High spin states in 210Pb

High spin states in nuclei in the ²⁰⁸Pb region were populated in deep inelastic collisions of ¹³⁶Xe and ²⁰⁸Pb projectiles with thick ²⁰⁸Pb targets at about 50 MeV above the Coulomb barrier. Prompt and prompt-delayed γ-ray coincidences were measured. Four new states above the 8⁺ isomer in ²¹⁰Pb were found and spins and parities assigned from theoretical expectations. The results are discussed in the frame of shell model theory.     

Spectrum of the high spin neutron hole states of205Pb

The high resolution (³He,α) reaction on²⁰⁶Pb shows the distribution of the 2f _7/2, 1h _9/2 and 1i _{1 3/2} neutron states of²⁰⁵Pb within the 6 MeV excitation energy of²⁰⁵Pb. The spectrum of these three-hole states is obtained within the hole-core vibrational coupling scheme. The shell model energies of the neutron hole states arising from the core-polarization effect are compared with the Bansal-French energy weighted sum rule. The possible implication of the present neutron hole energies has been discussed in the light of the deduced shell model wave functions of the collective states of²⁰⁶Pb.     

High spin states in the doubly-closed shell nucleus146Gd

High spin states of¹⁴⁶Gd, populated in heavyion induced reactions, have been investigated by means of in-beamγ-ray spectroscopy using the Compton-suppressed germanium detector arrays OSIRIS and ESSA30. 35 new levels and 47 new transitions could be placed in the level scheme. In addition to the extension to very high spins, a new cascade has been observed at intermediate spins.     

High spin shell model excitations in149Gd

The high spin level structure of the three-neutron nucleus¹⁴⁹Gd has been investigated by in-beamγ-ray and electron spectroscopy with (α, xn) reactions. The observed levels are characterized as members of the shell model multipletsνf ₇ ^2/3 ,νh _9/2 f ₇ ^2/2 ,νf ₇ ^2/3 ×3^?,νh _9/2 f ₇ ^2/2 ×3^?, and tentativelyνf ₇ ^2/3 ×(3^?)². The energies of theν f ₇ ^2/3 states agree only moderately with those calculated using empirical two-nucleon interactions taken from¹⁴⁸Gd, which indicates the importance of long range contributions already atN=85.     

Calculation of nuclear structure of205Pb relevant for the205Tl bdsolar neutrino detector

Energy spectrum and electromagnetic properties of²⁰⁵Pb have been studied in the cluster-vibration model (CVM). The lifetime of 0.3 ms was predicted for the 2.3 keV level which is of significance for considerations of the²⁰⁵Tl solar neutrino detector.     

Atomic masses above146Gd derived from a shell model analysis of high spin states

From a shell model analysis of high-spin states in neutron deficient nuclei above¹⁴⁶Gd we have derived the ground state masses of theN=82 and 83 isotones of Eu, Tb, Dy, Ho, and Er. The results can be used to calculate the energies of aligned multiparticle yrast configurations. They also link ten α-decay chains to the nuclei with known masses, providing many new absolute mass values which are compared with predictions. An examination of the two-proton separation energies atN=82 shows an 0.5 MeV break in the nuclear mass surface atZ=64.     

Spin projection in the shell model monte carlo method and the spin distribution of nuclear level densities

We introduce spin projection methods in the shell model Monte Carlo approach and apply them to calculate the spin distribution of level densities for iron-region nuclei using the complete (pf + g9/2) shell. We compare the calculated distributions with the spin-cutoff model and extract an energy-dependent moment of inertia. For even-even nuclei and at low excitation energies, we observe a significant suppression of the moment of inertia and odd-even staggering in the spin dependence of level densities.     

Off shell states in the dual model

We present a class of Lorentz invariant, gauge invariant off-shell amplitudes for the ordinary Veneziano and Ramond-Neveu-Schwarz dual models. They correspond to interactions with the string which are local in space-time.     

High spin states of some nuclei around the N=Z=28 double closed shell

A spectroscopic study is performed for high spin states of⁵⁵Fe,⁵⁵Co and⁵⁷Ni. To populate the investigated residues with a relevant cross section, the fusion evaporation reactions of³⁰Si(²⁸Si, 2pn)⁵⁵Fe,³⁰Si(²⁸Si, 2np)⁵⁵Co and⁴He(⁵⁴Fe,n)⁵⁷Ni were chosen. To identify the newγ transitions and to build the energy level schemes,γ — γ coincidence techniques together with excitation functions were employed. Angular distributions andγ — γ angular correlations allowed us to assign the spin values of the nuclear states. The previous level scheme of⁵⁵Fe is extended into the region between 6.5–11 MeV of excitation energy, up to spin 27/2, while the yrast decay paths of⁵⁷Ni and⁵⁵Co are reported here for the first time. Experimental data are fairly well reproduced by Glaudemans' shell model calculations.     

Description of resonant states in the shell model

A technique for describing scattering states within the nuclear shell model is proposed. This technique is applied to scattering of nucleons by particles based on ab initio No-Core Shell Model calculations of ⁵He and ⁵Li nuclei with JISP16 NN interaction.     

High spin states in the nucleus150Tb

Excited states in the nucleus¹⁵⁰Tb have been investigated up to spin 39? and 13 MeV excitation energy using the¹³⁰Te(²⁷Al, 7n) reaction and the EUROGAM array. The theoretical interpretation of the observed states has been performed in the framework of the deformed independent particle model. The analysis of the decay out of the yrast superdeformed band indicates that normal-deformed states with spins between 24? and 28? are fed.     

Hole states in nuclei and the continuum shell model

The hole spectral function which determines the cross section of direct nucleon removal processes is studied in the framework of the continuum shell model with residual interactions. An expression for the spectral function is derived which covers both the bound and continuous parts of the hole spectrum and allows for an exact inclusion of all correlations (except for continuum-continuum coupling) in a restricted space of shell-model configurations. The shell-model approach is compared to the Green function formulation of the spectral function, and some formal relationships between both formulations are established. The results of previous calculations of the spectral function via a second-order mass operator are discussed in the light of the shell-model formalism.     

Hartree-Fock theory of nuclear deformations and high spin states

A brief review of the Hartree-Fock approximation to nuclear shapes and nuclear spectra is presented. Various aspects of rotation-alignment effect and high spin states are illustrated in the Hartree-Fock model.     

Frontiers and challenges of the nuclear shell model

Two recent developments of the nuclear shell model are presented. One is a breakthrough in computational feasibility owing to the Monte Carlo Shell Model (MCSM). By the MCSM, the structure of low-lying states can be studied with realistic interactions for a wide, nearly unlimited basically, variety of nuclei. The magic numbers are the key concept of the shell model, and are shown to be different in exotic nuclei from those of stable nuclei. Its novel origin and robustness will be discussed. Received: 1 May 2001 / Accepted: 4 December 2001     

Long-lived nuclear spin states in the solution NMR of four-spin systems

The existence of long-lived nuclear spin states in four-spin systems is explored by solution-state NMR experiments. Long-lived states are proved to exist in three different natural product molecules, each containing either a AA'BB' or a AA'XX' proton spin system. The measured state lifetimes are between four and eight times the spin-lattice relaxation time constants.     

High spin states in the transitional nucleus88Mo

The reaction⁵⁸Ni(³⁶Ar,α qρ)⁸⁸Mo has been studied at 145 MeV beam energy. A detector array consisting of the OSIRIS spectrometer, four charged-particleΔE detectors and seven NE213 neutron detectors has been used to meaure the gamma radiation inγγ- and particle-γγ-coincidence mode. The level scheme of⁸⁸Mo has been extended up to 11.6 MeV excitation energy and probable spin 23?; some 70 transitions and 40 levels have been identified. Spin assignments have been proposed on the basis of measured DCO ratios. Hartree Fock cranking calculations of the Total Routhians and shell model calculations of the high spin states are presented which imply near-sphericity of the yrast line up to the highest spins found. A classification of the high spin states according to their leading seniority is proposed.     

High spin and mixed states in BI and BII

We present theoretical oscillator strengths and wavelengths for transitions between high spin states in BI and BII (e.g. BI 1s2s2p²3s⁶P - 1s2s2p³⁶S⁰), recently observed for the first time in Beam-Foil Spectroscopy, and between the ground state ²P⁰ and the ²S mixed (valence-Rydberg) excited states in BI.     

High spin states and evidence for octupole correlations in 117Xe

High-spin states of ¹¹⁷Xe were investigated by means of in-beam γ-ray spectroscopic techniques via the reaction of ²⁸Si bombarding a ⁹²Mo target at beam energies of 100-120 MeV. A positive-parity rotational band decaying into the yrast negative-parity band by a series of enhanced E1 transitions was observed for the first time, implying the existence of octupole correlations in ¹¹⁷Xe. The B(E1) values increase with spin. The νd_5/2 band was firmly established up to 27/2⁺ and the B(M1)/B(E2) ratios were extracted from the relative intensities of γ-rays in this band. The previously known νh_11/2 and νg_7/2 [413]5/2⁺α=−1/2 bands were confirmed and extended up to high spins and two bandcrossings are observed in the latter at ħω=0.33 and 0.44 MeV, respectively. The bandcrossings and configurations of these bands are discussed by TRS and CSM calculations. In a γ–γ–t measurement, the 11/2⁻ and 7/2⁻ levels were identified as two isomers with half-lives of 59.4±20 ns and 16.5±8.0 ns, respectively. Received: 17 June 1997 / Revised version: 29 September 1997     

High spin states in the closed-neutron-shell nucleus142Nd

High spin states of¹⁴²Nd have been investigated via the¹³⁰Te (¹⁶O,4n)-reaction by means of in-beam gamma ray spectroscopy using compton suppressed germanium detectors of the OSIRIS-12 facility. Spins up to at least I=24? were assigned and parities were determined by gamma angular distribution, gamma linear polarization and singles spectra measurements. The yrast states (I≤16?) of¹⁴²Nd have been compared with neighbouring N=82 nuclei.