Level structure of 116Sn and 117Sn from (p,d), (p,t) and (p,p′) reactions

The level structure of ¹¹⁶Sn has been investigated by the reactions ¹¹⁷Sn(p, d), ¹¹⁸Sn(p, t), and ¹¹⁶Sn(p, p′) with 55 MeV incident protons and that of ¹¹⁷Sn by ¹¹⁸Sn(p, d) and ¹¹⁷Sn(p, p′) reactions. The emitted particles have been analysed with a broad-range magnetic spectrometer. Angular distributions of emitted particles in the (p, d), (p, t) and (p, p′) reactions are analysed in terms of the DWBA method. A strong similarity between the ¹¹⁷Sn(p, d) and ¹¹⁸Sn(p, t) reactions is found in the excitation of all of the observed states in ¹¹⁶Sn. Three new 2⁺ states in ¹¹⁸Sn are identified both from the (p, d) and (p, t), and two excited 0⁺ states are established. Spectroscopic factors for 25 states extracted from the ^{117, 118}Sn (p, d) reactions are compared with theoretical predictions based on the pairing interaction plus quadrupole-quadrupole and octupole-octupole interactions. The agreement is reasonably good except for the 2⁺ states at E_x ≈ 4 MeV in ¹¹⁶Sn.     

Comparative analysis of (p,d), (d,t) and (3He, α) reactions on13C nucleus

The angular distributions of the (p, d), (d, t) and(³He, ) reactions on¹³C have been analysed within the framework of DWBA in which additional information on nuclear vertex constants was introduced. Although all these reactions seem to be similar single nucleon transfer, their mechanism is shown to be quite different and so is the information extracted thereof. While from the (p, d) reactions spectroscopic factors may be extracted unambiguously, from the (d, t) reactions it is possible to obtain directly the values of vertex constants only, which in turn are consistent with those determined by extrapolation of the experimental cross sections of the (p, d) reactions to the pole.In the case of (³He, ) reactions, however, the analysis indicates inadequacy of the DWBA concerning the calculations of central partial amplitudes. For a more reliable extraction of structural information, besides the correct normalization of peripheral amplitudes, a contribution of more complex mechanisms must be taken into account.     

3He(e,e′pp) and 3He(e,e′pn) reactions at AmPS and MAMI

This paper reports on measurements of the ³He(e,e′pp) reaction measured at AmPS and the ³He(e,e′pn) reaction measured at MAMI. The measurements were performed in similar kinematics to allow a comparison to be made between the cross sections of the two reactions. Results are shown for both reactions together with a comparison for the ³He(e,e′pp) data with continuum Faddeev calculations.     

Charge-exchange processes in the quasi-elastic (e,e′p) and (e,e′n) reactions

Calculations of charge-exchange processes in the final state of the quasi-elastic (e, e′N) reaction have been performed employing the Lane formalism. The Lane equations were decoupled by means of a transformation to the isospin representation. It is found that charge exchange has a small effect on the (e, e′p) cross section, but may play an appreciable role in the (e, e′n) reaction.     

Measurement of the exclusive D(p,e+e−)3He and D(p, γ)3He reactions at 98 and 176 MeV

A high resolution magnetic pair spectrometer for medium energy photons has been used for studies of the exclusive (p, e⁺e⁻) and (p, γ) reactions on deuterium at 98 and 176 MeV. The (p, e⁺e⁻) cross sections, obtained at 40° and 80°, are compared with the corresponding data for the (p, γ) reaction measured with the same apparatus. At small virtual photon masses the (p, e⁺e⁻) cross sections show significant enhancement over what is expected from model calculations, a behaviour which has earlier been observed also for the ¹¹B(p, e⁺e⁻)¹²C reaction.     

The nuclear structure of 126Te studied with (d,p), (d,3He) and (d,d′) reactions

At the Munich Tandem Accelerator the reactions ¹²⁵Te(d, p)¹²⁶Te, ¹²⁶Te(d, d′)¹²⁶Te and ¹²⁷I(d, ³He)¹²⁶Te were measured with deuteron energies between 24 and 28 MeV up to excitation energies of about 3.2 MeV. Using γ-lines from previous (n,γ), (n,n′γ) and (γ,γ′) experiments, a level scheme of ¹²⁶Te up to above 3 MeV was established. The results are compared with quasiparticle-phonon model calculations.     

(α, 3He) and (α, t) reactions on 40Ca

Angular distributions have been measured for several levels excited in the ⁴⁰Ca(α,³He) ⁴¹Ca and ⁴⁰Ca(α, t) ⁴¹Sc reactions at 40 MeV bombarding energy. ³He and triton groups corresponding to several known levels in ⁴¹Ca and ⁴¹Sc were observed, in addition to ⁴¹Sc levels at 3.356±0.020 and 3.905±0.020 MeV excitation energy which have not been reported previously. DWBA calculations were performed in both the zero- and finite-range approximations, and spectroscopic factors are compared with the results of other reactions. The (α, ³He) and (α, t) reactions appear to selectively excite analogue states in the ⁴¹Ca-⁴¹Sc mirror nuclei, most of which correspond to an l = 3 or l = 4 angular momentum transfer.     

Final-state interactions in (e,e′p) reactions with polarized nuclei

The cross section for coincidence, quasielastic proton knock-out by electrons from a polarized ³⁹K nucleus is computed in DWIA using an optical potential in describing the wave function of the ejected nucleon. The dependence of the FSI on the initial polarization angles of the nucleus is analyzed and explained in a new, semi-classical picture of the reaction in which the nuclear transparency decreases as a function of the amount of nuclear matter that the proton has to cross, thus providing a method for obtaining detailed information on its mean free path in finite nuclei. We propose a procedure to find the best initial kinematical conditions for minimizing the FSI which will be useful as a guide for future experiments with polarized nuclei.     

Tensor force manifestations in ab initio study of the 2H(d,γ)4He, 2H(d,p)3H, and 2H(d,n)3He reactions

The (2)H(d,p)(3)H, (2)H(d,n)(3)He, and (2)H(d,γ)(4)He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8' realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.     

(α, τ) and (α, t) reactions with 104 MeV α-particles

The differential cross sections for the one-nucleon stripping reactions and the elastic scattering of 104 MeV α-particles on ¹²C, ²⁷Al and ⁴⁰Ca were measured. The experimental results show that the (α, τ) cross sections are larger than those obtained from (α, t) reactions on the same target nuclei. The reaction data were analyzed in the framework of the DWBA. The calculations using the zero-range approximation are able to reproduce the measured angular distributions. In addition the effect of finite-range corrections were studied in the local energy approximation. From the analysis it becomes evident, that the inner part of the target nucleus contributes significantly to the reaction cross section. The larger yield of ³He particles compared to that of tritons can be explained mainly by different normalization factors for the (α, τ) and (α, t) reactions, respectively.     

Study of the 4He (γ, p)3H and 4He(γ, n)3He reactions

The cross sections and angular distributions for ⁴He(γ, p)³H and ⁴He(γ, n)³He have been measured.     

Nuclear structure studies of 125Te with (n,γ), (d,p) and (3He,α) reactions

Levels in ¹²⁵Te were investigated in the range up to 3.3 MeV excitation energy by the (n,γ), (d,p) and (³He,α) reactions. Over 160 levels and about 360 γ-transitions were established, most for the first time. The states below 2.3 MeV with the most complete spectroscopic information were interpreted in terms of the interacting boson-fermion model (IBFM). Unitary treatment of both positive- and negative-parity states is achieved with the same model parameter close to the intermediate case between O(6) and U(5) limits. Excitation energies, electromagnetic transition rates, γ-branchings and spectroscopic factors are discussed in connection with the possible structures. A family of low-spin negative-parity states has been identified and understood by the IBFM proving their antialigned origin.     

Determination of the reaction-matrix elements of the D(d,n)3He and D(d,p)3H reactions forE d ≤500 keV

All available data of the mirror fusion reactions D(d, n)³He and D(d, p)³H have been subjected to a new analysis in order to extract the matrix elements of all 16 transitions necessary for inclusion of alll2 waves. Their energy dependence was assumed to be governed solely by Coulomb penetrabilities. The Levenberg-Marquardt algorithm was used to fit all experimental data. The experimental data are reproduced satisfactorily. The results compare well with anR-matrix analysis and with refined resonating group calculations. No suppression of quintet entrance-state transitions and therefore no neutron suppression in polarized fusion can be derived from this analysis.This work was funded by the German Federal Ministers for Research and Technology (BMFT) under the contract numbers 06-OK-153 and 06-OK-272     

Comparison of Monte Carlo simulation and direct multistep scattering theory in (e,e′p) nuclear reactions

Two methods to deal with final state interactions in (e,e′p) reactions in nuclei are compared. One of them uses a Monte Carlo semiclassical approach while the other uses a statistical quantum mechanical approach. The comparison serves to give support to both approaches, showing at the same time their limitations.