V. G. Neudatchin

Form factors for various degrees of freedom in the 6Li nucleus

Abstract In the cluster model for the 6 Li nuclei we have calculated the form factors C0, C2, M1 (elastic and inelastic) and the form factors for the α-d and 3 He-t degrees of freedom which have been measured in experiments on the quasi-deuteron absorption of pions and on the quasi-elastic knock-out of 3 He or t. Various effective numbers of nucleon clusters were also calculated. The calculations are based on the antisymmetrized total wave functions ψ in which the wave function of the relative motion of clusters φ ( R ) has a shell-model node. The cluster model has proved to be a good tool for describing

A microscopically substantiated local optical potential for α-α- scattering

Abstract A deep l -independent local potential of the Woods-Saxon form for the description of the energy dependence of all α - α phase shifts measured is proposed. Wave functions in the α - α overlap region have the oscillator from 4S, 4D etc. The range of the S-phase shift variation equals 3 π . Application of the approach proposed to the 16 O - 16 O and NN-systems is discussed.

Microscopically substantiated local optical potentials for scattering of light nuclei

Abstract A potential approach to the scattering of light nuclei is analysed in detail. It is shown that the deep optical potentials we introduced earlier, for the scattering of light clusters, are essentially phase-equivalent local potentials for the tedious exchange kernels of the resonating-group method and lead, practically, to the same wave functions. We demonstrate that these deep potentials involve the shell-model states of a system, forbidden by the Pauli principle, as their own bound states. Requirements for optical potentials and for optical wave functions of light nuclei following from the properties of these forbidden states have been formulated. The supermultiplet and even-odd l-splitting of optical potentials is investigated. The concrete systems α-α, α-t, t-3He and α-d (optical potentials, etc.) are investigated. We also briefly discuss the optical potentials for the scattering of heavy ions such as16O-16O and the relationship between our deep optical potentials and the commonly used shallow phenomenological potentials containing the repulsive core.

The giant dipole resonance in light nuclei and related phenomena

The present-day status of the giant dipole resonance (GDR) in light nuclei is discussed with main emphasis on the supermultiplet and configurational splitting of GDR, which are its most important features. A great wealth of experimental data, which confirm the existence of the above phenomenon are presented. Consideration is also given to the related problems, such as radiative pion capture and muon capture, spin-isospin dipole excitations, the role of the supermultiplet structure of nuclear levels in the formation of hypernuclear states in processes of the coherent substitution of hyperons for nucleons.

On magnetic colour attraction in the NN system

Abstract Magnetic colour NN attraction arises if the nodeless NN wave function φ(RNN) is substituted by a function with one node. The latter corresponds to the quark configuration (1 s ) 4 (1 p ) 2 , [ƒ] X = [42], [ƒ] CS = [42] with the predominance of symmetric qq pairs in the CS space. As a result, the increased kinetic energy is roughly compensated and the quark configurations (1s)6 and (1s)4(1p)2(become approximately degenerate.

The 12C nucleus as a 3α system with forbidden states

Abstract We have calculated the 0 1 + ground state and the 0 2 + and 0 3 + first excited states of 12 C in the model of three α-particles whose interaction is described using a local attractive potential with forbidden states, which well reproduces the α-α scattering phases. The methods of projection of the states forbidden by the Pauli exclusion principle in a system of three composite particles are discussed. The results of the calculation show that the condition of orthogonality to the forbidden states is sufficient to prevent the system from collapse. The binding energy value obtained (15.06 MeV) is somewhat overestimated. This discrepancy seems to come from neglecting triple exchanges of nucleons of different α-particles and from the fact that the 12 C real nucleus differs from the 3α system.

SEPARABLE APPROACH TO THE MUTUAL SCATTERING OF CLUSTERS.

Abstract A new class of one-term separable potentials for cluster-cluster (d, t, α) scattering is proposed. The analytical form of the potential form factors for the proposed potentials is obtained directly from the cluster representation of the shell-model wave functions with the corresponding shell-model parameters, and thus a single analytical expression is taken for all (essential) partial waves for the given pair of nuclei. In particular, the S-, D- and G-scattering phases in the 4 He- 4 He system and the S-phase for 4 He-d scattering have been investigated. A quite adequate description of the phase shifts and radial wave functions in the continuum is obtained. This is due to the fact that in the systems concerned only one (quasi)-stationary state predominates in a given scattering channel. A very simple general relation connecting the positions of the zeros of the phase shifts and the zeros of the oscillator Laguerre polynomials in the momentum representation valid for different partial waves and different cluster pairs is given. Application of the proposed potentials to other two- and three-cluster systems is discussed.

The high energy limit for the α-d and τ-t form factors in the 6Li nucleus and the problem of experimental investigation of the nodes of the corresponding wave functions

Abstract The cluster model form factors α-d and τ-t of the 6Li nucleus have been calculated in analytical form. The optical potential description of the corresponding scattering phases is given. The Young scheme [42] involves only even τ-t phases and the Young scheme [33] only odd ones.

Generalized conception of fractional parentage and the (α-d) - (3He-t) duality in the 6Li nucleaus

Abstract The fractional parentage concept is generalized for the case of the nucleon cluster model. In terms of this, model calculations are made for the 6 Li nucleus of the wave functions of mutual cluster motion α-d and 3 He-t. Fourier-images of which are measured in the quasielastic knock-out reactions. Also obtained are the reduced widths θ 2 in the channels α-d and 3 He-t. The 3 He-t channel is only slightly depressed. θ t 2 ≈ 0.5 . The wave function of ( 3 He-t) is appreciably more localized than the function (α-d), which is reflected in the form factors.

A nonrelativistic potential model with forbidden states for the nucleon-nucleon interaction at small distances

Abstract The potential considered being as effective as the L -dependent Reid potential in the region E lab MeV , gives a new unified description of phase shifts at higher energies and eliminates the disagreement with experiment of M1 electronic from factor for a deutron. The procedure of exclusion of forbidden states in the three-body problem is breifly outlined.