Search

Relativistic Dirac coupled channel analyses are performed phenomenologically using an optical potential model for the intermediate energy proton inelastic scatterings from nickel isotopes, 58Ni and 60Ni. The first-order rotational collective model is used for the transition optical potentials to describe the low-lying excited collective states of the ground state rotational band. The complicated Dirac coupled channel equations are solved phenomenologically by varying the optical potential and the deformation parameters to reproduce the experimental data, using a computer program that uses a sequential iteration method. The channel-coupling effects of the multistep transition process for the excited states of the ground state rotational band are found to be strong and lead the calculation results to better agreement with the experimental data when the channel coupling between the excited states is added in the calculation. The Dirac equations are reduced to the second-order differential equations to obtain the Schrödinger equivalent effective central and spin–orbit optical potentials, and the obtained effective potentials are analyzed.

The rotational part of the phenomenological collective model of Bohr and Mottelson and others is derived microscopically, starting with the Schrödinger equation written in projection form and introducing a new set of "relative Euler angles." In order to derive the local Schrödinger equation of the collective model, it is assumed that the intrinsic wave functions give strong peaking properties to the overlapping kernels.

The neutron yield from photo-reactions in nine elements has been measured as a function of the maximum energy of the University of Saskatchewan Betatron. Cross sections are given for each of the reactions as calculated from these data. The integrated cross sections are compared with theoretical sum-rule predictions of Levinger and Bethe and good agreement is obtained with x = ½. The data support the conclusions reached in a preceding paper by Montalbetti, Katz, and Goldemberg. The competition between (γ, n) and (γ, p) reactions in chromium and in nickel is analyzed in the light of these experimental results. Good agreement with statistical theory is obtained in both cases.

Photoneutron energy spectra from 40Ar have been measured at bremsstrahlung end-point energies from 13 to 23 MeV in 1 MeV steps. The differential cross section at 90° for the reaction 40Ar(γ, n0)39Ar revealed some 26 previously unreported excited states of 40Ar in the region below 13 MeV. The envelope of these states suggests a single particle resonance involving the valence 1f7/2 neutrons. The measured total neutron cross section exhibits a marked change from this single particle behavior at about 14 MeV where collective effects begin to dominate and neutrons are emitted to highly excited states of 39Ar.

Lifetimes of energy levels in 25Mg have been measured using the Doppler-shift attenuation method. The levels were exicted by the 25Mg(p, p′γ) reaction with incident proton energies between 3.8 and 7.0 MeV. The gamma rays were detected in a three-crystal spectrometer consisting of a 40 cm3 Ge(Li) detector surrounded by a large NaI(Tl) crystal in the form of a split annulus. Mean lifetimes found, given in fs, are: τ(1611-keV level) = [Formula: see text], τ(1962) = [Formula: see text], τ(2565) = 59 ± 26, τ(2736) = 288 ± 20, τ(2803) = 27 ± 6, τ(3399) = 33 ± 19, τ(3408) < 20, τ(3903) < 20, τ(3969) = 24 ± 11, τ(4055) = 53 ± 10, and τ(5005) < 26. The decay modes and branching ratios of levels up to 4055-keV excitation are given. The results are compared with the mirror nucleus 25Al and discussed in terms of the collective model.

Calculations based on the collective model with intermediate coupling between the surface oscillations of the even–even core 54Fe and 29th neutron have been carried out. Level energies, spectroscopic factors, and electromagnetic properties are obtained in good agreement with experiment.

Rotational energy levels of axially asymmetric nuclei have been calculated in the manner of Davydov and Filippov, and a comparison with experiment shows good quantitative agreement. It is suggested that agreement may be improved by introducing the Bohr–Mottelson vibration–rotation interaction and a centrifugal stretching correction analogous to the type used in molecular spectra. The D–F method seems to be particularly useful for nuclei in the transition regions between "rotational" and "near-harmonic" modes of collective excitation.

It is shown that the 5/2+ spins of the ground states in 25Al and 25Mg are evidence for hexadecapole contributions to the Nilsson model for the self-consistent field.