values for the β- decay of 6 He, 12 B and 13 B provide three calibrations of the (n, p) reaction as a probe of Gamow-Teller strength for isospin raising transitions.

Gamow-Teller strength and giant resonances in 90Zr(n,p) at 198 MeV☆

Abstract The 90 Zr(n,p) 90 Y reaction has been studied at a bombarding energy of 198 MeV in a search of GT + strength. Up to 10 MeV excitation in 90 Y, we obtain a firm upper limit of S β + ⩽ 3.6. The majority of the strength at low excitations is identified as spin dipole.

A study of spin isovector giant resonances with the208Pb(n, p)208Tl reaction

Abstract The 208 Pb(n, p) 208 Tl reaction was studied at 198 and 458 MeV in a search for isovector spin giant resonances. Peaks at 5.1 MeV and 13.6 MeV excitation in 208 Tl are observed and discussed as candidates for the T > spin giant dipole resonance (SGDR), the spin isovector monopole resonance (SIVM), and the spin isovector quadrupole resonance (SIVQ).

Distribution of spin dipole transition strength in the sup 15 N( n , p ) sup 15 C reaction

The reaction {sup 15}N({ital n},{ital p}){sup 15}C was studied at a neutron energy of 288 MeV using the TRIUMF ({ital n},{ital p}) charge-exchange facility and a high-pressure gas target. The angular distributions for spin dipole ({Delta}{ital L}=1) transitions to the states in {sup 15}C at energies 0 and 0.740 MeV, as well as for higher excitation energies, were measured and the results were compared with distorted-wave impulse approximation calculations. The measured distribution of the spin dipole strength agrees well with shell-model predictions, indicating that a rather simple model provides a satisfactory description of the {sup 15}N ground state, and of positive-parity states in {sup 15}C up to about 18 MeV excitation. The magnitude of the peak cross sections (at {congruent}7{degree}) is described well by the calculations when the theoretical cross section is renormalized by a factor of 0.7. The calculated cross sections near 0{degree} are generally smaller than experimental data. If this is a general feature of {Delta}{ital L}=1 transitions, it suggests that estimates of Gamow-Teller strength based on a multipole decomposition of measured cross sections may be too high.