Munetake Ichimura

The magnetic moments of nuclei with a closed shell plus or minus one nucleon

Abstract The deviations of the observed values of the magnetic moments from the Schmidt values are considered for nuclei with a doubly closed shell plus or minus one nucleon in L-S coupling. To explain the origin of these deviations, we estimate the contributions from the configuration mixing by the second-order perturbation and those of the meson exchange current. The results are given in the form of a renormalization factor for the gyromagnetic ratios. The calculated deviations for 15N and 17O are in the correct direction but too large; that for 41Ca is consistent with experiment.

Study of Deuteron Stripping Reaction by Coupled Channel Theory. II Properties of Interaction Kernel and Method of Numerical Solution

The purpose of the present series of papers is to study the deuteron stripping reaction in terms of the method of coupled channels in order to investigate the theoretical back ground of distorted wave Born approximation (DWBA) for the nuclear rearrangement collision which has been studied only inadequately compared with the nuclear inelastic scattering, in contrast to the great success of DWBA in the actual analysis of the experiment.

Effects of channel non-orthogonality in (d, p) reactions

Abstract Coupled channel calculations for (d, p) reactions were performed in which a strong coupling between the d and p channels was assumed. Reactions investigated were 16O(d, p) 17O(2s) and 40Ca(d, p) 41Ca(2p) at Ed =10.5 MeV and the related (d, d) and (p, p) scattering processes. The nonorthogonality of the d- and p-channels were taken into account. The results of these calculations are presented and are compared with the coupled channel calculations neglecting the channel nonorthogonality and also compared with the DWBA and optical model calculations.

Exact Treatment of a Charge Independent Pairing Interaction in a Degenerate Model

A charge independent pairing interaction in j-j coupling scheme and a charge-spin independent pairing interaction in L-S coupling scheme are exactly solved in a degenerate model by the aid of group theory. Groups used here are independent of the number of states concerned unlike the usual shell model technique. Our method is deeply connected with the generalized Bogoliubov transformation and it is conjectured that this transformation combined with projection into the definite number and the isospin (symmetry) state is very useful for the treatment of pair-interacting many body system. The classification of states through the group used here are equivalent to the seniority scheme generalized for unlike particles and degenerate levels. Our method simplifies mathematics somewhat and derives easily some new properties of seniority scheme for unlike particles.

Two-Step Contribution to Intermediate Energy (p, p ) and (p, n) Reactions

We calculate the two-step contribution to (p, p � ) and( p, n) reactions at intermediate energy. We describe the motion of the incident nucleon with a plane wave and compare the contribution from two-step processes with that from one-step processes. To describe the two-step processes, we extendthe response functions to nond iagonal forms with respect to the momentum transfer q. We performeda numerical calculation for the cross sections of the 12 C, 40 Ca(p, p � ) scattering andthe spin longitud inal andspin transverse cross sections of the 12 C, 40 Ca(p, n) reactions at 346 MeV and494 MeV. We foundthat the two-step contribution is appreciable in comparison with the one-step processes in the higher-energy transfer region for the spin longitudinal and the spin transverse (p, n) reactions. We also foundthat the two-step processes give larger contributions to the spin transverse (p, n) reaction than to the spin longitudinal reaction. This finding is very encouraging to interpret the discrepancy between the DWIA calculation andthe experimental results of the spin longitud inal andthe spin transverse cross sections.

Nonuniqueness of the current operators and gauge invariance

Abstract For a point-like Dirac particle we describe a class of time-dependent unitary transformations which bring about an explicitly gauge invariant one-body current operator. We do not resort to the 1/ m expansion scheme but retain all orders in 1/ m . We exploit the nonuniqueness (unitary equivalence) inherent to the time-dependent unitary transformation method, and investigate its consequences on the nuclear electromagnetic interactions. We show that the nonuniqueness of the one-body current should influence the exchange current up to the quantity which is expressed in terms of the commutator of the nuclear interaction hamiltonian with the generator of the unitary transformation. We apply the result to the electromagnetic interaction of a nucleon in a relativistic mean field.

A numerical study of the validity of DWBA for (d, p) reactions

Abstract The S -matrix of (d, p)-reactions was calculated by (a) Coulobm wave Born approximation (CWBA), (b) DWBA and (c) coupled channels method (CC): The angular momentum space can be divided into three regions according as (I) CWBA = DWBA = CC, (II) CWBA ≠ DWBA = CC and (III) CWBA ≠ DWBA ≠ CC.

CROSS SECTIONS AND COMPLETE POLARIZATION TRANSFER MEASUREMENTS FOR THE 2H(P, N)PP REACTION AT 346 MEV

Abstract Cross sections and complete polarization transfer coefficients D ij for the charge-exchange 2 H ( p , n )pp reaction have been measured at E p = 346 MeV and θ lab = 0° – 22°. In the forward angles the prominent narrow peak due to the strong 1 S 0 final state interaction (FSI) between the two residual protons is observed while at the large angles the broad bump due to the quasi-free scattering (QFS) becomes prominent. Characteristic features of FSI and QFS are well described by the simple plane-wave impulse approximation (PWIA) calculations.

Spin-isospin response functions in quasi-elastic region☆

Abstract We calculate the isovector spin-longitudinal and -transverse response functions R L and R T in the quasi-elastic region by means of a continuum RPA with the Δ-hole configurations. We treat the Landau-Migdal parameters g ′ NN , g ′ NΔ and g ′ ΔΔ independently. Effects of Δ and dependence on g ′s are studied. The spin-transverse structure function S T obtained by ( e , e ′) is compared with the results by various effective interactions. The cross sections as well as spin observables of ( p , n ) are calculated by DWIA. Distortion reduces the ratio R L / R T , though RPA makes it too large. Free response functions with distortion reproduce the observed ratio reasonably well.

A semiclassical approximation for massive transfer

Abstract A semiclassical approximation for the transition matrix for transfer reactions between heavy ions is developed from the distorted-wave Born approximation by means of the three-dimensional WKB approximation. It is designed to be applicable to massive transfer without adopting various assumptions and approximations of previous semiclassical approaches which are reasonable only for few-nucleon transfer. The final expression obtained is of a simple closed form similar to that of the Brink model. It gives a way of seeing the validity of the idea of Brink in massive transfer. Numerical study of illustrative examples indicates promising applicability of the present method to massive transfer.