K. Ramavataram

Levels excited in the reaction 58Ni (p,t) 56Ni

Abstract Angular distributions have been obtained for triton groups in the reaction 58Ni(p,t)56Ni corresponding to levels up to 8.5 MeV excitation. Spin assignments are presented and the level structure of 56Ni is discussed.

A microscopic description of the negative parity resonances in the mass-4 system by the coupled-channel method

Abstract The coupled-channels method for the treatment of the continuum is used to study the negative parity excited states of the 4He nucleus in the Tamm-Damcoff approximation. It is shown that the splittings within the SU(4) supermultiplet are well reproduced in this calculation when the spin-dependent forces responsible for the removal of the degeneracy are taken appropriately into account. The location of the T = 0, 1− resonance and the admixture of spurious c.m. excitation in the intrinsic excitation are discussed. In addition to interpreting the observed spectrum, the available experimental data for the particle channels are well described by the theory.

A shell-model calculation for 5He and 5Li

Abstract Shell-model calculations using the Kurath force and the Tabakin separable potential for the residual interactions have been performed to interpret the experimental data now available for the T = 1 2 states in 5 He and 5 Li above 16 MeV excitation. For both forces the three sd-shell single-particle energies were varied to obtain agreement with the experimental spectrum. This fitting procedure allowed us to determine the sd-shell single-particle energies and to predict the spins and parities of two other T = 1 2 levels at 22 and 25 MeV. The Kurath force predicts the correct sequence of levels but an inadequate amount of splitting between levels. The Tabakin potential gives larger splittings between levels. The wave functions obtained for the two cases are discussed from the point of view of the “S-forbiddenness” selection rule observed in the two-nucleon pick-up reactions on 7 Li.

A unique set of phase shifts for the scattering of protons by helium

Abstract The polarization in the elastic scattering of 10 MeV protons from 4 He has been measured between 109.5° and 118.5° lab in steps of 1.5°. A phase-shift analysis presented which leads to a unique set of phase shifts after a thorough search using random starting values. Accurate differential cross sections and polarizations have been calculated using this phase-shift solution which should facilitate accurate proton polarization determinations at 10 MeV using helium analysers.

Phase-shift analysis of polarization and differential cross section in p-4He elastic scattering between 25 and 29 MeV

Abstract Phase-shift analyses have been carried out on the polarization and cross-section data in p +4He elastic scattering between 25 and 29 MeV. The results show that the spin and parity of the 20 MeV resonance in 5Li are 5 2 + . From the phase-shift set obtained for this partial wave, the parameters of this resonance are estimated. The results also indicate a resonance with Kπ = 1 2 + at about 18 MeV excitation in the 5Li system.

Study of the11B(p, n)11C reaction below the giant dipole resonance in12C

SummaryThe11B(p, n)11C reaction has been studied for proton energies in the range (3 ÷ 6) MeV. Relative cross-sections were measured with a 4π counter in 15 to 20 keV steps. Absolute cross-sections were measured by using the activation technique to an accuracy of ± 10% at six different energies covering the range mentioned above. The observed resonance structure in the excitation function is compared with the predictions of an extended coupled-channel calculation.RiassuntoSi è studiata la reazione11B(p, n)11C per energie del protone comprese nell’intervallo (3 ÷ 6) MeV. Si sono misurate sezioni d’urto relative misurate con un contatore 4π ogni 15, 20 keV. Si sono misurate sezioni d’urto assolute per mezzo della tecnica di attivazione con una precisione del ± 10% e a 6 diverse energie che comprendono l’intervallo suddetto. Si confronta la struttura di risonanza osservata nella funzione d’eccitazione con le predizioni di un calcolo esteso per canali accoppiati.

Elastic and inelastic widths of analogue states in 65Cu

Abstract Elastic and inelastic excitation of IAR were studied using protons of 3 to 5 MeV energy incident on 64 Ni. The spins of some of the analogue states as well as their elastic and inelastic widths are obtained from the experimental results. Spectroscopic factors were deduced from the resonance parameters and calculated single-particle widths and are compared with the shell-model predictions.

Measurement of polarization and differential cross section in p-4He elastic scattering between 25 and 29 MeV

Abstract p- 4 He polarization and elastic differential cross-section angular distributions have been measured at 25.0, 26.1, 27.1. 28.2 and 29.2 MeV incident proton energy. The angular distributions were measured in 5° intervals from 20° to 160° (lab) for the polarization and from 30° to 160° (lab) for the differential cross section. The polarization measurements were generally such that δ p ≦ ±0.03 whilst the differential cross-section errors were ≦3% except at forward angles. The normalization accuracies were determined to be ±1% for the polarization and ±3.5% for the differential cross section.

A continuum calculation of the neutron polarisation in the 3H+p reaction and the resonant states of 4He

Abstract The energy dependence of the neutron polarisation P n in the 3 H(p, n) 3 He reaction is calculated using the 1p−1h coupled-channel model of nuclear reactions proposed earlier by Ramavataram et al. to describe the formation and decay of the negative parity excited states of A = 4. It is shown that the polarisation data provides tangible evidence for the T = 0, 1 − resonance predicted by them. Two positive parity T = 0 resonances proposed experimentally are also confirmed in this calculation. Inclusion of a 1 + , T = 0 resonance around 25 MeV and a 2 + , T = 0 resonance around 29 MeV is necessary to obtain agreement with experiment. It is shown that among these resonances the 1 + , T = 0 resonance can be generated at about the right energy in the coupled-channel calculation but that the 2 + , T = 0 resonance is too high in energy and it may be necessary to include 2p−2h configurations in this case. The proposed level scheme also provides a consistent description of the angular dependence of the differential cross section and polarisation P p in the elastic channel as well as the P n angular distribution.

Continuum model and the iso-spin splitting of the giant quadrupole resonance in 16O

Abstract The 1p-1h coupled channels model of photo-nuclear reactions is shown to reproduce the observed splitting of the iso-scalar and iso-vector E2 strengths in 16 O. The two relatively intense T = 0 resonances predicted at 14.8 and 19.4 MeV are in good agreement with the 2 + states observed in the (p, γ) and (α, γ) reactions. The continuum calculation predicts satisfactorily the energy, width and intensity of the giant quadrupole resonance around 27 MeV excitation.