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Electric monopole transitions: What they can tell us about nuclear structure

Description: A brief survey of E0 strength in a number of nuclei in different regions of the nuclear chart is presented. The connection between E0 strength and shape coexistence is reviewed. Nuclear structure information obtained from measurements of electric monopole transitions in {sup 184}Pt and {sup 187}Au is discussed. Plans for future experiments utilizing radioactive ion beams and E0 internal pair formation is presented.
Date: July 2, 1997
Creator: Zganjar, E.F. & Wood, J.L.
Partner: UNT Libraries Government Documents Department

Electric monopole transitions: What they can tell us about nuclear structure

Description: A brief survey of E0 strength in a number of nuclei in different regions of the nuclear chart is presented. The connection between E0 strength and shape coexistence is reviewed. Nuclear structure information obtained from measurements of electric monopole transitions in {sup 184}Pt and {sup 187}Au is discussed. Plans for future experiments utilizing radioactive ion beams and E0 internal-pair-formation is presented.
Date: December 31, 1995
Creator: Zganjar, E.F. & Wood, J.L.
Partner: UNT Libraries Government Documents Department

Nuclear structure research. Annual progress report

Description: The most significant development this year has been the realization of a method for estimating EO transition strength in nuclei and the prediction that the de-excitation (draining) of superdeformed bands must take place, at least in some cases, by strong EO transitions. A considerable effort has been devoted to planning the nuclear structure physics that will be pursued using the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge. A significant effort has been devoted to HRIBF target development. This is a critical component of the HRIBF project. Exhaustive literature searches have been made for a variety of target materials with emphasis on thermodynamic properties. Vapor pressure measurements have been carried out. Experimental data sets for radioactive decays in the very neutron-deficient Pr-Eu and Ir-Tl regions have been under analysis. These decay schemes constitute parts of student Ph.D. theses. These studies are aimed at elucidating the onset of deformation in the Pr-Sm region and the characteristics of shape coexistence in the Ir-Bi region. Further experiments on shape coexistence in the neutron-deficient Ir-Bi region are planned using {alpha} decay studies at the FMA at ATLAS. The first experiment is scheduled for later this year.
Date: July 31, 1995
Creator: Wood, J.L.
Partner: UNT Libraries Government Documents Department

Nuclear structure research. Annual progress report

Description: The most significant development this year has been the realization that EO transition strength is a fundamental manifestation of nuclear mean-square charge radius differences. Thus, EO transitions provide a fundamental signature for shape coexistence in nuclei. In this sense, EO transitions are second only to E2 transitions for signaling (quadrupole) shapes in nuclei and do so when shape differences occur. A major effort has been devoted to the review of EO transitions in nuclei. Experiments have been carried out or are scheduled at: ATLAS/FMA ({alpha} decay of very neutron-deficient Bi isotopes); MSU/NSCL ({beta} decay of {sup 56}Cu); and HRIBF/RMS (commissioning of tape collector, internal conversion/internal-pair spectrometer; {beta} decay of {sup 58}Cu). A considerable effort has been devoted to planning the nuclear structure physics that will be pursued using HRIBF. Theoretical investigations have continued in collaboration with Prof. K. Heyde, Prof. D.J. Rowe, Prof. J.O. Rasmussen, and Prof. P.B. Semmes. These studies focus on shape coexistence and particle-core coupling.
Date: December 31, 1996
Creator: Wood, J.L.
Partner: UNT Libraries Government Documents Department

Nuclear structure research. Annual progress report

Description: The most significant development this year has been the outcome of a survey of EO transition strength, {rho}{sup 2}(EO), in heavy nuclei. The systematics of {rho}{sup 2}(EO) reveals that the strongest EO`s are between pairs of excited states with the same spin and parity. This is observed in the regions Z,N = 38,60; 48,66; 64,88; and 80,106. Unlike other multipoles it is rare that nuclear ground states are strongly connected to excited states by monopole transitions. Another significant finding is in the results of the experimental study of levels in {sup 187}Au. Two bands of states are observed with identical spin sequences, very similar excitation energies, and EO transitions between the favored band members but not between the unfavored band members. This is interpreted in terms of nearly identical diabatic structures. Experimental data sets for the radioactive decays of {sup 183}Pt and {sup 186}Au to {sup 183}Ir and {sup 186}Pt, respectively, have been under analysis. The studies are aimed at elucidating shape coexistence and triaxiality in the A = 185 region. An extensive program of systematics for nuclei at and near N = Z has been continued in preparation for the planned nuclear structure research program using the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge. A considerable effort has been devoted to HRIBF target development.
Date: October 31, 1994
Creator: Wood, J.L.
Partner: UNT Libraries Government Documents Department

Nuclear structure research. Annual progress report

Description: The most significant development this year has been the successful elucidation of the low-energy systematics of the very neutron-deficient Pr, Nd, Pm, and Sm isotopes. This includes an extensive set of Nilsson bandheads in {sup 133}Nd. Some serious errors in earlier decay scheme work were found. The results require some significant reassessments of mean-field calculations in this region. Part of our program continues to focus on shape coexistence and electric monopole (E0) transitions in nuclei. Following the discovery of coexisting ``gamma`` bands connected by E0 transitions in {sup 184}Pt, a similar behavior in {sup 186}Pt was established from {sup 186}Au decay data. This includes a pure E0 transition between states with J{sup {pi}} = 3{sup +}, just as was seen in {sup 184}Pt. Progress has been made in elucidating the low-energy systematics of the neutron-deficient Ir isotopes. A search for the population of the superdeformed band in {sup 194}Pb in the decay of {sup 194}Bi was unsuccessful. An extensive program of systematics for nuclei at and near N = Z has been initiated.
Date: October 31, 1993
Creator: Wood, J. L.
Partner: UNT Libraries Government Documents Department

The structure of nuclei far from stability. Progress report, May 15, 1992--May 14, 1993

Description: Studies on nuclei near Z=82 contributed to the establishment of a new region of nuclear deformation and a new class of nuclear structure at closed shells. A important aspect of this work is the establishment of the connection between low-lying 0{sup +} states in even{endash}even nuclei and the occurrence of shape coexistence in the odd-mass neighbors (E0 transitions in {sup 185}Pt, shape coexistence in {sup 184}Pt and {sup 187}Au). A new type of picosecond lifetime measurement system capable of measuring the lifetime of states that decay only by internal conversion was developed and applied to the {sup 186,188}Tl decay to determine the lifetime of the 0{sub 2}{sup +} and 2{sub 2}{sup +} deformed states in {sup 186,188}Hg. A search for the population of superdeformed states in {sup 192}Hg by the radioactive decay of {sup 192}Tl was accomplished by using a prototype internal pair formation spectrometer.
Date: May 1, 1993
Creator: Zganjar, E. F.
Partner: UNT Libraries Government Documents Department

The ATLAS Positron Experiment -- APEX

Description: APEX -- the ATLAS Positron Experiment -- is designed to measure electrons and positrons emitted in heavy-ion collisions. Its scientific goal is to gain insight into the puzzling positron-line phenomena observed at the GSI Darmstadt. It is in operation at the ATLAS accelerator at Argonne National Lab. The assembly of the apparatus is finished and beginning 1993 the first positrons produced in heavy-ion collisions were observed. The first full scale experiment was carried out in December 1993, and the data are currently being analyzed. In this paper, the principles of operation are explained and a status report on the experiment is given.
Date: March 1, 1994
Creator: Ahmad, I.; Back, B. B.; Betts, R. R.; Dunford, R.; Kutschera, W.; Rhein, M. D. et al.
Partner: UNT Libraries Government Documents Department

Low energy E0 transitions in odd-mass nuclei of the neutron deficient 180 < A < 200 region

Description: The region of neutron-deficient nuclei near Z = 82 and N = 104 provides the most extensive example of low-energy shape coexistence anywhere on the mass surface. It is shown that E0 and E0 admixed transitions may be used as a fingerprint to identify shape coexistence in odd-mass nuclei. It is also shown that all the known cases of low energy E0 and E0 admixed transitions in odd-mass nuclei occur where equally low-lying O/sup +/ states occur in neighboring even-even nuclei. A discussion of these and other relevant data as well as suggestions for new studies which may help to clarify and, more importantly, quantify the connection between E0 transitions and shape coexistence are presented. 60 refs., 7 figs., 4 tabs.
Date: January 1, 1987
Creator: Zganjar, E.F.; Kortelahti, M.O.; Wood, J.L. & Papanicolopulos, C.D.
Partner: UNT Libraries Government Documents Department

Summary remarks and future prospects for on-line nuclear orientation

Description: Results from various groups which use on-line low temperature nuclear orientation techniques are presented. Several nuclear parameters have been successfully studied: rotational levels, nuclear deformation, and decay modes. Future prospects include multiparameter analysis, relaxation and pre-orientation, new separators, and alpha decay studies. 33 refs., 5 figs. (WRF)
Date: January 1, 1984
Creator: Krane, K.S. & Hamilton, J.H.
Partner: UNT Libraries Government Documents Department

Monopole strength as a probe of nuclear shape mixing

Description: The monopole strength, MS, within a single set of nuclear shape excitations is compared with the MS between different shapes. After misconceptions are pointed out concerning the spin dependence of B(E2) values, MS properties are juxtaposed with gamma-ray and beta-decay properties of /sup 70/Se, /sup 96/Zr, /sup 102/Pd, and the N = 60 isotones to illustrate the utility of combined investigations and evidence is given for the observation of a two-phonon octupole multiplet. Finally, consideration is given to the dominance of the /sup 3/S/sub 1/ force in producing deformation in the N > 50 1g nuclei. 23 refs., 4 figs.
Date: August 17, 1987
Creator: Meyer, R.A.
Partner: UNT Libraries Government Documents Department

The structure of nuclei far from stability. [Dept. of Physics and Astronomy, Louisiana State Univ. , Baton Rouge, Louisiana]

Description: Studies on nuclei near Z=82 contributed to the establishment of a new region of nuclear deformation and a new class of nuclear structure at closed shells. A important aspect of this work is the establishment of the connection between low-lying 0[sup +] states in even[endash]even nuclei and the occurrence of shape coexistence in the odd-mass neighbors (E0 transitions in [sup 185]Pt, shape coexistence in [sup 184]Pt and [sup 187]Au). A new type of picosecond lifetime measurement system capable of measuring the lifetime of states that decay only by internal conversion was developed and applied to the [sup 186,188]Tl decay to determine the lifetime of the 0[sub 2][sup +] and 2[sub 2][sup +] deformed states in [sup 186,188]Hg. A search for the population of superdeformed states in [sup 192]Hg by the radioactive decay of [sup 192]Tl was accomplished by using a prototype internal pair formation spectrometer.
Date: January 1, 1993
Creator: Zganjar, E.F.
Partner: UNT Libraries Government Documents Department

Photon decay of giant resonances

Description: Measurements have been made of the photon decay of the giant multipole resonances in /sup 208/Pb. The giant resonances were excited by inelastic scattering of 380 MeV /sup 17/O projectile and the photons were detected in the ORNL Spin Spectrometer. The results show a quadrupole resonance ground state gamma branch of 20% while only less than or equal to 2% of the GQR decay proceeds through the 2.6 MeV, 3/sup -/ state. Nearly one half of the GQR decay through a 3/sup -/ state at 4.974 MeV. Photon decay from the dipole and monopole resonances and high spin resonances (4+,6+) are also observed.
Date: January 1, 1984
Creator: Bertrand, F.E.; Beene, J.R. & Halbert, M.L.
Partner: UNT Libraries Government Documents Department

Nuclear structure from radioactive decay. [School of Physics, Georgia Inst. of Tech]

Description: The most important aspect of the wind-up of UNISOR-based research is completion of student theses. Analysis is proceeding on extensive studies in the neutron-deficient rare earth isotopes with N < 82 and the neutron-deficient region below Z = 82. These studies address the onset of deformation in the N < 82, Z > 50 open shell region and shape coexistence in the N [approximately] 104, Z [le] 82 region, respectively. The main ongoing topics are shape coexistence in nuclei and the microscopic structure of collective motion in nuclei from a phenomenological point of view. New topics this year focus on the structure of nuclei near the N = Z line. Two topics have been chosen for detailed study: shape coexistence and electric monopole transition strengths.
Date: September 30, 1992
Creator: Wood, J.L.
Partner: UNT Libraries Government Documents Department

In-beam spectroscopy using the (t,p) reaction: recent results near A = 100

Description: Charged particle spectroscopy using the (t,p) reaction has been employed for more than two decades to study the low-energy structure of nuclei. This reaction has contributed significantly to the elucidation of single-particle and collective phenomena for neutron rich nuclei in virtually every mass region. We have begun to use the (t,p) reaction in conjunctionuclei with in-beam ..gamma..-ray and conversion-electron spectroscopy to bring additional understanding to low-energy nuclear structure. In this report we briefly discuss the experimental considerations in using this reaction for in-beam spectroscopy, and present some results for nuclei with mass near 100.
Date: September 4, 1985
Creator: Henry, E.A.; Estep, R.J.; Meyer, R.A.; Kantele, J.; Decman, D.J.; Mann, L.G. et al.
Partner: UNT Libraries Government Documents Department

Study of heavy element structure with in-beam. cap alpha. /sup -/,. beta. /sup -/ and. gamma. -ray spectroscopy

Description: We describe our in-beam superconducting conversion electron spectrometer and its use in a (t,p) proton-conversion electron coincidence mode. Several examples of completed and on-going investigations are presented. These include: E0 strength from the /sup 238/U fission isomer; electromagnetic properties of the J/sup ..pi../ = 6/sup +/ and 8/sup +/ states of /sup 210/Pb; single particle and cluster states of /sup 213/Fr; the J/sup ..pi../ = 21/2/sup +/ isomer in /sup 197/Au and /sup 199/Au; and the cluster states of /sup 199/Au. Results of the study of odd-odd deformed /sup 244/Am are presented. The latter results performed using neutron-capture gamma-ray and conversion electron techniques are compared to recent developments in the modeling of deformed odd-odd nuclei. 23 refs., 10 figs., 1 tab.
Date: May 10, 1984
Creator: Meyer, R.A.; Decman, D.J.; Henry, E.A.; Hoff, R.W.; Mann, L.G.; Struble, G.L. et al.
Partner: UNT Libraries Government Documents Department