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Potential energy surface calculations have predicted the existence of the island of triaxial strongly deformed (TSD) nuclei with N~94 and Z~72. Experimental discoveries of TSD bands have been first reported in Lu. Subsequent calculations indicated that Hf would be the most favorable even-even nuclei in the island region for finding low-lying TSD structures. However, experimental investigation of Hf nuclei performed with Euroball and Gammasphere produced negative results on the two nuclei. In the Gammasphere experiment three TSD bands were discovered in the main reaction product Hf. This success motivated an extension of the search for TSD bands in the region to heavier Hf-isotopes and neighboring Lu-isotopes. In order to search for TSD bands and the characteristic wobbling mode in Lu, the experiment using Sb ( Ca, xn) reaction was performed in Lawrence Berkeley National Laboratory (LBNL) with Gammasphere. Based on coincidence data acquired in the experiment, a new level structure for Lu was developed. Compared to level schemes in previous work, previously observed bands were extended to higher spins. Four new bands were assigned to Lu for the first time, and one of them was identified as a triaxial strongly deformed (TSD) band.

With growing interest in devices that utilize the spin degree of freedom of the charge carriers, there is an extensive research effort into materials with high spin polarization. Two types of materials that have attracted particular attention are the half metallic (HM) ferromagnets and dilute magnetic semiconductors (DMS). I report on a series of experiments which probe the level spin polarization in HM CrO2 and the DMS Ga1−xMnxAs. In order to accurately determine the spin polarization, P, of CrO2 in a realistic device structure I have developed a method to chemically modify the surface of CrO2 to obtain a consistent and reproducible barrier, which preserves the bulk spin polarization. Using this method I have been able to produce high quality CrO2 based planar junctions with either superconducting (SC) or ferromagnetic (FM) counter electrodes. Analysis of both zero field and Zeeman split conductance data from CrO2-SC junctions consistently yield P values close to 100%, providing unambiguous evidence that the high P of CrO2 is maintained at and across an artificial barrier in a realistic device structure. Magnetic tunnel junctions (MTJ) fabricated with CrO2 and Co electrodes display a low field inverse magneto-resistance with a maximum magneto-resistance (MR) of -24% occurring at 5K. The origin of this inverse sign is discussed in terms of selective spin transport due to variations in the type of interfacial bonding between the electrodes and the barrier. A strong linear bias dependence of the MR, similar to what is seen in the CrO2-SC junctions, is observed. This linear background is attributed to a continuum of inelastic states in the barrier region. Measurements of the MR as a function of temperature display a rapid decrease in MR as temperature increases. Additionally we have carried out the first direct measurement of the degree of spin polarization of the magnetic semiconductor Ga1−xMnxAs using Andreev reflection spectroscopy. Analysis of the conductance spectra of high transparency Ga0.95Mn0.05As/Ga junctions consistently yields an intrinsic value for P greater than 85%. Our experiments also revealed an extreme sensitivity of the measured spin polarization to the nature and quality of the interface for this material. / Dissertation / PhD

Spin-2 particles, or gravitons, present both virtues and vices not displayed by their lower spin peers. A massless graviton can only be described consistently by a single theory---general relativity---while mutual couplings among ``colored'' gravitons are simply not allowed. A massive graviton is also believed to admit a unique set of interactions, ones that are however pestered by superluminal perturbations and a rather limited effective field theory. And then there is the third member of the clique, the partially massless graviton, who lives in a universe with a naturally small cosmological constant, but which nonetheless seems not to exist at all. The aim of this thesis is to explore this enormously rich and tightly fettered realm of classical theories of spin-2 fields.

>Magister Scientiae - MSc / The focus for this work is on 152Gd produced by the 150Sm( , 2n)152Gd reaction at a beam energy of 25 MeV. The nucleus has been previously studied for both low spin states and high spin states at di erent energies. The most recent work on 152Gd was done by S. P. Bvumbi using the 152Sm( , 4n)152Gd reaction at a beam energy of 45 MeV where she was able to populate low spin states and assign spins and parities to the levels as shown in Fig. 1.1. The nucleus 152Gd, with proton number Z=64 subshell closure, belongs to a set of isotones having N=88 in the transitional region with just 6 neutrons outside the N=82 closed shell and lies just before the N=90 permanently deformed region. The isotope 152Gd is in the transitional region, consequently its nuclear collective motion will quickly evolve from vibrational to rotational motion. The low lying K =0+2 bands in N=88 and 90 nuclei appear at low excitation energies and are poorly understood. Key to these studies is the crucial question about the legitimacy of the low lying K =0+2 bands being described as vibrations along the symmetry axis. The current work examines the K =0+2 band with the objective of providing more understanding. Previous studies of N=88 isotones saw consistent E1 transitions both from and to the K =0+2 bands and octupole bands, namely 144Ba, 146Ce, 148Nd, 150Sm and 154Dy nuclei. The experimental systematics of the low lying negative parity states in N=88 isotones are remarkably well reproduced by theoretical calculations of the quadrupole octupole coupling (QOC) modelas shown in Fig. 1.2.

Thesis (M.S.)--Mississippi State University. Department of Physics and Astronomy. / Title from title screen. Includes bibliographical references.

>Magister Scientiae - MSc / High spin excited stats in¹⁹²Tl were studied using gamma-ray spectroscopy. The study included taking an active part in performing the experiment, understanding the experimental procedure, electronics and data acquisition in this experiment. The high spin states in ¹⁹²Tl were produced using a ³⁷Cl beam and ¹⁶⁰Gd target. The nine clovers of the AFRODITE array were placed at 90° and 135°. The target was thin, allowing the residual thallium nuclei to recoil in vacuum. Two weeks of data was acquired and analysed in this work. In addition more data was acquired in order to perform DSAM lifetime measurements, but this is beyond the scope of this work. The preliminary data analysis of the thin target data involved energy and time-gain matching calibrations as well as Doppler shift and gain drift corrections. Then the data were sorted into matrices and spectra for the actual analysis. The known level scheme of ¹⁹²Tl was extended by more than 50 new transitions placed in three new bands. A chiral partner to the yrast band in ¹⁹²92Tl was searched for but not found. But there is still a possibility such a band to be discovered, when the additional three weekends of data (including the DSAM lifetime measurements) undergo such an analysis.