S. Hayashibe

1 g/sub 9/2/ neutron state in nuclei with neutron numbers between 52 and 82

Spectra of deuterons from (p d) reactions on 18 nuclei with neu tron numbers N between 52 and 82 were measured at an angle of 20 deg with 52-MeV incident protons. In each spectrum a broad bump with the distinct top is observed at excitation energies of several MeV or higher. From the systematic behavior of the bump it is inferred that the top of the bump stands for an approximate position of the 1g/sub 9/2/ neutron state, and energies of this state are estimated from the observed spectra. The estimated energies are compared with calculated ones and a reasonable agreement is obtained. The systematics of the enengy diffurence between the top of the bump and the ground state in the residual nucleus is discussed on the basis of the simple pairing theory, and results which are well consisient with the above interference about the top of the bump are obtained. (auth)

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.

A new EMIS facility at the Tohoku University cyclotron

Abstract An EMIS facility has begun operation at one of the beam lines of a multipurpose cyclotron of K = 50 MeV. The separator is of a Scandinavian type of 55° deflection and 1500 mm dispersion, and is equipped with three beam-transport lines to which are connected a tape-transport system for ISOL study, a retardation system for implantation work and an optical spectrometer for surface analysis. The status and developments of this facility are reported here for the first time.

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.

A Study of the Decay Scheme of Eu146

The level scheme of Sm 146 fed from (4.59±0.03)-days Eu 146 has been investigated with scintillation spectrometers, beta-ray spectrometers, gamma-gamma and Ke - -gamma coincidences, and directional correlation techniques. From the measurements of internal conversion electrons, several new transitions were found in addition to those reported by the previous workers. Levels in Sm 146 were established at the following energies: 750 (2 + ), 1387, 2056, 2287, 2448 and 2686 keV, and also 1654 and 1820 keV. Besides these, about 10 levels were postulated on the basis of energy, intensity and coincidence considerations. From analysis of the positrons and from the fact of absence of crossover transition to the ground state, the spin-parity of the second-excited level at 1387 keV was expected to be 4 + . This assignment, however, was not consistent with the results of the directional correlation measurement for the de-excitation gamma-ray cascade and the K -conversion coefficient for the transition proceeding from t...

A precision measurement of the hyperfine structure of87Sr

The ground state hyperfine splitting of87Sr+ was measured with a precision of 1×10−8. The experiments were performed with an RF ion trap connected to an ISOL (isotope separator on-line), where all the possible transitions between Zeeman sublevels were observed by a laser-microwave double resonance method. The magnetic dipole hyperfine constant was determined to beA=−1 000 473.673 (11) kHz.

Level Structure of Nd144

The energies and spins of lower excited levels in Nd 144 have been established by studies of the beta decay of Ce 144 –Pr 144 and the electron capture decay of Pm 144 . The experiments include the energy and relative intensity measurements, and directional correlation measurements of gamma rays by several NaI (T1) scintillation counters. The level of Nd 144 is populated at the 695 keV and 2190 keV from decay of Pr 144 , and the 695 keV, 1310 keV, and 1780 keV from the decay of Pm 144 . The levels at the 1220 keV and the 1560 keV which have been found by the neutron capture gamma ray measurements could not be found in both decay in the limit of about one percent.

Nuclear laser spectroscopy using a laser-microwave double-resonance method with an ion trap

With an RF-trap connected to an Isotope Separator On-Line (ISOL), we aim to study nuclear magnetic properties of nuclei far from stability through the hyperfine interaction by a laser-microwave double-resonance method. As a first step, the hyperfine splitting of the ground state of87Sr+ was measured, and the magnetic dipole hyperfine constant was precisely determined to beA=−1,000,470.8(2.4) kHz.

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.