F.A. Gareev

Single-particle energies and wave functions for the saxon-woods potential and the levels of odd-A nuclei in the actinide region

Abstract The Saxon-Woods single-particle energies and wave functions are given for the description of deformed nuclei in the region 234 ≦ A ≦ 250. The energies and the wave functions for the non-rotational states of odd- A nuclei are calculated taking into account the interaction of quasiparticles with phonons. The latter is found to be more important for nuclei in the actinide region than in the rare-earth one. A rather good description of the energies of low-lying non-rotational states in 235 U, 237 U, 241 Pu, 245 Cm, 247 Cm, 249 Cm, 237 Np, 241 Am and 249 Bk is obtained. The calculated Saxon-Woods single-particle energies and wave functions may serve as a basis for calculating various characteristics of nuclei in the actinide region.

Expansion of continuum functions on resonance wave functions and amplitudes

Abstract The pole expansion (Mittag-Leffler expansion) of wave functions, scattering amplitudes, and Green functions at positive energies are discussed in a mathematically rigorous way. The general proofs of convergence are supplemented by numerical calculations, which, for a simple example, show the convergence to be fast. Applications of the method to nuclear structure calculations are discussed.

Projectile delta excitation in alpha-proton scattering

Abstract The (α, α′) reaction in the Δ-region is a clear example of projectile delta excitation. We study the reaction theoretically and compare the results to a recent experiment. The agreement is rather good. On the other hand the reaction offers a test for models of coherent pion production. Finally, the use of the present model should provide the appropriate background to extract the excitation strength of the Roper resonance observed in the same reaction.

Rainbows in Nuclear Reactions and the Optical Potential

Nucleus-nucleus scattering and charge-exchange reactions are studied in a region where rainbow-like phenomena are seen. Optical potentials are found which give fits to the cross sections, but in spite of the rainbow-like phenomena and contrary to apparently accepted expectations, not determined unambiguously. Other possibilities of resolving the ambiguities are discussed.

Wave functions and particle transfer form factors of 42Ca and 18O

Abstract Wave functions and energies of 0 + states of 42 Ca and 18 O are calculated using an expansion in Sturm-Liouville functions. The method is an alternative to the inclusion of continuum wave functions in shell model calculations and represents a considerable simplification compared to this. The wave functions are used to calculate cross sections of two-particle transfer.

Direct Experimental Evidence for a Soft-Dipole Response in 6He

The differential cross-sections of the charge exchange reaction 6Li(7Li, 7Be) 6He were measured at beam energies 78 and 82 MeV. In addition to the 0+ bound state and sharp 2+ resonance, three wide bumps were identified in the experimental continuum spectrum of 7Be at small angles. The maximum at excitation energy of ~ 6 MeV (Γ ~ 5 MeV FWHM) is consistent with a soft-dipole response, expected in nuclei with neutron halo.

A new method for solving the two-center problem with realistic potentials

A method has been proposed for the solution of the two-center problem with realistic potentials. It consists of two steps: first, we make a separable approximation to the single-particle potentials, and then the two-center problem with these separable potentials is solved exactly. The only approximations are introduced at the first stage, and in a well controllable way. As an example, we have calculated the single-particle energies and wave functions in the field of two 16O-like Woods-Saxon potentials as functions of their distance R.

Scattering of 3He on 12C and the inelastic form factor

Abstract Measurements of inelastic scattering of 3He on 12C at EHe = 72 MeV with excitation of low lying 2+, 3−, 0+ states of the target are reported. The data were analyzed both by DWBA and coupled-channels approximation, the latter leading to only minor changes, and we argue that nuclear rainbow effects are present. It is possible to reproduce the main features of the 2+ and 3− inelastic angular distributions by means of the optical model potential previously selected for the reaction (3He, t) on 13,14C targets, only if the derivative excitation form factors are modified in the vicinity of the strong absorption radius. The fit is improved in detail and can be made nearly perfect if more flexible model-independent form factors are employed. An alternative potential is also discussed.

Microscopic DWIA analysis of the (p, n) reactions

Abstract The charge-exchange nuclear excitations for the isobars 48 Ca → 48 Sc , 90 Zr → 90 Nb and 208 Pb → 208 Bi are considered in the framework of the theory of finite Fermi systems by exactly taking into account the particle-hole continuum. The distorted-wave impulse approximation (DWIA) is employed to calculate the angular distributions for the isobaric analogue states (IAS), Gamow-Teller resonances (GTR), dipole ( L = 1, S = 0), spin-dipole ( L = 1, S = 1), and so on, up to L = 7 excitations in the (p, n) reactions at bombarding proton energies E p between 100 and 200 MeV. The results obtained are compared with experimental data and the conclusions concerning both the effective nucleon-nucleon interaction in the chargeexchange channel and the local quasiparticle charge e q [ στ ] with respect to the στ fields are discussed. It occurred that just below the GTR at small angles there is essentially no background from transitions with L > 0. It is shown that the theory describes fairly well the experimental data with the Landau-Migdal spin-isospin strength parameter g ′ = 1.1 ( G ′ = 330 MeV · fm 3 ) and e q [ στ ] = 0.8. The latter characterizes the quenching of the low-energy spin-isospin-flip transitions, i.e. the renormalization of the axial-vector vertices in nuclear matter.

A study of the 14C(6Li, 6He)14N reaction at 93 MeV

Abstract The reaction 14 C( 6 Li, 6 He) 14 N was investigated with 93 MeV 6 Li ions in an angular interval of 7–26°. Angular distributions were analysed for the four most intense groups of 6 He nuclei, corresponding to transitions to the ground (1 1 + ) and the excited (1 2 + , 2 1 − , 4 1 − ) states of 14 N. In the theoretical analysis a mechanism of the spin-isospin excitation was suggested in the DWBA frame with the finite range of interaction and recoil in the light system ( 6 Li 6 He) taken into account. In the calculations both shell-model wave functions and transition densities obtained in the theory of finite Fermi systems (FFS) were used. From the comparison between theory and experiment the Landau-Migdal force constant g ′ is estimated in order to obtain some information on the degree of nuclear proximity to the threshold of pion condensation.