The nuclear structure of the semi-magic isotope Sn-125 was investigated by means of the Sn-124(n(th), gamma gamma)Sn-125 reaction and the Sn-124((d) over right arrow, p)Sn-125 reaction. More than 400 levels, in most cases with their spin, parity, (d, p) spectroscopic factor, and gamma decay, were identified. About 750 gamma transitions from our (n, gamma gamma) experiment form the essentially complete gamma-decay scheme following thermal neutron capture. Using this extensive gamma-decay scheme the neutron binding energy was determined to be 5733.5(2) keV. The strong correlation of the (d, p) strengths and the (n, gamma) intensities for more than 50 levels gives evidence for the direct neutron capture process, which was studied in detail. The experimental data were compared with predictions of the quasiparticle phonon model.

The excitation spectra in the deformed nucleus Th-230 were studied by means of the (p, t) reaction, using the Q3D spectrograph facility at the Munich Tandem accelerator. The angular distributions of tritons are measured for about 200 excitations seen in the triton spectra up to 3.3 MeV. Firm 0(+) assignments are made for 16 excited states by comparison of experimental angular distributions with the calculated ones using the CHUCK code. Additional assignments are possible, with assignments for four states relatively firm and another four tentative. Assignments up to spin 6(+) are made for other states. Sequences of the states are selected that can be treated as rotational bands and as multiplets of excitations. Experimental data are compared with interacting boson model (IBM) and quasiparticle-phonon model (QPM) calculations.

A. I. Levon, G. Graw, Y. Eisermann, R. Hertenberger, N. Yu. Shirikova, A. V. Sushkov, P. G. Thirolf, H.-F. Wirth, N. V. Zamfir Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv Fakultät für Physik, Ludwig-Maximilians-Universität Muüchen, Garching, Germany Joint Institute for Nuclear Research, Dubna, Russia H. Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania Experimental data for the excited states in the deformed nucleus Th studied in the (p, t) reaction are analyzed. Sequences of the states are selected which can be treated as rotational bands and as multiplets of excitations. Experimental data are compared with the interacting boson model (IBM) and the quasiparticle-phonon model (QPM) calculations.

Experimental data for the excited states in the deformed nucleus 230Th studied in the (p, t) reaction are analyzed. Sequences of the states are selected which can be treated as rotational bands and as multiplets of excitations. Experimental data are compared with the interacting boson model (IBM) and the quasiparticle-phonon model (QPM) calculations.

The excitation spectra in the deformed nucleus 230Th were studied by means of the (p, t) reaction, using the Q3D spectrograph facility at the Munich Tandem accelerator. The angular distributions of tritons are measured for about 200 excitations seen in the triton spectra up to 3.3 MeV. Firm 0+ assignments are made for 16 excited states by comparison of experimental angular distributions with the calculated ones using the CHUCK3 code and relatively firm - for 4 states. Assignments up to spin 6+ are made for other states. Analysis of the obtained data will be presented in forthcoming paper.

By means of the (p, t) reaction we studied the excitation spectra of 0+ states in the deformed nuclei 228Th, 230Th, and 232U, using the Q3D magnetic spectrograph facility at the Munich tandem accelerator. At small reaction angles the 0+ transfer angular distributions have steeply rising cross sections which allow identifying these states in otherwise very complicated and dense spectra. For each of these nuclei we resolve typically about ten excited states with safe 0+ assignments. The studied excitation energies range up to 2.5, 2.7, and 2.3 MeV, respectively. The results are compared with IBA calculations in the spdf-boson space. This highly schematic collective model description, including octupole collectivity, but neglecting other relevant degrees of freedom, gives numbers of excited 0+ states in these actinide nuclei that are rather close to the observed ones. Sequences of states are selected which can be treated as rotational bands. Inertial parameters are obtained at fitting energies of these bands and they are discussed in connection with the IBM calculations.

lie fission probability of U-234,U-236 as a function of the excitation energy has been measured with high energy resolution using the U-233,U-235(d, pf) reactions in order to study hyperdeformed (HD) rotational bands. Rotational band structures with a moment of inertia of Theta = 238 +/- 42 h(2)/MeV and Theta = 217 +/- 38 h(2)/MeV have been observed for U-234,U-236, respectively, corresponding to hyperdeformed configurations. From the level density of the rotational bands the excitation energy of the ground state in the third minimum was determined to be E-III = 3.1 +/- 0.4 MeV and E-III = 2.7 +/- 0.4 MeV, for U-234 and for U-236, respectively. The excitation energy of the lowest hyperdeformed transmission resonance and the energy dependence of the fission isomer population probability enabled the determination of the height of the inner fission barrier of U-236 E-A = 5.15 +/- 0.20 MeV and its curvature parameter h omega(A)=1.2 MeV. Using this new method the long-standing uncertainties in determining the height of the inner potential barrier in uranium isotopes could be resolved.

The isotopes in vicinity of the closed shell Z=50, the long chain of odd Te isotopes from Te-119 to Te-131, Sn-125 and Sn-123, have been investigated by means of (d,p), (d(pol),p), (d(pol),t), (3He,alpha) and (n,gamma) reactions. The experimental data were interpreted within the framework of Interacting Boson Fermion Model (IBFM) and Quasiparticle Phonon Model (QPM).

The nuclear structure of 127Te has been investigated with the Te126(n,γγ)Te127 reaction using thermal neutrons and with the Te126(d→,p)Te127 reaction at Ed=20MeV. About 190 levels were identified in a region to 4.1 MeV excitation energy, in most cases including spin, parity and γ-decay. The γ-decay scheme after neutron capture is essentially complete containing about 100% of the population of the 11/2− isomer and of the ground state. The thermal neutron capture cross section and isomer production of the 11/2− state at 88.3 keV were determined to be 0.44(6) b and 0.069(10) b, respectively. The neutron binding energy was determined to be 6287.6(1) keV. A significant number of the (d,p) angular distributions of cross section and asymmetry are anomalous with respect to the distorted-wave Born-approximation calculations and could be accounted for by inelastic multi-step mechanisms. The observed strong correlation of the (d,p) and primary (n,γ) strengths gives evidence for the direct neutron capture process which is mainly responsible for the primary population of 16 levels. The experimental level scheme is compared with predictions of the interacting boson–fermion model and of the quasiparticle phonon model.

The fission probability of U-236 as a function of the excitation energy has been measured with high energy resolution using the U-235(d, pf) reaction in order to study hyperdeformed (HD) rotational bands. Rotational band structures with a moment of inertia of theta = 217 +/- 38 h(2)/MeV have been observed, corresponding to hyperdeformed configurations. From the level density of the rotational bands the excitation energy of the ground state in the third minimum was determined to be 2.7 +/- 0.4 MeV.The excitation energy of the lowest hyperdeformed transmission resonance and the energy dependence of the fission isomer population probability enabled the determination of the height of the inner fission barrier E-A = 5.05 +/- 0.20 MeV and its curvature parameter h omega(A) = 1.2 MeV. Using this new method the long-standing uncertainties in determining the height of the inner potential barrier in uranium isotopes could be resolved. (c) 2005 Elsevier B.V. All rights reserved.

The design of our source of negatively charged, intense and brilliant DC beams of polarized hydrogen and deuterium ions was motivated by the excellent performance of the HERMES atomic beam source and the successful operation of a polarized ion source at TUNL. Deviating from their 30 K atomic beam technology we combine an 80 K atomic beam source (ABS) with subsequent ionization in an electron cyclotron resonance (ECR) plasma. In a separate unit, negative ions are obtained by successive two electron pickup from cesium in a vapour jet target. Our ABS provides a flux of 6.4×1016atoms/s for hydrogen and of about 5×1016atoms/s for deuterium into a compression tube of 10 mm diameter and 100 mm length. Polarized negative D-⇒/H-⇒ ion beams of about 9μA/15μA with an emittance of 20πmmradeV have been observed. After tandem acceleration we have polarized beam intensity of 2μA on target of the Q3D spectrograph. The measured vector polarizations of the D⇒ and H⇒ ion beams are 72% and 67%, respectively, in accordance with expectations from source operation data. Using an external gas inlet for the ECR region, intense beams of unpolarized 1H-, 2D-, 3He-, and 4He- ions are obtained.

High energy resolution studies of Cd-113 have been performed with the (d, p) and (d, I) reactions, using polarized beams. In both reactions, a large number of levels (about 80) have been observed up to 2.6 MeV excitation energy, for many of them unambiguous spin and parity assignment being made. Together with previous data from other experiments, the level scheme has probably become essentially complete up to this energy. A detailed comparison is made between the experimental levels and calculations performed with the interacting boson-fermion model-1 (IBFM-1) and with the quasiparticle phonon model (QPM), which allows a good understanding of the level scheme up to about 2 MeV excitation. This nucleus is a special case for the QPM, where due to a strong anharmonicity rather complex configurations must be taken into account in order to get a good description even at low excitation energies. The multiplet structures arising from the coupling of the 3s(1/2), 2d(3/2), 2d(5/2), and 1g(7/2) neutron orbitals to the quadrupole one-phonon excitation of the core nucleus Cd-112 have been assigned, and the possible identification of 1/2(+) and 3/2(+) "intruder" states (based on two particle-two hole excitations of the core) is discussed. The observation of many l = 1 transitions above 2 MeV excitation gives a clue to the way by which the 11/2(-) isomeric state can be populated in the (n, gamma) and (gamma, gamma) reactions.

The level structure of 185W has been studied using the prompt and delayed gamma–gamma coincidences from thermal neutron capture in 184W accompanied with the one-nucleon transfer reactions (d,p) and (d,t) with polarized beams. From these data and those of previous studies a total of 183 levels has been established for energies below 3 MeV. Many of these states have been grouped into rotational bands built on 28 intrinsic states of quasiparticle and quasiparticle-plus-phonon character. Although the DWBA analysis permitted definite spin–parity assignments for most of states a large number of particle transitions have ‘anomalous’ angular and asymmetry shapes with respect to the DWBA which indicate an influence of strong mixing between particle and hole states. The extra exchange of phonons and the significance of configurational ΔN=±2 mixing across the Fermi surface lead to a fine structure in the fragmentation of most single-particle strengths and at the same time has the effect of breakdown of the individual properties of Nilsson states. The accumulated l=1 (d,p) sum is about a factor two smaller than the equivalent (d,t) strength. Thus, the previously observed loss of the (d,p) strength in the W nuclei with A=184,185 is presumably because of their redistribution amongst particle- and hole-type states. The observed states below 2 MeV are compared with predictions of the quasiparticle–phonon nuclear model.

The nuclear structure of Te-127 has been investigated with the Te-126(n, gamma gamma) 127Te reaction using thermal neutrons and with the Te-126((d) over bar, p) Te-127 reaction at E-d = 20 MeV. About 190 levels were identified in a region to 4.1 MeV excitation energy, in most cases including spin, parity and gamma-decay. The gamma-decay scheme after neutron capture is essentially complete containing about 100% of the population of the 11/2(-) isomer and of the ground state. The thermal neutron capture cross section and isomer production of the 11/2(-) state at 88.3 keV were determined to be 0.44(6) b and 0.069(10) b, respectively. The neutron binding energy was determined to be 6287.6(1) keV A significant number of the (d, p) angular distributions of cross section and asymmetry are anomalous with respect to the distorted-wave Born-approximation calculations and could be accounted for by inelastic multi-step mechanisms. The observed strong correlation of the (d, p) and primary (n, gamma) strengths gives evidence for the direct neutron capture process which is mainly responsible for the primary population of 16 levels. The experimental level scheme is compared with predictions of the interacting boson-fermion model and of the quasiparticle phonon model. (c) 2005 Elsevier B.V. All rights reserved.

By means of the (p,t) reaction we study the excitation spectra of 0(+) states in the deformed nuclei Th-228, Th-230, and U-232, using the Q3D magnetic spectrograph facility at the Munich tandem accelerator. At small reaction angles the 0(+) transfer angular distributions have steeply rising cross sections which allow us to identify these states in otherwise very complicated and dense spectra. For each of these nuclei we resolve typically about ten excited states with safe 0(+) assignments. The studied excitation energies range up to 2.5, 2.7, and 2.3 MeV, respectively, and the summed transfer strengths add to more than 60% of the ground state strength. As in a recent study of Gd-158 we compare with interacting boson approximation (IBA) calculations in the spdf boson space. This highly schematic collective model description, including octupole collectivity, but neglecting other relevant degrees of freedom, gives numbers of excited 0(+) states in these actinide nuclei that are rather close to the observed ones.

The well deformed atomic nucleus Gd-159 was investigated by means of radiative neutron capture and single neutron transfer reactions. Nearly 70 secondary gamma rays from the (n,gamma) reaction studied with high-resultion bent-crystal spectrometers at Grenoble are assigned to Gd-159. About 200 levels with spin up to 11/2 are observed in this nucleus below 2.3 MeV in (d,p) and (d,t) reactions investigated at the Tandem Van de Graaff accelerator in Garching using unpolarized (18 MeV) and polarized (22 MeV) deuteron beams, respectively. The proposed level scheme for this nucleus is arranged into 21 rotational bands. Experimentally observed levels are interpreted using predictions obtained within the quasiparticle-phonon model and the quasiparticle-rotor approach for a well deformed nucleus.

By means of the (p,t) reaction the excitation spectra of 0(+) states in Gd-158 [(1)], Th-228, Th-230, and U-232 have been studied using the Q3D magnetic spectrograph facility at the Munich tandem accelerator. The 0(+) transfer angular distributions have very large cross sections at very small reaction angles, a feature that allows to identify these states in otherwise very complicated and dense spectra. We resolved for each of these nuclei typically 12 excited states with safe 0(+) assignments. The studied excitation energy range is up to 3.1, 2.5, 2.5, and 2.1 MeV, resp. As for Gd-158 [(2)], we compare the data with spdf-IBA calculations. The parameters are chosen to reproduce the low lying spectra of these axially symmetric, statically deformed nuclei, especially the bands of negative parity. For the energy ranges considered, the IBA predicts five excited 0(+) states of pure sd (quadrupolar) bosonic structure for all these nuclei, but three, six, seven, and four excited 0(+) states resp., which have two bosons in the pf boson space. They are related to - or represent octupole two phonon excitations. The collective model descriptions provide nearly quantitatively the number of the observed excited 0(+) states in these actinide nuclei.

To provide information for comparison with predictions from a dynamical supersymmetry, the odd-odd nucleus Au-196 was studied via transfer reactions. With a polarized deuteron beam we measured ((d) over right arrow ,t) and ((d) over right arrow,alpha), and with unpolarized beams we measured (p,d), (He-3,d), and (alpha,d) transfer reactions. From the high-resolution Au-197(p,d) Au-196 spectrum, a rather complete set of excitation energies was obtained. Quantum numbers and spectroscopic factors were obtained from angular distributions of single-neutron transfer in Au-197((d) over right arrow ,t) Au-196, single-proton transfer in Pt-195(He-3,d) Au-196, and two-nucleon transfer Hg-198((d) over right arrow, alpha) Au-196. We obtain firm J(pi) assignments for 21 out of the 27 states with negative parity observed up to 490 keV excitation energy, by combining our data with that taken using gammagamma and conversion electron spectroscopy. The number of states and the firm or restricted assignments are in agreement with the predictions from the dynamical U-nu(6/12)circle times U-pi(6/4) supersymmetric scheme. Including our (alpha, d) data, we can deduce spectroscopic factors for four different transfer channels. When model predictions of spectroscopic factors become available, these data will provide a further critical test as to what extent this symmetry is realized in nature.

The well deformed atomic nucleus $^{159}\mathrm{Gd}$ was investigated by means of radiative neutron capture and single neutron transfer reactions. Nearly 70 secondary $\ensuremath{\gamma}$ rays from the $(n,\ensuremath{\gamma})$ reaction studied with high-resultion bent-crystal spectrometers at Grenoble are assigned to $^{159}\mathrm{Gd}$. About 200 levels with spin up to $\frac{11}{2}$ are observed in this nucleus below $2.3\phantom{\rule{0.3em}{0ex}}\mathrm{MeV}$ in $(d,p)$ and $(\mathbf{d},t)$ reactions investigated at the Tandem Van de Graaff accelerator in Garching using unpolarized $(18\phantom{\rule{0.3em}{0ex}}\mathrm{MeV})$ and polarized $(22\phantom{\rule{0.3em}{0ex}}\mathrm{MeV})$ deuteron beams, respectively. The proposed level scheme for this nucleus is arranged into 21 rotational bands. Experimentally observed levels are interpreted using predictions obtained within the quasiparticle-phonon model and the quasiparticle-rotor approach for a well deformed nucleus.