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The level density and radiative strength function for 146,147Sm and 163,164Dy have been extracted from primary γ spectra using the Oslo method. As one approaches the closed N = 82 neutron shell, the structures in the level density become more pronounced due to shell effects. The experimental level densities can be used to explore thermodynamic properties of the nucleus within the microcanonical ensemble. Pygmy resonances, which are based on the scissors mode and seen in deformed rare-earth nuclei, are not observed in near-spherical 146,147Sm, as expected. Pygmy resonances in 163,164Dy were studied after 3He-induced reactions and their width was found to be twice as wide as compared to results reported after neutron-capture reactions. [ABSTRACT FROM AUTHOR]

The nuclear physics group at the Oslo Cyclotron Laboratory has developed a method to extract nuclear level density and γ-ray strength function from first-generation γ-ray spectra. This method is applied on the nuclei 44,45Sc and 50,51V in this work. The experimental level densities of 44,45Sc are compared to calculated level densities using a microscopic model based on BCS quasiparticles within the Nilsson level scheme. The γ-ray strength functions are also compared to theoretical expectations, showing an unexpected enhancement of the γ-ray strength for low γ energies (Eγ<=3 MeV) in all the isotopes studied here. The physical origin of this enhancement is not yet understood. [ABSTRACT FROM AUTHOR]

The nuclear level densities of 44,45Sc and 50,51V have been measured using the Oslo method. From the level density thermal properties such as entropy and temperature are deduced. Also the radiative strength functions (RSF) of 50,51V have been extracted. The gross properties of the RSF are generally described by the low-energetic tail of the giant electric dipole resonance (GEDR). At γ energies below ∼ 3 MeV, the RSFs show an unexpected enhancement. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The level density and the γ-strength function have been extracted experimentally. From the level densities thermodynamical quantities such as temperature and heat capacity can be found. Structures in the micro-canonical temperature are interpreted as the onset of new degrees of freedom by the breaking of Cooper pairs. The S-shape in the heat capacity curves, found within the canonical ensemble, indicates the pairing-phase transition, and a critical temperature for the quenching of pair correlations is found. The pygmy resonance at 3.3(1) MeV in 172Yb has now been established with a strength of B(M1)=6.5(15)μN2 and M1 multipolarity, the so-called scissors mode. In addition, a strong unexpected enhancement of the radiative strength function (RSF) has been found at low γ-ray energy in medium light Fe nuclei and also in the heavier Mo nuclei. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

A method has been developed where primary γ-rays after nuclear reactions with one ejectile only, can be projected out from the total γ-ray spectrum. These primary γ-ray spectra are shown to be, under certain conditions, a new source for determination of nuclear level densities and γ-ray strength functions. Results for [sup 162]Dy, [sup 166]Er and [sup 172]Yb are presented. The level density is used for determination of nuclear temperature and heat capacity. Fine structures in the level density and the temperature suggest changes in the pair correlation. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The nuclear physics group at the Oslo Cyclotron Laboratory (OCL) has developed a method to extract nuclear level density and γ-ray strength function simultaneously from primary γ-ray spectra. The resulting γ-ray strength functions of 44,45Sc and 50,51V show an unexpected, large enhancement at low γ-ray energies, indicating an increased probability of emitting low-energy γ rays in the quasi-continuum. [ABSTRACT FROM AUTHOR]

The Oslo method has been tested on 205–208Pb nuclei utilizing the neutron pick-up and inelastic scattering reactions for the extraction of the level density and γ strength function. The preliminary results agree well with the known characteristics of these nuclei. [ABSTRACT FROM AUTHOR]

The energy dependent nuclear level densities of 205–208Pb nuclei below the nuclear binding energies were determined by using the Oslo method. The experimental primary γ-ray per excitation energy bin have been extracted for scattering and transfer reactions. The Axel-Brink hypothesis was then used to separate out level density and γ-strength function from the primary γ spectra. The influence of closed shells is quite obvious in the measured level densities. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]