N. Kawamura

Some evidence for neutron pick-up from the interior core through the (p, d) reaction

Abstract The (p, d) reactions on 94, 98, 100 Mo were studied with 52 MeV protons. Deuteron spectra were measured up to 12 MeV of excitation in the residual nuclei. The angular distributions for the three reactions integrated over the final levels in a range of excitation from 2 to 6 MeV are in good agreement with each other, though the relevant parts of the deuteron spectra apparently show isotope-dependent structures. From a comparison of the results obtained in this study with those from the (p, d) reactions on neutron closed-shell nuclei 90 Zr and 92 Mo, it is indicated that the (p, d) transitions to the levels in this particular range of excitation in 93, 97, 99 Mo are mainly due to neutron pick-up from the N = 29–50 major shell and that the transition strengths integrated over these transitions are in fair agreement with the sum-rule limit. A comparison is also made between the results obtained in this study and those from the (p, d) reactions on 117, 118 Sn, from which it is suggested that the broad peaks found in the deuteron spectra from the latter two reactions at excitation energies between 7–12 MeV in 116 Sn and 5–10 MeV in 117 Sn are mainly due to neutron pick-up from the N = 29–50 shell. Again, the transition strengths for the broad peaks are estimated to be in fair agreement with the sum-rule limit.

In-beam study of the level crossing resonance on the 4 μs 2 9+ isomer of69Ge in a Zn single crystal

The time-integral angular distribution was measured as a function of an external magnetic field for γ-rays from the 398 keV29+ state of69Ge populated by bombarding a Zn single crystal with a natural α-beam from a cyclotron. Clear resonances of dispersion as well as Lorentz type having a narrow width consistent with the natural width (τ=4 μs) were observed at Bres=9.15 kG corresponding to the first level-crossing resonance of the29+ state due to the combined collinear magnetic and quadrupole interactions. The effects of noncollinearity were also demonstrated and compared with theory. As an application of this resonance method, the temperature dependence of the quadrupole interaction frequency was measured.

Photoprotons in Giant Resonance Region for 31P

S>The energy spectra of photoprotons were measured for /sup 31/P with the electrodisintegration at 90 deg . The differential cross sections of the ( gamma ,p/sub 0/) and the ( gamma ,p/sub 1/) reactions are derived from them. Many fine structures are found in the results. The most of the structures found in the spectra can be explained by the ( gamma ,p/sub 0/) component. The result of the ( gamma ,p/sub 0/)~ cross section is compared with the /sup 32/S( gamma ,p /sub 0/)/sup 31/P cross section. Both the results agree well with each other in the gross structures, but the absolute value of the /sup 31/P( gamma ,p/sub 0/)/ sup 30/S i differential cross section is much smaller than that of the /sup 32/S( gamma ,p/sub 0/)/su p 31/ P reaction. The ( gamma ,p/sub 1/) differential cross section seems to show some gross structures though the errors of the result are rather large. Discussions are made with a single particle excitation process of the valence nucleon. (auth)

A systematic study of the (p, d) strength for transitions to deeply bound hole states

Abstract The (p, d) reactions on 95, 98Mo, 112, 116Cd, 115In, 124Sn, 130Te and 141Pr have been studied with 52 MeV protons. In each deuteron spectrum, a giant-resonance-like gross structure was observed at excitation energies where those deuterons are expected to appear which result from direct neutron pickup from the outermost inner shell in these nuclei, consisting of the 1 g 9 2 , 2 p 1 2 , 2 p 3 2 and 1 f 5 2 subshells. A DWBA analysis of the angular distribution of the gross structure suggests that the structure contains a substantial part of the whole strength or shell-model limit of the outermost inner shell and no significant contribution of processes other than the direct neutron pickup.

In-beam spectroscopic study of 107In

Abstract The nuclear level structure of 107In has been studied with the 106Cd(α, p2n)107In and 106Cd(3He, pn)107In reactions. In addition to the ordinary in-beam measurements of γ-rays and conversion electrons, p-γ coincidence measurements were performed in order to identify the γ-transitions in 107In. The experimental data of positive parity states are compared with predictions of a hole-phonon coupling model, in which a g 9 2 proton hole couples to the quadrupole core vibration. This simple model appears to be inadequate to describe the observed level properties of 107In.

Nuclear level-crossing resonance of the 398-keV 9/2+ state of69Ge in a Zn single crystal

The time-integral angular distribution was measured as a function of an external magnetic field for γ-rays from the 398-keV 9/2 state of69Ge populated by bombarding a Zn single crystal with a natural α-beam from a cyclotron. Clear resonances of dispersion as well as Lorentz types having a natural width (τ=4 μs) were observed at Bres=9.14 kG corresponding to the first level-crossing resonance of the 9/2 state due to the combined collinear magnetic and electric interactions. The effects of non-collinearity were also demonstrated, and compared with theory.

An active magnetic channels system for in-beam study of hyperfine interactions

An active magnetic channels system has been constructed, in which the beam deflection is compensated by a pair of electromagnets close to the main magnet together with a steering magnet upstream. The residual beam deflection on the target is estimated to be ¦Δφ¦≤0.6°.

Magnetic moment of the 2140.2 keV 5− state in136Ba

We have determined theg-factor of the 2140.2 keV 5− state of136Ba using the timeintegral perturbed angular correlation (IPAC) method at an external magnetic field of 17.0 kG;g=−0.38±0.04. The half-lives of the 2140.2 keV 5− and 2207.1 keV 6+ states were redetermined to be 1.5±0.1 ns and 3.1±0.1 ns, respectively. The radioactive source of136Cs was prepared by the138Ba(γ, pn) reaction.

Nuclear g-factor of the 172+ isomeric state in 63Cu

Abstract The nuclear g-factor of the 4498 keV 17 2 + isomeric state in 63Cu was measured with the in-bearn perturbed angular distribution method, through the 62Ni(α, p2nγ)63Cu reaction, to be gexp = 0.184 ± 0.012. This value is in good agreement with a semiempirical g-factor for the three-quasiparticle configuration [π2p 3 2 (v1f 5 2 , 1g 9 2 )7] 17 2 + calculated using the experimental single-particle g-factors of neighbouring nuclei. At the same time the internal magnetic field at the Cu nuclei in Ni metal was obtained to be Bint = −46.6 ± 1.3 kG.

Characteristics of an ionization chamber using tetramethylgermanium

Abstract The material compatibility and the radiation resistivity of liquid tetramethylgermanium have been examined by monitoring the ionization yield and the electron lifetime in a pulse ionization chamber. There is no deterioration of the liquid quality with hardened lead during one year. Irradiation with 1000 Gy of γ-rays causes some deterioration of the liquid. The electron lifetime for the damage liquid was almost restored to its initial value by repeating the purification several times.