(3He,7Be) reaction on12C and spin-orbit folding (original) (raw)
Physical Review C, 1991
Angular distributions have been measured for 0+~1+ transitions with the (' C, ' B) reaction on targets of ' C, Mg, 5 Fe, 'Ni, and Zr and with the (' C, ' N) reaction on targets of ' C and ' Fe. The bombarding energy was E/A =70 MeV, and small-angle data were obtained. A comparison of the cross sections measured for the (' C, ' 8) reaction with the results of distorted-wave-approximation calculations indicates that 0+-+1+ transitions are predominantly one step at E/A =70 MeV. The calculated cross sections are generally in good agreement (to within 40% in magnitude) with the measured cross sections, and the angular distributions are well described quantitatively in many cases. A correlation between cross sections and known Gamow-Teller (GT) strengths B(GT) for the corresponding transitions has been found. This correlation, which is weakly dependent on the target mass, establishes a calibration for the reactions. It is used to determine B(GT) values of astrophysical interest for two low-lying 1+ levels in Mn from the cross sections measured for the Fe(' C, ' N) Mn reaction. The results are compared with two shell-model calculations performed to obtain B(GT) for ' Fe-+ Mn transitions and with another calculation from the literature. Computational tests were performed to evaluate (a) the contribution to the cross sections of terms not present in nucleon-induced charge-exchange reactions and (b) the extent to which the cross sections provide a measure of GT strength.
7Be-induced α-transfer reaction on 12C
The European Physical Journal Special Topics, 2007
The reaction 12 C( 7 Be, 3 He) has been studied at E( 7 Be) = 34 MeV. Angular distributions to levels with excitation energies up to 21 MeV in the residual 16 O have been measured at θ lab = 13-50 degrees. This reaction selectively populates states known to have a large 12 C+α component in their structure, implying that direct processes dominates at this energy. PACS. 24.10.Eq Coupled-channel and distorted-wave models -24.50.+g Direct reactions -25.40.Hs transfer reactions -25.45.De Elastic and inelastic scattering -21.10.Jx Spectroscopic factors
Spin-Orbit Electronic Structure of the ScBr Molecule
Journal of Modern Physics, 2011
A theoretical investigation of the spin-orbit electronic states of the molecule ScBr has been performed via CASSCF and MRCI (single and double excitations with Davidson correction) calculations. Spin-orbit effects have been introduced through semi-empirical spin orbit pseudo-potential for scandium while they have been neglected for bromine. Potential energy curves for 42 electronic states in the representation ±) have been determined along with the corresponding spectroscopic constants. The comparison of the present results with those available in the literature shows a good agreement. New results have been investigated in present work for 30 electronic states in the representation ±) for the first time.
Analysis of the 11B(7Li,7Be)11Be reaction at 57 MeV in a microscopic approach
Nuclear Physics A, 2004
The 11 B( 7 Li, 7 Be) 11 Be charge exchange reaction has been studied at an incident energy of 57 MeV. Spectra were measured at forward angles, θ cm 35 • . The good energy resolution (∼50 keV) allowed the identification of transitions both to the 7 Be (3/2 − , gs) and 7 Be(1/2 − , 429 keV) exit channels and hence the direct measurement of the ratio of the respective cross sections and angular distributions. Besides the bound ground and first excited state of 11 Be several low lying excitations just above the neutron threshold are observed. A structure seen at E * = 9.4 MeV with FWHM ∼7 MeV is compatible with the spin dipole resonance (SDR). The data are analysed in a many-body approach. For the projectile transitions shell model results are used. In order to account properly for the special features of the weakly bound 11 Be system the target transitions are described microscopically by Hartree-Fock-Bogoliubov (HFB) and quasi-particle random phase approximation (QRPA) theory. The HFB ground state densities and the QRPA transition densities, respectively, are used in folding calculations for the optical potentials and transition form factors. Spectra and β-decay transitions strengths are reasonably well described. The measured cross section are well reproduced by one-step direct charge exchange distorted wave born approximation (DWBA) calculations. A dominance of unnatural parity transitions is found. This is explained in terms of the spin transfer behaviour of the nucleon-nucleon isovector interaction at low bombarding energy.
Physical Review C, 2013
Background: The (spin and isospin zero) α-particle is an efficient projectile for the excitation of the isoscalar, natural-parity states of 12 C. Among those states that have pronounced α-cluster structure, the Hoyle state (0 + 2 state at 7.65 MeV) has been observed in many (α, α) experiments while the second 2 + state of 12 C, predicted at E x ≈ 10 MeV as an excitation of the Hoyle state, has not been observed until a recent high-precision experiment of the α+ 12 C scattering at E α = 386 MeV. A plausible reason is a strong population of the narrow 3 − 1 state at 9.64 MeV and broad 0 + 3 resonance at 10.3 MeV that hinder the weak 2 + 2 peak in the (α, α) spectrum. Purpose: The accurate determination of the electric Eλ transition strengths of the isoscalar states of 12 C, including a E2 component at E x ≈ 10 MeV that can be assigned to the 2 + 2 state, based on a detailed folding model + coupled channel analysis of the (α, α) data measured at E α = 240 and 386 MeV. Method: The complex optical potential and inelastic form factor given by the folding model for the α+ 12 C scattering are used to calculate the (α, α) cross sections for the known isoscalar states of 12 C in an elaborate coupled channel approach. The strengths of the form factors for these states are then fine tuned against the (α, α) data to deduce the corresponding Eλ transition strengths. Results: A significant E2 transition strength has been obtained for the 2 + 2 state from the present analysis of the (α, α) data measured at E α = 240 and 386 MeV. The Eλ transition strengths of the 0 + 2 , 3 − 1 , 0 + 3 , and 1 − 1 states were also carefully deduced, and some difference from the results of earlier analyses has been found and qualitatively understood. Conclusion: Despite a strong hindrance by the 3 − 1 and 0 + 3 excitations, the presence of the 2 + 2 state in the (α, α) spectra measured at E α = 240 and 386 MeV has been consistently confirmed by the present folding model + coupled channel analysis.
Response Theory and Calculations of Spin-Orbit Coupling Phenomena in Molecules
Advances in Quantum Chemistry, 1996
We review response theory and calculations of molecular properties involving spinorbit interactions. The spin-orbit coupling is evaluated for reference states described by singleor multi-configuration self-consistent field wave functions. The calculations of spin-orbit related properties rest on the formalism of linear and quadratic response functions for singlet and triplet perturbations when no permutational symmetry in the two-electron operators is assumed and from which various triplet as well as singlet response properties are derived. The spin-orbit coupling matrix elements between singlet and triplet states are evaluated as residues of (multi-configuration) linear response functions, and are therefore automatically determined between orthogonal and non-interacting states. Spin-forbidden radiative transition intensities and lifetimes are determined from the spin-orbit coupling induced dipole transitions between two electronic states of different multiplicity and are obtained as residues of quadratic response functions. The potential of the theory and its range of applications is illustrated by a selection of recent investigations covering different molecular phenomena. The applications include second-order energy contributions, intensity rearrangement in electron spectra, calculation of predissociative lifetimes of dicationic states, assignment of triplet bands in absorption spectra, intersystem crossings and reactivity, external heavy atom effects on S-T transitions, phosphorescence spectra and radiative lifetimes of triplet states. We give an outlook on spin-orbit interaction induced phenomena in extended systems and on applications to general spin catalysis phenomena. Abstract 2
Experimental study of bound states in 12Be through low-energy 11Be(d,p)-transfer reactions
Physical Review C - Nuclear Physics, 2013
The bound states of 12 Be have been studied through a 11 Be(d,p) 12 Be transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11 Be was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in 12 Be. The gamma-ray detection enabled a clear identification of the four known bound states in 12 Be, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from DWBA calculations and have been compared to previous experimental and theoretical results.
The 6He scattering and reactions on 12C and cluster states of 14C
Nuclear Physics A, 2004
The 6 He + 12 C elastic and inelastic scattering and the 6 He + 12 C → α + 14 C reaction have been measured using a 18.0 MeV 6 He beam. Experimental results for the elastic scattering are in fair agreement with optical model predictions, using the potentials found in the analysis of 6 Li scattering on 12 C at similar energies. In triple coincidences, the 6 He + 12 C → 10 Be + 2α reactions were clearly seen, with the 10 Be nucleus left in ground and several excited states. The dominant mechanism of this reaction is sequential decay through cluster states of 14 C.
Experimental determination of the components of the spin-dipole resonance in 12B
Physics Letters B, 2007
The inclusive 12 C( d, 2 He) and exclusive 12 C( 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 11 B. 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.