Excitation and decay of Δ L = 1 modes in 12N via the 12C(3He, tp) reaction

doi:10.1016/0375-9474(83)90326-3

Nuclear Physics A

Volume 405, Issue 1, 22 August 1983, Pages 109-125

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Abstract

A study of the nucleus ¹²N has been performed using the ¹²C(³He, t) reaction at bombarding energies of 75 and 81 MeV. Differential cross sections were measured and interpreted using an effective projectile-nucleon interaction and microscopic wave functions. Proton decay to final states in ¹¹C was measured by recording coincidences tritons emitted at 0° and protons detected at several backward angles. From the triton angular distributions and the triton-proton angular correlations strong suggestions can be made about the location of J^π = 2⁻, 1⁻ and 0⁻ strengths in ¹²N. The ΔL = 1 strength distributions are compared with the results of shell-model calculations.

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Energy levels of light nuclei A = 12
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Experimental determination of the Jπ components of the spin-dipole resonance in 12B
2007, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
The inclusive ${}^{12}C (\vec{d}, {}^{2}{He})$ and exclusive ${}^{12}C (\vec{d}, {}^{2}{He} + n)$ reactions have been studied with a beam energy of 171 MeV and scattering angles for the $(d, {}^{2}{He})$ reaction $θ = 0 °$ and 3°. The studies focused on the separation of the isovector spin-dipole resonance (IVSGDR) into its components by measuring tensor-analysing powers and observing the direct neutron decay to the low-lying proton-hole states in ¹¹B. Merging the information obtained from both measurements resulted in the first-time verification of model-independent predictions of tensor-analysing powers at extreme forward angles and the experimental decomposition of the IVSGDR into its $J^{π}$ components. The experimental results are in reasonable agreement with theoretical estimates based on shell-model calculations.
(t,3He) reaction; new tool for studying spin-isospin excitations in neutron rich nuclei
1997, Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Initial experiments were carried out to study spin-isospin transitions in nuclei using (t,³He) measurements. A triton beam was produced from the breakup reaction (⁴He,t-p) on a 9.25 g/cm² Be production target using a ⁴He beam of 620 MeV. With a beam of 70 enA a yield of 381 MeV tritons with 4.5 × 10⁶ particles/s was achieved. The first half of the A1200 beam transport system at NSCL was used to analyze the triton beam. The energy spread at the target position was estimated to be about 23 MeV. The second half of the A1200 was used to analyze the energy of ³He particles from the (t,³He) reaction. The dispersion matching method was applied to obtain good energy resolution despite the significant energy spread of the incident tritons. The achromatic properties of the A1200 system made it possible to obtain high-resolution (t,³He) spectra at θ = 0° with a resolution of $ΔE E = 0.002$ (ΔE = 780 keV).
Spin-isospin excitations studied by polarized beams
1996, Nuclear Physics A
The spin-parity J^π of the spin dipole resonances (SDR) in ¹²N and ¹²B are investigated via the measurements of polarization observables, the transverse polarization transfer conefficient D_NN for the ( $p$ , $n$ ) reaction at 197 and 295 MeV and the tensor analyzing power A_xx for the ( $d,^{2} He$ ) reaction at 270 MeV. The polarization observables, D_NN and A_xx for the peak at 4.5 MeV are consistent with the DWIA prediction with 2⁻ but those for the peak at 7.5 MeV contradict the predictions with an expected J^π = 1⁻. Neither polarization observables could detect any concentration of 0⁻ strength. The usefulness of these spin observables in identifying J^π is shown.
Tensor analyzing power of the (d, 2He) reaction at 270 MeV
1995, Physics Letters B
The (3He,tp) reaction: A means to study the microscopic structure of spin-isospin modes
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The microscopic structure of both the Gamow-Teller resonance (GTR) at E_χ = 15.6 MeV and the spin-flip ΔL=1 resonances at higher excitation energies in ²⁰⁸Bi has been investigated by observing their direct proton decay to the $3_{p12}$ , $2f_{52}$ , $3 p_{32}$ , $1 i_{32}$ and $2f_{72}$ neutron-hole states in ²⁰⁷Pb, following their excitation via the ²⁰⁸Pb (³He,t) reaction at $E (^{3} He) = 450 MeV$ . Decay protons were measured at backward angles in coincidence with tritons detected at very forward angles including θ = 0°. The total widths of the resonances as well as total and partial proton escape widths were determined and compared to theoretical estimates for the GTR. Using the same experimental set-up and conditions proton decay of the spin-flip ΔL=1 resonances in ¹²C was also measured.

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Nuclear Physics A

Abstract

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Spin-isospin excitations studied by polarized beams

Tensor analyzing power of the (d, <sup>2</sup>He) reaction at 270 MeV

The (<sup>3</sup>He,tp) reaction: A means to study the microscopic structure of spin-isospin modes