Investigations of γ spectra of certain (p, γ) resonances

Abstract

The investigation of ? spectra of the isobaric analogue resonances gives useful information about the structure of the nuclei. Our original airo was to look for isobaric analogue resonances in (p, 7,) reactions on several nuclei, and to study the systematics of their ~ spectra. ExperimentalThe experiments were performed with the proton beato of the 2.5 MeV Van de Graaff generator with ah energy spread and calibration uncertainty of about 1 keV. The excitation functions ~vere measured with a 3" • 3" NaJ(T1) scintillation counter while the ? spectra were taken by a 15 cm 3 Ge(Li) detector located at 90 o. The targets were evaporated on thick Ta and Au backings from natural metals, except 44Ca when the target material was enriched 44CACO3. The thiekness of the targets was about 1--2 keV, for 2 MeV protons. 44Ca(p, ?)45ScThis reaction has been investigated by several authors [1, 2]. Surprisingiy, the measured exeitation functions did not show any striking resonance in the region of bombarding proton energy corresponding to the position of the isobar analogue of the Ex = 1904 keV (3/2-) state in the 4~Ca nucleus. From (d, p) stripping measurements [3] it is known that this level has a relatively large spectroscopic factor, namely (2J + 1)S n = 2.56. This fact suggests the idea that the isobaric analogue of this level should be found in the 45Sc nucleus. From the estimation of the Coulomb displacement energy, the expected position of the IAR is about 1670 keV bombarding proton energy. We have also measured the excitation function ( Fig. 1) in the 1.550--1750 keV proton energy region, in 2 keV steps with ah overall resolution of about 3 keV. As is seen