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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

NUCLEAR SPECTROSCOPY OF YTTRIUM (90) AND NIOBIUM (92)

Unknown Date (has links)
Levels in ('90)Y were studied using the ('91)Zr(t,(alpha))('90)Y and ('89)Y(n,(gamma))('90)Y reactions. The results of these studies were used to locate the members of the (pi)(p1/2)('1) (upsilon)(d5/2)('1), (pi)(g9/2)('1) (upsilon)(d5/2)('1), (pi)(p3/2)('-1) (upsilon)(d5/2)('1), and (pi)(f5/2)('-1) (upsilon)(d5/2)('1) configurations. Of particular interest is the anomalously high energy of the 0- state of the (pi)(f5/2)('-1) (upsilon)(d5/2)('1) multiplet. In addition to this several new low spin levels were discovered in the ('89)Y(n,(gamma))('90)Y reaction. / The structure of ('92)Nb was investigated by the ('91)Zr(('3)He,d)('92)Nb reaction. The members of the (pi)(g9/2)('1) (upsilon)(d5/2)('1) configuration were strongly populated and have spectroscopic factors with simple 2J(,f)+1 structure. Several states are populated with (,p) = 1 angular distributions. Also a large portion of the (,p) = 2 spectroscopic strength is observed to be fragmented over many T(,<) states. / The energy spectra of ('90)Y and ('92)Nb were calculated using finite-range matrix elements including both central and tensor potentials. The tensor force is found to have a large effect on the low spin negative parity states of ('90)Y. / Source: Dissertation Abstracts International, Volume: 41-03, Section: B, page: 1008. / Thesis (Ph.D.)--The Florida State University, 1980.
32

LOW-ENERGY STRUCTURE STUDIES OF ODD-ODD DEFORMED NUCLEI AND THE CORIOLIS AND RESIDUAL INTERACTIONS

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 41-07, Section: B, page: 2660. / Thesis (Ph.D.)--The Florida State University, 1980.
33

CORIOLIS-DECOUPLED HIGH-SPIN E2 BANDS IN ODD-A RUBIDIUM AND KRYPTON ISOTOPES

Unknown Date (has links)
Heavy-ion reactions have been used to study high-spin bands in odd-A nuclei in the mass A (TURNEQ) 80 region. A previously unobserved band of E2 transitions has been assigned to ('79)Rb. Six reactions were used to rule out other assignments. Bands of E2 transitions have also been assigned to ('79)Kr and ('81)Kr. The bands in ('79)Rb, ('79)Kr and ('81)Kr were studied using (gamma)-ray singles, (gamma)-(gamma) coincidence, angular distribution, and excitation function measurements. Relative reaction cross sections were deduced for the ('10)B + ('72)Ge and ('11)B + ('73)Ge reactions at 40 MeV. The experimental cross sections were in fair agreement with evaporation-model calculations made with the code ALICE. / The ('79)Rb band was compared with the ('81)Rb decoupled band. These bands were interpreted using the RAC (rotation-aligned coupling) model as arising from the decoupling of a g(,9/2) proton from the ('78)Kr and ('80)Kr cores, respectively. The ('79)Kr and ('81)Kr bands were interpreted as arising from the partial decoupling of g(,9/2) neutrons from the ('78)Kr and ('80)Kr cores, respectively, and a comparison was made with the ('77)Kr band. The amount of decoupling in the Rb isotopes was compared to that in the Kr isotopes. / Source: Dissertation Abstracts International, Volume: 41-11, Section: B, page: 4162. / Thesis (Ph.D.)--The Florida State University, 1980.
34

IN-BEAM GAMMA-RAY SPECTROSCOPY WITH THE REACTIONS IRON-54 + SILICON-28 AND IRON-56 + SILICON-28

Unknown Date (has links)
In-beam gamma-ray spectroscopy with the reactions ('54)Fe + ('28)Si and ('56)Fe + ('28)Si were used for studying high-spin states in neutron-deficient nuclei in the mass A(TURN)80 region. Measurements of gamma-ray energies, intensities, angular distributions, excitation functions, and gamma-gamma coincidence experiments were used to assign new levels in ('79)Rb and ('80)Sr. In addition a high-spin level sequence has been assigned to ('81)Sr which was not known previously. The new levels are consistent with and extend the systematics of quasi-rotational bands in this mass region. There is a steady increase in the moment of inertia both the even and odd mass Kr and Sr isotopes as the neutron number decreases from the shell closure at N = 50. / Experimental excitation functions for the reaction products produced in the ('54)Fe + ('28)Si and ('56)Fe + ('28)Si reaction, were measured from 80 to 99 MeV in 5 MeV steps. The experimental excitation functions were then compared to the compound nuclear evaporation model calculations ALICE and LILITA. The results of these calculations suggest that angular momentum effects in the exit channel are important. These calculations are very sensitive to the level density parameters and these parameters are poorly known in the mass A(TURN)80 region. Deficiencies in the calculations may possibly be explained by the uncertainties in the continuum level density parameters a. / Source: Dissertation Abstracts International, Volume: 42-08, Section: B, page: 3318. / Thesis (Ph.D.)--The Florida State University, 1981.
35

Analyzing powers in light systems and lithium(6,7) beam polarization studies

Unknown Date (has links)
Elastic and inelastic cross-section and analyzing power (iT$\sb{11},$ T$\sb{20},$ T$\sb{21},$ and T$\sb{22})$ angular distribution data are reported for $\sp4He(\sp6\vec Li,\sp6Li)\ \alpha$ at E$\rm \sb{CM}$ 11.1 MeV, and also elastic cross-section data for the same reaction at E$\rm\sb{CM}$ 15.0 MeV. The angular range covered is from 10$\sp\circ$-160$\sp\circ$ c.m., and all analyzing powers reported have large magnitudes except for the elastic T$\sb{21}.$ Also reported are elastic and inelastic cross-section angular distributions for $\sp7Li(\alpha,\alpha)\ \sp7Li$ at E$\rm\sb{CM}$ 11.8 and 15.9 MeV, and an analyzing power excitation function for $\sp4He(\sp6\vec Li,\sp6Li)\ \alpha$ between E$\rm\sb{LAB}$ 25.7 and 29.8 MeV. / After discussing the physical setup of the FSU Optically Pumped Polarized Lithium Ion Source (OPPLIS), experimental data are reported documenting OPPLIS beam polarization optimization and the determination of $\sp7$Li Wien filter curves. Two theorems are advanced, proven and then utilized to perform calculations for the on-target calibration of the $\sp{6.7}$Li beam polarizations. Results of both optical model, finite range DWBA and channel coupling calculations are then presented, including an analysis of the $\sp6$Li bound state spectroscopic amplitude $b\sb{D}$ and coupling to several $\sp6$Li excited states. / The optical model analysis shows the need for an explicit spin orbit potential and the J-dependent potential term indicates the presence of channel coupling effects. The DWBA analysis confirms earlier predictions that the $\alpha$-exchange mechanism is important in $\sp6$Li + $\alpha$ scattering and is primarily important at the back-angles, as well as more recent predictions of a very small and negative $\sp6$Li $b\sb{D}.$ The coupled channels analysis explores the effects of cluster-folded central, spin-orbit and tensor potentials in a four channel calculation, these being the $\sp6$Li ground state, the 2.186 MeV 1st excited state, and the 2$\sp+$ and 1$\sp+$ resonances at 4.31 and 5.65 MeV, respectively. The 4-channel calculations confirm the optical model prediction that the forward angle iT$\sb{11}$ is extremely sensitive to channel coupling. Only the cluster-folded central and spin-orbit potentials are required along with channel coupling to give good agreement with the experimental data. / Source: Dissertation Abstracts International, Volume: 57-01, Section: B, page: 0428. / Major Professor: Kirby W. Kemper. / Thesis (Ph.D.)--The Florida State University, 1995.
36

Complete and incomplete momentum transfer processes in the reaction oxygen + silicon(nat)

Unknown Date (has links)
Complete and incomplete fusion components from the nuclear reaction $\sp{16}$O + $\sp{nat}$Si were studied at 39.2, 59.0, 80.6, 96.4, 112.4, and 127.8 MeV bombarding energy. Inclusive measurements of evaporation residues (ERs) were made at all energies; ER/$\alpha$-particle coincidence measurements were made at 127.8 MeV. / Theoretical predictions of observable features of fusion and incomplete fusion reactions are discussed, for inclusive and coincidence measurements. / The design, construction, and calibration of a new time of flight (TOF) heavy ion spectrometer for the detection of ERs from this reaction is discussed. Incorporation of a silicon surface-barrier E-$\Delta$E $\alpha$-particle detector into the spectrometer for coincidence measurements is also discussed. / A model-independent method for extracting complete and incomplete momentum transfer components (CMT and ICMT) of the inclusive data, which are expected to correspond to complete and incomplete fusion (CF and ICF), is presented. A means of analysing coincidence data is discussed. / Results of the collection and analysis of both the inclusive and coincidence data are presented. From the inclusive data, the mass, velocity, and angular distributions of the ERs resulting from CMT processes were found in agreement with predictions for CF reactions. From the ERs resulting from ICMT processes, the velocity distributions were found to agree with a two-body projectile fragmentation model; net absorption of clusters of one, two, or three $\alpha$-particles seems to be the predominant process. In the coincidence data no clearly separable signature distinguishing CF and ICF reactions could be found, however fits to coincident $\alpha$-particle energy spectra indicate that the signature is there but masked by a large fusion-evaporation component. / Source: Dissertation Abstracts International, Volume: 51-12, Section: B, page: 5938. / Major Professor: Lawrence C. Dennis. / Thesis (Ph.D.)--The Florida State University, 1990.
37

A study of vector polarized lithium-6 scattering

Unknown Date (has links)
The elastic scattering vector analyzing powers for $\sp6$Li + $\sp{16}$O at 25.7 MeV and $\sp6$Li + $\sp{12}$C at 30 MeV have been measured in detail. In addition, the first analyzing power measurements for inelastic $\sp6$Li scattering have been made; specifically for the 2$\sp+$ (4.44 MeV) state in $\sp{12}$C. The emphasis in the experiment was to obtain the highest quality data possible, which is a difficult task when working with a polarized ion source. The present vector analyzing power data, along with previous elastic and inelastic scattering cross section data, provide a severe test of current heavy ion scattering models. / The data have been analyzed in the coupled channels framework, employing the double folding model for the real part of the nuclear scattering potential. Unlike previous studies of polarized Li scattering, the coupling strengths in the CC calculations were unambiguously determined from inelastic scattering cross section data. The only free parameters in the calculations were the imaginary term of the scattering potential and the strength of the folded potential. / The analysis shows that the vector analyzing power arises from a complicated interference between channel coupling effects and the spin orbit potential. In contrast to the results of Sakuragi, an explicit spin orbit potential was required to describe the data. It was found that both the first 3$\sp+$ and 2$\sp+$ excitations in $\sp6$Li were important to the coupling scheme. / Coupled channels calculations for the $\sp{12}$C, 2$\sp+$ state predicted zero analyzing power in the angular range of the data. Thus, only the explicit spin orbit potential will contribute to the analyzing power. This may allow the shape and strength of the heavy ion spin orbit potential to be investigated more closely since there is no interference from coupling effects. / Source: Dissertation Abstracts International, Volume: 50-02, Section: B, page: 0625. / Major Professor: Kirby W. Kemper. / Thesis (Ph.D.)--The Florida State University, 1988.
38

50 MeV lithium-6 scattering from carbon-12, oxygen-16, and beryllium-9 and the calibration of the tensor-polarized lithium-6 beam

Unknown Date (has links)
The experimental work reported consists of (1) the measurements of the angular distributions for the scattering of $\sp6$Li from the targets $\sp9$Be, $\sp{12}$C, and $\sp{16}$O at a lithium bombarding energy of 50 MeV, and (2) the measurement of the tensor polarization of the FSU polarized $\sp6$Li source. 50 MeV data were taken for elastic and inelastic scattering to the 2$\sp+$ (4.44 MeV), 0$\sp+$ (7.65 MeV), and 3$\sp-$ (9.64 MeV) states in $\sp{12}$C, the 5/2$\sp-$ (2.43 MeV) state in $\sp9$Be, and the unresolved 0$\sp+$/3$\sp-$ (6.05/6.13 MeV) and $2\sp{+}/1\sp{-}$ (6.92/7.12 MeV) states in $\sp{16}$O. The measurement of the tensor polarization of the FSU $\sp6$Li source allowed the absolute polarization efficiency of the source-accelerator system to be determined. / The analytical work reported consists of a determination of the energy dependence of the optical potential parameters for $\sp6$Li + $\sp{12}$C scattering over the energy range from 11 MeV to 210 MeV. This has been attempted previously and the results have not been successful. A large body of data for $\sp6$Li + $\sp{12}$C allows more severe constraints than in previous studies. The inclusion of an angular momentum-dependent imaginary potential provides a good description of the elastic scattering data and the parameters determined in this study are smoothly varying with energy using Woods-Saxon form factors for the real and imaginary potentials. Inelastic scattering to the 2$\sp+$ (4.44 MeV), 0$\sp+$ (7.65 MeV), and 3$\sp-$ (9.64 MeV) states in $\sp{12}$C are described well using the constructed energy dependent potentials in DWBA calculations. Analysis using the double folded real potential and a Woods-Saxon imaginary potential were performed on the same $\sp6$Li + $\sp{12}$C scattering data from 11 MeV to 210 MeV. / The scattering data for 50 MeV $\sp6$Li scattering from the targets $\sp{16}$O and $\sp9$Be are described using optical potentials and DWBA calculations. Less information is obtained from these analyses because data do not exist at this time over a wide enough energy range to provide a constraint on the interaction potentials. / Source: Dissertation Abstracts International, Volume: 50-08, Section: B, page: 3543. / Major Professor: Kirby W. Kemper. / Thesis (Ph.D.)--The Florida State University, 1989.
39

The role of the nucleon virtual mass in quark distributions of nuclei

Unknown Date (has links)
A simple model which allows explicit calculations of the nuclear structure function in terms of the nucleon structure function for the deuteron as well as heavier nuclei is proposed. The impulse approximation in the DIS which leads to the convolution form of the nuclear structure function is examined and forms the basis of the model. The nucleus is viewed as a bound state of nucleons in constant motion with virtual mass less than the mass of a free nucleon. The EMC effect is discussed in the context of the model. Quantitative agreement with the nuclear DIS data is obtained. It was found that most of the nucleus momentum fraction is carried by the nucleons while a small portion is carried by other constituents presumed to be responsible for binding. The momentum fraction of these binding constituents showed "saturation" behavior similar to that found for the Fermi momentum as the atomic mass number of the nucleus increases, thereby suggesting a relationship between the two. Comparison is made between the model and other possible EMC effect interpretations. Lastly, a decisive test for the convolution form in general and the nuclear virtual mass, in particular, is provided. As predicted by the model, the ratio of nuclear to nucleon $\rm Q\sp2$-moments are shown to be $\rm Q\sp2$-independent and the values of this ratio for various nuclei are given. / Source: Dissertation Abstracts International, Volume: 49-12, Section: B, page: 5368. / Major Professor: Don Robson. / Thesis (Ph.D.)--The Florida State University, 1988.
40

A three alpha-particle coincidence search for collective high spin states in carbon-12

Unknown Date (has links)
A search for theoretically predicted collective high spin states in $\sp{12}$C is made by making a kinematically complete measurement of the three alpha-particles produced in the decay of excited $\sp{12}$C. This is accomplished by using a system of position sensitive detectors to detect the three alpha-particles in coincidence. The excited $\sp{12}$C is produced in the system $\sp{12}$C + $\sp{12}$C, with a lab energy of 90 MeV. / From event reconstruction, different reaction and decay processes in this system are identified and separated as much as kinematically allowed. The event reconstruction is accomplished with general computer programs written for this work. In addition, a general purpose program was written to do Monte Carlo simulations of these detector systems to determine detection efficiency for a particular reaction and decay process, and for use in calculating double-differential cross sections. / Many known states in $\sp{12}$C were identified with good resolution, including two states (and possibly two other states as well) not previously seen in this system. In addition, a significant amount of highly excited $\sp{16}$O is produced, which decays to the same four-body final state resulting from the decay of $\sp{12}$C. Many states in $\sp{16}$O were observed, including structures at excitation energies of about 25 MeV and 30 MeV, which have been observed previously. For both the $\sp{12}$C and the $\sp{16}$O observed in the spectra, a sequential decay process is strongly indicated. It is estimated that less than 5% of the $\sp{12}$C decays observed are the result of direct breakup, or ternary decay. The production and decay of $\sp{20}$Ne could not be identified in the data. / Despite the low background and relatively good energy resolution, no predicted, but as yet unseen, states were uncovered in this work. However, from the event reconstruction and the calculation of detection efficiency, the branching fraction for the decay of $\sp{12}$C from the 4$\sp+$ state at 14.08 MeV excitation is calculated to be 0.81 with an estimated uncertainty of about 0.05. / Source: Dissertation Abstracts International, Volume: 51-04, Section: B, page: 1888. / Major Professor: Neil R. Fletcher. / Thesis (Ph.D.)--The Florida State University, 1990.

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