D.C. Weisser

The mass of 18C from a heavy ion double-charge-exchange reaction

Abstract The mass of 18 C has been measured using the double-charge-exchange reaction 48 Ca( 18 O, 18 C) 48 Ti at an 18 O energy of 112 MeV. The 18 C ions were detected at the focal plane of a magnetic spectrometer. The mass excess of 18 C was found to be 24.923 ± 0.030 MeV, and the first excited state was observed at an excitation energy of 1.62 ± 0.02 MeV. At the same time, an independent measurement of the mass excess of 17 C was obtained from the 48 Ca( 18 O, 17 C) 49 Ti reaction, and the value 21.039 ± 0.020 MeV is in excellent agreement with an earlier measurement. The first excited state of 17 C is at 295 ± 10 keV.

4 He Decay of Excited States in 14 C

A study of the 7Li(9Be,4He 10Be)2H reaction at E{beam}=70 MeV has been performed using resonant particle spectroscopy techniques and provides the first measurements of alpha-decaying states in 14C. Excited states are observed at 14.7, 15.5, 16.4, 18.5, 19.8, 20.6, 21.4, 22.4 and 24.0 MeV. The experimental technique was able to resolve decays to the various particle bound states in 10Be, and provides evidence for the preferential decay of the high energy excited states into states in 10Be at ~6 MeV. The decay processes are used to indicate the possible cluster structure of the 14C excited states.

Classical and potential descriptions of 9Be+28Si and 9Be + 40Ca elastic scattering cross sections at E(9Be) = 45 and 60 MeV

Abstract The elastic scattering angular distributions for 9 Be + 28 Si and 9 Be + 40 Ca have been measured at 9 Be bombarding energies of 45 and 60 MeV over an angular range in which σ σ R varied from 1 (i.e. Rutherford scattering) to values ≲ 0.001. The measured cross sections are analyzed classically using Wegner plots and quantum mechanically using both an optical potential of Woods-Saxon form and a double-folding potential with a realistic nucleon-nucleon interaction. 9 Be appears to exhibit somewhat different behaviour from both the lighter projectiles such as p and α and from its heavier neighbours such as 12 C and 16 O.

Lithium-induced reactions on carbon at 48 MeV

Abstract Angular distributions have been measured for transitions to states in 13N and 13C populated by the 12C(7Li, 6He)13N and the 12C(7Li, 6Li)13C reactions at E = 48 MeV. Elastic scattering of 7Li at 48 MeV on 12C and 12Li on 13C at 40 MeV were measured. Optical-model parameters extracted from fits to these data were used in the DWBA analysis of inelastic scattering to levels in 12C and 7Li and for particle transfers to levels in 13N and 13C. The calculations generally reproduced the data, except for the 3.09 MeV 1 2 + level in 13C, which was seriously out of phase. Spectroscopic factors were obtained from the transfer data and deformation lengths from the inelastic scattering to the 4.44 MeV 2+, and the 9.64 MeV 3− levels in 12C and to the 0.48 MeV 1 2 − level in 7Li.

12C and 13C induced reactions on N = 28 nuclei at energies near the Coulomb barrier

Abstract Excitation functions for elastic scattering, inelastic scattering and single neutron transfer reactions on N = 28 nuclei have been measured for energies spanning the Coulomb barrier at ∼ 120° and ∼ 150° to the beam direction. The elastic data were fitted using the optical model. The inelastic scattering and the transfer data were analysed using the distorted wave Born approximation. Spectroscopic factors, B(E2)s and βNs extracted from the data are shown to be in good agreement with values obtained from other work.

Isobaric analogue resonance studies in some rare-earth nuclei

Abstract Isobaric analogue resonances have been investigated by proton scattering on 160 Gd, 162 Dy, 164 Dy, 166 Er, 168 Er, 170 Er and 174 Yb. The resonance fits to the (p, p 0 ) data support orbital angular momentum assignments based on (d, p) studies except in the case of 162 Dy(p, p 0 ). Single particle widths, calculated using the Lane model with an absorptive potential have been used with the present results to obtain values of C ji 2 for comparison with (d, p) data and the Nilsson model values. Coulomb displacement energies have been determined in all cases and the systematics of these and other data show that a local maximum, within the deformation minimum, exists at A ≈ 170.

Energy dependence of the 24Mg(16O, 12C)28Si reaction

Abstract Excitation functions for the reaction 24 Mg( 16 O, 12 C) 28 Si(g.s., 2 + 1 ) were measured at 5°(lab) in the energy range 32 E c.m. E c.m. = 37.5, 40.2 and 43.5 MeV. Angular distribution measurements at these energies yield spin assignments, from P 2 j (cos θ ) comparisons, of 27, 29 and 31, respectively. Attempts to find a consistent optical-model fit to the elastic scattering in the entrance channel and an exact finite-range DWBA fit to the four-nucleon transfer reaction in this energy range were unsuccessful. Such a failure is to be expected if strong couplings between the elastic channel and inelastic channels of either the initial or final system are important. The features of the resonance phenomena in the transfer reaction are discussed within a band crossing model framework.

Elastic and inelastic scattering of 6Li and 7Li by 54Fe at E = 36–50 MeV

Abstract Detailed angular distributions for the elastic and inelastic scattering of 7 Li at E = 36, 42, and 48 MeV and of 6 Li at E = 38, 44, and 50 MeV by 54 Fe have been measured. It is not possible to describe both sets of data with the same set of optical-model parameters. The ratio of U W is 0.8 for 7 Li and 1.4 for 6 Li at the strong absorption radius, implying stronger absorption for 7 Li than for 6 Li. No energy dependence in the optical-model parameters was necessary for either 6 Li or 7 Li. The inelastic scattering from the 54 Fe 2 + , 1.41 MeV state was well described by the DWBA and the extracted deformation length ( βR = 0.62) was the same for both 6 Li and 7 Li scattering. It was not possible to describe the 7 Li projectile excitation data with collective-model DWBA calculations showing that more detailed calculations for the projectile excitation are necessary.

New measurements of the masses of 15B and 19N

Abstract The neutron-rich nuclei 15 B and 19 N have been produced in reactions between 18 O and 48 Ca. Mass excesses of 28.968 ± 0.025 MeV and 15.872 ± 0.020 MeV respectively were deduced from the reaction Q -values. These results are compared with previous measurements and theoretical predictions. Updated predictions using two different mass formulae are presented.

The 208Pb(7Li, 6He)209Bi reaction at 52 MeV

Abstract Single proton transfer to low-lying levels in 209 Bi from the 208 Pb( 7 Li, 6 He) reaction at 52 MeV have been measured and spectroscopic factors derived from an EFR-DWBA analysis. Relative spectroscopic factors are in good agreement with light-ion results and previous heavy-ion work. Absolute spectroscopic factors were generally too large and the peaks of the angular distributions were out of phase with the DWBA calculations by 1°−4°.