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Sample records for excited compound nuclei

  1. Stochastic model of angular distributions of fragments originating from the fission of excited compound nuclei

    SciTech Connect

    Hiryanov, R. M.; Karpov, A. V.; Adeev, G. D.

    2008-08-15

    The anisotropy of angular distributions of fission fragments and the average multiplicity of prescission neutrons were calculated within a stochastic approach to fission dynamics on the basis of three-dimensional Langevin equations. This approach was combined with a Monte Carlo algorithm for the degree of freedom K (projection of the total angular momentum I onto the fission axis). The relaxation time {tau}{sub K} in the coordinate K was considered as a free parameter of the model; it was estimated on the basis of a fit to experimental data on the anisotropy of angular distributions. Specifically, the relaxation time {tau}{sub K} was estimated at 2 x 10{sup -21} s for the compound nuclei {sup 224}Th and {sup 225}Pa and at 4 x 10{sup -21} s for the heavier nuclei {sup 248}Cf, {sup 254}Fm, and {sup 264}Rf. The potential energy was calculated on the basis of the liquid-drop model with allowance for finiteness of the range of nuclear forces and for the diffuseness of the nuclear surface. A modified one-body viscosity mechanism featuring a coefficient k{sub s} that takes into account the reduction of the contribution from the wall formula was used to describe collective-energy dissipation. The coefficient k{sub s} was also treated as a free parameter and was estimated at 0.5 on the basis of a fit to experimental data on the average prescission multiplicity of neutrons.

  2. Two-dimensional Langevin modeling of fission dynamics of the excited compound nuclei 188Pt, 227Pa and 251Es

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2016-02-01

    A stochastic approach based on one- and two-dimensional Langevin equations is applied to calculate the pre-scission neutron multiplicity, fission probability, anisotropy of fission fragment angular distribution, fission cross section and the evaporation cross section for the compound nuclei 188Pt, 227Pa and 251Es in an intermediate range of excitation energies. The chaos weighted wall and window friction formula are used in the Langevin equations. The elongation parameter, c, is used as the first dimension and projection of the total spin of the compound nucleus onto the symmetry axis, K, considered as the second dimension in Langevin dynamical calculations. A constant dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, is used in two-dimensional calculations to reproduce the above mentioned experimental data. Comparison of the theoretical results of the pre-scission neutron multiplicity, fission probability, fission cross section and the evaporation cross section with the experimental data shows that the results of two-dimensional calculations are in better agreement with the experimental data. Furthermore, it is shown that the two-dimensional Langevin equations together with a dissipation coefficient of K, γK = 0.077(MeV zs)-1/2, can satisfactorily reproduce the anisotropy of fission fragment angular distribution for the heavy compound nucleus 251Es. However, a larger value of γK = 0.250(MeV zs)-1/2 is needed to reproduce the anisotropy of fission fragment angular distribution for the lighter compound nucleus 227Pa.

  3. Complex fragment emission from hot compound nuclei

    SciTech Connect

    Moretto, L.G.

    1986-03-01

    The experimental evidence for compound nucleus emission of complex fragments at low energies is used to interpret the emission of the same fragments at higher energies. The resulting experimental picture is that of highly excited compound nuclei formed in incomplete fusion processes which decay statistically. In particular, complex fragments appear to be produced mostly through compound nucleus decay. In the appendix a geometric-kinematic theory for incomplete fusion and the associated momentum transfer is outlined. 10 refs., 19 figs.

  4. Quartet excitations in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Cseh, J.

    2016-06-01

    The recently invented phenomenologic and semimicroscopic algebraic quartet models, as well as their relations to other approaches are discussed. The semimicroscopic model is applied to the 20Ne and 28Si nuclei.

  5. Fusion excitation functions involving transitional nuclei

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    Measurements of fusion excitation functions involving transitional nuclei {sup 78}Kr and {sup 100}Mo showed a different behavior at low energies, if compared to measurements with {sup 86}Kr and {sup 92}Mo. This points to a possible influence of nuclear structure on the fusion process. One way to characterize the structure of vibrational nuclei is via their restoring force parameters C{sub 2} which can be calculated from the energy of the lowest 2{sup +} state and the corresponding B(E2) value. A survey of the even-even nuclei between A = 28-150 shows strong variations in C{sub 2} values spanning two orders of magnitude. The lowest values for C{sub 2} are observed for {sup 78}Kr, {sup 104}Ru and {sup 124}Xe followed by {sup 74,76}Ge, {sup 74,76}Se, {sup 100}Mo and {sup 110}Pd. In order to learn more about the influence of {open_quotes}softness{close_quotes} on the sub-barrier fusion enhancement, we measured cross sections for evaporation residue production for the systems {sup 78}Kr + {sup 104}Ru and {sup 78}Kr + {sup 76}Ge with the gas-filled magnet technique. For both systems, fusion excitation functions involving the closed neutron shell nucleus {sup 86}Kr were measured previously. The data are presently being analyzed.

  6. Dilute Excited States in Light Nuclei

    NASA Astrophysics Data System (ADS)

    Demyanova, A. S.; Ogloblin, A. A.; Danilov, A. N.; Goncharov, S. A.; Belyaeva, T. L.; Trzaska, W. H.

    2015-11-01

    A review of measurements of the radii of 11B, 12C and 13C nuclei in some excited states, whose structure recently attracted a lot of attention, is presented. The differential cross-sections of the inelastic α-scattering were measured. The radii values were extracted from the date using the Modified Diffraction Model (MDM). The evidence that the famous Hoyle state (0+, 7.65 MeV) in 12C has the enhanced dimensions and is the head of a new rotational band (besides the known band based on the 12C ground state) was obtained. The radius of the second 2+ member state (E* = 9.8 or 9.6 MeV) was seen to be similar to that of the Hoyle state (~3.0 fm). A 4+ state was identified at E* = 13.75 MeV. The radii of the 8.86 MeV, 1/2- state in 13C and 8.56 MeV, 3/2- state in 11B are found to be close to that of the Hoyle state and these states can be considered as analogues of the latter. Comparison of the data with the predictions of some theoretical models, e.g., alpha condensation, has been made. The obtained results show that one may speak only about rudimentary manifestation of the condensate effects.

  7. Intrinsic excitations in doubly odd nuclei

    SciTech Connect

    Sood, P.C.

    1985-01-15

    A procedure is outlined for predicting the bandhead energies of the two-particle (intrinsic) states of odd-odd deformed nuclei based on a quantitative evaluation of the zero range n-p residual interaction energy. We present our results for 250Bk, where many such levels are experimentally known, and for 236Np and 246Am, where the information is very scarce and that too uncertain, to illustrate the effectiveness of this approach.

  8. The quest for novel modes of excitation in exotic nuclei

    NASA Astrophysics Data System (ADS)

    Paar, N.

    2010-06-01

    This paper provides an insight into several open problems in the quest for novel modes of excitation in nuclei with isospin asymmetry, deformation and finite-temperature characteristics in stellar environments. Major unsolved problems include the nature of pygmy dipole resonances, the quest for various multipole and spin-isospin excitations both in neutron-rich and proton drip-line nuclei mainly driven by loosely bound nucleons, excitations in unstable deformed nuclei and evolution of their properties with the shape phase transition. Exotic modes of excitation in nuclei at finite temperatures characteristic of supernova evolution present open problems with a possible impact in modeling astrophysically relevant weak interaction rates. All these issues challenge self-consistent many-body theory frameworks at the frontiers of on-going research, including nuclear energy density functionals, both phenomenological and constrained by the strong interaction physics of QCD, models based on low-momentum two-nucleon interaction Vlow-k and correlated realistic nucleon-nucleon interaction VUCOM, supplemented by three-body force, as well as two-nucleon and three-nucleon interactions derived from the chiral effective field theory. Joined theoretical and experimental efforts, including research with radioactive isotope beams, are needed to provide insight into dynamical properties of nuclei away from the valley of stability, involving the interplay of isospin asymmetry, deformation and finite temperature.

  9. Core excitation effects in the breakup of halo nuclei

    SciTech Connect

    Moro, A. M.; Diego, R. de; Lay, J. A.; Crespo, R.; Johnson, R. C.; Arias, J. M.; Gomez-Camacho, J.

    2012-10-20

    The role of core excitation in the structure and dynamics of two-body halo nuclei is investigated. We present calculations for the resonant breakup of {sup 11}Be on protons at an incident energy of 63.7 MeV/nucleon, where core excitation effects were shown to be important. To describe the reaction, we use a recently developed extension of the DWBA formalism which incorporates these core excitation effects within the no-recoil approximation. The validity of the no-recoil approximation is also examined by comparing with DWBA calculations which take into account core recoil. In addition, calculations with two different continuum representations are presented and compared.

  10. Neutron star structure and collective excitations of finite nuclei

    NASA Astrophysics Data System (ADS)

    Paar, N.; Moustakidis, Ch. C.; Marketin, T.; Vretenar, D.; Lalazissis, G. A.

    2014-07-01

    A method is introduced that establishes relations between properties of collective excitations in finite nuclei and the phase transition density nt and pressure Pt at the inner edge separating the liquid core and the solid crust of a neutron star. A theoretical framework that includes the thermodynamic method, relativistic nuclear energy density functionals, and the quasiparticle random-phase approximation is employed in a self-consistent calculation of (nt,Pt) and collective excitations in nuclei. Covariance analysis shows that properties of charge-exchange dipole transitions, isovector giant dipole and quadrupole resonances, and pygmy dipole transitions are correlated with the core-crust transition density and pressure. A set of relativistic nuclear energy density functionals, characterized by systematic variation of the density dependence of the symmetry energy of nuclear matter, is used to constrain possible values for (nt,Pt). By comparing the calculated excitation energies of giant resonances, energy-weighted pygmy dipole strength, and dipole polarizability with available data, we obtain the weighted average values: nt=0.0955±0.0007 fm-3 and Pt=0.59±0.05 MeV fm-3. This approach crucially depends on experimental results for collective excitations in nuclei and, therefore, accurate measurements are necessary to further constrain the structure of the crust of neutron stars.

  11. Bulk Properties of Nuclear Matter From Excitations of Nuclei

    SciTech Connect

    Shlomo, Shalom

    2007-10-26

    We consider the predictive power of Hartree-Fock (HF) approximation in determining properties of finite nuclei and thereby in extracting bulk properties of infinite nuclear matter (NM) by extrapolation. In particular, we review the current status of determining the value of NM incompressibility coefficient K, considering the most sensitive method of analyzing the recent accurate experimental data on excitation strengths of compression modes of nuclei within microscopic relativistic and non-relativistic theoretical models. We discuss the consequences of common violations of self-consistency in HF based random-phase-approximation calculations of strength functions and present results of highly accurate calculations of centroid energies and excitation cross sections of giant resonances. Explanations (resolutions) of long standing discrepancies in the value of K are presented.

  12. Excitation Spectra of Carbon Nuclei near η ' Emission Threshold

    NASA Astrophysics Data System (ADS)

    Itahashi, Kenta; Ayyad, Yassid; Benlliure, Jose; Brinkmann, Kai-Thomas; Friedrich, Stefan; Fujioka, Hiroyuki; Geissel, Hans; Gellanki, Jnaneswari; Guo, Chenlei; Gutz, Eric; Haettner, Emma; Harakeh, Muhsin N.; Hayano, Ryugo S.; Higashi, Yuko; Hirenzaki, Satoru; Hornung, Christine; Igarashi, Yoichi; Ikeno, Natsumi; Iwasaki, Masahiko; Jido, Daisuke; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Knoebel, Ronja; Kurz, Nikolaus; Metag, Volker; Mukha, Ivan; Nagae, Tomofumi; Nagahiro, Hideko; Nanova, Mariana; Nishi, Takahiro; Ong, Hooi Jin; Pietri, Stephane; Prochazka, Andrej; Rappold, Christophe; Reiter, Moritz P.; Rodríguez-Sánchez, José L.; Scheidenberger, Christoph; Simon, Haik; Sitar, Branislav; Strmen, Peter; Sun, Baohua; Suzuki, Ken; Szarka, Imrich; Takechi, Maya; Tanaka, Yoshiki K.; Tanihata, Isao; Terashima, Satoru; Watanabe, Yuni N.; Weick, Helmut; Widmann, Eberhard; Winfield, John S.; Xu, Xiaodong; Yamakami, Hiroki; Zhao, Jianwei

    We measured an excitation spectrum of 12C(p, d) reaction near the η' emission threshold using a 2.5 GeV proton beam. The measured spectrum shows no peak structures which are associated to formation of η'-mesic nuclei. Further analysis is ongoing to deduce upper limits of the formation cross section and to set constraints in the η'-nucleus interaction.

  13. Triaxial shape fluctuations and quasiparticle excitations in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Chen, Fang-Qi; Egido, J. Luis

    2017-02-01

    The deformation parameters (β ,γ ) together with two-quasiparticle excitations are taken into account, for the first time, as coordinates within a symmetry conserving (angular momentum and particle number) generator coordinate method. The simultaneous consideration of collective as well as single-particle degrees of freedom allows us to describe soft and rigid nuclei as well as the transition region in between. We apply the new theory to the study of the spectra and transition probabilities of the Er-172156 isotopes with a pairing-plus-quadrupole residual interaction. Good agreement with the experimental results is obtained for most of the observables studied and with the same quality for the very soft and the strongly deformed nuclei.

  14. The liquid to vapor phase transition in excited nuclei

    SciTech Connect

    Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.

    2001-05-08

    For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.

  15. Calculation of nuclear reaction cross sections on excited nuclei with the coupled-channels method

    SciTech Connect

    Kawano, T.; Talou, P.; Lynn, J. E.; Chadwick, M. B.; Madland, D. G.

    2009-08-15

    We calculate nuclear cross sections on excited nuclei in the fast neutron energy range. We partition the whole process into two contributions: the direct reaction part and the compound nuclear reactions. A coupled-channels method is used for calculating the direct transition of the nucleus from the initial excited state, which is a member of the ground-state rotational band, to the final ground and excited low-lying levels. This process is strongly affected by the channel coupling. The compound nuclear reactions on the excited state are calculated with the statistical Hauser-Feshbach model, with the transmission coefficients obtained from the coupled-channels calculation. The calculations are performed for a strongly deformed nucleus {sup 169}Tm, and selected cross sections for the ground and first excited states are compared. The calculation is also made for actinides to investigate possible modification to the fission cross section when the target is excited. It is shown that both the level coupling for the entrance channel, and the different target spin, change the fission cross section.

  16. Recent results on giant dipole resonance decays in highly excited nuclei

    SciTech Connect

    Snover, K.A.

    1991-01-01

    Some recent results on Giant Dipole Resonance (GDR) decays in highly excited, equilibrated nuclei, are discussed based primarily on work done at Seattle. Four sections address the following topics: oblate shapes of rotating, highly excited Zr--Mo nuclei; adiabatic versus motionally narrowed' GDR decay; large spin-driven deformations observed in hot medium-mass nuclei; and search for entrance channel effects in GDR decay following [sup 58]Ni [plus] [sup 92]Zr fusion. 22 refs.

  17. Recent results on giant dipole resonance decays in highly excited nuclei

    SciTech Connect

    Snover, K.A.

    1991-12-31

    Some recent results on Giant Dipole Resonance (GDR) decays in highly excited, equilibrated nuclei, are discussed based primarily on work done at Seattle. Four sections address the following topics: oblate shapes of rotating, highly excited Zr--Mo nuclei; adiabatic versus `motionally narrowed` GDR decay; large spin-driven deformations observed in hot medium-mass nuclei; and search for entrance channel effects in GDR decay following {sup 58}Ni {plus} {sup 92}Zr fusion. 22 refs.

  18. Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei.

    PubMed

    Fujita, Y; Fujita, H; Adachi, T; Bai, C L; Algora, A; Berg, G P A; von Brentano, P; Colò, G; Csatlós, M; Deaven, J M; Estevez-Aguado, E; Fransen, C; De Frenne, D; Fujita, K; Ganioğlu, E; Guess, C J; Gulyás, J; Hatanaka, K; Hirota, K; Honma, M; Ishikawa, D; Jacobs, E; Krasznahorkay, A; Matsubara, H; Matsuyanagi, K; Meharchand, R; Molina, F; Muto, K; Nakanishi, K; Negret, A; Okamura, H; Ong, H J; Otsuka, T; Pietralla, N; Perdikakis, G; Popescu, L; Rubio, B; Sagawa, H; Sarriguren, P; Scholl, C; Shimbara, Y; Shimizu, Y; Susoy, G; Suzuki, T; Tameshige, Y; Tamii, A; Thies, J H; Uchida, M; Wakasa, T; Yosoi, M; Zegers, R G T; Zell, K O; Zenihiro, J

    2014-03-21

    Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

  19. Core excitation effects in halo nuclei using a transformed oscillator basis

    SciTech Connect

    Lay, J. A.; Arias, J. M.; Moro, A. M.; Gomez-Camacho, J.

    2013-06-10

    A recent generalization of the Transformed Harmonic Oscillator basis, intended to consider core excitations in the structure of one nucleon halo nuclei, is applied to the break up of {sup 11}Be. The reaction studied is {sup 11}Be+{sup 208}Pb at 69 MeV/nucleon. The experimental set up is designed to ensure pure dipole Coulomb excitations. Making use of the Equivalent Photon Method and the electromagnetic transition probabilities obtained with the transformed oscillator basis, a relevant contribution of the quadrupole excitations of the core is found. The inclusion of core excitations is, therefore, necessary for the correct extraction of the dipole electromagnetic transition probability of halo nuclei.

  20. A statistical approach to describe highly excited heavy and superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Chen, Peng-Hui; Feng, Zhao-Qing; Li, Jun-Qing; Zhang, Hong-Fei

    2016-09-01

    A statistical approach based on the Weisskopf evaporation theory has been developed to describe the de-excitation process of highly excited heavy and superheavy nuclei, in particular for the proton-rich nuclei. The excited nucleus is cooled by evaporating γ-rays, light particles (neutrons, protons, α etc) in competition with binary fission, in which the structure effects (shell correction, fission barrier, particle separation energy) contribute to the processes. The formation of residual nuclei is evaluated via sequential emission of possible particles above the separation energies. The available data of fusion-evaporation excitation functions in the 28Si+198Pt reaction can be reproduced nicely within the approach. Supported by Major State Basic Research Development Program in China (2015CB856903), National Natural Science Foundation of China Projects (11175218, U1332207, 11475050, 11175074), and Youth Innovation Promotion Association of Chinese Academy of Sciences

  1. Low lying electric dipole excitations in nuclei of the rare earth region

    SciTech Connect

    von Brentano, P.; Zilges, A.; Herzberg, R.D. . Inst. fuer Kernphysik); Zamfir, N.V. ); Kneissl, U.; Heil, R.D.; Pitz, H.H. . Inst. fuer Strahlenphysik); Wesselborg, C. . Inst. fuer Kernphysik)

    1992-01-01

    From many experiments with low energy photon scattering on deformed rare earth nuclei we have obtained detailed information about the distribution of electric dipole strength below 4 MeV. Apart from some weaker transitions between 2 and 4 MeV we observed one, and sometimes two, very strong El-groundstate transitions around 1.5 MeV in all examined nuclei. They arise from the de-excitation of the bandheads of the (J[sup [pi

  2. Excited bands in even-even rare-earth nuclei

    SciTech Connect

    Vargas, Carlos E.; Hirsch, Jorge G.

    2004-09-13

    The energetics of states belonging to normal parity bands in even-even dysprosium isotopes, and their B(E2) transition strengths, are studied using an extended pseudo-SU(3) shell model. States with pseudospin 1 are added to the standard pseudospin 0 space, allowing for a proper description of known excited normal parity bands.

  3. Electromagnetic excitation of aligned /sup 7/Li nuclei

    SciTech Connect

    Weller, A.; Egelhof, P.; Caplar, R.; Karban, O.; Kraemer, D.; Moebius, K.; Moroz, Z.; Rusek, K.; Steffens, E.; Tungate, G.

    1985-07-29

    Electric ground-state properties of /sup 7/Li have been measured in a consistent way by observation of the Coulomb interaction of aligned /sup 7/Li ions with heavy target nuclei. Besides the quadrupole moment (Q/sub s/ = 3.70 +- 0.08 e/sup 2/ fm/sup 2/) and the B(E2,(3/2)/sup -/..-->..(1/2)/sup -/) value (8.3 +- 0.5 e/sup 2/ fm/sup 4/), the tensor moments of the nuclear polarizability tau/sub 12/ and tau/sub 11/ were determined (tau/sub 12/ = tau/sub 11/ = 0.23 +- 0.06 fm/sup 3/). Present theoretical investigations on the structure of /sup 7/Li reveal difficulties in providing a unified description of all four properties.

  4. Properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei

    SciTech Connect

    Gorelik, M. L. Shlomo, Sh. Tulupov, B. A. Urin, M. H.

    2015-07-15

    The recently developed particle-hole dispersive optical model is applied to describe properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. In particular, the double transition density averaged over the energy of the isoscalar monopole excitations is considered for {sup 208}Pb in a wide energy interval, which includes the isoscalar giant monopole resonance and its overtone. The energy-averaged strength functions of these resonances are also analyzed.

  5. Exotic modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2011-05-06

    Low-lying dipole excitation mode in neutron-rich Mg isotopes close to the drip line is investigated in the framework of the Hartree-Fock-Bogoliubov and the quasiparticle random-phase approximation employing the Skyrme and the pairing energy-density functionals. It is found that the low-lying dipole-strength distribution splits into the K{sup {pi}} = 0{sup -} and 1{sup -} components due to the nuclear deformation. The low-lying dipole strength increases as the neutron drip-line is approached.

  6. H2 line emission in three Seyfert nuclei: Evidence against UV-excitation

    NASA Technical Reports Server (NTRS)

    Geballe, T. R.

    1990-01-01

    Line emission from vibrationally excited molecular hydrogen has been detected in a considerable number of active galactic nuclei (AGNs), including those generally believed to contain compact and luminous central engines (e.g., Seyfert nuclei) and those in which the luminosity is believed to arise from massive bursts of star formation (starburst nuclei). In most of these AGNs, only the bright 1-0 S(1) line (rest wavelength 2.12 microns) has been searched for and detected to date. Line-emitting H2 can be excited directly either by energetic collisions created by shock waves or by absorption of UV radiation. Each of these excitation mechanisms has been clearly identified in galactic and extragalactic regions. In active galactic nuclei strong sources of UV and (in some case) x rays are present. If the nuclear molecular matter is quiescent (i.e., isolated from the active nucleus and not set into motion by episodes of star formation) the H2 line emission will be dominated by fluorescence, or possibly by thermal emission due to heating by x rays (Krolik, this conference). However, it is expected or indeed observed that a significant fraction of the interstellar medium in and near these nuclei is undergoing rapid motions; either generated by the central engine or by a nuclear starburst, which are capable of producing strong shock phenomena in nearby molecular gas. Thus, a priori it is not obvious which mechanism is responsible for the H2 line emission from the nucleus of an active galaxy.

  7. Survey of Excited State Neutron Spectroscopic Factors for Z=8-28 Nuclei

    NASA Astrophysics Data System (ADS)

    Tsang, M. B.; Lee, Jenny; Su, S. C.; Dai, J. Y.; Horoi, M.; Liu, H.; Lynch, W. G.; Warren, S.

    2009-02-01

    We have extracted 565 neutron spectroscopic factors of sd and fp shell nuclei by systematically analyzing more than 2000 measured (d, p) angular distributions. We are able to compare 125 of the extracted spectroscopic factors to values predicted by large-basis shell-model calculations and evaluate the accuracies of spectroscopic factors predicted by different shell-model interactions in these regions. We find that the spectroscopic factors predicted for most excited states of sd-shell nuclei using the latest USDA or USDB interactions agree with the experimental values. For fp shell nuclei, the inability of the current models to account for the core excitation and fragmentation of the states leads to considerable discrepancies. In particular, the agreement between data and shell-model predictions for Ni isotopes is not better than a factor of 2 using either the GXPF1A or the XT interaction.

  8. Nucleon-content effect on the fission lifetime of excited nuclei

    SciTech Connect

    Gontchar, I. I.; Ponomarenko, N. A.

    2007-12-15

    It was shown previously that the fission lifetime of a nucleus excited to about 100 MeV depends strongly and nonmonotonically on the initial value of its angular momentum L{sub 0}. This result was obtained on the basis of a refined version of the combined dynamical and statistical model. The present study is devoted to a theoretical analysis of the dependence of the fission time on the nucleonic composition of the nucleus involved. The respective calculations were performed within the same model. The dependence of the average fission time on the initial fissility parameter (Z{sup 2}/A){sub 0} appears to be of a resonance type and is similar to its dependence on L{sub 0}. This dependence of the average fission time on (Z{sup 2}/A){sub 0} stems both from statistical calculations and from a dynamical simulation of the fission mode with allowance for friction. The conditions under which the average fission time reaches a maximum are specified. The dependence of the average fission time on (Z{sup 2}/A){sub 0} remains nonmonotonic in the fusion-fission reaction as well, in which case the distribution of compound nuclei with respect to the initial angular momentum is broad.

  9. Open-shell nuclei and excited states from multireference normal-ordered Hamiltonians

    NASA Astrophysics Data System (ADS)

    Gebrerufael, Eskendr; Calci, Angelo; Roth, Robert

    2016-03-01

    We discuss the approximate inclusion of three-nucleon (3 N ) interactions into ab initio nuclear structure calculations using a multireference formulation of normal ordering and Wick's theorem. Following the successful application of single-reference normal ordering for the study of ground states of closed-shell nuclei, e.g., in coupled-cluster theory, multireference normal ordering opens a path to open-shell nuclei and excited states. Based on different multideterminantal reference states we benchmark the truncation of the normal-ordered Hamiltonian at the two-body level in no-core shell-model calculations for p -shell nuclei, including 6Li,12C, and 10B. We find that this multireference normal-ordered two-body approximation is able to capture the effects of the 3 N interaction with sufficient accuracy, both for ground-state and excitation energies, at the computational cost of a two-body Hamiltonian. It is robust with respect to the choice of reference states and has a multitude of applications in ab initio nuclear structure calculations of open-shell nuclei and their excitations as well as in nuclear reaction studies.

  10. Emission of charged particles from excited compound nuclei

    SciTech Connect

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2010-10-15

    The process of complex fragment emission is studied within the dinuclear system model. Cross sections of complex fragment emission are calculated and compared with experimental data for the reactions {sup 3}He+{sup nat}Ag, {sup 78,86}Kr+{sup 12}C, and {sup 63}Cu+{sup 12}C. The mass distributions of the products of these reactions, isotopic distributions for the {sup 3}He+{sup nat}Ag and {sup 78}Kr+{sup 12}C reactions, and average total kinetic energies of the products of the {sup 78}Kr+{sup 12}C reaction are predicted.

  11. Theoretical Investigation of the Angular-Momentum Dependence of the Mean Fission Lifetime of Excited Nuclei

    SciTech Connect

    Gontchar, I.I.; Ponomarenko, N.A.; Turkin, V.V.; Litnevsky, L.A.

    2004-11-01

    Mean fission lifetimes of nuclei excited to energies of 80 to 400 MeV were recently measured at the GANIL accelerator by the crystal-blocking technique. Those experiments served as a motivation for us to perform systematic calculations of the time distributions of fission events and the mean fission lifetimes versus the angular momentum, the initial excitation energy, and the fissility of a primary excited nucleus. The mean fission lifetimes are given as a function of the angular momentum L. The calculations were performed within the refined version of the combined dynamical-statistical model. It turned out that, if the height of the fission barrier at L = 0 is sizably greater than the neutron binding energy, the L dependence of the mean fission lifetimes has a resonance character. Such behavior of the mean fission lifetimes is obtained both from statistical calculations and from a dynamical simulation of the fission process with allowance for friction. It is shown that the maximum in the L dependence of is due to the fission of nuclei that lost a considerable part of the initial excitation energy through the emission of neutrons. The majority of the calculations were performed for {sup 190}Pt at an initial excitation energy of 150 eV. It is shown that the resonance behavior disappears with increasing fissility, but that it survives over a broad range of initial excitation energies. Systematic experimental studies are required for confirming or disproving our theoretical predictions.

  12. Interplay of projectile breakup and target excitation in reactions induced by weakly bound nuclei

    NASA Astrophysics Data System (ADS)

    Gómez-Ramos, M.; Moro, A. M.

    2017-03-01

    Background: Reactions involving weakly bound nuclei require formalisms able to deal with continuum states. The majority of these formalisms struggle to treat collective excitations of the systems involved. For continuum-discretized coupled channels (CDCC), extensions to include target excitation have been developed but have only been applied to a small number of cases. Purpose: In this work, we reexamine the extension of the CDCC formalism to include target excitation and apply it to a variety of reactions to study the effect of breakup on inelastic cross sections. Methods: We use a transformed oscillator basis to discretize the continuum of the projectiles in the different reactions and use the extended CDCC method developed in this work to solve the resulting coupled differential equations. A new code has been developed to perform the calculations. Results: Reactions 58Ni(d ,d )*58Ni , 24Mg(d ,d )*24Mg , 144Sm(6Li,6Li)*144Sm , and 9Be(6Li,6Li)*9Be are studied. Satisfactory agreement is found between experimental data and extended CDCC calculations. Conclusions: The studied CDCC method has proven to be an accurate tool to describe target excitation in reactions with weakly bound nuclei. Moderate effects of breakup on inelastic observables are found for the reactions studied. Cross-section magnitudes are not modified much, but angular distributions present smoothing when opposed to calculations without breakup.

  13. Excitation energies of double isobar-analog states in heavy nuclei

    SciTech Connect

    Poplavskii, I. V.

    1988-12-01

    Several new relationships are established for isomultiplets on the basis of a theory in which the Coulomb coupling constant (CCC) is allowed to be complex. In particular, the following rule is formulated: the energies for fission or decay of members of an isomultiplet into a charged cluster and members of the corresponding daughter isomultiplet are equidistant. This relationship is well satisfied for isomultiplets with /ital A/less than or equal to60. By extrapolating the rule for fission and decay energies to the region of heavy nuclei, the excitation energies /ital E//sub /ital x// of double isobar-analog states (DIASs) are found for the nuclei /sup 197,199/Hg, /sup 205/Pb, /sup 205 - -209/Po, /sup 209/At, and /sup 238/Pu. A comparison of the computed energies /ital E//sub /ital x// with the experimentally measured values for /sup 208/Po attest to the reliability and good accuracy of the method proposed here when used to determine the excitation energies of DIASs in heavy nuclei.

  14. Fragmentation of mixed-symmetry excitations in stable even-even tellurium nuclei

    SciTech Connect

    Hicks, S. F.; Vanhoy, J. R.; Yates, S. W.

    2008-11-15

    The lowest six excited 2{sup +} levels of the even-even {sup 122-130}Te nuclei have been investigated using {gamma}-ray spectroscopy following inelastic neutron scattering. These levels have been identified and their decay properties have been characterized from {gamma}-ray excitation functions and {gamma}-ray angular distributions; additionally, lifetimes of these levels have been deduced using the Doppler-shift attenuation method. Electromagnetic transition rates and E2/M1 multipole mixing ratios from the 2{sub x}{sup +}[x=2-6]{yields}2{sub 1}{sup +} transitions have been examined to identify the lowest mixed-symmetry states in these nuclei. In each nucleus, the mixed-symmetry strength appears to be fragmented between more than one level. The summed M1 strength from the 2{sub x}{sup +}[x=2-6] states to the 2{sub 1}{sup +} level agrees rather well with neutron-proton interacting boson model predictions in the U(5) or O(6) limits for these Te nuclei.

  15. Microscopic description of low-lying M1 excitations in odd-mass actinide nuclei

    NASA Astrophysics Data System (ADS)

    Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar

    2017-01-01

    A restoration method of a broken symmetry which allows self-consistent determination of the separable effective restoration forces is now adapted to odd-mass nuclei in order to restore violated rotational invariance (RI-) of the Quasiparticle Phonon Nuclear Model (QPNM) Hamiltonian. Because of the self-consistency of the method, these effective forces contain no arbitrary parameters. Within RI-QPNM, the properties of the low-lying magnetic dipole excitations in odd-mass deformed 229-233Th and 233-239U nuclei have been investigated for the first time. It has been shown that computed fragmentation of the M1 strengths below 4 MeV in these nuclei is much stronger than that in neighboring doubly even 228-232Th and 232-238U nuclei. For 235U the summed M1 strength in the energy range 1.5-2.8 MeV is in agreement with the relevant experimental data where the missing strength was extracted by means of a fluctuation analysis.

  16. Dipole Excitation of Soft and Giant Resonances in 132Sn and neighboring unstable nuclei

    NASA Astrophysics Data System (ADS)

    Boretzky, Konstanze

    2006-04-01

    The evolution of dipole-strength distributions above the one-neutron threshold was investigated for exotic neutron-rich nuclei in a series of experiments using the electromagnetic projectile excitation at beam energies around 500 MeV/u. For halo nuclei, the large observed dipole strength (shown here for 11Be) is explained within the direct-breakup model to be of non-collective character. For neutron-rich oxygen isotopes, the origin of the observed low-lying strength is concluded to be due to single-particle transitions on theoretical grounds. The dipole strength spectra for 130,132Sn exhibit resonance-like structures observed at energies around 10 MeV exhausting a few percent of the Thomas-Reiche-Kuhn (TRK) sum rule, separated clearly from the dominant Giant Dipole Resonance (GDR). The data agree with predictions for a new dipole mode related to the oscillation of excess neutrons versus the core nucleons ("pygmy resonance").

  17. Study of ground and excited state decays in N ≈ Z Ag nuclei

    NASA Astrophysics Data System (ADS)

    Moschner, K.; Blazhev, A.; Warr, N.; Boutachkov, P.; Davies, P.; Wadsworth, R.; Ameil, F.; Baba, H.; Bäck, T.; Dewald, M.; Doornenbal, P.; Faestermann, T.; Gengelbach, A.; Gerl, J.; Gernhäuser, R.; Go, S.; Górska, M.; Grawe, H.; Gregor, E.; Hotaka, H.; Isobe, T.; Jenkins, D. G.; Jolie, J.; Jung, H. S.; Kojouharov, I.; Kurz, N.; Lewitowicz, M.; Lorusso, G.; Merchan, E.; Naqvi, F.; Nishibata, H.; Nishimura, D.; Nishimura, S.; Pietralla, N.; Schaffner, H.; Söderström, P.-A.; Steiger, K.; Sumikama, T.; Taprogge, J.; Thöle, P.; Watanabe, H.; Werner, V.; Xu, Z. Y.; Yagi, A.; Yoshinaga, K.; Zhu, Y.

    2015-05-01

    A decay spectroscopy experiment was performed within the EURICA campaign at RIKEN in 2012. It aimed at the isomer and particle spectroscopy of excited states and ground states in the mass region below the doubly magic 100Sn. The N = Z nuclei 98In, 96Cd and 94Ag were of particular interest for the present study. Preliminary results on the neutron deficient nuclei 93Ag and 94Ag are presented. In 94Ag a more precise value for the half-life of the ground state's superallowed Fermi transition was deduced. In addition the energy spectra of the mentioned decay could be reproduced through precise Geant4 simulations of the used active stopper SIMBA. This will enable us to extract Qβ values from the measured data. The decay of 93Ag is discussed based on the observed implantation-decay correlation events.

  18. Excited-State Deactivation of Branched Phthalocyanine Compounds.

    PubMed

    Zhu, Huaning; Li, Yang; Chen, Jun; Zhou, Meng; Niu, Yingli; Zhang, Xinxing; Guo, Qianjin; Wang, Shuangqing; Yang, Guoqiang; Xia, Andong

    2015-12-21

    The excited-state relaxation dynamics and chromophore interactions in two phthalocyanine compounds (bis- and trisphthalocyanines) are studied by using steady-state and femtosecond transient absorption spectral measurements, where the excited-state energy-transfer mechanism is explored. By exciting phthalocyanine compounds to their second electronically excited states and probing the subsequent relaxation dynamics, a multitude of deactivation pathways are identified. The transient absorption spectra show the relaxation pathway from the exciton state to excimer state and then back to the ground state in bisphthalocyanine (bis-Pc). In trisphthalocyanine (tris-Pc), the monomeric and dimeric subunits are excited and the excitation energy transfers from the monomeric vibrationally hot S1 state to the exciton state of a pre-associated dimer, with subsequent relaxation to the ground state through the excimer state. The theoretical calculations and steady-state spectra also show a face-to-face conformation in bis-Pc, whereas in tris-Pc, two of the three phthalocyanine branches form a pre-associated face-to-face dimeric conformation with the third one acting as a monomeric unit; this is consistent with the results of the transient absorption experiments from the perspective of molecular structure. The detailed structure-property relationships in phthalocyanine compounds is useful for exploring the function of molecular aggregates in energy migration of natural photosynthesis systems.

  19. Thorium silicate compound as a solid-state target for production of isomeric thorium-229 nuclei by electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Borisyuk, P. V.; Vasilyev, O. S.; Lebedinskii, Y. Y.; Krasavin, A. V.; Tkalya, E. V.; Troyan, V. I.; Habibulina, R. F.; Chubunova, E. V.; Yakovlev, V. P.

    2016-09-01

    In this paper, we discuss an idea of the experiment for excitation of the isomeric transition in thorium-229 nuclei by irradiating with electron beam targets with necessary physical characteristics. The chemical composition and bandgap of ThSi10O22 were determined by X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. It was found that the energy gap is equal to 7.7 eV and does not change when the target is exposed to a medium energy electron beam for a long time. This indicates that the compound possesses high electron-beam resistance. A quantitative estimation of the output function of isomeric thorium-229 nuclei generated by interaction of nuclei with the secondary electron flow formed by irradiating the solid-state ThSi10O22-based target is given. The estimation shows that ThSi10O22 is a promising thorium-containing target for investigating excitation of the nuclear low-lying isomeric transition in the thorium-229 isotope using medium-energy electrons.

  20. Low lying electric dipole excitations in nuclei of the rare earth region

    SciTech Connect

    von Brentano, P.; Zilges, A.; Herzberg, R.D.; Zamfir, N.V.; Kneissl, U.; Heil, R.D.; Pitz, H.H.; Wesselborg, C.

    1992-10-01

    From many experiments with low energy photon scattering on deformed rare earth nuclei we have obtained detailed information about the distribution of electric dipole strength below 4 MeV. Apart from some weaker transitions between 2 and 4 MeV we observed one, and sometimes two, very strong El-groundstate transitions around 1.5 MeV in all examined nuclei. They arise from the de-excitation of the bandheads of the (J{sup {pi}},K)=(l{sup {minus}},0) and (J{sup {pi}},K)=(l{sup {minus}},1) octupole vibrational bands. It is shown that the decay branching ratios and the absolute transition strengths of these states can be reproduced rather well with an improved T(El)-operator in the sdf-Interacting Boson Model. Another class of octupole states has been investigated in the region of the semimagic nucleus {sup 142}Nd. Here a quintuplet of collective excitations around 3.5 MeV is expected due to the coupling of the 3{minus}-octupole vibration with the 2+-quadrupole vibration. We performed photon scattering experiments on the odd A neighboring nucleus {sup 141}Pr and found first evidence for the existence of 3{sup {minus}}{circle_times}2+{circle_times}particle-states.

  1. Precise Coulomb excitation B(E2) measurements for first 2+states of projectile nuclei near the doubly magic nuclei 78Ni and 132Sn

    NASA Astrophysics Data System (ADS)

    Galindo-Uribarri, A.

    2012-09-01

    Coulomb excitation is a very precise tool to measure excitation probabilities and provide insight on the collectivity of nuclear excitations and in particular on nuclear shapes. In the last few years radioactive ion beam facilities such as HRIBF opened unique opportunities to explore the structure of nuclei in the regions near the doubly magic nuclei 78Ni (Z=28 and N=50) and 132Sn (Z=50 and N=82). For this purpose we have developed specialized methods and instrumentation to measure various observables. There is also the opportunity to perform precision experiments with stable beams using exactly the same state-of-the-art instrumentation and techniques as with their radioactive ion beam counterpart. I describe some of the recent efforts at HRIBF to do more precise measurements using particle-gamma techniques.

  2. Contribution of excited states to stellar weak-interaction rates in odd-A nuclei

    NASA Astrophysics Data System (ADS)

    Sarriguren, P.

    2016-05-01

    Weak-interaction rates, including β decay and electron capture, are studied in several odd-A nuclei in the p f -shell region at various densities and temperatures of astrophysical interest. Special attention is paid to the relative contribution to these rates of thermally populated excited states in the decaying nucleus. The nuclear structure involved in the weak processes is studied within a quasiparticle random-phase approximation with residual interactions in both particle-hole and particle-particle channels on top of a deformed Skyrme Hartree-Fock mean field with pairing correlations. In the range of densities and temperatures considered, it is found that the total rates do not differ much from the rates of the ground state fully populated. In any case, the changes are not larger than the uncertainties due to the nuclear-model dependence of the rates.

  3. Coulomb Excitation of n-rich nuclei along the N = 50 shell closure

    NASA Astrophysics Data System (ADS)

    Padilla-Rodal, E.; Galindo-Uribarri, A.; Batchelder, J. C.; Beene, J. R.; Bingham, C.; Brown, B. A.; Lagergren, K. B.; Mueller, P. E.; Radford, D. C.; Stracener, D. W.; Urrego-Blanco, J. P.; Varner, R. L.; Yu, C.-H.

    2008-04-01

    Recently, we have been investigating characteristics of nuclear states around the neutron-rich mass A=80 region [1]. Using the Radioactive Ion Beams (RIBs) produced at HRIBF, we have successfully measured the B(E2) values for ^78,80,82Ge , using Coulomb excitation in inverse kinematics. For the germanium isotopes, these data allow a study of the systematic trend between the subshell N= 40 and the N=50 shell. Using the same technique, we have measured the B(E2) value of various nuclei along the N=50 shell including the radioactive nucleus ^84Se. This value together with our previously measured ^82Ge, and the recent result on ^80Zn from ISOLDE [2] are providing basic experimental information needed for a better understanding of the neutron-rich nuclei around A˜80. We report the new results and compare with shell model calculations. [1] E. Padilla-Rodal et al., Phys. Rev. Lett. 94 (2005) 122501. [2] J. Van de Walle et al., Phys. Rev. Lett. 99 (2007) 142501.

  4. Emission of charged particles from excited compound nucleus

    SciTech Connect

    Kalandarov, Sh. A.; Adamian, G. G.; Antonenko, N. V.

    2010-11-24

    The formation and decay of excited compound nucleus are studied within the dinuclear system model[1]. The cross sections of complex fragment emission are calculated and compared with experimental data for the reactions {sup 3}He+{sup 108}Ag, {sup 78,82}Kr+{sup 12}C. Angular momentum dependence of cluster emission in {sup 78}Kr+{sup 12}C and {sup 40}Ca+{sup 78}Kr reactions is demonstrated.

  5. Excitation of discrete levels of {sup 63}Cu and {sup 65}Cu nuclei in (e, e') reactions

    SciTech Connect

    Denyak, V. V. Khvastunov, V. M.; Paschuk, S. A.; Schelin, H. R.; Khomich, A. A.; Shevchenko, N. G.

    2010-03-15

    Inelastic electron scattering on {sup 63}Cu and {sup 65}Cu nuclei at excitation energies of up to 5 MeV was studied. Information about the reduced probability and multipolarity of transitions was obtained for 11 low-lying levels and groups of levels of the {sup 63}Cu nucleus and for 17 such levels and groups of levels of the {sup 65}Cu nucleus. It was shown that the experimental form factors for inelastic scattering accompanied by the excitation of discrete levels and group of levels of these nuclei with a nonzero spin can be described in terms of a single multipolarity, even though the law of angular-momentum conservation admits the existence of several more multipolarities yielding the same parity of an excited state.

  6. Theoretical study of different features of the fission process of excited nuclei in the framework of the modified statistical model and four-dimensional dynamical model

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2017-02-01

    Evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity for the excited compound nuclei {}168{{Y}}{{b}}, {}172{{Y}}{{b}}, {}178{{W}} and {}227{{P}}{{a}} produced in fusion reactions have been calculated in the framework of the modified statistical model and multidimensional dynamical model. In the dynamical calculations, the dynamics of fission of excited nuclei has been studied by solving three- and four-dimensional Langevin equations with dissipation generated through the chaos-weighted wall and window friction formula. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis, K, were considered in the four-dimensional dynamical model. A non-constant dissipation coefficient of K, {γ }k, was applied in the four-dimensional dynamical calculations. A comparison of the results of the three- and four-dimensional dynamical models with the experimental data showed that the results of the four-dimensional dynamical model for the evaporation residue cross section, fission probability, anisotropy of fission fragment angular distribution, mass and energy distributions of fission fragments and the pre-scission neutron multiplicity are in better agreement with the experimental data. It was also shown that the modified statistical model can reproduce the above-mentioned experimental data by choosing appropriate values of the temperature coefficient of the effective potential, λ , and the scaling factor of the fission-barrier height, {r}s.

  7. The Fe II Emission in Active Galactic Nuclei: Excitation Mechanisms and Location of the Emitting Region

    NASA Astrophysics Data System (ADS)

    Marinello, M.; Rodríguez-Ardila, A.; Garcia-Rissmann, A.; Sigut, T. A. A.; Pradhan, A. K.

    2016-04-01

    We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

  8. THE Fe II EMISSION IN ACTIVE GALACTIC NUCLEI: EXCITATION MECHANISMS AND LOCATION OF THE EMITTING REGION

    SciTech Connect

    Marinello, M.; Rodríguez-Ardila, A.; Garcia-Rissmann, A.; Sigut, T. A. A.; Pradhan, A. K.

    2016-04-01

    We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

  9. Crossover from skin mode to proton-neutron mode in E1 excitations of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Nakada, H.; Inakura, T.; Sawai, H.

    2013-03-01

    The character of the low-energy E1 excitations is investigated by analyzing transition densities obtained from the RPA calculations in the doubly magic nuclei. We propose a decomposition method of the E1 excitations into the pn mode (i.e., oscillation between protons and neutrons) and the skin mode (i.e., oscillation of the neutron skin against the inner core) via the transition densities, by which their mixing is handled in a straightforward manner. Crossover behavior of the E1 excitations is found, from the skin mode at low energy to the pn mode at higher energy. The ratio of the skin-mode strength to the full strength turns out to be insensitive to the nuclides and to the effective interactions in the energy region of the crossover. Depending on the excitation energy, the observed low-energy E1 excitations are not necessarily dominated by the skin mode, as exemplified for 90Zr.

  10. A new differentially pumped plunger device to measure excited-state lifetimes in proton emitting nuclei

    NASA Astrophysics Data System (ADS)

    Taylor, M. J.; Cullen, D. M.; Smith, A. J.; McFarlane, A.; Twist, V.; Alharshan, G. A.; Procter, M. G.; Braunroth, T.; Dewald, A.; Ellinger, E.; Fransen, C.; Butler, P. A.; Scheck, M.; Joss, D. T.; Saygi, B.; McPeake, C. G.; Grahn, T.; Greenlees, P. T.; Jakobsson, U.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nieminen, P.; Pakarinen, J.; Peura, P.; Rahkila, P.; Ruotsalainen, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Uusitalo, J.

    2013-04-01

    A new plunger device has been designed and built to measure the lifetimes of unbound states in exotic nuclei beyond the proton drip-line. The device has been designed to work in both vacuum and dilute-gas environments made possible through the introduction of a low-voltage stepping motor. DPUNS will be used in conjunction with the gas-filled separator RITU and the vacuum separator MARA at the accelerator laboratory of the University of Jyväskylä, Finland, to measure the lifetimes of excited states with low population cross-sections. This is achieved by eliminating the need for a carbon foil to isolate the helium gas of RITU from the beam line thus reducing the background from beam-foil reactions. The inclusion of a high-sampling rate data acquisition card increases further the sensitivity of the device. The plunger will be used to address many key facets of nuclear structure physics with particular emphasis on the effect of deformation on proton emission rates.

  11. Do nuclei go pear-shaped? Coulomb excitation of 220Rn and 224Ra at REX-ISOLDE (CERN)

    NASA Astrophysics Data System (ADS)

    Scheck, M.; Gaffney, L. P.; Butler, P. A.; Hayes, A. B.; Wenander, F.; Albers, M.; Bastin, B.; Bauer, C.; Blazhev, A.; Boenig, S.; Bree, N.; Cederkall, J.; Chupp, T.; Cline, D.; Cocolios, T. E.; Davinson, T.; De Witte, H.; Diriken, J.; Grahn, T.; Herzan, A.; Huyse, M.; Jenkins, D. G.; Joss, D. T.; Kesteloot, N.; Konki, J.; Kowalczyk, M.; Kroell, Th.; Kwan, E.; Lutter, R.; Moschner, K.; Napiorkowski, P.; Pakarinen, J.; Pfeiffer, M.; Radeck, D.; Reiter, P.; Reynders, K.; Rigby, S. V.; Robledo, L. M.; Rudigier, M.; Sambi, S.; Seidlitz, M.; Siebeck, B.; Stora, T.; Thoele, P.; Van Duppen, P.; Vermeulen, M. J.; von Schmid, M.; Voulot, D.; Warr, N.; Wimmer, K.; Wrzosek-Lipska, K.; Wu, C. Y.; Zielinska, M.

    2015-05-01

    The IS475 collaboration conducted Coulomb-excitation experiments with post-accelerated radioactive 220Rn and 224Ra beams at the REX-ISOLDE facility. The beam particles (Ebeam: 2.83 MeV/u) were Coulomb excited using 60Ni, 114Cd, and 120Sn scattering targets. De-excitation γ-rays were detected employing the Miniball array and scattered particles were detected in a silicon detector. Exploiting the Coulomb-excitation code GOSIA for each nucleus several matrix elements could be obtained from the measured γ-ray yields. The extracted ‹3-||E3||0+› matrix element allows for the conclusion that, while 220Rn represents an octupole vibrational system, 224Ra has already substantial octupole correlations in its ground state. This finding has implications for the search of CP-violating Schiff moments in the atomic systems of the adjacent odd-mass nuclei.

  12. Investigation of the energy-averaged double transition density of isoscalar monopole excitations in medium-heavy mass spherical nuclei

    NASA Astrophysics Data System (ADS)

    Gorelik, M. L.; Shlomo, S.; Tulupov, B. A.; Urin, M. H.

    2016-11-01

    The particle-hole dispersive optical model, developed recently, is applied to study properties of high-energy isoscalar monopole excitations in medium-heavy mass spherical nuclei. The energy-averaged strength functions of the isoscalar giant monopole resonance and its overtone in 208Pb are analyzed. In particular, we analyze the energy-averaged isoscalar monopole double transition density, the key quantity in the description of the hadron-nucleus inelastic scattering, and studied the validity of the factorization approximation using semi classical and microscopic one body transition densities, respectively, in calculating the cross sections for the excitation of isoscalar giant resonances by inelastic alpha scattering.

  13. Monopole effects, isomeric states, and cross-shell excitations in the A =129 hole nuclei near 132Sn

    NASA Astrophysics Data System (ADS)

    Wang, Han-Kui; Kaneko, Kazunari; Sun, Yang; He, Yi-Qi; Li, Shao-Feng; Li, Jian

    2017-01-01

    We present results of large-scale shell-model calculations for the A =129 hole nuclei below 132Sn. We discuss structures of 129Sn, 129In, and 129Cd with emphasis on the monopole effects and excitations across the neutron N =82 shell gap, and further predict low-lying levels for the more exotic 129Ag. It is demonstrated that the monopole corrections in the Hamiltonian, which dynamically affect occupations of relevant orbits, can lead to interesting consequences for the shell evolution. It is found especially that the monopole terms, previously introduced to reproduce the cross-shell excitations of the 17 /2+ and 21 /2+ states in 131In, shows more pronounced effects on the A =129 nuclei. In 129In, the cross-shell excitations of 17 /2+ and 21 /2+ are pushed down significantly by the monopole terms, and in 129Cd, the same monopole terms reverse the order of the single-hole states of ν d3 /2 and ν h11 /2 , causing 11/2 - as the ground state for this nucleus. The structure of isomeric states in the A =129 nuclei is also discussed.

  14. Coulomb Excitation and One-Neutron Transfer Studies of Stable and Radioactive Nuclei at HRIBF-ORNL

    SciTech Connect

    Allmond, James M

    2015-01-01

    Several stable and radioactive nuclei ranging from $A=58$ to 208 were recently studied in inverse kinematics by Coulomb excitation and heavy-ion induced one-neutron transfer at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory. These studies used a CsI-HPGe detector array to detect scattered charged particles and emitted $\\gamma$ rays from the in-beam reactions. A Bragg-curve detector was used to measure the energy loss of the various beams through the targets and to measure the radioactive beam compositions. Stable nickel, strontium, zirconium, molybdenum, tin, tellurium, and lead isotopes and neutron-rich radioactive tin and tellurium isotopes were among the nuclei recently studied. Coulomb excitation was used to measure the electromagnetic moments of the first excited states and heavy-ion induced one-neutron transfer was used to measure the absolute cross sections and lifetimes of the excited single-particle states. A sample of these results are presented here with an emphasis on the tin isotopes. In particular, a survey of the Bragg-curve measurements, Doppler corrections, and inconclusive $i_{13/2}$ candidate in $^{133}$\\textrm{Sn} are presented.

  15. Interplay of collective and single-particle properties of excited states of deformable odd nuclei {sup 155}Eu and {sup 161}Tm

    SciTech Connect

    Sharipov, Sh.; Ermamatov, M. J. Bayimbetova, J. K.

    2008-02-15

    The properties of excited states of two deformable odd nuclei are investigated within the nonadiabatic model previously developed by the present authors. The results of relevant calculations are compared with available experimental data.

  16. X-ray excited Auger transitions of Pu compounds

    SciTech Connect

    Nelson, Art J. Grant, William K.; Stanford, Jeff A.; Siekhaus, Wigbert J.; Allen, Patrick G.; McLean, William

    2015-05-15

    X-ray excited Pu core–valence–valence and core–core–valence Auger line-shapes were used in combination with the Pu 4f photoelectron peaks to characterize differences in the oxidation state and local electronic structure for Pu compounds. The evolution of the Pu 4f core-level chemical shift as a function of sputtering depth profiling and hydrogen exposure at ambient temperature was quantified. The combination of the core–valence–valence Auger peak energies with the associated chemical shift of the Pu 4f photoelectron line defines the Auger parameter and results in a reliable method for definitively determining oxidation states independent of binding energy calibration. Results show that PuO{sub 2}, Pu{sub 2}O{sub 3}, PuH{sub 2.7}, and Pu have definitive Auger line-shapes. These data were used to produce a chemical state (Wagner) plot for select plutonium oxides. This Wagner plot allowed us to distinguish between the trivalent hydride and the trivalent oxide, which cannot be differentiated by the Pu 4f binding energy alone.

  17. The reduced transition probabilities for excited states of rare-earths and actinide even-even nuclei

    SciTech Connect

    Ghumman, S. S.

    2015-08-28

    The theoretical B(E2) ratios have been calculated on DF, DR and Krutov models. A simple method based on the work of Arima and Iachello is used to calculate the reduced transition probabilities within SU(3) limit of IBA-I framework. The reduced E2 transition probabilities from second excited states of rare-earths and actinide even–even nuclei calculated from experimental energies and intensities from recent data, have been found to compare better with those calculated on the Krutov model and the SU(3) limit of IBA than the DR and DF models.

  18. Evolution of collectivity near mid-shell from excited-state lifetime measurements in rare earth nuclei

    NASA Astrophysics Data System (ADS)

    Werner, V.; Cooper, N.; Régis, J.-M.; Rudigier, M.; Williams, E.; Jolie, J.; Cakirli, R. B.; Casten, R. F.; Ahn, T.; Anagnostatou, V.; Berant, Z.; Bonett-Matiz, M.; Elvers, M.; Heinz, A.; Ilie, G.; Radeck, D.; Savran, D.; Smith, M. K.

    2016-03-01

    The B (E 2 ) excitation strength of the first excited 2+ state in even-even nuclei should directly correlate with the size of the valence space and maximize at mid-shell. A previously found saturation of B (E 2 ) strengths in well-deformed rotors at mid-shell is tested through high-precision measurements of the lifetimes of the lowest-lying 2+ states of the 168Hf and 174W rare earth isotopes. Measurements were performed using fast LaBr3 scintillation detectors. Combined with the recently remeasured B (E 2 ;21+→01+) values for Hf and W isotopes the new data remove discrepancies observed in the differentials of B (E 2 ) values for these isotopes.

  19. Dynamical Model for the Decay of Hot and Rotating Compound Nuclei

    SciTech Connect

    Gupta, Raj K.; Singh, Dalip; Arun, Sham K.; Niyti; Kumar, Raj

    2009-03-04

    As an alternative to the well known Hauser-Feshbach analysis and statistical fission model, a dynamical collective clusterization model, called the dynamical cluster-decay model (DCM), is developed for the decay of hot and rotating compound nuclei (CN) formed in the low-energy heavy ion reactions. The model is a non-statistical description for the decay of a CN to light particles (LPs), intermediate mass fragments (IMFs), fusion-fission (FF) and quasi-fission (QF)(equivalently, capture) processes. The model considers all decay products as dynamical mass motions of preformed fragments or clusters through the interaction barrier, thereby including structure effects of the CN, and is applicable to CN from different mass regions.

  20. Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods

    DOE PAGES

    Petters, M. D.; Kreidenweis, S. M.; Ziemann, P. J.

    2016-01-19

    A wealth of recent laboratory and field experiments demonstrate that organic aerosol composition evolves with time in the atmosphere, leading to changes in the influence of the organic fraction to cloud condensation nuclei (CCN) spectra. There is a need for tools that can realistically represent the evolution of CCN activity to better predict indirect effects of organic aerosol on clouds and climate. This work describes a model to predict the CCN activity of organic compounds from functional group composition. Following previous methods in the literature, we test the ability of semi-empirical group contribution methods in Köhler theory to predict themore » effective hygroscopicity parameter, kappa. However, in our approach we also account for liquid–liquid phase boundaries to simulate phase-limited activation behavior. Model evaluation against a selected database of published laboratory measurements demonstrates that kappa can be predicted within a factor of 2. Simulation of homologous series is used to identify the relative effectiveness of different functional groups in increasing the CCN activity of weakly functionalized organic compounds. Hydroxyl, carboxyl, aldehyde, hydroperoxide, carbonyl, and ether moieties promote CCN activity while methylene and nitrate moieties inhibit CCN activity. The model can be incorporated into scale-bridging test beds such as the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to evaluate the evolution of kappa for a complex mix of organic compounds and to develop suitable parameterizations of CCN evolution for larger-scale models.« less

  1. Prediction of cloud condensation nuclei activity for organic compounds using functional group contribution methods

    NASA Astrophysics Data System (ADS)

    Petters, M. D.; Kreidenweis, S. M.; Ziemann, P. J.

    2016-01-01

    A wealth of recent laboratory and field experiments demonstrate that organic aerosol composition evolves with time in the atmosphere, leading to changes in the influence of the organic fraction to cloud condensation nuclei (CCN) spectra. There is a need for tools that can realistically represent the evolution of CCN activity to better predict indirect effects of organic aerosol on clouds and climate. This work describes a model to predict the CCN activity of organic compounds from functional group composition. Following previous methods in the literature, we test the ability of semi-empirical group contribution methods in Köhler theory to predict the effective hygroscopicity parameter, kappa. However, in our approach we also account for liquid-liquid phase boundaries to simulate phase-limited activation behavior. Model evaluation against a selected database of published laboratory measurements demonstrates that kappa can be predicted within a factor of 2. Simulation of homologous series is used to identify the relative effectiveness of different functional groups in increasing the CCN activity of weakly functionalized organic compounds. Hydroxyl, carboxyl, aldehyde, hydroperoxide, carbonyl, and ether moieties promote CCN activity while methylene and nitrate moieties inhibit CCN activity. The model can be incorporated into scale-bridging test beds such as the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to evaluate the evolution of kappa for a complex mix of organic compounds and to develop suitable parameterizations of CCN evolution for larger-scale models.

  2. Excited State Properties in Neutron-rich Nuclei near N = 40

    NASA Astrophysics Data System (ADS)

    Crider, B. P.; Prokop, C. J.; Liddick, S. N.; Chiara, C. J.; Ayangeakaa, A. D.; Carroll, J. J.; Chen, J.; David, H. M.; Go, S.; Grzywacz, R.; Harker, J.; Janssens, R. V. F.; Lauritsen, T.; Seweryniak, D.; Walters, W. B.

    2015-10-01

    The neutron-rich nuclei near N = 40 have recently been the focus of many experimental and theoretical efforts. In this region, the competing energy cost for promoting pairs of nucleons across either Z = 28 or N = 40 and the energy gain from residual nucleon-nucleon interactions gives rise to several low-energy 0+ states and is a hallmark of shape coexistence. Low-energy 0+ states have been observed in 68Ni, and predicted for other nuclei in the region. Recent theoretical calculations are able to reproduce the energies of known states in 68Ni and stress the importance of the tensor component of the monopole interaction. Yet, while energies of the levels are a useful comparison, a more stringent test is the reproduction of level lifetimes, where the predicted half-lives can vary by several orders of magnitude depending on the interaction. To further benchmark theoretical calculations in this region, a setup designed to measure level lifetimes has been constructed. A description of the array and preliminary results will be presented. This work was supported by the DOE NNSA Award No. DE-NA0000979, NSF Contract No. PHY1102511, DOE SC NP Contract No. DE-AC-06CH11357 and Grant No. DE-FG02-94ER40834.

  3. Statistical properties of excited nuclei in the mass range 47 ⩽ A ⩽ 59

    NASA Astrophysics Data System (ADS)

    Zhuravlev, B. V.; Lychagin, A. A.; Titarenko, N. N.; Demenkov, V. G.; Trykova, V. I.

    2012-09-01

    Level densities and their energy dependences for nuclei in the mass range of 47 ≤ A ≤ 59 were determined from the results obtained by measuring neutron-evaporation spectra in respective ( p, n) reactions. The spectra of neutrons originating from the ( p, n) reactions on 47Ti, 48Ti, 49Ti, 53Cr, 54Cr, 57Fe, and 59Co nuclei were measured in the proton-energy range of 7-11 MeV. These measurements were performed with the aid of a fast-neutron spectrometer by the time-of-flight method over the base of the EGP-15 pulsed tandem accelerator installed at the Institute for Physics and Power Engineering (Obninsk, Russia). A high resolution of the spectrometer and its stability in the time of flight made it possible to identify reliably discrete low-lying levels along with the continuum part of neutron spectra. Our measured data were analyzed within the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed with the aid of the Hauser-Feshbach formalismof statistical theory supplemented with the generalized model of a superfluid nucleus, the back-shifted Fermi gas model, and the Gilbert-Cameron composite formula for nuclear level densities. Nuclear level densities for 47V, 48V, 49V, 53Mn, 54Mn, 57Co, and 59Ni and their energy dependences were determined. The results are discussed and compared with available experimental data and with recommendations of model-based systematics.

  4. Charge-changing particle-hole excitation of {sup 16}N and {sup 16}F nuclei

    SciTech Connect

    Taqi Al-Bayati, Ali H.; Darwesh, Sarah S.

    2013-12-16

    The nuclear structure of {sup 16}N (closed shell + ν − π) and {sup 16}F (closed shell + π − ν) nuclei is studied using particle-hole proton-neutron Tamm-Dancoff Approximation pn TDA and particle-hole proton-neutron Random Phase Approximation pn RPA. The particle-hole Hamiltonian of PSD model space is to be diagonalized in the presence of the PSDMWKPN interaction: for P-space the Cohen-Kurath interaction, for SD-space the Wildenthal Interaction, for the coupling matrix elements between P- and SD-spaces the Millener-Kurath interaction is used, spurious components were eliminated with CM contribution. The results containing energy level schemes and electromagnetic transition strength are compared with the available experimental data.

  5. Charge-changing particle-hole excitation of 16N and 16F nuclei

    NASA Astrophysics Data System (ADS)

    Taqi Al-Bayati, Ali H.; Darwesh, Sarah S.

    2013-12-01

    The nuclear structure of 16N (closed shell + ν - π) and 16F (closed shell + π - ν) nuclei is studied using particle-hole proton-neutron Tamm-Dancoff Approximation pn TDA and particle-hole proton-neutron Random Phase Approximation pn RPA. The particle-hole Hamiltonian of PSD model space is to be diagonalized in the presence of the PSDMWKPN interaction: for P-space the Cohen-Kurath interaction, for SD-space the Wildenthal Interaction, for the coupling matrix elements between P- and SD-spaces the Millener-Kurath interaction is used, spurious components were eliminated with CM contribution. The results containing energy level schemes and electromagnetic transition strength are compared with the available experimental data.

  6. Effect of the initial excitation energy on the average fission lifetime of nuclei

    SciTech Connect

    Gontchar, I. I. Ponomarenko, N. A. Litnevsky, A. L.

    2008-07-15

    The dependence of the fission time on the initial nuclear excitation energy E{sub tot0}* is studied on the basis of a refined combined dynamical and statistical model. It is shown that this dependence may be nonmonotonic, in which case it features a broad maximum. It turns out that the form of the average fission time as a function of E{sub tot0}* depends greatly on the orbital angular momentum L{sub n} carried away by prescission neutrons.

  7. Deformation increase of high-spin core-excited isomers in the astatine nuclei

    SciTech Connect

    Scheveneels, G.; Hardeman, F.; Neyens, G.; Coussement, R. )

    1991-06-01

    Quadrupole moments of six high-spin isomers in the At isotopes have been measured with the level-mixing-spectroscopy method: {sup 208}At(16{sup {minus}}), {sup 209}At(29/2{sup +}), {sup 210}At(19{sup +},15{sup {minus}}), {sup 211}At(39/2{sup {minus}},29/2{sup +}). The results show that level mixing spectroscopy is a promising technique to determine quadrupole moments of isomers that are difficult to measure by other in-beam hyperfine interaction methods. A large increase of the quadrupole moment is observed if neutrons are excited across or removed from the {ital N}=126 shell closure. This behavior is explained in terms of an enhanced core softness for fewer core neutrons; the aligned valence particles, moving in equatorial orbits, then easily polarize the core towards oblate deformation.

  8. Possible conservation of the K-quantum number in excited rotating nuclei

    SciTech Connect

    Bracco, A.; Bosetti, P.; Leoni, S. |

    1996-12-31

    The {gamma}-cascades feeding into low-K and high-K bands in the nucleus {sup 163}Er are investigated by analyzing variances and covariances of the spectrum fluctuations. The study of the covariance between pairs of gated spectra reveals that the cascades feeding into the low-K bands are completely different from those feeding the high-K bands. In addition, the number of decay paths obtained analyzing the ridge and the valley in spectra gated by high-K transitions is different than that deduced from the total spectrum. This result is well reproduced with microscopic calculations of strongly interacting bands. It is concluded that the K-selection rules are effective for the excited rotational bands within the angular momentum region probed by the experiment, 30{Dirac_h} {le} I {le} 40{Dirac_h}.

  9. Charge-exchange modes of excitation in deformed neutron-rich nuclei

    SciTech Connect

    Yoshida, Kenichi

    2015-10-15

    Gamow-Teller (GT) mode of excitation and β-decay properties of deformed neutron-rich even-N Zr isotopes are investigated in a self-consistent Skyrme energy-density-functional approach, in which the Hartree-Fock-Bogoliubov equation is solved in the coordinate space and the proton-neutron Quasiparticle-RPA equation is solved in the quasiparticle basis. It is found that a stronger collectivity is generated for the GT giant resonance as an increase in the neutron number. Furthermore, we find that the T = 0 pairing enhances the low-lying GT strengths cooperatively with the T = 1 pairing correlation depending on the microscopic structure of the low-lying mode and the shell structure around the Fermi levels, and that the enhanced strength shortens the β-decay half-lives by at most an order of magnitude.

  10. Role of nuclear couplings in the inelastic excitation of weakly-bound neutron-rich nuclei

    SciTech Connect

    Dasso, C.H.; Lenzi, S.M.; Vitturi, A.

    1996-12-31

    Much effort is presently devoted to the study of nuclear systems far from the stability line. Particular emphasis has been placed in light systems such as {sup 11}Li, {sup 8}B and others, where the very small binding energy of the last particles causes their density distribution to extend considerably outside of the remaining nuclear core. Some of the properties associated with this feature are expected to characterize also heavier systems in the vicinity of the proton or neutron drip lines. It is by now well established that low-lying concentrations of multipole strength arise from pure configurations in which a peculiar matching between the wavelength of the continuum wavefunction of the particles and the range of the weakly-bound hole states occurs. To this end the authors consider the break-up of a weakly-bound system in a heavy-ion collision and focus attention in the inelastic excitation of the low-lying part of the continuum. They make use of the fact that previous investigations have shown that the multipole response in this region is not of a collective nature and describe their excited states as pure particle-hole configurations. Since the relevant parameter determining the strength distributions is the binding energy of the last bound orbital they find it most convenient to use single-particle wavefunctions generated by a sperical square-well potential with characteristic nuclear dimensions and whose depth has been adjusted to give rise to a situation in which the last occupied neutron orbital is loosely-bound. Spin-orbit couplings are, for the present purpose, ignored. The results of this investigation clearly indicate that nuclear couplings have the predominant role in causing projectile dissociation in many circumstances, even at bombarding energies remarkably below the Coulomb barrier.

  11. Characterization of the multifragment decay channel in highly excited nuclei. [Indiana Univ. , Bloomington, Indiana

    SciTech Connect

    de Souza, R.T.

    1992-10-01

    Characteristics of multifragment decay in heavy-ion induced reactions at intermediate energies are explored. Evolution of the timescale for emission of intermediate mass fragments (IMF: 3[le]Z[le]20) is investigated. Fragments associated with central collisions in the reactions [sup 36]Ar + [sup 197]Au at E/A = 50, 80, and 110 MeV are emitted on an extremely fast timescale, [tau] [le] 75 fm/c, comparable to the transit time of the projectile past the target nucleus. With increasing incident energy, mean fragment emission times decrease, consistent with statistical decay from highly excited systems or fast dynamical processes. To examine the importance of expansion effects in multifragmentation, the transverse kinetic energy of fragments was investigated. Evidence for expansion effects in the system [sup 36]Ar + [sup 197]Au at E/A = 50, 80, and 110 MeV was indicated by the charge dependence of the mean isotropic kinetic energy. At the highest incident energy the data suggest the onset of volume emission. Construction and performance of low-threshold high-resolution detector telescopes is discussed. Three-body Coulomb trajectory calculations are being used to probe kinematical correlations associated with neck emission of IMFs during fission. Initial design and testing of position sensitive parallel plate avalanche counters for upcoming ternary fission experiments is discussed.

  12. A visual Fortran 90 program for the two-particle or two-hole excitations of nuclei: The PPRPA program

    NASA Astrophysics Data System (ADS)

    Taqi, Ali H.

    Random Phase Approximation (RPA) is one of the main approximation tools in studying nuclear structure. Here, we present a graphical user interface (GUI) Fortran code: Particle-Particle Random Phase Approximation (PPRPA) version 1, 2015. The code performs Tamm-Dancoff approximation (TDA) and Random Phase Approximation (RPA) calculations of nuclear structure of nuclei having A ± 2 nucleons in the total angular momenta and isospin (JT) scheme. The Hamiltonian is diagonalized with a given input model space, single-particle energies and interaction. Space function has been expanded to include orbits s, p, d, f, g and h. The current version of the code allows the user to test 20 orbits only. All possible eigenvalues and amplitudes within a model space are calculated. The single-particle density, charge distribution density and transition density are calculated in the basis of the harmonic oscillator potential. The primary utility of the PPRPA code is providing a visual tool to implementation and understanding of the collective excitation techniques TDA and RPA. Impact of the program includes all students, researchers and all those interested in knowing the facts about the structure of the atom nucleus and about the success of approximation methods in different branches of science.

  13. Monitor RNA synthesis in live cell nuclei by using two-photon excited fluorescence lifetime imaging microscopy

    NASA Astrophysics Data System (ADS)

    Peng, Xiao; Lin, Danying; Wang, Yan; Qi, Jing; Yan, Wei; Qu, Junle

    2015-03-01

    Probing of local molecular environment in cells is of significant value in creating a fundamental understanding of cellular processes and molecular profiles of diseases, as well as studying drug cell interactions. In order to investigate the dynamically changing in subcellular environment during RNA synthesis, we applied two-photon excited fluorescence lifetime imaging microscopy (FLIM) method to monitor the green fluorescent protein (GFP) fused nuclear protein ASF/SF2. The fluorescence lifetime of fluorophore is known to be in inverse correlation with a local refractive index, and thus fluorescence lifetimes of GFP fusions provide real-time information of the molecular environment of ASF/SF2- GFP. The FLIM results showed continuous and significant fluctuations of fluorescence lifetimes of the fluorescent protein fusions in live HeLa cells under physiological conditions. The fluctuations of fluorescence lifetime values indicated the variations of activities of RNA polymerases. Moreover, treatment with pharmacological drugs inhibiting RNA polymerase activities led to irreversible decreases of fluorescence lifetime values. In summary, our study of FLIM imaging of GFP fusion proteins has provided a sensitive and real-time method to investigate RNA synthesis in live cell nuclei.

  14. First spectroscopic information from even-even nuclei in the region "southeast" of 132Sn: Neutron-excitation dominance of the 21+ state in 132Cd

    NASA Astrophysics Data System (ADS)

    Wang, H.; Aoi, N.; Takeuchi, S.; Matsushita, M.; Motobayashi, T.; Steppenbeck, D.; Yoneda, K.; Baba, H.; Dombrádi, Zs.; Kobayashi, K.; Kondo, Y.; Lee, J.; Liu, H.; Minakata, R.; Nishimura, D.; Otsu, H.; Sakurai, H.; Sohler, D.; Sun, Y.; Tian, Z.; Tanaka, R.; Vajta, Zs.; Yang, Z.; Yamamoto, T.; Ye, Y.; Yokoyama, R.

    2016-11-01

    The neutron-rich nucleus 132Cd has been studied at the RIKEN Radioactive Isotope Beam Factory using in-beam γ -ray spectroscopy with two-proton removal reactions from 134Sn. A γ -ray transition was observed at 618(8) keV and was assigned to the 21+→0g.s . + decay. The 21+ state provides the first spectroscopic information from the even-even nuclei located in the region "southeast" of the doubly magic nucleus 132Sn. By comparing with the 21+ excitation energies in the semimagic nuclei 134Sn and 130Cd, it is found that neutron excitations dominate the 21+ state in 132Cd, in a similar manner to 136Te. The results are discussed in terms of proton-neutron configuration mixing.

  15. Study of two-photon excitation spectra of organic compounds absorbing in the UV region

    SciTech Connect

    Babenko, V A; Sychev, Andrei A

    2004-12-31

    A method is proposed for recording two-photon excitation (TPE) spectra of organic compounds with the help of picosecond pulses from a dye laser tunable in the range from 550 to 640 nm. The TPE spectra are obtained for organic scintillators and drugs: paraterphenyl in liquid and solid phases, stilbene single crystal and Streptocid powder, having a one-photon absorption band in the region from 270 to 350 nm. It is shown that the vibronic structure in the TPE spectra of these compounds is independent of their aggregate state and is an individual characteristic of each of the compounds. (active media)

  16. Excitation of Fe and Cu sputtered from compounds holding different electronic core configurations

    NASA Astrophysics Data System (ADS)

    Gade, D.; Larsen, K. B.; Palle, K. T.; Veje, E.

    Some chemical compounds of either copper or iron have been bombarded with 80 keV Ar + ions, and the excitation of sputtered particles has been studied with the use of optical spectrometry. The scope was primarily to study whether the initial charge state (i.e. valence) of the metal element in the undisturbed compound influences the excitation process. All data have been taken at dynamic equilibrium conditions. It is found that the relative line intensities of different core configurations depend only weakly on the valence of the metal in the undisturbed compound. As an example, for sputtering of excited, neutral Cu, the relative distribution of excitation among levels of core configurations 3d 9 and 3d 10 does not depend on whether the copper atoms initially have core configuration 3d 9 (i.e. divalent as e.g. in CuCl 2) or 3d 10 (monovalent as in CuCl). Actually, for both cases the relative line intensitive are very close to those obtained with a pure, elemental Cu target. The results are compatible with previous findings, that when a composite targe is bombarded for such a long time that steady-state conditions are reached, the surface region of the target will be so depleted in the electronegative element that it is almost metallic.

  17. Singlet-Triplet Excitations in the Unconventional Spin-Peierls TiOBr Compound

    NASA Astrophysics Data System (ADS)

    Clancy, J. P.; Gaulin, B. D.; Adams, C. P.; Granroth, G. E.; Kolesnikov, A. I.; Sherline, T. E.; Chou, F. C.

    2011-03-01

    We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source at Oak Ridge National Laboratory. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which we associate with n=1 and n=2 triplet excitations out of the singlet ground state. These results represent the first direct measurement of the singlet-triplet energy gap in TiOBr, which has a value of Eg=21.2±1.0meV.

  18. What lurks in ULIRGs?—Probing the chemistry and excitation of molecular gas in the nuclei of Arp 220 and NGC 6240

    NASA Astrophysics Data System (ADS)

    Manohar, Swarnima; Scoville, Nick

    2017-02-01

    We have imaged the dense star-forming regions of Arp 220 and NGC 6240 in the 3 mm band transitions of CO, HCN, HCO+, HNC, and CS at 0.″5–0.″8 resolution using CARMA. Our data set images all these lines at similar resolutions and high sensitivity, and can be used to derive line ratios of faint high excitation lines. In both the nuclei of Arp 220, the HCN/HNC ratios suggest chemistry of X-ray Dominated Regions (XDRs)—a likely signature of an active galactic nucleus. In NGC 6240, there is no evidence of XDR type chemistry, but there the bulk of the molecular gas is concentrated between the nuclei rather than on them. We calculated molecular H2 densities from excitation analysis of each of the molecular species. It appears that the abundances of HNC and HCO+ in Ultra Luminous Infrared Galaxies may be significantly different from those in galactic molecular clouds. The derived H2 volume densities are ∼5 × 104 cm‑3 in the Arp 220 nuclei and ∼104 cm‑3 in NGC 6240.

  19. Triplet-state energies and substituent effects of excited aroyl compounds in the gas phase.

    PubMed

    Lin, Z P; Aue, W A

    2000-01-01

    Triplet-state energy values obtained from the gas phase are still scarce. In this study, the triplet-state energies of 58 aroyl compounds, introduced as gas chromatographic peaks at atmospheric pressure and typically 473 K, have been determined from the 0-0 bands of their n --> pi* type phosphorescence spectra in excited nitrogen. Correlations of those gas-phase triplet-state energies with Hammett constants could be observed for substituted acetophenones, benzaldehydes and benzophenones.

  20. Non-toxic, water-soluble photocalorimetric reference compounds for UV and visible excitation

    NASA Astrophysics Data System (ADS)

    Abbruzzetti, Stefania; Viappiani, Cristiano; Murgida, Daniel H.; Erra-Balsells, Rosa; Bilmes, Gabriel M.

    1999-04-01

    A set of non-toxic, water-soluble photocalorimetric reference compounds has been characterized. These compounds are brilliant blue G, brilliant black BN, new coccine, indigo carmine, and tartrazine. Neutral aqueous solutions of all compounds are photochemically stable under UV-visible excitation ( λ>300 nm). None of these dyes are fluorescent or show optical transients detectable by laser flash photolysis on the nano- to microsecond time scale. The relationship between the amplitude of the photoacoustic signal and the laser fluence is linear up to at least 350 J/m 2. The fraction of absorbed energy delivered to the medium as heat within the integration time of the instrument ( α) is equal to 1 for all of the samples, within the experimental error (±0.05). With the exception of tartrazine, no photoinduced structural volume changes were detected for any of the dyes.

  1. Decay analysis of compound nuclei with masses A ≈30 - 200 formed in reactions involving loosely bound projectiles

    NASA Astrophysics Data System (ADS)

    Kaur, Mandeep; Singh, BirBikram; Sharma, Manoj K.; Gupta, Raj K.

    2015-08-01

    The dynamics of compound nuclei formed in the reactions using loosely bound projectiles are analyzed within the framework of the dynamical cluster-decay model (DCM) of Gupta and Collaborators. We have considered the reactions with neutron-rich and neutron-deficient projectiles, respectively, as 7Li , 9Be , and 7Be , on various targets at three different Elab energies, forming compound nuclei in the mass region A ˜30 - 200. For these reactions, the contributions of light-particle (LP, A ≤4 ) cross sections σLP, energetically favored intermediate-mass-fragment (IMF, 5 ≤A2≤20 ) cross sections σIMF, as well as the fusion-fission ff cross sections σff constitute the σfus(=σLP+σIMF+σff ), i.e., the contributions of the emitted LPs, IMFs, and ff fragments are added for all the angular momenta up to the ℓmax value for the respective reactions. Interestingly, we find that the empirically fitted neck-length parameter Δ Remp , the only parameter of the DCM, is uniquely fixed to address σfus for all the reactions having the same loosely bound projectile at a chosen incident laboratory energy. It may be noted that, in DCM, the dynamical collective mass motion of preformed LPs, IMFs, and ff fragments or clusters, through the modified interaction potential barrier, are treated on parallel footing. The modification of the barrier is due to nonzero Δ Remp , and the values of corresponding modified interaction-barrier heights Δ VBemp for such reactions are almost of the same order, specifically at the respective ℓmax value.

  2. Direct detection of radical generation in rat liver nuclei on treatment with tumour-promoting hydroperoxides and related compounds.

    PubMed

    Greenley, T L; Davies, M J

    1994-04-12

    EPR spin trapping has been employed to directly detect radical production in isolated rat liver nuclei on exposure to a variety of hydroperoxides and related compounds which are known, or suspect, tumour promoters. The hydroperoxides, in the absence of reducing equivalents, undergo oxidative cleavage, generating peroxyl radicals. In the presence of NADPH (and to a lesser extent NADH) reductive cleavage of the O-O bond generates alkoxyl radicals. These radicals undergo subsequent rearrangements and reactions (dependent on the structure of the alkoxyl radical), generating carbon-centred radicals. Acyl peroxides and peracids appear to undergo only reductive cleavage of the O-O bond. With peracids this cleavage can generate aryl carboxyl (RCO2.) or hydroxyl radicals (HO.); with acyl peroxides, aryl carboxyl radicals are formed and, in the case of t-butyl peroxybenzoate, alkoxyl radicals (RO.). The radicals detected with each peroxide are similar in type to those detected in the rat liver microsomal fraction, although the extent of radical production is lower. The subsequent reactions of the initially generated radicals are similar to those determined in homogeneous chemical systems, suggesting that they are in free solution. Experiments with NADPH/NADH, heat denaturation of the nuclei and various inhibitors suggest that radical generation is an enzymatic process catalysed by haemoproteins, in particular cytochrome P-450, and that NADPH/cytochrome P-450 reductase is involved in the reductive cleavage of the O-O bond. The generation of these radicals by the rat liver nuclear fraction is potentially highly damaging for the cell due to the proximity of the generating source to DNA. Several previous studies have shown that some of the radicals detected in this study, such as aryl carboxyl and aryl radicals, can damage DNA, via various reactions which result in the generation of strand breaks and adducts to DNA bases: these processes are suggested to play an important role

  3. Physics of Unstable Nuclei

    NASA Astrophysics Data System (ADS)

    Khoa, Dao Tien; Egelhof, Peter; Gales, Sydney; Giai, Nguyen Van; Motobayashi, Tohru

    2008-04-01

    Studies at the RIKEN RI beam factory / T. Motobayashi -- Dilute nuclear states / M. Freer -- Studies of exotic systems using transfer reactions at GANIL / D. Beaumel et al. -- First results from the Magnex large-acceptance spectrometer / A. Cunsolo et al. -- The ICHOR project and spin-isospin physics with unstable beams / H. Sakai -- Structure and low-lying states of the [symbol]He exotic nucleus via direct reactions on proton / V. Lapoux et al. -- Shell gap below [symbol]Sn based on the excited states in [symbol]Cd and [symbol]In / M. Górska -- Heavy neutron-rich nuclei produced in the fragmentation of a [symbol]Pb beam / Zs. Podolyák et al. -- Breakup and incomplete fusion in reactions of weakly-bound nuclei / D.J. Hinde et al. -- Excited states of [symbol]B and [symbol]He and their cluster aspect / Y. Kanada-En'yo et al. -- Nuclear reactions with weakly-bound systems: the treatment of the continuum / C. H. Dasso, A. Vitturi -- Dynamic evolution of three-body decaying resonances / A. S. Jensen et al. -- Prerainbow oscillations in [symbol]He scattering from the Hoyle state of [symbol]C and alpha particle condensation / S. Ohkubo, Y. Hirabayashi -- Angular dispersion behavior in heavy ion elastic scattering / Q. Wang et al. -- Microscopic optical potential in relativistic approach / Z.Yu. Ma et al. -- Exotic nuclei studied in direct reactions at low momentum transfer - recent results and future perspectives at fair / P. Egelhof -- Isotopic temperatures and symmetry energy in spectator fragmentation / M. De Napoli et al. -- Multi-channel algebraic scattering theory and the structure of exotic compound nuclei / K. Amos et al. -- Results for the first feasibility study for the EXL project at the experimental storage ring at GSI / N. Kalantar-Nayestanaki et al. -- Coulomb excitation of ISOLDE neutron-rich beams along the Z = 28 chain / P. Van Duppen -- The gamma decay of the pygmy resonance far from stability and the GDR at finite temperature / G. Benzoni et al

  4. Dynamical simulation of the fission process and anisotropy of the fission fragment angular distributions of excited nuclei produced in fusion reactions

    NASA Astrophysics Data System (ADS)

    Eslamizadeh, H.

    2016-10-01

    Abstract. A stochastic approach based on four-dimensional Langevin equations was applied to calculate the anisotropy of fission fragment angular distributions, average prescission neutron multiplicity, and the fission probability in a wide range of fissile parameters for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf produced in fusion reactions. Three collective shape coordinates plus the projection of total spin of the compound nucleus to the symmetry axis K were considered in the four-dimensional dynamical model. In the dynamical calculations, nuclear dissipation was generated through the chaos-weighted wall and window friction formula. Furthermore, in the dynamical calculations the dissipation coefficient of K ,γk was considered as a free parameter, and its magnitude inferred by fitting measured data on the anisotropy of fission fragment angular distributions for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf. Comparison of the calculated results for the anisotropy of fission fragment angular distributions with the experimental data showed that the results of the calculations are in good agreement with the experimental data by using values of the dissipation coefficient of K equal to (0.185-0.205), (0.175-0.192), (0.077-0.090), and (0.075-0.085) (MeVzs ) -1 /2 for the compound nuclei 197Tl,225Pa,248Cf , and 264Rf, respectively. It was also shown that the influence of the dissipation coefficient of K on the results of the calculations of the prescission neutron multiplicity and fission probability is small.

  5. Mass yields and kinetic energy of fragments from fission of highly-excited nuclei with A≲220

    NASA Astrophysics Data System (ADS)

    Denisov, V. Yu.; Margitych, T. O.; Sedykh, I. Yu.

    2017-02-01

    It is shown that the potential energy surface of the two separated fragments has the saddle point, which takes place at small distance between the surfaces of well-deformed fragments. The height of this two-body saddle point is larger than the height of one-body fission barrier for nuclei with A ≲ 220. The mass yields of the fission fragments, which are appearing at the fission of nuclei with A ≲ 220, are related to the number of states of the two-fragment systems at the two-body saddle points. The characteristics of kinetic energy of fragments are described by using the trajectory motion equations with the dissipation terms. The Gaussian distribution of the final kinetic energy around the classical value of this energy induced by the stochastic fluctuations is taken into account at an evaluation of the total kinetic energy distributions of the fission fragments.

  6. Inelastic electron scattering form factors involving the second excited 2+ levels in the nuclei 48Ti and 50Cr

    NASA Astrophysics Data System (ADS)

    Mukherjee, G.; Sharma, S. K.

    1985-02-01

    A microscopic description of the recent data on the Coulomb form factors for the 0g.s.+-->2+2 transitions in the nuclei 48Ti and 50Cr is attempted in terms of the prolate and oblate intrinsic states resulting from realistic effective interactions operating in the 2p-1f shell. The results for the higher momentum-transfer region show significant improvements compared to the form factor estimates obtained in some recent shell model calculations involving the fn7/2+fn-17/2p3/2 configurations.

  7. Calculation of core-level excitation in some MAX-phase compounds

    NASA Astrophysics Data System (ADS)

    Wang, Liaoyuan; Rulis, Paul; Ching, W. Y.

    2013-07-01

    We report first-principles spectroscopic calculation of core level excitations in five MAX-phase compounds. The spectra of Ti-K edges in Ti2AlC and Ti2AlN, C-K edge in Ti2AlC, N-K edge in Ti2AlN, and Nb-K edge in Nb2AlC are calculated and found to be in good agreement with reported experimental measurements. Based on this agreement, the Al-K and Al-L3 edges in the same five phases plus the Cr-K and C-K edges in Cr2AlC and the C-K edge in Nb2AlC are calculated as theoretical predictions. We further analyze the anisotropy in the calculated spectra to gain additional insights on the structure-properties relationships in these MAX-phase compounds. These results are further discussed in the context of the local atomic environments of the M, A, and X elements in MAX-phase compounds and in relation to their fundamental electronic structures.

  8. Ionization, excitation, and electron transfer in MeV-energy collisions between light nuclei and C{sup 5+}(1s) ions studied with a Sturmian basis

    SciTech Connect

    Winter, Thomas G.

    2004-04-01

    Cross sections have been determined for direct excitation, ionization, and electron transfer in collisions between H, He, Li, and Be nuclei and C{sup 5+}(1s) target ions at nuclear energies 1-24 MeV/nucleon, extending earlier work [Phys. Rev. A 56, 2903 (1997)] to higher energies. Coupled Sturmian pseudostates of principal quantum number at least up to 30 have been included for each angular momentum s, p, d, and f centered on the C nucleus, as well as a 1s state centered on the projectile. Detailed basis-convergence studies have been carried out. Cross sections have been compared with the corresponding Born results, and scaling rules have also been examined.

  9. Ab initio molecular dynamics study on the excitation dynamics of psoralen compounds

    NASA Astrophysics Data System (ADS)

    Nakai, H.; Yamauchi, Y.; Nakata, A.; Baba, T.; Takahashi, H.

    2003-08-01

    Ab initio molecular dynamics (AIMD) simulations are performed for studying the S0→T1 excitation dynamics of psoralen compounds; namely, nonsubstituted psoralen, 5-methoxypsoralen (5-MOP), and 8-methoxypsoralen (8-MOP). The density functional theory calculations at the B3LYP/D95V level are used for evaluating the atomic forces in every AIMD step. The specific behavior of 8-MOP in the T1 state, which has been reported by the experimental study, is found to be due to a unique open-ring structure, which leads to a different spin distribution in comparison with the cases of psoralen and 5-MOP and further to a crossing between the S0 and T1 states.

  10. Primary photochemistry of nitrated aromatic compounds: excited-state dynamics and NO· dissociation from 9-nitroanthracene.

    PubMed

    Plaza-Medina, Eddy F; Rodríguez-Córdoba, William; Morales-Cueto, Rodrigo; Peon, Jorge

    2011-02-10

    We report results of femtosecond-resolved ex-periments which elucidate the time scale for the primary photoinduced events in the model nitroaromatic compound 9-nitroanthracene. Through time-resolved fluorescence measurements, we observed the ultrafast decay of the initially excited singlet state, and through transient absorption experiments, we observed the spectral evolution associated with the formation of the relaxed phosphorescent T(1) state. Additionally, we have detected for the first time the accumulation of the anthryloxy radical which results from the nitro-group rearrangement and NO(•) dissociation from photoexcited 9-nitroanthracene, a photochemical channel which occurs in parallel with the formation of the phosphorescent state. The spectral evolution in this molecule is highly complex since both channels take place in similar time ranges of up to a few picoseconds. Despite this complexity, our experiments provide the general time scales in which the primary products are formed. In addition, we include calculations at the time-dependent density functional level of theory which distinguish the molecular orbitals responsible for the n-π* character of the "receiver" vibronic triplet states that couple with the first singlet state and promote the ultrafast transfer of population between the two manifolds. Comparisons with the isoelectronic compounds anthracene-9-carboxylic acid and its conjugated base, which are highly fluorescent, show that in these two compounds the near-isoenergeticity of the S(1) with an appropriate "receiver" triplet state is disrupted, providing support to the idea that a specific energy coincidence is important for the ultrafast population of the triplet manifold, prevalent in polycyclic nitrated aromatic compounds.

  11. Competing analysis of α and 2p2n-emission from compound nuclei formed in neutron induced reactions

    NASA Astrophysics Data System (ADS)

    Kaur, Amandeep; Sharma, Manoj K.

    2017-01-01

    The decay mechanism of compound system 61Ni* formed in fast neutron induced reactions is explored within the collective clusterization approach of the Dynamical Cluster-decay Model (DCM) in reference to a recent experiment over an energy spread of En = 1- 100 MeV. The excitation functions for the decay of the compound nucleus 61Ni* formed in the n +60Ni reaction show a double humped variation with incident beam energy where the peak at lower energy corresponds to α-emission while the one at higher energy originates from 2 p 2 n-emission. The experimentally observed transmutation of α-emission at lower energy into 2 p 2 n-emission at higher incident energies is explained on the basis of temperature dependence of the binding energies used within the framework of DCM. The cross-sections for the formation of the daughter nucleus 57Fe after emission of α-cluster from the 61Ni* nucleus are addressed by employing the neck length parameter (ΔR), finding decent agreement with the available experimental data. The calculations are done for non-sticking choice of moment of inertia (INS) in the centrifugal potential term, which forms the essential ingredient in DCM based calculations. In addition to this, the effect of mass (and charge) of the compound nucleus is exercised in view of α and 2 p 2 n emission and comparative study of the decay profiles of compound systems with mass A = 17-93 is employed to get better description of decay patterns.

  12. The investigation of dipole excitations in double-even 184W nuclei at the spectroscopic energy region

    NASA Astrophysics Data System (ADS)

    Zenginerler, Zemine; Ertugral, Filiz; Guiyev, Ekber; Kuliev, Ali Ekber

    2014-03-01

    The dipole excitations of double-even nucleus 184W are studied using the QRPA model with rotational, translational and Galilean invariant Hamilonian. This approach not only gives opportunity to test for the validity of the present theory and it also allows for the interpretation of the experimentally spin unknown states. The analysis of calculation shows that M1 strength, mainly an orbital character predicted from calculations of orbit-to-spin ratio, has a relative contribution, rougly 63% with summed M1 widths ΣΓ0red (M 1) = 5 . 3meV between 2<ωi<3.7 MeV, to summed ground-state decay widths of dipole mode. The experimental summed widths in the same energy interval is ΣΓored (exp) = 4.73 +/- 1.28 meV. On the other hand, several well pronounced electric dipole K = 1 excitation in spectroscopic region where mainly fulled with M1 dipole states is predicted. The total E1 widths with K = 1 is ΣΓ0red (E 1) = 2 . 62meV (30% of the summed widths), quite close to the experimental value with K = 0 ΣΓored (exp) = 2.09 +/- 0.59 meV. The theory also indicates a few positive (ΣΓ0red (M 1) = 0 . 24meV) and negative parity ΣΓ0red (E 1) = 0 . 34meV with K = 0 states with summed widths, respectively.

  13. Theoretical and experimental study on the intramolecular charge transfer excited state of the new highly fluorescent terpyridine compound

    NASA Astrophysics Data System (ADS)

    Song, Peng; Sun, Shi-Guo; Liu, Jian-Yong; Xu, Yong-Qian; Han, Ke-Li; Peng, Xiao-Jun

    2009-10-01

    Experimental and theoretical methods have been used to investigate the relaxation dynamics and photophysical properties of the donor-acceptor compound 4'-(4-N,N-diphenylaminophenyl)-2,2':6',2″-terpyridine (DPAPT), a compound which is found to exhibit efficient intramolecular charge transfer emission in polar solvents with relatively large Stokes shifts and strong solvatochromism. The difference between the ground and excited state dipole moments (Δ μ) is estimated to be 13.7 D on the basis of Lippert-Mataga models. To gain insight into the relaxation dynamics of DPAPT in the excited state, the potential energy curves for conformational relaxation are calculated. From the frontier molecular orbital (MO) pictures at the geometry of the twisted ICT excited state, the intramolecular charger transfer mainly takes place from HOMO (triphenylamine) to LUMO (terpyridine) in this donor-acceptor system.

  14. Characterization of the multifragment decay channel in highly excited nuclei. Progress report, March 15, 1992--September 14, 1993

    SciTech Connect

    de Souza, R.T.

    1992-10-01

    Characteristics of multifragment decay in heavy-ion induced reactions at intermediate energies are explored. Evolution of the timescale for emission of intermediate mass fragments (IMF: 3{le}Z{le}20) is investigated. Fragments associated with central collisions in the reactions {sup 36}Ar + {sup 197}Au at E/A = 50, 80, and 110 MeV are emitted on an extremely fast timescale, {tau} {le} 75 fm/c, comparable to the transit time of the projectile past the target nucleus. With increasing incident energy, mean fragment emission times decrease, consistent with statistical decay from highly excited systems or fast dynamical processes. To examine the importance of expansion effects in multifragmentation, the transverse kinetic energy of fragments was investigated. Evidence for expansion effects in the system {sup 36}Ar + {sup 197}Au at E/A = 50, 80, and 110 MeV was indicated by the charge dependence of the mean isotropic kinetic energy. At the highest incident energy the data suggest the onset of volume emission. Construction and performance of low-threshold high-resolution detector telescopes is discussed. Three-body Coulomb trajectory calculations are being used to probe kinematical correlations associated with neck emission of IMFs during fission. Initial design and testing of position sensitive parallel plate avalanche counters for upcoming ternary fission experiments is discussed.

  15. Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

    SciTech Connect

    Newman, Sarah F.; Genzel, Reinhard; Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter; Sternberg, Amiel; Gnat, Orly; Mancini, Chiara; Renzini, Alvio; Lilly, Simon J.; Carollo, C. Marcella; Burkert, Andreas; Cresci, Giovanni; Genel, Shy; Shapiro Griffin, Kristen; Hicks, Erin K. S.; and others

    2014-01-20

    Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

  16. Complex fragment emission at low and high excitation energy

    SciTech Connect

    Moretto, L.G.

    1986-08-01

    Complex fragment emission has been certified as a compound nucleus process at low energies. An extension of the measurements to heavy ion reactions up to 50 MeV/u shows that most complex fragments are emitted by highly excited compound nuclei formed in incomplete fusion reactions. 12 refs., 26 figs.

  17. Radiations from hot nuclei

    NASA Technical Reports Server (NTRS)

    Malik, F. Bary

    1993-01-01

    The investigation indicates that nuclei with excitation energy of a few hundred MeV to BeV are more likely to radiate hot nuclear clusters than neutrons. These daughter clusters could, furthermore, de-excite emitting other hot nuclei, and the chain continues until these nuclei cool off sufficiently to evaporate primarily neutrons. A few GeV excited nuclei could radiate elementary particles preferentially over neutrons. Impact of space radiation with materials (for example, spacecraft) produces highly excited nuclei which cool down emitting electromagnetic and particle radiations. At a few MeV excitation energy, neutron emission becomes more dominant than gamma-ray emission and one often attributes the cooling to take place by successive neutron decay. However, a recent experiment studying the cooling process of 396 MeV excited Hg-190 casts some doubt on this thinking, and the purpose of this investigation is to explore the possibility of other types of nuclear emission which might out-compete with neutron evaporation.

  18. Temperature and Excitation Power-Density Dependences of the Photoluminescence of BaZrO2.9 Compound

    NASA Astrophysics Data System (ADS)

    Dhahri, Kh.; Bejar, M.; Dhahri, E.; Graça, M. F. P.

    2017-02-01

    Temperature- and excitation density-dependent photoluminescence are presented and discussed in detail for the BaZrO2.9 compound prepared from the non-luminescent BaZrO3 sample. The thermal-quenching behavior of the photoluminescence peak intensity is described with two activation energies, E a1 = 185 and E a2 = 139 meV. The variation of the integrated photoluminescence intensity with the excitation density shows a linear behavior with the slope close to α = 1.06, indicating that the PL signal is attributed to the excitonic recombination.

  19. Electron delocalization and aromaticity in low-lying excited states of archetypal organic compounds.

    PubMed

    Feixas, Ferran; Vandenbussche, Jelle; Bultinck, Patrick; Matito, Eduard; Solà, Miquel

    2011-12-14

    Aromaticity is a property usually linked to the ground state of stable molecules. Although it is well-known that certain excited states are unquestionably aromatic, the aromaticity of excited states remains rather unexplored. To move one step forward in the comprehension of aromaticity in excited states, in this work we analyze the electron delocalization and aromaticity of a series of low-lying excited states of cyclobutadiene, benzene, and cyclooctatetraene with different multiplicities at the CASSCF level by means of electron delocalization measures. While our results are in agreement with Baird's rule for the aromaticity of the lowest-lying triplet excited state in annulenes having 4nπ-electrons, they do not support Soncini and Fowler's generalization of Baird's rule pointing out that the lowest-lying quintet state of benzene and septet state of cyclooctatetraene are not aromatic.

  20. Non-coplanar compact configurations of nuclei and non-compound-nucleus contribution in the fusion cross section of the 12C+93Nb reaction

    NASA Astrophysics Data System (ADS)

    Chopra, Sahila; Hemdeep, Kaur, Arshdeep; Gupta, Raj K.

    2016-02-01

    Background: In our earlier study of the 12C+93Nb→*105Ag reaction at three near- and below-barrier energies (Ec .m .=41.097 , 47.828, and 54.205 MeV), using the dynamical cluster-decay model (DCM) with various nuclear interaction potentials (the Blocki et al. pocket formula and others derived from the Skyrme energy density formalism) for compact, coplanar (Φc=00 ) nuclei, we found a large non-compound-nucleus (nCN) contribution in the measured fusion cross section of this reaction. Purpose: In the present work, we look for the effect of using non-coplanar, compact configurations (Φc≠00 ), in the Blocki et al. pocket formula of the nuclear proximity potential, on the non-compound-nucleus (nCN) contribution, using the DCM. Methods: Allowing the Φ degree of freedom in the DCM formalism, we calculate the compound-nucleus (CN) and nCN cross sections. The only parameter of the DCM is the neck-length parameter Δ R , which also fits the empirically determined nCN cross section nearly exactly, under the assumption of considering it like a quasifission process where the fragment preformation factor P0=1 . Results: With the Φ degree of freedom included, at the higher two energies the nCN cross section gets enhanced, and hence the pure CN cross section is decreased, since the calculated (total) fusion cross section is fitted to experimental data. The parameter Δ R for the nCN contribution is smaller, and hence the reaction time larger, than for the CN decay process. Also, the contributing angular momentum ℓmax value increases in going from Φc=00 to Φc≠00 for both the CN and nCN processes. The intermediate mass fragments (IMFs), measured up to mass 13 in this reaction, are shown extended up to mass 16, and the fusion-fission (f f ) region is identified as A /2 ±16 , the same as for the Φc=00 case. Conclusions: As a result of enhanced nCN cross section due to Φc≠00 , the CN fusion probability PCN for *105Ag changes its behavior from an increasing to a

  1. Measurements of the hygroscopic and deliquescence properties of organic compounds of different solubilities in water and their relationship with cloud condensation nuclei activities.

    PubMed

    Chan, Man Nin; Kreidenweis, Sonia M; Chan, Chak K

    2008-05-15

    The initial phase (solid or aqueous droplet) of aerosol particles prior to activation is among the critical factors in determining their cloud condensation nuclei (CCN) activity. Single-particle levitation in an electrodynamic balance (EDB)was used to measure the phase transitions and hygroscopic properties of aerosol particles of 11 organic compounds with different solubilities (10(-1) to 102 g solute/100 g water). We use these data and other literature data to relate the CCN activity and hygroscopicity of organic compounds with different solubilities. The EDB data show that glyoxylic acid, 4-methylphthalic acid, monosaccharides (fructose and mannose), and disaccharides (maltose and lactose) did not crystallize and existed as metastable droplets at low relative humidity (RH). Hygroscopic data from this work and in the literature support earlier studies showing that the CCN activities of compounds with solubilities down to the order of 10(-1) g solute/100 g water can be predicted by standard Köhler theory with the assumption of complete dissolution of the solute at activation. We also demonstrate the use of evaporation data (or efflorescence data), which provides information on the water contents of metastable solutions below the compound deliquescence RH that can be extrapolated to higher dilutions, to predict the CCN activity of organic particles, particularly for sparingly soluble organic compounds that do not deliquesce at RH achievable in the EDB and in the hygroscopic tandem differential mobility analyzer.

  2. Triplet excited states of cyclic disulfides and related compounds: electronic structures, geometries, energies, and decay.

    PubMed

    Ginagunta, Saroja; Bucher, Götz

    2011-02-03

    We have performed a computational study on the properties of a series of heterocycles bearing two adjacent heteroatoms, focusing on the structures and electronic properties of their first excited triplet states. If the heteroatoms are both heavy chalcogens (S, Se, or Te) or isoelectronic species, then the lowest excited triplet state usually has (π*, σ*) character. The triplet energies are fairly low (30-50 kcal mol(-1)). The (π*, σ*) triplet states are characterized by a significantly lengthened bond between the two heteroatoms. Thus, in 1,2-dithiolane (1b), the S-S bond length is calculated to be 2.088 Å in the singlet ground state and 2.568 Å in the first triplet excited state. The spin density is predicted to be localized almost exclusively on the sulfur atoms. Replacing one heavy chalcogen atom by an oxygen atom or an NR group results in a significant destabilization of the (π*, σ*) triplet excited state, which then no longer is lower in energy than an open-chain biradical. The size of the heterocyclic ring also contributes to the stability of the (π*, σ*) triplet state, with five-membered rings being more favorable than six-membered rings. Benzoannulation, finally, usually lowers the energy of the (π*, σ*) triplet excited states. If one of the heteroatoms is an oxygen or nitrogen atom, however, the corresponding lowest triplet states are better described as σ,π-biradicals.

  3. Electronic excitation transport in photosynthesis and crystal and molecular structures of porphyrin compounds

    SciTech Connect

    Yang, Shumei.

    1991-04-22

    The excitation energy transfer in three photosynthetic organism samples, Bacteriochlorophyll a-protein from Prosthecochloris aestuarii, and enriched photosystem I particles from spinach chloroplasts, have been investigated by pump-probe ultrafast spectroscopy. The isotropic photobleaching profiles were best described by two exponential decay components in one Bchl a-protein complex, and three exponential decay components in another. The experimental results from the three samples show that nonrandom chromophore orientations exist and Sauer's pebble mosaic'' model is an appropriate one for excitation transfer in these samples. The polarized pump-probe transients have been analyzed in terms of an exciton hopping model that incorporates the known geometry of the Bchl a-protein. The crystal and molecular structures of four metalloporphyrins have been determined by X-ray diffraction and molecular mechanics. 207 refs., 44 figs., 15 tabs.

  4. Joint gamma generation and radiation heat regime (GG&RH) theory for gamma laser screening in the first approach of soft prompt transplantation of excited nuclei

    NASA Astrophysics Data System (ADS)

    Karyagin, Stanislav V.

    2001-03-01

    Joint theory of gamma-generation and radiation-heat regime in active medium of (gamma) -laser (GL) was created and applied for the analyses of the total world experience in the GL-problem in order to choose those nuclei-candidates, active media, GL-schemes which are indeed actual for the GL- creation.

  5. DFT spin-orbit coupling between singlet and triplet excited states: A case of psoralen compounds

    NASA Astrophysics Data System (ADS)

    Chiodo, Sandro G.; Russo, Nino

    2010-04-01

    We present a computational protocol in which our method is used to compute spin-orbit (SO) matrix elements on time-dependent-density functional theory (TD-DFT). These SO contributions, computed employing our SO program package, MolSOC, have been expressed, in turn, in terms of weighted coefficients and SO matrix elements between singlet and triplet wave functions arising from a given one-electron transition. The protocol has been applied to study psoralen compound and its derivatives obtained from the replacement of one oxygen with sulfur or selenium. The obtained results have been compared with those reported in literature.

  6. Properties of nuclei probed by laser light

    NASA Astrophysics Data System (ADS)

    Neugart, Rainer

    2017-03-01

    Viewing objects as small as atomic nuclei by visible light sounds quite unrealistic. However, nuclei usually appear as constituents of atoms whose excitations are indeed associated with the absorption and emission of light. Nuclei can thus interact with light via the atomic system as a whole.

  7. Excitation Wavelength Dependent O2 Release from Copper(II)-Superoxide Compounds: Laser Flash-Photolysis Experiments and Theoretical Studies

    PubMed Central

    Saracini, Claudio; Liakos, Dimitrios G.; Zapata Rivera, Jhon E.; Neese, Frank; Meyer, Gerald J.; Karlin, Kenneth D.

    2014-01-01

    Irradiation of the copper(II)-superoxide synthetic complexes [(TMG3tren)CuII(O2)]+ (1) and [(PV-TMPA)CuII(O2)]+ (2) with visible light resulted in direct photo-generation of O2 gas at low temperature (from −40 °C to −70°C for 1 and from −125 °C to −135 °C for 2) in 2-methyltetrahydrofuran (MeTHF) solvent. The yield of O2 release was wavelength dependent: λexc = 436 nm, ϕ = 0.29 (for 1), ϕ = 0.11 (for 2), and λexc = 683 nm, ϕ = 0.035 (for 1), ϕ = 0.078 (for 2), which was followed by fast O2-recombination with [(TMG3tren)CuI]+ (3) and [(PV-TMPA)CuI]+ (4). Enthalpic barriers for O2 re-binding to the copper(I) center (~ 10 kJ mol−1) and for O2 dissociation from the superoxide compound 1 (45 kJ mol−1) were determined. TD-DFT studies, carried out for 1, support the experimental results confirming the dissociative character of the excited states formed upon blue or red light laser excitation. PMID:24428309

  8. Excitation wavelength dependent O2 release from copper(II)-superoxide compounds: laser flash-photolysis experiments and theoretical studies.

    PubMed

    Saracini, Claudio; Liakos, Dimitrios G; Zapata Rivera, Jhon E; Neese, Frank; Meyer, Gerald J; Karlin, Kenneth D

    2014-01-29

    Irradiation of the copper(II)-superoxide synthetic complexes [(TMG3tren)Cu(II)(O2)](+) (1) and [(PV-TMPA)Cu(II)(O2)](+) (2) with visible light resulted in direct photogeneration of O2 gas at low temperature (from -40 °C to -70 °C for 1 and from -125 to -135 °C for 2) in 2-methyltetrahydrofuran (MeTHF) solvent. The yield of O2 release was wavelength dependent: λexc = 436 nm, ϕ = 0.29 (for 1), ϕ = 0.11 (for 2), and λexc = 683 nm, ϕ = 0.035 (for 1), ϕ = 0.078 (for 2), which was followed by fast O2-recombination with [(TMG3tren)Cu(I)](+) (3) and [(PV-TMPA)Cu(I)](+) (4). Enthalpic barriers for O2 rebinding to the copper(I) center (∼10 kJ mol(-1)) and for O2 dissociation from the superoxide compound 1 (45 kJ mol(-1)) were determined. TD-DFT studies, carried out for 1, support the experimental results confirming the dissociative character of the excited states formed upon blue- or red-light laser excitation.

  9. Dirac-Hartree-Bogoliubov calculation for spherical and deformed hot nuclei: Temperature dependence of the pairing energy and gaps, nuclear deformation, nuclear radii, excitation energy, and entropy

    NASA Astrophysics Data System (ADS)

    Lisboa, R.; Malheiro, M.; Carlson, B. V.

    2016-02-01

    Background: Unbound single-particle states become important in determining the properties of a hot nucleus as its temperature increases. We present relativistic mean field (RMF) for hot nuclei considering not only the self-consistent temperature and density dependence of the self-consistent relativistic mean fields but also the vapor phase that takes into account the unbound nucleon states. Purpose: The temperature dependence of the pairing gaps, nuclear deformation, radii, binding energies, entropy, and caloric curves of spherical and deformed nuclei are obtained in self-consistent RMF calculations up to the limit of existence of the nucleus. Method: We perform Dirac-Hartree-Bogoliubov (DHB) calculations for hot nuclei using a zero-range approximation to the relativistic pairing interaction to calculate proton-proton and neutron-neutron pairing energies and gaps. A vapor subtraction procedure is used to account for unbound states and to remove long range Coulomb repulsion between the hot nucleus and the gas as well as the contribution of the external nucleon gas. Results: We show that p -p and n -n pairing gaps in the S10 channel vanish for low critical temperatures in the range Tcp≈0.6 -1.1 MeV for spherical nuclei such as 90Zr, 124Sn, and 140Ce and for both deformed nuclei 150Sm and 168Er. We found that superconducting phase transition occurs at Tcp=1.03 Δp p(0 ) for 90Zr, Tcp=1.16 Δp p(0 ) for 140Ce, Tcp=0.92 Δp p(0 ) for 150Sm, and Tcp=0.97 Δp p(0 ) for 168Er. The superfluidity phase transition occurs at Tcp=0.72 Δn n(0 ) for 124Sn, Tcp=1.22 Δn n(0 ) for 150Sm, and Tcp=1.13 Δn n(0 ) for 168Er. Thus, the nuclear superfluidity phase—at least for this channel—can only survive at very low nuclear temperatures and this phase transition (when the neutron gap vanishes) always occurs before the superconducting one, where the proton gap is zero. For deformed nuclei the nuclear deformation disappear at temperatures of about Tcs=2.0 -4.0 MeV , well above the

  10. IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Radiative and photochemical properties of organic compounds excited by high-power XeCl laser radiation

    NASA Astrophysics Data System (ADS)

    Kopylova, T. N.; Kuznetsova, Rimma T.; Svetlichnyi, Valerii A.; Sergeev, A. K.; Tel'minov, E. N.; Filinov, D. N.

    2000-06-01

    Radiative and photochemical properties of a number of laser dyes excited by focused radiation of a XeCl laser with intensity up to 200 MW cm-2 were studied. A method for measuring the gain of organic molecules under high-power excitation is proposed. The dependence of the dye transmittance for the pump radiation on its intensity was studied. It is shown that changes in energy, spectral, and time characteristics of radiation and the photostability of compounds under high-power excitation are associated with the formation of superluminescence.

  11. Nuclear spectroscopy above isomers in {sub 67}{sup 148}Ho{sub 81} and {sub 67}{sup 149}Ho{sub 82} nuclei: Search for core-excited states in {sup 149}Ho

    SciTech Connect

    Kownacki, J.; Napiorkowski, P. J.; Zielinska, M.; Kordyasz, A.; Srebrny, J.; Droste, Ch.; Morek, T.; Grodner, E.; Ruchowska, E.; Korman, A.; Czarnacki, W.; Kisielinski, M.; Kowalczyk, M.; Wrzosek-Lipska, K.; Hadynska-KlePk, K.; Mierzejewski, J.; Lieder, R. M.; Perkowski, J.; Andrzejewski, J.; Krol, A.

    2010-04-15

    The excited states of {sup 148}Ho and {sup 149}Ho isotopes are studied using gamma-ray and electron spectroscopy in off-beam and in-beam modes following {sup 112,114}Sn({sup 40}Ar,xnyp) reactions. Experiments include measurements of single gamma-rays and conversion electron spectra as well as gamma-gamma, electron-gamma, gamma-t, and gamma-gamma-t coincidences with the use of the OSIRIS-II 12-HPGe array and conversion electron spectrometer. Based on the present results, the level schemes of {sup 148}Ho and {sup 149}Ho are revised and significantly extended, up to about 4 and 5 MeV of excitation energy, respectively. Spin and parity of 5{sup -} are assigned to the 9.59-s isomer in {sup 148}Ho based on conversion electron results. Previously unobserved gamma rays feeding the 10{sup +} isomer in {sup 148}Ho and the 27/2{sup -} isomer in {sup 149}Ho nuclei are proposed. Shell-model calculations are performed. Possible core-excited states in {sup 149}Ho are discussed.

  12. Exotic Orbital Modes in Nuclei

    NASA Astrophysics Data System (ADS)

    von Neumann-Cosel, P.

    2003-06-01

    Experimental evidence for two types of collective excitations in nuclei generated by orbital motion is discussed, viz. a magnetic quadrupole twist mode observed in 180° electron scattering experiments and a toroidal electric dipole mode. The latter may be a source of low-energy pygmy dipole resonances observed in many nuclei. This is discussed in detail for the example of 208Pb based on the recent finding of a resonance at particle threshold in a high-resolution (γ, γ') experiment.

  13. Photoresponse of 60Ni below 10-MeV excitation energy: Evolution of dipole resonances in fp-shell nuclei near N=Z

    NASA Astrophysics Data System (ADS)

    Scheck, M.; Ponomarev, V. Yu.; Fritzsche, M.; Joubert, J.; Aumann, T.; Beller, J.; Isaak, J.; Kelley, J. H.; Kwan, E.; Pietralla, N.; Raut, R.; Romig, C.; Rusev, G.; Savran, D.; Schorrenberger, L.; Sonnabend, K.; Tonchev, A. P.; Tornow, W.; Weller, H. R.; Zilges, A.; Zweidinger, M.

    2013-10-01

    Background: Within the last decade, below the giant dipole resonance the existence of a concentration of additional electric dipole strength has been established. This accumulation of low-lying E1 strength is commonly referred to as pygmy dipole resonance (PDR).Purpose: The photoresponse of 60Ni has been investigated experimentally and theoretically to test the evolution of the PDR in a nucleus with only a small neutron excess. Furthermore, the isoscalar and isovector M1 resonances were investigated.Method: Spin-1 states were excited by exploiting the (γ,γ') nuclear resonance fluorescence technique with unpolarized continuous bremsstrahlung as well as with fully linearly polarized, quasimonochromatic, Compton-backscattered laser photons in the entrance channel of the reaction.Results: Up to 10 MeV a detailed picture of J=1 levels was obtained. For the preponderant number of the individual levels spin and parity were firmly assigned. Furthermore, branching ratios, transition widths, and reduced B(E1) or B(M1) excitation probability were calculated from the measured scattering cross sections. A comparison with theoretical results obtained within the quasiparticle phonon model allows an insight into the microscopic structure of the observed states.Conclusions: Below 10 MeV the directly observed E1 strength [∑B(E1)↑=(153.8±9.5) e2(fm)2] exhausts 0.5% of the Thomas-Reiche-Kuhn sum rule. This value increases to 0.8% of the sum rule [∑B(E1)↑=(250.9±31.1) e2(fm)2] when indirectly observed branches to lower-lying levels are considered. Two accumulations of M1 excited spin-1 states near 8 and 9 MeV excitation energy are identified as isoscalar and isovector M1 resonances dominated by proton and neutron f7/2→f5/2 spin-flip excitations. The B(M1)↑ strength of these structures accumulates to 3.94(27)μN2.

  14. Fission barriers for Po nuclei produced in complete fusion reactions with heavy ions

    SciTech Connect

    Sagaidak, R. N.; Andreyev, A. N.

    2009-05-15

    Evaporation residues and fission excitation functions obtained in complete fusion reactions leading to Po compound nuclei have been analyzed in the framework of the standard statistical model. Macroscopic fission barriers deduced from the cross-section data analysis are compared with the predictions of various theoretical models and available data. A drop in the Po barriers with the decrease in a neutron number was found, which is stronger than predicted by any theory. The presence of entrance channel effects and collective excitations in the compound nucleus decay is considered as a possible reason for the barrier reduction.

  15. Superdeformed nuclei

    SciTech Connect

    Janssens, R.V.F.; Khoo, Teng Lek.

    1991-01-01

    This paper reviews the most recent advances in the understanding of the physics of superdeformed nuclei from the point of view of the experimentalists. It covers among other subjects the following topics: (1) the discovery of a new region of superdeformed nuclei near A=190, (2) the surprising result of the occurrence of bands with identical transition energies in neighboring superdeformed nuclei near A=150 and A=190, (3) the importance of octupole degrees of freedom at large deformation and (4) the properties associated with the feeding and the decay of superdeformed bands. The text presented hereafter will appear as a contribution to the Annual Review of Nuclear and Particle Science, Volume 41. 88 refs., 11 figs.

  16. Application of the Broad Energy Germanium detector: A technique for elucidating β-decay schemes which involve daughter nuclei with very low energy excited states

    NASA Astrophysics Data System (ADS)

    Venhart, M.; Wood, J. L.; Boston, A. J.; Cocolios, T. E.; Harkness-Brennan, L. J.; Herzberg, R.-D.; Joss, D. T.; Judson, D. S.; Kliman, J.; Matoušek, V.; Motyčák, Š.; Page, R. D.; Patel, A.; Petrík, K.; Sedlák, M.; Veselský, M.

    2017-03-01

    A technique for elucidating β-decay schemes of isotopes with a large density of states at low excitation energy has been developed, in which a Broad Energy Germanium (BEGe) detector is used in conjunction with coaxial hyper-pure germanium detectors. The power of this technique is demonstrated using the example of 183Hg decay. Mass-separated samples of 183Hg were produced by a deposition of the low-energy radioactive-ion beam delivered by the ISOLDE facility at CERN. The excellent energy resolution of the BEGe detector allowed γ-ray energies to be determined with a precision of a few tens of eV, which was sufficient for the analysis of the Rydberg-Ritz combinations (in conjunction with γ-γ coincidences) in the level scheme. The timestamped structure of the data was used for unambiguous separation of γ rays arising from the decay of 183Hg from those due to the daughter decays.

  17. Label-free fluorescence detection of aromatic compounds in chip electrophoresis applying two-photon excitation and time-correlated single-photon counting.

    PubMed

    Beyreiss, Reinhild; Geißler, David; Ohla, Stefan; Nagl, Stefan; Posch, Tjorben Nils; Belder, Detlev

    2013-09-03

    In this study, we introduce time-resolved fluorescence detection with two-photon excitation at 532 nm for label-free analyte determination in microchip electrophoresis. In the developed method, information about analyte fluorescence lifetimes is collected by time-correlated single-photon counting, improving reliable peak assignment in electrophoretic separations. The determined limits of detection for serotonin, propranolol, and tryptophan were 51, 37, and 280 nM, respectively, using microfluidic chips made of fused silica. Applying two-photon excitation microchip separations and label-free detection could also be performed in borosilicate glass chips demonstrating the potential for label-free fluorescence detection in non-UV-transparent devices. Microchip electrophoresis with two-photon excited fluorescence detection was then applied for analyses of active compounds in plant extracts. Harmala alkaloids present in methanolic plant extracts from Peganum harmala could be separated within seconds and detected with on-the-fly determination of fluorescence lifetimes.

  18. One electron oxidation potential as a predictor of rate constants of N-containing compounds with carbonate radical and triplet excited state organic matter.

    PubMed

    Arnold, William A

    2014-04-01

    Photo-generated transient species, such as the carbonate radical and triplet excited state natural organic matter, mediate the oxidation of pollutants in various sunlit or artificially irradiated systems. In this work, one-electron oxidation potentials for 70 nitrogen-containing compounds were computed, and literature data were used to develop quantitative structure-activity relationships (QSARs) for prediction of the second order reaction rate constants with these two oxidants. For carbonate radical, separate QSARs were necessary for compounds with and without resonance stabilization of the resulting radical, and predicted rate constants were, on average, within a factor of three of experimental values. With the limited data set available, results suggest that one-electron oxidation potential is also a viable descriptor variable for predictions of rate constants with triplet excited states.

  19. Cosmogenic nuclei

    NASA Technical Reports Server (NTRS)

    Raisbeck, G. M.

    1986-01-01

    Cosmogenic nuclei, nuclides formed by nuclear interactions of galactic and solar cosmic rays with extraterrestrial or terrestrial matter are discussed. Long lived radioactive cosmogenic isotopes are focused upon. Their uses in dating, as tracers of the interactions of cosmic rays with matter, and in obtaining information on the variation of primary cosmic ray flux in the past are discussed.

  20. Fusion probability in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Banerjee, Tathagata; Nath, S.; Pal, Santanu

    2015-03-01

    Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions. Purpose: A systematic study of average fusion probability, , is undertaken to obtain a better understanding of its dependence on various reaction parameters. The study may also help to clearly demarcate onset of non-CN fission (NCNF), which causes fusion probability, PCN, to deviate from unity. Method: ER excitation functions for 52 reactions leading to CN in the mass region 170-220, which are available in the literature, have been compared with statistical model (SM) calculations. Capture cross sections have been obtained from a coupled-channels code. In the SM, shell corrections in both the level density and the fission barrier have been included. for these reactions has been extracted by comparing experimental and theoretical ER excitation functions in the energy range ˜5 %-35% above the potential barrier, where known effects of nuclear structure are insignificant. Results: has been shown to vary with entrance channel mass asymmetry, η (or charge product, ZpZt ), as well as with fissility of the CN, χCN. No parameter has been found to be adequate as a single scaling variable to determine . Approximate boundaries have been obtained from where starts deviating from unity. Conclusions: This study quite clearly reveals the limits of applicability of the SM in interpreting experimental observables from fusion reactions involving two massive nuclei. Deviation of from unity marks the beginning of the domain of dynamical models of fusion. Availability of precise ER cross

  1. Exotic Nuclei

    SciTech Connect

    Galindo-Uribarri, Alfredo {nmn}

    2010-01-01

    Current experimental developments on the study of exotic nuclei far from the valley of stability are discussed. I start with general aspects related to the production of radioactive beams followed by the description of some of the experimental tools and specialized techniques for studies in reaction spectroscopy, nuclear structure research and nuclear applications with examples from selected topical areas with which I have been involved. I discuss some of the common challenges faced in Accelerator Mass Spectrometry (AMS) and Radioactive Ion Beam (RIB) science.

  2. Magnetic excitations in the S =1/2 antiferromagnetic-ferromagnetic chain compound BaCu2V2O8 at zero and finite temperature

    NASA Astrophysics Data System (ADS)

    Klyushina, E. S.; Tiegel, A. C.; Fauseweh, B.; Islam, A. T. M. N.; Park, J. T.; Klemke, B.; Honecker, A.; Uhrig, G. S.; Manmana, S. R.; Lake, B.

    2016-06-01

    Unlike most quantum systems which rapidly become incoherent as temperature is raised, strong correlations persist at elevated temperatures in S =1/2 dimer magnets, as revealed by the unusual asymmetric line shape of their excitations at finite temperatures. Here, we quantitatively explore and parametrize the strongly correlated magnetic excitations at finite temperatures using high-resolution inelastic neutron scattering of the model compound BaCu2V2O8 which we show to be an alternating antiferromagnetic-ferromagnetic spin -1/2 chain. Comparison to state of the art computational techniques shows excellent agreement over a wide temperature range. Our findings hence demonstrate the possibility to quantitatively predict coherent behavior at elevated temperatures in quantum magnets.

  3. {gamma}-vibrational states in superheavy nuclei

    SciTech Connect

    Sun Yang; Long Guilu; Al-Khudair, Falih; Sheikh, Javid A.

    2008-04-15

    Recent experimental advances have made it possible to study excited structure in superheavy nuclei. The observed states have often been interpreted as quasiparticle excitations. We show that in superheavy nuclei collective vibrations systematically appear as low-energy excitation modes. By using the microscopic Triaxial Projected Shell Model, we make a detailed prediction on {gamma}-vibrational states and their E2 transition probabilities to the ground state band in fermium and nobelium isotopes where active structure research is going on, and in {sup 270}Ds, the heaviest isotope where decay data have been obtained for the ground-state and for an isomeric state.

  4. Magnetic excitations from an S=1/2 diamond-shaped tetramer compound Cu2PO4OH

    DOE PAGES

    Matsuda, Masaaki; Dissanayake, Sachith E.; Abernathy, Douglas L.; ...

    2015-11-30

    Inelastic neutron scattering experiments have been carried out on a powder sample of Cu2PO4OH, which consists of diamond-shaped tetramer spin units with S=1/2. We have observed two nearly dispersionless magnetic excitations at E1 ~2 and E2 ~0 meV, whose energy width are broader than the instrumental resolution. The simplest square tetramer model with one dominant interaction, which predicts two sharp excitation peaks at E1 and E2(=2E1), does not explain the experimental result. We found that two diagonal intratetramer interactions compete with the main interaction and weak intertetramer interactions connect the tetramers. The main intratetramer interaction is found to split intomore » two inequivalent ones due to a structural distortion below 160 K. Cu2PO4OH is considered to be a good material to study the S=1/2 Heisenberg tetramer system.« less

  5. Optical Model Potentials for {alpha}-Particles Scattering around the Coulomb Barrier on Medium-Mass Nuclei

    SciTech Connect

    Avrigeanu, M.; Roman, F.L.; Avrigeanu, V.

    2005-05-24

    Following a semi-microscopic and phenomenological analyses of {alpha}-particle elastic scattering on A{approx}100 nuclei at energies below 32 MeV, a regional optical potential is involved in (n,{alpha}) reaction cross-sections analysis for the stable Mo isotopes. Focus on the uncertainties in the OMP parameters found to describe the {alpha}-particle emission from excited compound residual nuclei is thus obtained, looking for understanding of the related questions on the basis of microscopic models.

  6. Excited states of selected hydrazo-compounds on the example of 5-nitro-2-(2-phenylhydrazinyl)pyridine and its 3-, 4- or 6-methyl isomers

    NASA Astrophysics Data System (ADS)

    Michalski, J.; Kucharska, E.; Sąsiadek, W.; Lorenc, J.; Hanuza, J.

    2016-11-01

    Syntheses of 5-nitro-2-(2-phenylhydrazinyl)pyridine (5-nitro-2-phenylhydrazopyridine), 3-methyl-5-nitro-2-(2-phenylhydrazinyl)pyridine (3-methyl-5-nitro-2-phenylhydrazopyridine), 4-methyl-5-nitro-2-(2-phenylhydrazinyl)pyridine (4-methyl-5-nitro-2-phenylhydrazopyridine) and 6-methyl-5-nitro-2-(2-phenylhydrazinyl)pyridine (6-methyl-5-nitro-2-phenylhydrazo-pyridine) have been described. Electronic absorption and emission spectra of the compounds in the solid state and in various solvents have been measured at room temperature and discussed in terms of DFT quantum chemical calculations. The molecular structures and energy sequences of the singlet and triplet states have been determined in the B3LYP/6-311G(2d,2p) approximations. The Mulliken analysis and non-bonding orbital approach have been used in characterization of the studied compounds. It has been shown that the HOMO-LUMO transition of the studied compounds is observed in the range 23,900 ÷ 29,300 cm-1 and in this excitation the π-electrons of phenyl ring are transferred to nitro group of pyridine ring. In such a transition the hydrazo-bridge should take part as a mediator. The luminescence of the studied hydrazo-compounds is weak, not measureable in the solid state but measureable in solution.

  7. Excited state localization and internuclear interactions in asymmetric ruthenium(II) and osmium(II) bpy/tpy based dinuclear compounds.

    PubMed

    Halpin, Yvonne; Dini, Danilo; Ahmed, Hamid M Younis; Cassidy, Lynda; Browne, Wesley R; Vos, Johannes G

    2010-03-15

    The synthesis of two asymmetric dinuclear complexes with the formula [M(bpy)(2)(bpt)Ru(tpy)Cl](2+), where M = Ru (1a), Os(2a); bpy = 2,2'-bipyridyl; Hbpt = 3,5-bis(pyridin-2-yl)1,2,4-triazole and tpy = 2,2',6',2''-terpyridine, is reported. The compounds obtained are characterized by mass spectrometry, (1)H NMR, UV/vis/NIR absorption, luminescence, and resonance Raman spectroscopy. Deuterium isotope labeling facilitates assignment of the (1)H NMR and resonance Raman spectra. The interaction between the two metal centers, mediated by the bridging 1,2,4-triazolato moiety in the mixed valent state, is assigned as type II based on the observation of metal to metal charge transfer absorption bands at 7090 and 5990 cm(-1) for 1a and 2a, respectively. The extent of localization of the emissive excited state was determined by transient resonance Raman and emission spectroscopy. Both 1a and 2a show phosphorescence at the same wavelengths; however, whereas for compound 1a the emission is based on the Ru(tpy)Cl- center, for 2a the emissive state is localized on the Os(bpy)(2)- unit. This indicates that also in the excited state there is efficient interaction between the two metal centers.

  8. Specific features of magnetic order in a multiferroic compound CuCrO2 determined using NMR and NQR data for 63, 65Cu nuclei

    NASA Astrophysics Data System (ADS)

    Smol'nikov, A. G.; Ogloblichev, V. V.; Verkhovskii, S. V.; Mikhalev, K. N.; Yakubovskii, A. Yu.; Furukawa, Y.; Piskunov, Yu. V.; Sadykov, A. F.; Barilo, S. N.; Shiryaev, S. V.

    2017-02-01

    Results of studying the paramagnetic and ordered phases of a CuCrO2 single crystal using nuclear magnetic and nuclear quadrupole resonances on 63,65Cu nuclei are presented. The measurements have been carried out in wide ranges of temperature ( T = 4.2-300 K) and magnetic-field strength ( H = 0-94 kOe), with the magnetic fields being directed along a and c axes of the crystal. The components of the electric-field gradient tensor and the magnetic-shift tensor ( K a,c) have been determined. The temperature dependences K a( H || a) and K c( H || c) for the paramagnetic phase are described by the Curie-Weiss law and reproduce the behavior of the magnetic susceptibility (χa,c). The hyperfine field on a copper nucleus has been determined, which is equal to h hf a,c = 33 kOe/μB. Below the temperature T N = 23.6 K, nuclear magnetic resonance and nuclear quadrupole resonance spectra for 63,65Cu nuclei have been recorded typical of helical magnetic structures, which are incommensurable with the lattice period.

  9. Compound

    NASA Astrophysics Data System (ADS)

    Suzumura, Akitoshi; Watanabe, Masaki; Nagasako, Naoyuki; Asahi, Ryoji

    2014-06-01

    Recently, Cu-based chalcogenides such as Cu3SbSe4, Cu2Se, and Cu2SnSe3 have attracted much attention because of their high thermoelectric performance and their common feature of very low thermal conductivity. However, for practical use, materials without toxic elements such as selenium are preferable. In this paper, we report Se-free Cu3SbS4 thermoelectric material and improvement of its figure of merit ( ZT) by chemical substitutions. Substitutions of 3 at.% Ag for Cu and 2 at.% Ge for Sb lead to significant reductions in the thermal conductivity by 37% and 22%, respectively. These substitutions do not sacrifice the power factor, thus resulting in enhancement of the ZT value. The sensitivity of the thermal conductivity to chemical substitutions in these compounds is discussed in terms of the calculated phonon dispersion and previously proposed models for Cu-based chalcogenides. To improve the power factor, we optimize the hole carrier concentration by substitution of Ge for Sb, achieving a power factor of 16 μW/cm K2 at 573 K, which is better than the best reported for Se-based Cu3SbSe4 compounds.

  10. Skyrmions and Nuclei

    NASA Astrophysics Data System (ADS)

    Battye, R. A.; Manton, N. S.; Sutcliffe, P. M.

    We review recent work on the modelling of atomic nuclei as quantised Skyrmions, using Skyrme's original model with pion fields only. Skyrmions are topological soliton solutions, whose conserved topological charge B is identified with the baryon number of a nucleus. Apart from an energy and length scale, the Skyrme model has just one dimensionless parameter m, proportional to the pion mass. It has been found that a good fit to experimental nuclear data requires m to be of order 1. The Skyrmions for B up to 7 have been known for some time, and are qualitatively insensitive to whether m is zero or of order 1. However, for baryon numbers B = 8 and above, the Skyrmions have quite a compact structure for m of order 1, rather than the hollow polyhedral structure found when m = 0. One finds for baryon numbers which are multiples of four, that the Skyrmions are composed of B = 4 sub-units, as in the α-particle model of nuclei. The rational map ansatz gives a useful approximation to the Skyrmion solutions for all baryon numbers when m = 0. For m of order 1, it gives a good approximation for baryon numbers up to 7, and generalisations of this ansatz are helpful for higher baryon numbers. We briefly review the work from the 1980s and 90s on the semiclassical rigidbody quantisation of Skyrmions for B = 1, 2, 3 and 4. We then discuss more recent work extending this method to B = 6, 7, 8, 10 and 12. We determine the quantum states of the Skyrmions, finding their spins, isospins and parities, and compare with the experimental data on the ground and excited states of nuclei up to mass number 12.

  11. Photonics of a conjugated organometallic Pt-Ir polymer and its model compounds exhibiting hybrid CT excited states.

    PubMed

    Soliman, Ahmed M; Fortin, Daniel; Zysman-Colman, Eli; Harvey, Pierre D

    2012-04-13

    Trans- dichlorobis(tri-n-butylphosphine)platinum(II) reacts with bis(2- phenylpyridinato)-(5,5'-diethynyl-2,2'-bipyridine)iridium(III) hexafluorophosphate to form the luminescent conjugated polymer poly[trans-[(5,5'-ethynyl-2,2'-bipyridine)bis(2- phenylpyridinato)-iridium(III)]bis(tri-n-butylphosphine)platinum(II)] hexafluorophosphate ([Pt]-[Ir])n. Gel permeation chromatography indicates a degree of polymerization of 9 inferring the presence of an oligomer. Comparison of the absorption and emission band positions and their temperature dependence, emission quantum yields, and lifetimes with those for models containing only the [Pt] or the [Ir] units indicates hybrid excited states including features from both chromophores.

  12. Properties of fission fragments for Z =112 -116 superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Kaur, Gurjit; Sandhu, Kirandeep; Sharma, Manoj K.

    2016-07-01

    The dynamical cluster decay model (DCM) is applied to understand the dynamics of 48Ca+238U,244Pu,248Cm reactions at comparable excitation energies across the barrier. To understand the capture stage of *286112 ,*292114 , and *296116 nuclei, the compound nucleus formation probability is calculated. The indication of PC N<1 in the DCM framework demonstrates the fact that some competing process such as quasifission may occur at the capture stage of the 48Ca induced reactions. To understand this further, the comparative decay analysis of *286112 ,*292114 and *296116 , nuclei is carried out using β2 i deformations within hot optimum orientation criteria, and the calculated fission cross sections find nice agreement with available data. The fission mass distribution shows a double humped structure where a symmetric peak observed around the Sn region appears to find its genesis in a symmetric quasifission component. On the other hand, the emergence of peaks around Pb in the decay of Z =112 , 114, and 116 nuclei signify the possible presence of asymmetric quasifission. Higher and broader asymmetric quasifission peaks are observed for *296116 and *292114 nuclei as compared to *286112 nucleus. Beside this, the total kinetic energy (TKE) distribution of the decay fragments is also explored by using different proximity potentials, such as Prox-77, Prox-88, and Prox-00. Prox-88 seems to perform better and the calculated TKE values find relatively better comparison at lower angular momentum states. The possible role of different radii of the decaying nuclei is also exercised to understand the TKE ¯ dynamics of 48Ca+238U,244Pu,248Cm reactions.

  13. A compilation of information on the {sup 31}P(p,{alpha}){sup 28}Si reaction and properties of excited levels in the compound nucleus {sup 32}S

    SciTech Connect

    Miller, R.E.; Smith, D.L.

    1997-11-01

    This report documents a survey of the literature, and provides a compilation of data contained therein, for the {sup 31}P(p,{alpha}){sup 28}Si reaction. Attention is paid here to resonance states in the compound-nuclear system {sup 32}S formed by {sup 31}P + p, with emphasis on the alpha-particle decay channels, {sup 28}Si + {alpha} which populate specific levels in {sup 28}Si. The energy region near the proton separation energy for {sup 32}S is especially important in this context for applications in nuclear astrophysics. Properties of the excited states in {sup 28}Si are also considered. Summaries of all the located references are provided and numerical data contained in them are compiled in EXFOR format where applicable.

  14. The Peculiarities of the Production and Decay of Superheavy Nuclei

    NASA Astrophysics Data System (ADS)

    Itkis, M. G.; Beghini, S.; Behera, B. R.; Bogachev, A. A.; Bouchat, V.; Corradi, L.; Dorvaux, O.; Fioretto, E.; Hanappe, F.; Itkis, I. M.; Jandel, M.; Kliman, J.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Krupa, L.; Latina, A.; Materna, T.; Montagnoli, G.; Oganessian, Yu. Ts.; Pokrovsky, I. V.; Prokhorova, E. V.; Rowley, N.; Rusanov, A. Ya.; Sagaidak, R. N.; Scarlassara, F.; Schmitt, C.; Stefanini, A. M.; Stuttge, L.; Szilner, S.; Trotta, M.

    2006-08-01

    The interest in the study of the fission process of superheavy nuclei mainly deals with the opportunity to obtain information about the cross-section of the compound nucleus (CN) formation at excitation energies E*≈15-30 MeV. It allows one to estimate the survival probability of the superheavy composite system after evaporation of 1-3 neutrons, i.e. in "cold" or "warm" fusion reactions. However, in order to solve this problem deeper understanding of the coalescence processes between colliding nuclei, the competition between fusion-fission and quasi-fission processes is needed. The characteristics of both processes, their manifestation in the experimental observables and the relative contribution to the capture cross-section in dependence on the excitation energies, reaction entrance channel etc were investigated for a wide range of target-projectile combinations. Results of the experiments devoted to the study of the fusion-fission and quasi-fission processes in the reactions of the formation of the superheavy nuclei with Z = 102-122 are presented. The heavy ions 26Mg, 48Ca, 50Ti, 58Fe and 64Ni were used as projectiles. The choice of the reactions with 48Ca and actinide-targets was inspired by the experiments on the production of the isotopes 283112, 289114 and 283116 in Dubna using the same reactions. The 50Ti, 58Fe and 64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia) and the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) using the time-of-flight spectrometer of fission fragments CORSET. The role of the shell effects, the influence of the entrance channel asymmetry and the deformations of colliding nuclei on the mechanism of the fusion-fission and the competitive process of quasi-fission are discussed. The recent results on synthesis of

  15. Synthesis of wurtzite-zincblende Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals: insight into the structural selection of quaternary and ternary compounds influenced by binary nuclei

    NASA Astrophysics Data System (ADS)

    Li, Yingwei; Han, Qifeng; Kim, Tae Whan; Shi, Wangzhou

    2014-03-01

    Nearly monodispersed wurtzite-dominant Cu2ZnSnS4 and zincblende-dominant Cu2ZnSnSe4 nanocrystals were successfully synthesized by mixing metal salts with heated thiourea or selenourea in oleylamine. A perspective of the structural relationship between quaternary and ternary semiconductors was investigated through the application of different anion sources to prepare Cu2SnS3 and Cu2SnSe3 nanocrystals. Investigations on copper-based binary compounds found that CuSe (or CuS) and Cu2Se (or Cu1.96S, Cu9S5) nuclei were primarily responsible for the formation of zincblende or wurtzite structures, respectively. Further management over these binary intermediates corresponded to slight structural transformations of the quaternary nanocrystals which could be observed not only in XRD patterns, but from optical and electrical properties as well. According to these results, Cu2ZnGeS4 nanocrystals with wurtzite-dominant structures were first reported using SC(NH2)2, which also verified that the binary semiconductors are the determinative factors.Nearly monodispersed wurtzite-dominant Cu2ZnSnS4 and zincblende-dominant Cu2ZnSnSe4 nanocrystals were successfully synthesized by mixing metal salts with heated thiourea or selenourea in oleylamine. A perspective of the structural relationship between quaternary and ternary semiconductors was investigated through the application of different anion sources to prepare Cu2SnS3 and Cu2SnSe3 nanocrystals. Investigations on copper-based binary compounds found that CuSe (or CuS) and Cu2Se (or Cu1.96S, Cu9S5) nuclei were primarily responsible for the formation of zincblende or wurtzite structures, respectively. Further management over these binary intermediates corresponded to slight structural transformations of the quaternary nanocrystals which could be observed not only in XRD patterns, but from optical and electrical properties as well. According to these results, Cu2ZnGeS4 nanocrystals with wurtzite-dominant structures were first reported

  16. α versus non-α cluster decays of the excited compound nucleus *124Ce using various formulations of the nuclear proximity potential

    NASA Astrophysics Data System (ADS)

    Kaur, Arshdeep; Chopra, Sahila; Gupta, Raj K.

    2015-06-01

    The earlier study of *124Ce formed in the 32S+92Mo reaction at an above barrier beam energy of 150 MeV, using the pocket formula of Blocki et al. for the nuclear proximity potential in the dynamical cluster-decay model (DCM), is extended to the use of other nuclear interaction potentials derived from the Skyrme energy density functional (SEDF) based on the semiclassical extended Thomas Fermi (ETF) approach under the frozen density approximation. The Skyrme forces used are the old SII, SIII, SIV, SKa, SkM, and SLy4 and new GSkI and KDE0(v1), given for both normal and isospin-rich nuclei. It is found that the α -nucleus structure, over the non-α nucleus structure, is preferred for only two Skyrme forces, the SIII and KDE0(v1). An extended intermediate mass fragments (IMFs) window, along with the new decay region of heavy mass fragments (HMFs) and the near-symmetric and symmetric fission fragments which, on adding the complementary heavy fragments, corresponds to (A /2 )±12 mass region of the fusion-fission (ff) process, are predicted by considering cross sections of orders observed in the experiment under study. For the predicted (total) fusion cross section, the survival probability Psurv of the compound nucleus (CN) against fission is shown to be very small because of the very large predicted ff component. On the other hand, the CN formation probability PCN is found to be nearly equal to 1, and hence the decay under study is a pure CN decay for all the nuclear potentials considered, since the estimated noncompound nucleus (nCN) content is almost negligible. We have also applied the extended-Wong model of Gupta and collaborators, and find that the ℓmax values and total fusion cross sections are of the same order as for the DCM. Thus, the extended-Wong model, which describes only the total fusion cross section in terms of the barrier characteristics of the entrance channel nuclei, could be useful for initial experimental studies to be fully treated using the DCM

  17. Purification and Quantification of an Isomeric Compound in a Mixture by Collisional Excitation in Multistage Mass Spectrometry Experiments.

    PubMed

    Jeanne Dit Fouque, Dany; Maroto, Alicia; Memboeuf, Antony

    2016-11-15

    The differentiation, characterization, and quantification of isomers and/or isobars in mixtures is a recurrent problem in mass spectrometry and more generally in analytical chemistry. Here we present a new strategy to assess the purity of a compound that is susceptible to be contaminated with another isomeric side-product in trace levels. Providing one of the isomers is available as pure sample, this new strategy allows the detection of isomeric contamination. This is done thanks to a "gas-phase collisional purification" inside an ion trap mass spectrometer paving the way for an improved analysis of at least similar samples. This strategy consists in using collision induced dissociation (CID) multistage mass spectrometry (MS(2) and MS(3)) experiments and the survival yield (SY) technique. It has been successfully applied to mixtures of cyclic poly(L-lactide) (PLA) with increasing amounts of its linear topological isomer. Purification in gas phase of PLA mixtures was established based on SY curves obtained in MS(3) mode: all samples gave rise to the same SY curve corresponding then to the pure cyclic component. This new strategy was sensitive enough to detect traces of linear PLA (<3%) in a sample of cyclic PLA that was supposedly pure according to other characterization techniques ((1)H NMR, MALDI-HRMS, and size-exclusion chromatography). Moreover, in this case, the presence of linear isomer was undetectable according to MS/MS or MS/MS/MS analysis only as fragment ions are also of the same m/z values. This type of approach could easily be implemented in hyphenated mass spectrometric techniques to improve the structural and quantitative analysis of complex samples.

  18. Collisions of deformed nuclei and superheavy-element production

    SciTech Connect

    Iwamoto, Akira; Moeller, P. |||; Nix, J.R.; Sagawa, Hiroyuki, Sagawa

    1995-09-01

    A detailed understanding of complete fusion cross sections in heavy-ion collisions requires a consideration of the effects of the deformation of the projectile and target. The aim here is to show that deformation and orientation of the colliding nuclei have a very significant effect on the fusion-barrier height and on the compactness of the touching configuration. To facilitate discussions of fusion configurations of deformed nuclei, the authors develop a classification scheme and introduce a notation convention for these configurations. They discuss particular deformations and orientations that lead to compact touching configurations and to fusion-barrier heights that correspond to fairly low excitation energies of the compound systems. Such configurations should be the most favorable for producing superheavy elements. They analyze a few projectile-target combinations whose deformations allow favorable entrance-channel configurations and whose proton and neutron numbers lead to compound systems in a part of the superheavy region where a half-lives are calculated to be observable, that is, longer than 1 {micro}s.

  19. Breakup Densities of Hot Nuclei

    NASA Astrophysics Data System (ADS)

    Viola, V. E.; Kwiatkowski, K.; Natowitz, J. B.; Yennello, S. J.

    2004-09-01

    Breakup densities of hot 197Au-like residues have been deduced from the systematic trends of Coulomb parameters required to fit intermediate-mass-fragment kinetic-energy spectra. The results indicate emission from nuclei near normal nuclear density below an excitation energy E*/A≲2 MeV, followed by a gradual decrease to a near-constant value of ρ/ρ0˜0.3 for E*/A≳5 MeV. Temperatures derived from these data with a density-dependent Fermi-gas model yield a nuclear caloric curve that is generally consistent with those derived from isotope ratios.

  20. Superdeformation in the mercury nuclei

    SciTech Connect

    Janssens, R.V.F.; Carpenter, M.P.; Fernandez, P.B.; Moore, E.F.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H. ); Drigert, M.W. ); Ye, D.; Beard, K.B.; Garg, U.; Reviol, W. ); Bearden, I.G.; Benet, P.; Daly, P.J.; Grabowski, Z.W. )

    1990-01-01

    We shall first summarize the present experimental situation concerning {sup 192}Hg, the nucleus regarded as the analog of {sup 152}Dy for this superdeformation (SD) region in that gaps are calculated to occur at large deformation for Z = 80 and N = 112. Proton and neutron excitations out of the {sup 192}Hg core will then be reviewed with particular emphasis on {sup 191}Hg and {sup 193}Tl. The presentation will conclude with a brief discussion on limits of the SD region for neutron deficient Hg nuclei. 26 refs., 10 figs.

  1. The role of magnetic excitations in magnetoresistance and Hall effect of slightly TM-substituted BaFe2As2 compounds (TM = Mn, Cu, Ni)

    NASA Astrophysics Data System (ADS)

    Peña, J. P.; Piva, M. M.; Jesus, C. B. R.; Lesseux, G. G.; Garitezi, T. M.; Tobia, D.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Adriano, C.; Urbano, R. R.; Pagliuso, P. G.; Pureur, P.

    2016-12-01

    We report on electrical resistivity, magnetoresistance (MR) and Hall effect measurements in four non-superconducting BaFe2-xTMxAs2 (TM = Mn, Cu and Ni) single crystals with small values of the chemical substitution x. The spin density wave (SDW) ordering that occurs in these systems at temperatures T ∼ (120-140) K, in close vicinity to a tetragonal/orthorhombic transition, produces significant modifications in their magneto-transport properties. While in the magnetically ordered phase the MR is positive and its magnitude increases with decreasing temperatures, in the paramagnetic regime the MR becomes vanishingly small. Above the spin density wave transition temperature (TSDW) the Hall coefficient RH is negative, small and weakly temperature dependent, but a remarkable change of slope occurs in the RH versus T curves at T =TSDW . The Hall coefficient amplitude, while remaining negative, increases steadily and significantly as the temperature is decreased below TSDW and down to T = 20 K. The qualitative behavior of both MR and Hall coefficient is weakly dependent on the chemical substitution in the studied limit. The experiments provide strong evidence that scattering of charge carriers by magnetic excitations has to be taken into account to explain the behavior of the resistivity, magnetoresistance and Hall effect in the ordered phase of the studied compounds. Effects of multiple band conduction also must be considered for a complete interpretation of the results.

  2. Resonant inelastic X-ray scattering study of spin-wave excitations in the cuprate parent compound Ca2CuO2Cl2

    DOE PAGES

    Lebert, B. W.; Dean, M.; Nicolaou, A.; ...

    2017-04-07

    By means of resonant inelastic x-ray scattering at the Cu L3 edge, we measured the spin wave dispersion along <100> and <110> in the undoped cuprate Ca2CuO2Cl2. The data yields a reliable estimate of the superexchange parameter J = 135 ± 4 meV using a classical spin-1/2 2D Heisenberg model with nearest-neighbor interactions and including quantum fluctuations. Including further exchange interactions increases the estimate to J = 141 meV. The 40 meV dispersion between the magnetic Brillouin zone boundary points (1/2, 0) and (1/4, 1/4) indicates that next-nearest neighbor interactions in this compound are intermediate between the values found inmore » La2CuO4 and Sr2CuO2Cl2. Here by owing to the low-Z elements composing Ca2CuOCl2, the present results may enable a reliable comparison with the predictions of quantum many-body calculations, which would improve our understanding of the role of magnetic excitations and of electronic correlations in cuprates.« less

  3. Electronic structure, transport properties, and excited states in CoTiSb, CoZrSb, and CoHfSb half-Heusler compounds

    NASA Astrophysics Data System (ADS)

    Janotti, Anderson; Gui, Zhigang; Kawasaki, Jason; Palmstrom, Chris; Himmetoglu, Burak

    CoTiSb is a member of a large family of half-Heusler compounds with 18 valence electrons. CoTiSb is semiconductor material with a band gap a little over 1 eV, and it has been considered promising for thermoelectric applications. It can be grown on conventional III-V semiconductors, and could potentially be integrated in III-V devices. Here we present results of first-principles calculations of electronic structure, transport properties, and excited states in CoTiSb, as well as CoZrSb and CoHfSb. Electronic structures are studied using density functional theory within the local density approximation, hybrid functional and quasiparticle GW methods. Both room-temperature Seebeck coefficient and carrier mobility are calculated from first-principles. We also determine the band alignments to III-V semiconductors, and all the results are presented and discussed in the light of available experimental data. This work was supported by the DOE.

  4. Excited-state electronic coupling and photoinduced multiple electron transfer in two related ligand-bridged hexanuclear mixed-valence compounds.

    PubMed

    Pfennig, Brian W; Mordas, Carolyn J; McCloskey, Alex; Lockard, Jenny V; Salmon, Patty M; Cohen, Jamie L; Watson, David F; Bocarsly, Andrew B

    2002-08-26

    The synthesis, characterization, electrochemical, photophysical, and photochemical properties of two hexanuclear mixed-valence compounds are reported. Each supramolecular species consists of two cyano-bridged [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(3)L-NC-Fe(II)(CN)(5)] triads that are linked to each other through a Pt(IV)-L-Pt(IV) bridge, where L = 4,4'-dipyridyl (bpy) or 3,3'-dimethyl-4,4'-dipyridyl (dmb). The major difference between the two compounds is the electronic nature of the bridging ligand between the two Pt atoms. Both species exhibit a broad Fe(II) --> Pt(IV) intervalent (IT) absorption band at 421 nm with an oscillator strength that is approximately four times that for [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(5)] and twice that for [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(4)-NC-Fe(II)(CN)(5)].(4-) When L = bpy, the resonance Raman spectrum obtained by irradiating the IT band at 488 nm exhibits several dipyridyl ring modes at 1604, 1291, and 1234 cm(-1) which are not present in the spectrum when L = dmb. In addition, femtosecond pump-probe spectroscopy performed at 400 nm yields a transient bleach of the IT absorption band with a single exponential decay of 3.5 ps for L = bpy, compared with only 1.8 ps for L = dmb and 2.1 ps for [(NC)(5)Fe(II)-CN-Pt(IV)(NH(3))(4)-NC-Fe(II)(CN)(5)].(4-) Last, prolonged irradiation of the complexes at 488 nm leads to the formation of 4 equiv of ferricyanide with a quantum efficiency of 0.0014 for L = bpy and 0.0011 for L = dmb. The transient absorption, resonance Raman, and photochemical data suggest that the degree of excited electronic coupling in these compounds is tunable by changing the electronic nature of the Pt-L-Pt bridging ligand.

  5. Synthesis of wurtzite-zincblende Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals: insight into the structural selection of quaternary and ternary compounds influenced by binary nuclei.

    PubMed

    Li, Yingwei; Han, Qifeng; Kim, Tae Whan; Shi, Wangzhou

    2014-04-07

    Nearly monodispersed wurtzite-dominant Cu2ZnSnS4 and zincblende-dominant Cu2ZnSnSe4 nanocrystals were successfully synthesized by mixing metal salts with heated thiourea or selenourea in oleylamine. A perspective of the structural relationship between quaternary and ternary semiconductors was investigated through the application of different anion sources to prepare Cu2SnS3 and Cu2SnSe3 nanocrystals. Investigations on copper-based binary compounds found that CuSe (or CuS) and Cu2Se (or Cu1.96S, Cu9S5) nuclei were primarily responsible for the formation of zincblende or wurtzite structures, respectively. Further management over these binary intermediates corresponded to slight structural transformations of the quaternary nanocrystals which could be observed not only in XRD patterns, but from optical and electrical properties as well. According to these results, Cu2ZnGeS4 nanocrystals with wurtzite-dominant structures were first reported using SC(NH2)2, which also verified that the binary semiconductors are the determinative factors.

  6. Synthesis of superheavy elements and dinuclear-system concept of compound-nucleus formation

    SciTech Connect

    Antonenko, N.V.; Adamian, G.G.; Cherepanov, E.A.

    1996-12-31

    Dinuclear system concept is applied to the analysis of reactions used for the synthesis of elements with Z = 110, 112, 114, and 116. The inner fusion barriers obtained for these reactions are in good agreement with the experimental estimations resulted from the excitation energies of compound nuclei. A model is suggested for the calculation of the competition between complete fusion and quasifission in reactions with heavy nuclei. The fusion rate through the inner fusion barrier in mass asymmetry is found by using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation. The influence of dissipative effects on the dynamics of nuclear fusion is considered.

  7. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  8. Is Fusion Inhibited for Weakly Bound Nuclei?

    SciTech Connect

    Takahashi, J.; Munhoz, M.; Szanto, E.M.; Carlin, N.; Added, N.; Suaide, A.A.; de Moura, M.M.; Liguori Neto, R.; Szanto de Toledo, A.; Canto, L.F.

    1997-01-01

    Complete fusion of light radioactive nuclei is predicted to be hindered at near-barrier energies. This feature is investigated in the case of the least bound stable nuclei. Evaporation residues resulting from the {sup 6,7}Li+{sup 9}Be and {sup 6,7}Li+{sup 12}C fusion reactions have been measured in order to study common features in reactions involving light weakly bound nuclei. The experimental excitation functions revealed that the fusion cross section is significantly smaller than the total reaction cross section and also smaller than the fusion cross section expected from the available systematics. A clear correlation between the fusion probability and nucleon (cluster) separation energy has been established.The results suggest that the breakup process has a strong influence on the hindrance of the fusion cross section. {copyright} {ital 1996} {ital The American Physical Society}

  9. Invariant mass spectroscopy of halo nuclei

    SciTech Connect

    Nakamura, Takashi

    2008-11-11

    We have applied the invariant mass spectroscopy to explore the low-lying exited states of halo nuclei at intermediate energies around 70 MeV/nucleon at RIKEN. As examples, we show here the results of Coulomb breakup study for {sup 11}Li using the Pb target, as well as breakup reactions of {sup 14}Be with p and C targets. The former study revealed a strong Coulomb breakup cross section reflecting the large enhancement of E1 strength at low excitation energies (soft E1 excitation). The latter revealed the observation of the first 2{sup +} state in {sup 14}Be.

  10. Quantum Monte Carlo calculations for light nuclei

    SciTech Connect

    Wiringa, R.B.

    1998-08-01

    Quantum Monte Carlo calculations of ground and low-lying excited states for nuclei with A {le} 8 are made using a realistic Hamiltonian that fits NN scattering data. Results for more than 30 different (j{sup {prime}}, T) states, plus isobaric analogs, are obtained and the known excitation spectra are reproduced reasonably well. Various density and momentum distributions and electromagnetic form factors and moments have also been computed. These are the first microscopic calculations that directly produce nuclear shell structure from realistic NN interactions.

  11. Isolation of Nuclei.

    PubMed

    Nabbi, Arash; Riabowol, Karl

    2015-08-03

    The isolation of nuclei is often the first step in studying processes such as nuclear-cytoplasmic shuttling, subcellular localization of proteins, and protein-chromatin or nuclear protein-protein interactions in response to diverse stimuli. Therefore, rapidly obtaining nuclei from cells with relatively high purity and minimal subcellular contamination, protein degradation, or postharvesting modification is highly desirable. Historically, the isolation of nuclei involved a homogenization step followed by centrifugation through high-density glycerol or sucrose. Although clean nuclei with little cytoplasmic contamination can be prepared using this method, it is typically time consuming and can allow protein degradation, protein modification, and leaching of components from the nuclei to occur. We have developed a rapid and simple fractionation method that is based on the selective dissolution of the cytoplasmic membrane (but not the nuclear membrane) using a low concentration of a nonionic detergent and rapid centrifugation steps. Here we describe important considerations when isolating nuclei from cells, introduce our rapid method, and compare this method to a more traditional protocol for isolating nuclei, noting the strengths and limitations of each approach.

  12. Breakup Densities of Hot Nuclei.

    NASA Astrophysics Data System (ADS)

    Viola, Vic

    2006-04-01

    Breakup densities of hot ^197Au-like residues have been deduced from the systematic trends of Coulomb parameters required to fit intermediate-mass-fragment kinetic-energy spectra. The results indicate emission from nuclei near normal nuclear density below an excitation energy E*/A .3ex<˜x 2 MeV, followed by a gradual decrease to a near-constant value of ρ/ρ0˜ 3 for E*/A .3ex>˜x 5 MeV. Temperatures derived from these data with a density-dependent Fermi-gas model yield a nuclear caloric curve that is generally consistent with those derived from isotope ratios.

  13. Changes in the structure of nuclei between the magic neutron numbers 50 and 82 as indicated by a rotating-cluster analysis of the energy values of the first 2j excited states of isotopes of cadmium

    SciTech Connect

    Pauling, L.

    1981-09-01

    Values of R, the radius of rotation of the rotating cluster, are calculated from the observed values of the energy of the lowest 2/sup +/ states of the even isotopes of Cd, Sn, and Te with the assumption that the cluster is ..cap alpha.., pb, and ..cap alpha.., respectively. R shows a maximum at approx. N = 58, a minimum at approx. N = 62, and a second maximum at approx. N = 70. The increase to the first maximum is interpreted as resulting from the overcrowding of spherons (alphas and tritons) in the mantle (outer layer) of the nuclei, causing the cluster to change from rotating in the mantle to skimming over its surface; the decrease to the minimum results from the addition of three dineutrons to the core, expanding the mantle and permitting the rotating cluster to begin to drop back into it; and the increase to the second maximum results from the overcrowding of the larger mantle surrounding the core containing the semimagic number 14 of neutrons rather than the magic numbers 8 for N = 50. The decrease after the second maximum results from the further increase in the number of core neutrons to 20, corresponding to the magic number 82. Some additional evidence for the change to an intermediate structure between N = 50 and N = 82 is also discussed.

  14. Modeling level structures of odd-odd deformed nuclei

    SciTech Connect

    Hoff, R.W.; Kern, J.; Piepenbring, R.; Boisson, J.P.

    1985-01-15

    A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation were derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated configuration-specific values for the Gallagher-Moszkowski splittings were used. Calculated and experimental level structures for /sup 238/Np, /sup 244/Am, and /sup 250/Bk are compared, as well as those for several nuclei in the rare-earch region. The agreement for the actinide species is excellent, with bandhead energies deviating 22 keV and rotational parameters 5%, on the average. Corresponding average deviations for five rare-earth nuclei are 47 keV and 7%. Several applications of this modeling technique are discussed.

  15. Modeling level structures of odd-odd deformed nuclei

    SciTech Connect

    Hoff, R.W.; Kern, J.; Piepenbring, R.; Boisson, J.P.

    1984-09-07

    A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation were derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated configuration-specific values for the Gallagher-Moszkowski splittings were used. Calculated and experimental level structures for /sup 238/Np, /sup 244/Am, and /sup 250/Bk are compared, as well as those for several nuclei in the rare-earth region. The agreement for the actinide species is excellent, with bandhead energies deviating 22 keV and rotational parameters 5%, on the average. Corresponding average deviations for five rare-earth nuclei are 47 keV and 7%. Several applications of this modeling technique are discussed. 18 refs., 5 figs., 4 tabs.

  16. Light element production by low energy nuclei from massive stars

    NASA Technical Reports Server (NTRS)

    Vangioni-Flam, E.; Casse, M.; Ramaty, R.

    1997-01-01

    The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

  17. Cryogenic exciter

    DOEpatents

    Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

    2012-03-13

    The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

  18. Exotic Light Nuclei

    ERIC Educational Resources Information Center

    Cerny, Joseph; Poskanzer, Arthur M.

    1978-01-01

    Among the light elements, nuclei with unequal numbers of protons and neutrons are highly unstable. Some survive just long enough to be detected and exhibit unusual regimes of radioactive decay. ( Autor/MA)

  19. Observations of cometary nuclei

    NASA Astrophysics Data System (ADS)

    A'Hearn, M. F.

    Attempts to observe cometary nuclei and to determine fundamental physical parameters relevant to the relationship between comets and asteroids are reviewed. It has been found that cometary nuclei, at least of periodic comets, are bigger and blacker than generally thought as recently as five years ago. Geometric albedos may be typically three percent and typical radii are probably of order 5 km. Nuclei of periodic comets are probably highly prolate unless they are both oblate and rotating about one of the major axes. P/Halley images provide convincing evidence of the existence of mantles discussed in many models. Numerous pieces of evidence suggest a connection between cometary nuclei and A-A asteroids of types D and C.

  20. The Elusive Excited Quintet [superscript 5]D of Tb(III): A Source of Luminescence and Resonance Energy Transfer in Terbium Compounds

    ERIC Educational Resources Information Center

    Klier, Kamil

    2010-01-01

    The understanding of electronic structure of atomic and molecular term states involved in spectroscopic transitions is aided by projecting combinations of micro-configurations to multi-electron states with "good" quantum numbers of angular momenta. In rare-earth (RE) compounds, atomic term labels are justifiably carried over to compounds, because…

  1. Alternating-parity collective states of yrast and nonyrast bands in lanthanide and actinide nuclei

    SciTech Connect

    Nadirbekov, M. S. Yuldasheva, G. A.; Denisov, V. Yu.

    2015-03-15

    Excited collective states of even-even nuclei featuring quadrupole and octupole deformations are studied within a nonadiabatic collective model with a Gaussian potential energy. Rotational states of the yrast band and vibrational-rotational states of nonyrast bands are considered in detail. The energies of alternating-parity excited states of the yrast band in the {sup 164}Er, {sup 220}Ra, and {sup 224}Th nuclei; the yrast and first nonyrast bands in the {sup 154}Sm and {sup 160}Gd nuclei; and the yrast, first nonyrast, and second nonyrast bands in the {sup 224}Ra and {sup 240}Pu nuclei are described well on the basis of the proposed model.

  2. Single particle versus collectivity, shapes of exotic nuclei

    NASA Astrophysics Data System (ADS)

    Jungclaus, Andrea

    2016-03-01

    In this article some selected topics of nuclear structure research will be discussed as illustration of the progress reached in this field during the last thirty years. These examples evidence the improvement of our understanding of the atomic nucleus reached on the basis of countless experiments, performed to study both exotic nuclei (nuclei far-off the valley of stability) as well as nuclei under exotic conditions (high excitation energy/temperature or large angular momentum/rotational frequency), using stable and radioactive ion beams. The experimental progress, in parallel to the advancement of modern theoretical descriptions, led us to a much richer view of this fundamental many-body system.

  3. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    DOE PAGES

    Nishio, K.; Andreyev, A. N.; Chapman, R.; ...

    2015-06-30

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190 Hg formed in fusion reactions 36Ar + 144 Smand 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(180Hg) = 33-66 MeV and E*(190Hg) = 48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses more » $$\\overline{A}_L$$/$$\\overline{A}_H$$ = 79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of$$\\overline{A}_L$$/$$\\overline{A}_H$$ = 83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. In conclusion, this behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.« less

  4. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    NASA Astrophysics Data System (ADS)

    Nishio, K.; Andreyev, A. N.; Chapman, R.; Derkx, X.; Düllmann, Ch. E.; Ghys, L.; Heßberger, F. P.; Hirose, K.; Ikezoe, H.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Makii, H.; Nishinaka, I.; Ohtsuki, T.; Pain, S. D.; Sagaidak, R.; Tsekhanovich, I.; Venhart, M.; Wakabayashi, Y.; Yan, S.

    2015-09-01

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E* (180Hg) = 33- 66 MeV and E* (190Hg) = 48- 71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses AbarL /AbarH = 79 / 101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+ / EC -delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of AbarL /AbarH = 83 / 107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  5. Fission of actinide nuclei using multi-nucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    2014-09-01

    We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

  6. Static and Statistical Properties of Hot Rotating Nuclei in a Macroscopic Temperature-Dependent Finite-Range Model

    SciTech Connect

    Ryabov, E.G.; Adeev, G.D.

    2005-09-01

    A macroscopic temperature-dependent model that takes into account nuclear forces of finite range is used to calculate the static and statistical properties of hot rotating compound nuclei. The level-density parameter is approximated by an expression of the leptodermous type. The resulting expansion coefficients are in good agreement with their counterparts proposed previously by A.V. Ignatyuk and his colleagues. The effect of taking simultaneously into account the temperature of a nucleus and its angular momentum on the quantities under study, such as the heights and positions of fission barriers and the effective moments of inertia of nuclei at the barrier, is considered, and the importance of doing this is demonstrated. The fissility parameter (Z{sup 2}/A){sub crit} and the position of the Businaro-Gallone point are studied versus temperature. It is found that, with increasing temperature, both parameters are shifted to the region of lighter nuclei. It is shown that the inclusion of temperature leads to qualitatively the same effects as the inclusion of the angular momentum of a nucleus, but, quantitatively, thermal excitation leads to smaller effects than rotational excitation.

  7. Effective Interactions for Light Nuclei

    NASA Astrophysics Data System (ADS)

    Caldwell, Bryan R.

    The G-matrix technique in which one is able to easily calculate ground and excited states of many-body systems is used to calculate the ground state energies and some excited levels of ^3H and ^4He. Energy independent effective interactions are obtained for these nuclei using the technique of Suzuki and Lee which requires the G-matrix and its derivatives with respect to starting energy. It is found that accurate energy derivatives of the G-matrix are necessary to obtain energy independence and thus analytic expressions are presented for these derivatives in both center-of-mass/relative and shell model coordinate systems. Several rules of thumb are given pertaining to the convergence criteria in both coordinate systems. Further, since the G-matrix includes only intra -channel two-body correlations outside the active space, we explore the effect on the binding energies when the active space is enlarged to include several major shells. By enlarging the active space, we hope to include the most important many-body correlations explicitly. It is found that when the active space includes more than 2 major shells, the effective interaction is well approximated by the G-matrix. Our results essentially agree with exact Faddeev calculations for ^3 H but underbind by about.5 MeV in ^4 He as compared to exact Yabukovsky and Green function Monte Carlo calculations. A possible reason for this underbinding, the inclusion of unlinked diagrams in the energy expansion, is studied. The energy independent G-matrix technique is then applied to the p-shell (^5He, ^6Li and ^7Li) where the active space includes all excitations up to 2 hbaromega. Zero, one, two and three -body effective interactions are extracted and it is found that a schematic two-parameter three-body potential can be used to approximate the effective three-body potential that results from the truncation of the active space.

  8. Excitation energy and nuclear dissipation probed with evaporation-residue cross sections

    SciTech Connect

    Ye, W.

    2011-04-15

    Using a Langevin equation coupled with a statistical decay model, we calculate the excess of evaporation-residue cross sections over its standard statistical-model value as a function of nuclear dissipation strength for {sup 200}Hg compound nuclei (CNs) under two distinct types of initial conditions for populated CNs: (i) high excitation energy but low angular momentum (produced via proton-induced spallation reactions at GeV energies and via peripheral heavy-ion collisions at relativistic energies) and (ii) high angular momentum but low excitation energy (produced through fusion mechanisms). We find that the conditions of case (ii) not only amplify the effect of dissipation on the evaporation residues, but also substantially increase the sensitivity of this excess to nuclear dissipation. These results suggest that, in experiments, to obtain accurate information of presaddle nuclear dissipation strength by measuring evaporation-residue cross sections, it is best to choose the heavy-ion-induced fusion reaction approach to yield excited compound nuclei.

  9. Scattering Of Light Nuclei

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R

    2009-12-15

    The exact treatment of nuclei starting from the constituent nucleons and the fundamental interactions among them has been a long-standing goal in nuclear physics. Above all nuclear scattering and reactions, which require the solution of the many-body quantum-mechanical problem in the continuum, represent an extraordinary theoretical as well as computational challenge for ab initio approaches.We present a new ab initio many-body approach which derives from the combination of the ab initio no-core shell model with the resonating-group method [4]. By complementing a microscopic cluster technique with the use of realistic interactions, and a microscopic and consistent description of the nucleon clusters, this approach is capable of describing simultaneously both bound and scattering states in light nuclei. We will discuss applications to neutron and proton scattering on sand light p-shell nuclei using realistic nucleon-nucleon potentials, and outline the progress toward the treatment of more complex reactions.

  10. Measurement of fusion excitation functions in the system {sup 78}Kr + {sup 100}Mo

    SciTech Connect

    Rehm, K.E.; Jiang, C.L.; Esbensen, H.

    1995-08-01

    Earlier measurements of fusion reactions involving {sup 78}Kr and {sup 100}Mo projectiles and Ni-targets showed surprisingly large fusion yields at low energies which could not be explained by coupled-channels calculations. The main difference to similar measurements involving the neighboring {sup 86}Kr and {sup 92}Mo isotopes was the different slope of the excitation functions at sub-barrier energies. An analysis of a variety of experiments showed a correlation between the nuclear structure and the slope of the excitation functions, with the {open_quotes}soft{close_quotes} transitional nuclei ({sup 78}Kr, {sup 100}Mo) exhibiting shallower slopes than the {open_quotes}stiff{close_quotes} nuclei ({sup 86}Kr, {sup 92}Mo) measured at the same energies with respect to the barrier. In this experiment we studied the fusion excitation function involving two transitional nuclei {sup 78}Kr + {sup 100}Mo. The measurements were performed with {sup 78}Kr beams from the ECR source at energies between 285-370 MeV. Separation of the evaporation nucleus from the elastically scattered particles was achieved by measuring time-of-flight and magnetic rigidity in the gas-filled spectrograph. The data were completely analyzed. A comparison of the cross sections with measurements for the system {sup 86}Kr + {sup 92}Mo populating the same compound nucleus {sup 178}Pt. It shows good agreement at the highest energies, but quite different falloffs of the excitation functions toward lower energies. Coupled-channels calculations, including multi-phonon excitation for the two systems, are being performed.

  11. Disintegration of comet nuclei

    NASA Astrophysics Data System (ADS)

    Ksanfomality, Leonid V.

    2012-02-01

    The breaking up of comets into separate pieces, each with its own tail, was seen many times by astronomers of the past. The phenomenon was in sharp contrast to the idea of the eternal and unchangeable celestial firmament and was commonly believed to be an omen of impending disaster, especially for comets with tails stretching across half the sky. It is only now that we have efficient enough space exploration tools to see comet nuclei and even - in the particular case of small comet Hartley-2 in 2010 - to watch their disintegration stage. There are also other suspected candidates for disintegration in the vast family of comet nuclei and other Solar System bodies.

  12. The shapes of nuclei

    NASA Astrophysics Data System (ADS)

    Bertsch, G. F.

    Gerry Brown initiated some early studies on the coexistence of different nuclear shapes. The subject has continued to be of interest and is crucial for understanding nuclear fission. We now have a very good picture of the potential energy surface with respect to shape degrees of freedom in heavy nuclei, but the dynamics remain problematic. In contrast, the early studies on light nuclei were quite successful in describing the mixing between shapes. Perhaps a new approach in the spirit of the old calculations could better elucidate the character of the fission dynamics and explain phenomena that current theory does not model well.

  13. Sharp change-over from compound nuclear fission to quasifission

    SciTech Connect

    Ghosh, T. K.; Banerjee, K.; Bhattacharya, C.; Bhattacharya, S.; Kundu, S.; Mali, P.; Meena, J. K.; Mukherjee, G.; Mukhopadhyay, S.; Rana, T. K.; Bhattacharya, P.; Golda, K. S.

    2009-05-15

    Fission fragment mass distributions have been measured from the decay of the compound nucleus {sup 246}Bk that has been populated via two entrance channels. These entrance channels have a slight difference in their mass asymmetries that puts them on either side of the Businaro Gallone mass asymmetry parameter. Both target nuclei were deformed. Near the Coulomb barrier, at similar excitation energies, the width of the fission fragment mass distribution was found to be drastically different for the {sup 14}N+{sup 232}Th reaction compared to the {sup 11}B+{sup 235}U reaction. The entrance channel mass asymmetry was found to affect the fusion process sharply.

  14. A new non-microscopic study of cluster structures in light alpha-conjugate nuclei

    NASA Astrophysics Data System (ADS)

    Zoghi-Foumani, Niloufar; Shojaei, Mohammad Reza; Rajabi, Ali Akbar

    2017-01-01

    In this paper, the alpha-cluster state in light alpha-conjugate nuclei is studied and a new suitable local potential model for the α-cluster phase of these nuclei is suggested. Using the generalized Nikiforov-Uvarov (NU) method, the clusterization energy for 8Be, 12C, 16O and 20Ne nuclei is calculated. Based on the obtained results, the clustering phenomenon is more probable at energies among excited levels and it happens neither at ground state nor at excited states of light alpha-conjugate nuclei. It is found that the presented formulation for clustering phenomenon reproduces the results of previous experimental and theoretical attempts for the mentioned nuclei. The consistency of the obtained results with the previous experimental and theoretical predictions indicates the reliability of this formulation for various types of alpha-conjugate, nuclei.

  15. The Onset of Deformation in Neutron-Deficient At Nuclei

    SciTech Connect

    Smith, M.B.; Chapman, R.; Cocks, J.F.C.; Dorvaux, O.; Helariutta, K.; Jones, P.M.; Julin, R.; Juutinen, S.; Kankaanpaa, H.; Kettunen, H.; Kuusiniemi, P.; Le Coz, Y.; Leino, M.; Middleton, D.J.; Muikku, M.; Nieminen, P.; Rahkila, P.; Savelius, A.; Spohr, K.-M.

    1999-12-31

    Excited states in the {sup 197}At nucleus have been identified for the first time using the recoil-decay-tagging technique. The excitation energy of these states is found to be consistent with the systematics of neutron-deficient At nuclei and with calculations indicating that the nucleus may be deformed in its ground state. A more recent experiment, to study states in {sup 195}At, is discussed.

  16. The onset of deformation in neutron-deficient At nuclei

    SciTech Connect

    Smith, M. B.; Chapman, R.; Middleton, D. J.; Spohr, K.-M.; Cocks, J. F. C.; Dorvaux, O.; Helariutta, K.; Jones, P. M.; Julin, R.; Juutinen, S.; Kankaanpaeae, H.; Kettunen, H.; Kuusiniemi, P.; Leino, M.; Muikku, M.; Nieminen, P.; Rahkila, P.; Savelius, A.; Coz, Y. Le

    1999-11-16

    Excited states in the {sup 197}At nucleus have been identified for the first time using the recoil-decay-tagging technique. The excitation energy of these states is found to be consistent with the systematics of neutron-deficient. At nuclei and with calculations indicating that the nucleus may be deformed in its ground state. A more recent experiment, to study states in {sup 195}At, is discussed.

  17. Exciter switch

    NASA Technical Reports Server (NTRS)

    Mcpeak, W. L.

    1975-01-01

    A new exciter switch assembly has been installed at the three DSN 64-m deep space stations. This assembly provides for switching Block III and Block IV exciters to either the high-power or 20-kW transmitters in either dual-carrier or single-carrier mode. In the dual-carrier mode, it provides for balancing the two drive signals from a single control panel located in the transmitter local control and remote control consoles. In addition to the improved switching capabilities, extensive monitoring of both the exciter switch assembly and Transmitter Subsystem is provided by the exciter switch monitor and display assemblies.

  18. Magnetic excitations from an S=1/2 diamond-shaped tetramer compound Cu2PO4OH

    SciTech Connect

    Matsuda, Masaaki; Dissanayake, Sachith E.; Abernathy, Douglas L.; Totsuka, K.; Belik, A. A.

    2015-11-30

    Inelastic neutron scattering experiments have been carried out on a powder sample of Cu2PO4OH, which consists of diamond-shaped tetramer spin units with S=1/2. We have observed two nearly dispersionless magnetic excitations at E1 ~2 and E2 ~0 meV, whose energy width are broader than the instrumental resolution. The simplest square tetramer model with one dominant interaction, which predicts two sharp excitation peaks at E1 and E2(=2E1), does not explain the experimental result. We found that two diagonal intratetramer interactions compete with the main interaction and weak intertetramer interactions connect the tetramers. The main intratetramer interaction is found to split into two inequivalent ones due to a structural distortion below 160 K. Cu2PO4OH is considered to be a good material to study the S=1/2 Heisenberg tetramer system.

  19. Physics with Polarized Nuclei.

    ERIC Educational Resources Information Center

    Thompson, William J.; Clegg, Thomas B.

    1979-01-01

    Discusses recent advances in polarization techniques, specifically those dealing with polarization of atomic nuclei, and how polarized beams and targets are produced. These techniques have greatly increased the scope of possible studies, and provided the tools for testing fundamental symmetries and the spin dependence of nuclear forces. (GA)

  20. Transition from collective to noncollective rotation at high spin in N approx. = 87 nuclei

    SciTech Connect

    Baktash, C.

    1982-01-01

    The systematics of the (E2) ..gamma.. ray transition energies and the available lifetime data are used to characterize the excitation modes of the light rare-earth nuclei (N greater than or equal to 82) at different spins. The results, which include our recently obtained data on /sup 149/Gd, /sup 154/Ho, /sup 155/Er, /sup 157/Yb and /sup 158/Yb nuclei, indicate that, at low spins, the nuclear excitation mode (shapes) change from single-particle excitations (weakly oblate) in N less than or equal to 85 nuclei to quasi-vibrational (soft triaxial) in N = 86, weakly rotational (prolate) in N = 87, and rotational (prolate) in the N greater than or equal to 88 systems. At higher angular momenta, all these nuclei show a general tendency to traverse the (epsilon,..gamma..) plane towards the oblate axis, and to eventually adopt the aligned coupling mode of excitation.

  1. Cluster aspects of p-shell and sd-shell nuclei

    SciTech Connect

    Kanada-En'yo, Y.; Kobayashi, F.; Suhara, T.; Kimura, M.; Taniguchi, Y.

    2011-05-06

    We report some topics on cluster structures studied by using a theoretical method of antisymmetrized molecular dynamics(AMD). Cluster features of p-shell and sd-shell nuclei are discussed. In particular, three alpha cluster structures in the excited states of {sup 12}C and {sup 14}C are focused. Dineutron correlations in neutron-rich nuclei are also discussed.

  2. Borromean halo, Tango halo, and halo isomers in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Izosimov, Igor

    2016-01-01

    Structure of the ground and excited states in halo-like nuclei is discussed. Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei.Structure of the halo may be different for the different levels and resonances in atomic nuclei. Isobar analog, double isobar analog, configuration, and double configuration states can simultaneously have n-n, n-p, and p-p halo components in their wave functions. When the halo structure of the excited state differs from that of the ground state, or the ground state has non-halo structure, the γ-transition from the excited state to the ground state can be essentially hindered, i.e. the formation of a specific type of isomers (halo isomers) becomes possible. B(Mγ) and B(Eγ) values for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei which ground state does not exhibit halo structure but the excited state (halo isomer) may have one.

  3. Open sd-shell nuclei from first principles

    SciTech Connect

    Jansen, Gustav R.; Signoracci, Angelo J.; Hagen, Gaute; Navratil, Petr

    2016-07-05

    We extend the ab initio coupled-cluster effective interaction (CCEI) method to open-shell nuclei with protons and neutrons in the valence space, and compute binding energies and excited states of isotopes of neon and magnesium. We employ a nucleon-nucleon and three-nucleon interaction from chiral effective field theory evolved to a lower cutoff via a similarity renormalization group transformation. We find good agreement with experiment for binding energies and spectra, while charge radii of neon isotopes are underestimated. For the deformed nuclei 20Ne and 24Mg we reproduce rotational bands and electric quadrupole transitions within uncertainties estimated from an effective field theory for deformed nuclei, thereby demonstrating that collective phenomena in sd-shell nuclei emerge from complex ab initio calculations.

  4. Open sd-shell nuclei from first principles

    DOE PAGES

    Jansen, Gustav R.; Signoracci, Angelo J.; Hagen, Gaute; ...

    2016-07-05

    We extend the ab initio coupled-cluster effective interaction (CCEI) method to open-shell nuclei with protons and neutrons in the valence space, and compute binding energies and excited states of isotopes of neon and magnesium. We employ a nucleon-nucleon and three-nucleon interaction from chiral effective field theory evolved to a lower cutoff via a similarity renormalization group transformation. We find good agreement with experiment for binding energies and spectra, while charge radii of neon isotopes are underestimated. For the deformed nuclei 20Ne and 24Mg we reproduce rotational bands and electric quadrupole transitions within uncertainties estimated from an effective field theory formore » deformed nuclei, thereby demonstrating that collective phenomena in sd-shell nuclei emerge from complex ab initio calculations.« less

  5. Scissors mode of Gd nuclei studied from resonance neutron capture

    SciTech Connect

    Kroll, J.; Baramsai, B.; Becker, J. A.; and others

    2012-10-20

    Spectra of {gamma} rays following the neutron capture at isolated resonances of stable Gd nuclei were measured. The objectives were to get new information on photon strength of {sup 153,155-159}Gd with emphasis on the role of the M1 scissors-mode vibration. An analysis of the data obtained clearly indicates that the scissors mode is coupled not only to the ground state, but also to all excited levels of the nuclei studied. The specificity of our approach ensures unbiasedness in estimating the sumed scissors-mode strength {Sigma}B(M1){up_arrow}, even for odd product nuclei, for which conventional nuclear resonance fluorescence measurements yield only limited information. Our analysis indicates that for these nuclei the sum {Sigma}B(M1){up_arrow} increases with A and for {sup 157,159}Gd it is significantly higher compared to {sup 156,158}Gd.

  6. Open s d -shell nuclei from first principles

    NASA Astrophysics Data System (ADS)

    Jansen, G. R.; Schuster, M. D.; Signoracci, A.; Hagen, G.; Navrátil, P.

    2016-07-01

    We extend the ab initio coupled-cluster effective interaction (CCEI) method to open-shell nuclei with protons and neutrons in the valence space and compute binding energies and excited states of isotopes of neon and magnesium. We employ a nucleon-nucleon and three-nucleon interaction from chiral effective field theory evolved to a lower cutoff via a similarity renormalization group transformation. We find good agreement with experiment for binding energies and spectra, while charge radii of neon isotopes are underestimated. For the deformed nuclei 20Ne and 24Mg, we reproduce rotational bands and electric quadrupole transitions within uncertainties estimated from an effective field theory for deformed nuclei, thereby demonstrating that collective phenomena in s d -shell nuclei emerge from complex ab initio calculations.

  7. Energetic Nuclei, Superdensity and Biomedicine

    ERIC Educational Resources Information Center

    Baldin, A. M.

    1977-01-01

    High-energy, relativistic nuclei were first observed in cosmic rays. Studing these nuclei has provided an opportunity for analyzing the composition of cosmic rays and for experimentally verifying principles governing the behavior of nuclear matter at high and super-high temperatures. Medical research using accelerated nuclei is suggested.…

  8. The Structure of Nuclei Far from Stability

    SciTech Connect

    Zganjar, E.F.

    1999-02-25

    From among a number of important nuclear structure results that have emerged from our research program during the past few years, two stand out as being of extra significance. These are: (a) the identification of a diabatic coexisting structure in {sup 187}Au which arises solely from differences in proton occupation of adjacent oscillator shells, and (b) the realization of a method for estimating EO strength in nuclei and the resulting prediction that the de-excitation of superdeformed bands may proceed, in some cases, by strong EO transitions.

  9. Evaporation of particles from hot nuclei

    NASA Astrophysics Data System (ADS)

    Zejun, He; Jianshi, Wu; Wolfgang, Nörenberg

    1988-11-01

    For particle evaporation from hot nuclei a model is proposed which is applicable to high excitation energies where the mean free path of nucleons becomes comparable to or smaller than the size of the nucleus. The formalism allows to calculate the time evolution of the emitting system and the evaporation rates and spectra of the emitted particles. The nucleus 133Cs with an initial temperature of 18 MeV is studied as an example. Implications for intermediate-energy heavy-ion collisions are indicated.

  10. Statistical (?) decay of light hot nuclei

    NASA Astrophysics Data System (ADS)

    Baiocco, G.; Bruno, M.; D'Agostino, M.; Morelli, L.

    2012-07-01

    The reaction 12C+12C at 95 MeV beam energy has been measured using the GARFIELD+RCo apparatuses at Laboratori Nazionali di Legnaro LNL - INFN, Italy, in the framework of an experimental campaign proposed by the NUCL-EX collaboration. The aim is to progress in the understanding of statistical properties of light nuclei at excitation energies above particle emission thresholds, by measuring exclusive fusion-evaporation data. A theoretical study of the system, performed with a newly developed Monte Carlo Hauser-Feshbach code, is shown, together with preliminary results of the data analysis.

  11. Nuclei and Fundamental Symmetries

    NASA Astrophysics Data System (ADS)

    Haxton, Wick

    2016-09-01

    Nuclei provide marvelous laboratories for testing fundamental interactions, often enhancing weak processes through accidental degeneracies among states, and providing selection rules that can be exploited to isolate selected interactions. I will give an overview of current work, including the use of parity violation to probe unknown aspects of the hadronic weak interaction; nuclear electric dipole moment searches that may shed light on new sources of CP violation; and tests of lepton number violation made possible by the fact that many nuclei can only decay by rare second-order weak interactions. I will point to opportunities in both theory and experiment to advance the field. Based upon work supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics and SciDAC under Awards DE-SC00046548 (Berkeley), DE-AC02-05CH11231 (LBNL), and KB0301052 (LBNL).

  12. Introducing the working group on excited baryons at the CEBAF 1986 workshop

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    Several important issues related to excited baryons are outlined. These include the questions of why to study electromagnetic excitation of baryons, which excited baryons to study, and what new physics to expect. Also considered are amplitude ambiguities for ..gamma..BB* and theoretical problems of extracting the resonant amplitude. Excited baryons in nuclei and future experiments are considered. (LEW)

  13. Depopulation of highly excited singlet states of DNA model compounds: quantum yields of 193 and 245 nm photoproducts of pyrimidine monomers and dinucleoside monophosphates.

    PubMed

    Gurzadyan, G G; Görner, H

    1996-02-01

    Formation of uracil and orotic acid photodimers, uridine and 5'-UMP photohydrates, TpT photodimers and (6-4)photoproducts, dCpT photohydrates and (6-4)photoproducts and UpU, CpC and CpU photohydrates were studied in neutral deoxygenated aqueous solution at room temperature upon irradiation at either 193 or 254 nm. The photoproducts were identified and quantified and the contribution from photoionization to substrate decomposition, using lambda irr = 193 nm, was separated. The ratio of the quantum yields of respective stable products, eta = phi 193/phi 254, is indicative of the yield of internal conversion from the second to the first excited singlet state, S2-->S1. For the observed photodimers eta decreases from 0.94 for uracil to 0.7 for TpT and further to 0.55 for orotic acid. For the (6-4)photoproducts of TpT and dCpT eta = 0.5-0.8 and for the photohydrates in the cases of UpU, CpC, CpU and dCpT eta ranges from 0.55 to 1.

  14. The scission point configuration of fissioning nuclei

    NASA Astrophysics Data System (ADS)

    Ivanyuk, Fedir

    2016-06-01

    We define the optimal shape which fissioning nuclei attain just before the scission and calculate the deformation energy as function of the mass asymmetry at the scission point. The calculated deformation energy is used in quasi-static approximation for the estimation of mass distribution, total kinetic and excitation energy of fission fragments, and the total number of prompt neutrons. The calculated results reproduce rather well the experimental data on the position of the peaks in the mass distribution of fission fragments, the total kinetic and excitation energy of fission fragments. The calculated value of neutron multiplicity is somewhat larger than experimental results. The saw-tooth structure of neutron multiplicity is qualitatively reproduced.

  15. Exciting Pools

    ERIC Educational Resources Information Center

    Wright, Bradford L.

    1975-01-01

    Advocates the creation of swimming pool oscillations as part of a general investigation of mechanical oscillations. Presents the equations, procedure for deriving the slosh modes, and methods of period estimation for exciting swimming pool oscillations. (GS)

  16. Coulomb excitation of radioactive nuclear beams in inverse kinematics

    SciTech Connect

    Zamfir, N.V. |||; Barton, C.J.; Brenner, D.S.; Casten, R.F. |; Gill, R.L.; Zilges, A. |

    1996-12-31

    Techniques for the measurement of B (E2:0{sub 1}{sup +} {r_arrow} 2{sub 1}{sup +}) values by Coulomb excitation of Radioactive Nuclear Beams in inverse kinematics are described. Using a thin, low Z target, the Coulomb excited beam nuclei will decay in flight downstream of the target. For long lifetimes (nanosecond range) these nuclei decay centimeters downstream of the target and for shorter lifetimes (picoseconds or less) they decay near the target. Corresponding to these two lifetime regimes two methods have been developed to measure {gamma} rays from the Coulomb excited nuclei: the lifetime method in which the lifetime of the excited state is deduced from the decay curve and the integral method in which the B(E2) value is extracted from the measured total Coulomb excitation cross section.

  17. Measuring the collectivity of neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Görgen, Andreas

    2012-10-01

    Measuring the lifetimes of excited nuclear states provides direct information on electromagnetic transition rates and on the collectivity of nuclear excitations. The recoil distance Doppler-shift (RDDS) method is a well-established technique for measuring picosecond lifetimes of excited states, which has been extensively used in combination with fusion-evaporation reactions to measure lifetimes in neutron-deficient nuclei. Here we discuss novel ways of combining the RDDS technique with multi-nucleon transfer and fusion-fission reactions, which allow measurement of picosecond lifetimes in neutron-rich nuclei. Experiments were performed at both GANIL and Legnaro National Laboratories (LNL) with the goal to investigate the onset of collectivity around 68Ni and the evolution of shapes and shape coexistence in medium-heavy fission fragments.

  18. Applications of Skyrme energy-density functional to fusion reactions for synthesis of superheavy nuclei

    SciTech Connect

    Wang Ning; Scheid, Werner; Wu Xizhen; Liu Min; Li Zhuxia

    2006-10-15

    The Skyrme energy-density functional approach has been extended to study massive heavy-ion fusion reactions. Based on the potential barrier obtained and the parametrized barrier distribution the fusion (capture) excitation functions of a lot of heavy-ion fusion reactions are studied systematically. The average deviations of fusion cross sections at energies near and above the barriers from experimental data are less than 0.05 for 92% of 76 fusion reactions with Z{sub 1}Z{sub 2}<1200. For the massive fusion reactions, for example, the {sup 238}U-induced reactions and {sup 48}Ca+{sup 208}Pb, the capture excitation functions have been reproduced remarkably well. The influence of structure effects in the reaction partners on the capture cross sections is studied with our parametrized barrier distribution. By comparing the reactions induced by double-magic nucleus {sup 48}Ca and by {sup 32}S and {sup 35}Cl, the ''threshold-like'' behavior in the capture excitation function for {sup 48}Ca-induced reactions is explored and an optimal balance between the capture cross section and the excitation energy of the compound nucleus is studied. Finally, the fusion reactions with {sup 36}S, {sup 37}Cl, {sup 48}Ca, and {sup 50}Ti bombarding {sup 248}Cm, {sup 247,249}Bk, {sup 250,252,254}Cf, and {sup 252,254}Es, as well as the reactions leading to the same compound nucleus with Z=120 and N=182, are studied further. The calculation results for these reactions are useful for searching for the optimal fusion configuration and suitable incident energy in the synthesis of superheavy nuclei.

  19. Photodisintegration of 7Li with progeny nuclei in excited states

    NASA Astrophysics Data System (ADS)

    Wurtz, W. A.; Pywell, R. E.; Norum, B. E.; Kucuker, S.; Sawatzky, B. D.; Weller, H. R.; Stave, S.; Ahmed, M. W.

    2015-10-01

    We study the reaction channels 7Li+γ →n +6Li (2.19 ) , 7Li+γ →n +6Li(3.56 ) , and 7Li+γ →d +5He(1.27 )→n +d +4He by detecting neutrons produced by photodisintegration events. We find absolute cross sections and angular dependence for 7Li+γ →n +6Li(2.19 ) at photon energies 13 and 15 MeV and for 7Li+γ →n +6

  20. Metastable Interactions: Dissociative Excitation.

    DTIC Science & Technology

    1985-05-01

    participate. The mercuric halide compounds HgBr2 , HgCl 2 , and HgI2 are of recent interest because of laser output achieved on the B2 E - X2 E transition in...the * respective mercuric halide radicals in the range of 400-600 nm. Population inversion has been obtained by photodissociation and electron impact...excitation in mixtures o the mercuric - halide compounds and the rare gases. Chang and -* Burnham (3) have noted Improved laser efficiency and improved

  1. Pygmy Dipole Strength and Neutron Skins in Exotic Nuclei

    NASA Astrophysics Data System (ADS)

    Klimkiewicz, A.; Paar, N.; Adrich, P.; Fallot, M.; Boretzky, K.; Aumann, T.; Cortina-Gil, D.; Pramanik, U. Datta; Elze, Th. W.; Emling, H.; Geissel, H.; Hellström, M.; Jones, K. L.; Kratz, J. V.; Kulessa, R.; Nociforo, C.; Palit, R.; Simon, H.; Surówka, G.; Sümmerer, K.; Vretenar, D.; Waluś, W.

    2008-05-01

    Dipole strength distributions were determined for the neutron-rich nuclei 129-132Sn and 133,134Sb from electromagnetic excitation in an experiment using the FRS-LAND setup. For all nuclei, a sizeable fraction of ``pygmy'' dipole strength at excitation energies well below the giant dipole resonance was observed. The integrated low-lying dipole strength of the nuclei with low neutron separation energies can be compared to results for stable nuclei (e.g. N = 82 isotopes) determined for the energy regime of 5-9 MeV. A clear increase of the dipole strength with increasing asymmetry of the nuclei is observed. Comparing the ratio of the low-lying dipole over the giant dipole strength to recent relativistic mean field calculations, values for the parameters a4 and p0 of the symmetry energy and for the neutron skin thickness are derived. Averaged over 130Sn and 132Sn we extract a4 = 31.8+/-1.3 MeV and p0 = 2.2+/-0.5 MeV/fm3. The neutron skin sizes are determined to Rn-Rp = 0.23+/-0.03 fm and 0.24+/-0.03 fm for 130Sn and 132Sn, respectively. For 208Pb a neutron skin thickness of Rn-Rp = 0.18+/-0.035 fm follows, when applying the same method and using earlier published experimental findings on the dipole strength.

  2. Properties of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Rahe, J.; Vanysek, V.; Weissman, P. R.

    1994-01-01

    Active long- and short-period comets contribute about 20 to 30 % of the major impactors on the Earth. Cometary nuclei are irregular bodies, typically a few to ten kilometers in diameter, with masses in the range 10(sup 15) to 10(sup 18) g. The nuclei are composed of an intimate mixture of volatile ices, mostly water ice and hydrocarbon and silicate grains. The composition is the closest to solar composition of any known bodies in the solar system. The nuclei appear to be weakly bonded agglomerations of smaller icy planetesimals, and material strengths estimated from observed tidal disruption events are fairly low, typically 10(sup 2) to 10(sup 4) N m(sup -2). Density estimates range between 0.2 and 1.2 g cm(sup -3) but are very poorly determined, if at all. As comets age they develop nonvolitile crusts on their surfaces which eventually render them inactive, similar in appearance to carbonaceous asteroids. However, dormant comets may continue to show sporadic activity and outbursts for some time before they become truly extinct. The source of the long-period comets is the Oort cloud, a vast spherical cloud of perhaps 10(sup 12) to 10(sup 13) comets surrounding the solar system and extending to interstellar distances. The likely source for short-period comets is the Kuiper belt. a ring of perhaps 10(sup 8) to 10(sup 10) remnant icy planetesimals beyond the orbit of Neptune, though some short-period comets may also be long-period comets from the Oort cloud which have been perturbed into short-period orbits.

  3. Electroproduction of Strange Nuclei

    SciTech Connect

    E.V. Hungerford

    2002-06-01

    The advent of high-energy, CW-beams of electrons now allows electro-production and precision studies of nuclei containing hyperons. Previously, the injection of strangeness into a nucleus was accomplished using secondary beams of mesons, where beam quality and target thickness limited the missing mass resolution. We review here the theoretical description of the (e, e'K+) reaction mechanism, and discuss the first experiment demonstrating that this reaction can be used to precisely study the spectra of light hypernuclei. Future experiments based on similar techniques, are expected to attain even better resolutions and rates.

  4. Total photoabsorption in nuclei

    SciTech Connect

    Bianchi, N.

    1992-06-01

    The Frascati-Genova collaboration proposes to measure the total photonuclear cross section on a wide range of nuclei between 500 MeV and 2 GeV, to obtain informations on the interaction of baryon resonances with nucleons and on the onset of the shadowing effect. The experiment could be performed in the Hall B as soon as the tagging facility will be ready and before the end of the installation of the CLAS spectrometer. The requirements for the photon beam, like maximum energy, intensity and beam definition, are not so strong so that the experiment would also be a good first test of the tagged photon facility.

  5. Lattice QCD for nuclei

    NASA Astrophysics Data System (ADS)

    Beane, Silas

    2016-09-01

    Over the last several decades, theoretical nuclear physics has been evolving from a very-successful phenomenology of the properties of nuclei, to a first-principles derivation of the properties of visible matter in the Universe from the known underlying theories of Quantum Chromodynamics (QCD) and Electrodynamics. Many nuclear properties have now been calculated using lattice QCD, a method for treating QCD numerically with large computers. In this talk, some of the most recent results in this frontier area of nuclear theory will be reviewed.

  6. Isotopic dependence of the cross section for the induced fission of heavy nuclei

    SciTech Connect

    Bolgova, O. N.; Adamian, G. G.; Antonenko, N. V.; Zubov, A. S.; Ivanova, S. P.; Scheid, W.

    2009-06-15

    The cross sections for the induced fission of {sup 211-223}Ra, {sup 203-211}Rn, and {sup 221-231}Th nuclei undergoing peripheral collisions with {sup 208}Pb nuclei are calculated on the basis of the statistical model. The role of the N = 126 neutron shell is studied. The level density in excited nuclei is determined within the Fermi gas model and a model that takes into account the collective enhancement of the level density. The inclusion of a particle-hole excitation in addition to a collective Coulomb excitation makes it possible to obtain a satisfactory description of experimental cross sections for the fission of radium isotopes. The calculated ratios of the cross sections for the induced fission of {sup 236}U ({sup 237}U) and {sup 238}U ({sup 239}U) nuclei agree with experimental data.

  7. D mesic nuclei

    NASA Astrophysics Data System (ADS)

    García-Recio, C.; Nieves, J.; Tolos, L.

    2010-06-01

    The energies and widths of several D0 meson bound states for different nuclei are obtained using a D-meson selfenergy in the nuclear medium, which is evaluated in a selfconsistent manner using techniques of unitarized coupled-channel theory. The kernel of the meson-baryon interaction is based on a model that treats heavy pseudoscalar and heavy vector mesons on equal footing, as required by heavy quark symmetry. We find D0 bound states in all studied nuclei, from 12C up to 208Pb. The inclusion of vector mesons is the keystone for obtaining an attractive D-nucleus interaction that leads to the existence of D0-nucleus bound states, as compared to previous studies based on SU(4) flavor symmetry. In some cases, the half widths are smaller than the separation of the levels, what makes possible their experimental observation by means of a nuclear reaction. This can be of particular interest for the future P¯ANDA@FAIR physics program. We also find a D+ bound state in 12C, but it is too broad and will have a significant overlap with the energies of the continuum.

  8. Structure evolution and phase transition in odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Bucurescu, D.; Zamfir, N. V.

    2017-01-01

    The evolution of level structures due to the unique parity orbitals g9 /2, h11 /2, and i13 /2 in odd-mass nuclei from Zn to Am is studied within a unified framework, by correlations between ratios of excitation energies in both odd-mass nuclei and their even-even core nuclei. These plots reveal regularities that can be understood in terms of the particle-plus-rotor model, as evolutions along its three limiting coupling schemes: weak coupling, decoupling, and strong coupling, and transitions between them. Peculiar transitions between the decoupling and strong coupling schemes are found in both i13 /2 structures of neutron-odd nuclei and h11 /2 structures of proton-odd nuclei, at neutron numbers around 90 and 70, respectively. These are correlated with the critical shape phase transitions from vibrator to rotor from the even-even nuclei in the same regions and are characterized as critical phase transitions too. This behavior is corroborated with a nonmonotonic behavior of the differential variation of the two-neutron separation energies in the same nuclear regions.

  9. Heavy and Superheavy Atomic Nuclei

    NASA Astrophysics Data System (ADS)

    Sobiczewski, Adam

    2008-10-01

    The appearance and development of the concept of super-heavy atomic nuclei are described. The concept appeared during the studies of the limits of the nuclear chart and of the periodic table of the chemical elements. The article concentrates on theoretical studies of the properties of heaviest nuclei. Results of these studies are illustrated and discussed. Prospects for a nearest future of the research of heaviest nuclei are outlined.

  10. Optimal ultraviolet wavelength for in vivo photoacoustic imaging of cell nuclei.

    PubMed

    Yao, Da-Kang; Chen, Ruimin; Maslov, Konstantin; Zhou, Qifa; Wang, Lihong V

    2012-05-01

    In order to image noninvasively cell nuclei in vivo without staining, we have developed ultraviolet photoacoustic microscopy (UV-PAM), in which ultraviolet light excites nucleic acids in cell nuclei to produce photoacoustic waves. Equipped with a tunable laser system, the UV-PAM was applied to in vivo imaging of cell nuclei in small animals. We found that 250 nm was the optimal wavelength for in vivo photoacoustic imaging of cell nuclei. The optimal wavelength enables UV-PAM to image cell nuclei using as little as 2 nJ laser pulse energy. Besides the optimal wavelength, application of a wavelength between 245 and 275 nm can produce in vivo images of cell nuclei with specific, positive, and high optical contrast.

  11. Shell Model Description of the Odd-Odd Co and Cu Nuclei

    SciTech Connect

    Medina, N. H.; Allegro, P. R. P.; Oliveira, J. R. B. de; Ribas, R. V.; Seale, W. A.; Toufen, D. L.; Silveira, M. A. G.

    2007-10-26

    The known excited states of the odd-odd nuclei {sup 54,56,58,60}Co and 60,62,64,66Cu were interpreted in the framework of the large scale shell model (LSSM), using several effective interactions and configuration spaces. For the description of the negative parity states, we have allowed one particle excitation to the g{sub 9/2} orbital. The LSSM using the GXPF1 effective interaction reproduces well the first excited states in all of these nuclei.

  12. Selective estrogen receptor-beta (SERM-beta) compounds modulate raphe nuclei tryptophan hydroxylase-1 (TPH-1) mRNA expression and cause antidepressant-like effects in the forced swim test.

    PubMed

    Clark, J A; Alves, S; Gundlah, C; Rocha, B; Birzin, E T; Cai, S-J; Flick, R; Hayes, E; Ho, K; Warrier, S; Pai, L; Yudkovitz, J; Fleischer, R; Colwell, L; Li, S; Wilkinson, H; Schaeffer, J; Wilkening, R; Mattingly, E; Hammond, M; Rohrer, S P

    2012-11-01

    Estrogen acts through two molecularly distinct receptors termed estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) which bind estradiol with similar affinities and mediate the effects of estrogen throughout the body. ERα plays a major role in reproductive physiology and behavior, and mediates classic estrogen signaling in such tissues as the uterus, mammary gland, and skeleton. ERβ, however, modulates estrogen signaling in the ovary, the immune system, prostate, gastrointestinal tract, and hypothalamus, and there is some evidence that ERβ can regulate ERα activity. Moreover, ERβ knockout studies and receptor distribution analyses in the CNS suggest that this receptor may play a role in the modulation of mood and cognition. In recent years several ERβ-specific compounds (selective estrogen receptor beta modulators; SERM-beta) have become available, and research suggests potential utility of these compounds in menopausal symptom relief, breast cancer prevention, diseases that have an inflammatory component, osteoporosis, cardiovascular disease, and inflammatory bowel disease, as well as modulation of mood, and anxiety. Here we demonstrate an antidepressant-like effect obtained using two SERM-beta compounds, SERM-beta1 and SERM-beta2. These compounds exhibit full agonist activity at ERβ in a cell based estrogen response element (ERE) transactivation assay. SERM-beta1 and 2 are non-proliferative with respect to breast as determined using the MCF-7 breast cancer cell-based assay and non-proliferative in the uterus as determined by assessing the effects of SERM-beta compounds on immature rat uterine weight and murine uterine weight. In vivo SERM-beta1 and 2 are brain penetrant and display dose dependent efficacy in the murine dorsal raphe assays for induction of tryptophan hydroxylase mRNA and progesterone receptor protein. These compounds show activity in the murine forced swim test and promote hippocampal neurogenesis acutely in rats. Taken

  13. Exotic nuclei in astrophysics

    NASA Astrophysics Data System (ADS)

    Penionzhkevich, Yu. E.

    2012-07-01

    Recently the academic community has marked several anniversaries connected with discoveries that played a significant role in the development of astrophysical investigations. The year 2009 was proclaimed by the United Nations the International Year of Astronomy. This was associated with the 400th anniversary of Galileo Galilei's discovery of the optical telescope, which marked the beginning of regular research in the field of astronomy. An important contribution to not only the development of physics of the microcosm, but also to the understanding of processes occurring in the Universe, was the discovery of the atomic nucleus made by E. Rutherford 100 years ago. Since then the investigations in the fields of physics of particles and atomic nuclei have helped to understand many processes in the microcosm. Exactly 80 years ago, K. Yanski used a radio-telescope in order to receive the radiation from cosmic objects for the first time, and at the present time this research area of physics is the most efficient method for studying the properties of the Universe. Finally, the April 12, 1961 (50 years ago) launching of the first sputnik into space with a human being onboard, the Russian cosmonaut Yuri Gagarin, marked the beginning of exploration of the Universe with the direct participation of man. All these achievements considerably extended our ideas about the Universe. This work is an attempt to present some problems on the evolution of the Universe: the nucleosynthesis and cosmochronology from the standpoint of physics of particles and nuclei, in particular with the use of the latest results, obtained by means of radioactive nuclear beams. The comparison is made between the processes taking place in the Universe and the mechanisms of formation and decay of nuclei, as well as of their interaction at different energies. Examples are given to show the capabilities of nuclear-physics methods for studying cosmic objects and properties of the Universe. The results of

  14. Pulsars:. Gigantic Nuclei

    NASA Astrophysics Data System (ADS)

    Xu, Renxin

    What is the real nature of pulsars? This is essentially a question of the fundamental strong interaction between quarks at low-energy scale and hence of the non-perturbative quantum chromo-dynamics, the solution of which would certainly be meaningful for us to understand one of the seven millennium prize problems (i.e., "Yang-Mills Theory") named by the Clay Mathematical Institute. After a historical note, it is argued here that a pulsar is very similar to an extremely big nucleus, but is a little bit different from the gigantic nucleus speculated 80 years ago by L. Landau. The paper demonstrates the similarity between pulsars and gigantic nuclei from both points of view: the different manifestations of compact stars and the general behavior of the strong interaction.

  15. Nucleomorphs: enslaved algal nuclei.

    PubMed

    Cavalier-Smith, T

    2002-12-01

    Nucleomorphs of cryptomonad and chlorarachnean algae are the relict, miniaturised nuclei of formerly independent red and green algae enslaved by separate eukaryote hosts over 500 million years ago. The complete 551 kb genome sequence of a cryptomonad nucleomorph confirms that cryptomonads are eukaryote-eukaryote chimeras and greatly illuminates the symbiogenetic event that created the kingdom Chromista and their alveolate protozoan sisters. Nucleomorph membranes may, like plasma membranes, be more enduring after secondary symbiogenesis than are their genomes. Partial sequences of chlorarachnean nucleomorphs indicate that genomic streamlining is limited by the mutational difficulty of removing useless introns. Nucleomorph miniaturisation emphasises that selection can dramatically reduce eukaryote genome size and eliminate most non-functional nuclear non-coding DNA. Given the differential scaling of nuclear and nucleomorph genomes with cell size, it follows that most non-coding nuclear DNA must have a bulk-sequence-independent function related to cell volume.

  16. Allowance for the shell structure of colliding nuclei in the fusion-fission process

    SciTech Connect

    Litnevsky, V. L.; Kosenko, G. I.; Ivanyuk, F. A.; Pashkevich, V. V.

    2011-07-15

    The motion of two nuclei toward each other in fusion-fission reactions is considered. The state of the system of interacting nuclei is specified in terms of three collective coordinates (parameters). These are the distance between the centers of mass of the nuclei and the deformation parameter for each of them (the nose-to-nose orientation of the nuclei is assumed). The evolution of collective degrees of freedom of the system is described by Langevin equations. The energies of the Coulomb and nuclear (Gross-Kalinovsky potential) interactions of nuclei are taken into account in the potential energy of the system along with the deformation energy of each nucleus with allowance for shell effects. The motion of nuclei toward each other are calculated for two reaction types: reactions involving nuclei that are deformed ({sub 42}{sup 100}Mo + {sub 42}{sup 100}Mo {yields} {sub 84}{sup 200}Po) and those that are spherical ({sub 82}{sup 208}Pb + {sub 8}{sup 18}O {yields} {sub 90}{sup 226}Th) in the ground state. It is shown that the shell structure of interacting nuclei affects not only the fusion process as a whole (fusionbarrier height and initial-reaction-energy dependence of the probability that the nuclei involved touch each other) but also the processes occurring in each nucleus individually (shape of the nuclei and their excitation energies at the point of touching).

  17. Effective field theory for vibrations in odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Coello Pérez, E. A.; Papenbrock, T.

    2016-11-01

    Heavy even-even nuclei exhibit low-energy collective excitations that are separated in scale from the microscopic (fermion) degrees of freedom. This separation of scale allows us to approach nuclear vibrations within an effective field theory (EFT). In odd-mass nuclei collective and single-particle properties compete at low energies, and this makes their description more challenging. In this article we describe spherical odd-mass nuclei with ground-state spin I =1/2 by means of an EFT that couples a fermion to the collective degrees of freedom of an even-even core. The EFT relates observables such as energy levels, electric quadrupole transition strengths, and magnetic dipole moments of the odd-mass nucleus to those of its even-even neighbor and allows us to quantify theoretical uncertainties. For isotopes of rhodium and silver the theoretical description is consistent with data within experimental and theoretical uncertainties. Several testable predictions are made.

  18. Excited baryons

    SciTech Connect

    Mukhopadhyay, N.C.

    1986-01-01

    The status of the theory of the low-energy approach to hadron structure is reviewed briefly by surveying a few relevant models. A few examples of tests needed to sort out the predictions of different models pertaining to the quark-gluon structure of hadrons are discussed, and given the resulting physics objectives, a few experimental options for excited baryon research at CFBAF are suggested. (LEW)

  19. Quarks in Few Body Nuclei

    NASA Astrophysics Data System (ADS)

    Holt, Roy J.

    2016-03-01

    Electron scattering at very high Bjorken x from hadrons provides an excellent test of models, has an important role in high energy physics, and from nuclei, provides a window into short range correlations. Light nuclei have a key role because of the relatively well-known nuclear structure. The development of a novel tritium target for Jefferson Lab has led to renewed interest in the mass three system. For example, deep inelastic scattering experiments in the light nuclei provide a powerful means to determine the neutron structure function. The isospin dependence of electron scattering from mass-3 nuclei provide information on short range correlations in nuclei. The program using the new tritium target will be presented along with a summary of other experiments aimed at revealing the large-x structure of the nucleon.

  20. Spectroscopy of neutron-deficient nuclei around 36Ca

    SciTech Connect

    Buerger, A.; Azaiez, F.; Bourgeois, Ch.; Franchoo, S.; Ibrahim, F.; Verney, D.; Dombradi, Zs.; Algora, A.; Fueloep, Zs.; Sohler, D.; Al-Khatib, A.; Bringel, P.; Engelhardt, C.; Huebel, H.; Bastin, B.; Benzoni, G.; Borcea, R.; Rotaru, F.; Sorlin, O.

    2006-04-26

    An experiment was performed to extend the knowledge of excited states in neutron-deficient Ca isotopes. In particular, excited states in 36Ca were searched for to allow for a comparison with its stable mirror nucleus, 36S. Secondary beams of 37Ca and 36Ca were produced by fragmentation of a primary 40Ca beam with an energy of 95 {center_dot} A MeV on the SISSI target at GANIL. A variety of nuclei around 36Ca has been produced in a secondary Be target by neutron and proton-removal at beam energies around 61 {center_dot} A MeV. The produced nuclei were identified using the spectrometer SPEG, and prompt {gamma} rays were measured with the Chateau de Cristal. A preliminary value for the energy of the first 2+ state of 36Ca has been determined.

  1. Evolution Of Shapes And Collectivity In Exotic Nuclei

    SciTech Connect

    Goergen, Andreas; Ljungvall, Joa

    2010-04-30

    The coexistence of prolate and oblate shapes in light selenium and krypton isotopes has been investigated using the complementary techniques of low-energy Coulomb excitation with radioactive ions beams and lifetime measurements of excited states after fusion-evaporation reactions. The resulting B(E2) values and spectroscopic quadrupole moments represent a sensitive test for configuration mixing calculations going beyond the mean-field approach. The onset of collectivity for neutron-rich nuclei near {sup 68}Ni has been investigated using a new technique to measure lifetimes with the recoil distance Doppler shift method after multi-nucleon transfer reactions.

  2. Decay of {sup 118,122}Ba* compound nuclei formed in {sup 78,82}Kr+{sup 40}Ca reactions using the dynamical cluster-decay model of preformed clusters

    SciTech Connect

    Kumar, Raj; Gupta, Raj K.

    2009-03-15

    Application of the preformed clusters based dynamical cluster-decay model (DCM) is made to the recent data on decay of the compound systems {sup 118,122}Ba* at a relatively low bombarding energy of 5.5 MeV/A. The same model has been applied earlier to the intermediate mass fragment (IMF) data of {sup 116}Ba*, observed at medium and higher incident energies. For the heavier {sup 118,122}Ba* systems, however, a complete mass fragmentation spectrum is observed experimentally. Except for a small narrow region of heavier mass fragments (8{<=}Z{sub L}{<=}15), the DCM gives an overall reasonable description of the observed data on both the intermediate mass fragments and the fusion-fission cross-sections, whereas the statistical model calculations based on BUSCO and GEMINI codes describe the intermediate mass fragment data and the heavier mass fragment and fusion-fission data, respectively. Within the DCM (with preformation factor P{sub 0}=1), the possibility of non-compound-nucleus decay contributing to the region 8{<=}Z{sub L}{<=}15 of heavier mass fragments is also explored. All three models use the maximum angular momentum l{sub max} as a fitting parameter, which in the DCM is fixed via a neck-length parameter for the penetrability P{yields}1.

  3. Correlations of collective observables and the phonon structure of nuclei

    SciTech Connect

    Casten, R.F.; Zamfir, N.V. ||

    1994-07-01

    A ``horizontal`` view of nuclear structures is described in which various observables are correlated over broad mass ranges. This approach leads to a number of remarkable correlations, to new understanding of the evolution of structure, to a challenge to microscopic theories, and to new signatures of structure that will be especially useful with radioactive beam experiments. In particular, this and other evidence suggests a nearly universal and pervasive role of phonon and multi-phonon excitations in nuclei.

  4. Shape Evolution in Neutron-Rich Ru Nuclei

    NASA Astrophysics Data System (ADS)

    Söderström, P.-A.; Lorusso, G.; Watanabe, H.; Nishimura, S.; Doornenbal, P.; Browne, F.; Bruce, A. M.; Daido, R.; Fang, Y.; Gey, G.; Jung, H. S.; Nishizuka, I.; Patel, Z.; Rice, S.; Sinclair, L.; Sumikama, T.; Taprogge, J.; Vajta, Zs.; Wu, J.; Xu, Z. Y.; Baba, H.; Benzoni, G.; Carroll, R. J.; Chae, K. Y.; Crespi, F. C. L.; Fukuda, N.; Gernhäuser, R.; Ideguchi, E.; Inabe, N.; Isobe, T.; Jungclaus, A.; Kameda, D.; Kim, G. D.; Kim, Y.-K.; Kojouharov, I.; Kondev, F. G.; Kubo, T.; Kurz, N.; Kwon, Y. K.; Lalkovski, S.; Lane, G. J.; Li, Z.; Lozeva, R.; Montaner-Piza, A.; Moschner, K.; Naqvi, F.; Niikura, M.; Nishibata, H.; Odahara, A.; Orlandi, R.; Podolyak, Zs.; Regan, P. H.; Roberts, O. J.; Sakurai, H.; Schaffner, H.; Simpson, G. S.; Steiger, K.; Suzuki, H.; Takeda, H.; Tanaka, M.; Wendt, A.; Werner, V.; Wieland, O.; Yagi, A.; Yoshinaga, K.

    Recent experimental work has been carried out at the RIBF using the EURICA HPGe detector array. In this contribution, we discuss the recently published results on the shape evolution of the even-even isotopes 116,118Ru and present an outlook of β-delayed γ-ray spectroscopy of the odd-neutron nuclei and possibilities for life-time measurements of excited states.

  5. Gluon density in nuclei

    SciTech Connect

    Ayala, A.L.; Ducati, M.B.G.; Levin, E.M.

    1996-10-01

    In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.

  6. Adiabatic-nuclei calculations of positron scattering from molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Zammit, Mark C.; Fursa, Dmitry V.; Savage, Jeremy S.; Bray, Igor; Chiari, Luca; Zecca, Antonio; Brunger, Michael J.

    2017-02-01

    The single-center adiabatic-nuclei convergent close-coupling method is used to investigate positron collisions with molecular hydrogen (H2) in the ground and first vibrationally excited states. Cross sections are presented over the energy range from 1 to 1000 eV for elastic scattering, vibrational excitation, total ionization, and the grand total cross section. The present adiabatic-nuclei positron-H2 scattering length is calculated as A =-2.70 a0 for the ground state and A =-3.16 a0 for the first vibrationally excited state. The present elastic differential cross sections are also used to "correct" the low-energy grand total cross-section measurements of the Trento group [A. Zecca et al., Phys. Rev. A 80, 032702 (2009), 10.1103/PhysRevA.80.032702] for the forward-angle-scattering effect. In general, the comparison with experiment is good. By performing convergence studies, we estimate that our Rm=1.448 a0 fixed-nuclei results are converged to within ±5 % for the major scattering integrated cross sections.

  7. Quarks and gluons in hadrons and nuclei

    SciTech Connect

    Close, F.E. Tennessee Univ., Knoxville, TN )

    1989-12-01

    These lectures discuss the particle-nuclear interface -- a general introduction to the ideas and application of colored quarks in nuclear physics, color, the Pauli principle, and spin flavor correlations -- this lecture shows how the magnetic moments of hadrons relate to the underlying color degree of freedom, and the proton's spin -- a quark model perspective. This lecture reviews recent excitement which has led some to claim that in deep inelastic polarized lepton scattering very little of the spin of a polarized proton is due to its quarks. This lecture discusses the distribution functions of quarks and gluons in nucleons and nuclei, and how knowledge of these is necessary before some quark-gluon plasma searches can be analyzed. 56 refs., 2 figs.

  8. Single-particle states in transcurium nuclei.

    SciTech Connect

    Ahmad, I.

    1999-09-30

    Identification of single-particle states in the heaviest known nuclei is important because their energies can be used to test the single-particle potential in these high-Z elements. These states can be identified by studying the decay schemes of very heavy odd-mass nuclides. For neutrons, the heaviest odd-mass nuclide available in milliCurie quantities is the 20-h {sup 255}Fm and for protons the heaviest nuclide available is the 20-d {sup 253}Es. These two isotopes were obtained from the Transplutonium Element Production Program at Oak Ridge and their spectra were measured with high-resolution germanium spectrometers. From the results of these measurements we have identified states in {sup 251}Cf and {sup 249}Bk up to 1 MeV excitation energy.

  9. Mean field and collisions in hot nuclei

    SciTech Connect

    K /umlt o/hler, H.S.

    1989-06-01

    Collisions between heavy nuclei produce nuclear matter of high density and excitation. Brueckner methods are used to calculate the momentum and temperature dependent mean field for nucleons propagating through nuclear matter during these collisions. The mean field is complex and the imaginary part is related to the ''two-body'' collision, while the real part relates to ''one-body'' collisions. A potential model for the N-N interactions is avoided by calculating the Reaction matrix directly from the T-matrix (i.e., N-N phase shifts) using a version of Brueckner theory previously published by the author. Results are presented for nuclear matter at normal and twice normal density and for temperatures up to 50 MeV. 23 refs., 7 figs.

  10. Microscopic analysis of pear-shaped nuclei

    NASA Astrophysics Data System (ADS)

    Nomura, K.

    2015-10-01

    We analyze the quadrupole-octupole collective states based on the microscopic energy density functional framework. By mapping the deformation constrained self-consistent axially symmetric mean-field energy surfaces onto the equivalent Hamiltonian of the sd f interacting boson model (IBM), that is, onto the energy expectation value in the boson coherent state, the Hamiltonian parameters are determined. The resulting IBM Hamiltonian is used to calculate excitation spectra and transition rates for the positive- and negative-parity collective states in nuclei characteristic for octupole deformation and collectivity. Consistently with the empirical trend, the microscopic calculation based on the systematics of β2 - β3 energy maps, the resulting low-lying negative-parity bands and transition rates show evidence of a shape transition between stable octupole deformation and octupole vibrations characteristic for β3-soft potentials.

  11. Spin Modes in Nuclei and Nuclear Forces

    SciTech Connect

    Suzuki, Toshio; Otsuka, Takaharu

    2011-05-06

    Spin modes in stable and unstable exotic nuclei are studied and important roles of tensor and three-body forces on nuclear structure are discussed. New shell model Hamiltonians, which have proper tensor components, are shown to explain shell evolutions toward drip-lines and spin properties of both stable and exotic nuclei, for example, Gamow-Teller transitions in {sup 12}C and {sup 14}C and an anomalous M1 transition in {sup 17}C. The importance and the necessity of the repulsive monopole corrections in isospin T = 1 channel to the microscopic two-body interactions are pointed out. The corrections are shown to lead to the proper shell evolutions in neutron-rich isotopes. The three-body force, in particular the Fujita-Miyazawa force induced by {Delta} excitations, is pointed out to be responsible for the repulsive corrections among the valence neutrons. The important roles of the three-body force on the energies and transitions in exotic oxygen and calcium isotopes are demonstrated.

  12. Constrained Hartree-Fock Theory and Study of Deformed Structures of Closed Shell Nuclei

    NASA Astrophysics Data System (ADS)

    Praharaj, Choudhury

    2016-03-01

    We have studied some N or Z = 50 nuclei in a microscopic model with effective interaction in a reasonably large shell model space. Excitation of particles across 50 shell closure leads to well-deformed excited prolate configurations. The potential energy surfaces of nuclei are studied using Hartree-Fock theory with quadrupole constraint to explore the various deformed configurations of N = 50 nuclei 82Ge , 84Se and 86Kr . Energy spectra are calculated from various intrinsic states using Peierls-Yoccoz angular momentum projection technique. Results of spectra and electromagnetic moments and transitions will be presented for N = 50 nuclei and for Z = 50 114Sn nucleus. Supported by Grant No SB/S2/HEP-06/2013 of DST.

  13. Experimental level-structure determination in odd-odd actinide nuclei

    SciTech Connect

    Hoff, R.W.

    1985-04-04

    The status of experimental determination of level structure in odd-odd actinide nuclei is reviewed. A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei is applied to actinide species where new experimental data have been obtained by use of neutron-capture gamma-ray spectroscopy. The input parameters required for the calculation are derived from empirical data on single-particle excitations in neighboring odd-mass nuclei. Calculated configuration-specific values for the Gallagher-Moszkowski splittings are used. Calculated and experimental level structures for /sup 238/Np, /sup 244/Am, and /sup 250/Bk are compared, as well as those for several nuclei in the rare-earth region. The agreement for the actinide species is excellent, with bandhead energies deviating 22 keV and rotational parameters 5%, on the average. Applications of this modeling technique are discussed.

  14. Isospin-symmetry-breaking effects in A∼70 nuclei within beyond-mean-field approach

    SciTech Connect

    Petrovici, A.; Andrei, O.

    2015-02-24

    Particular isospin-symmetry-breaking probes including Coulomb energy differences (CED), mirror energy differences (MED), and triplet energy differences (TED) manifest anomalies in the A∼70 isovector triplets of nuclei. The structure of proton-rich nuclei in the A∼70 mass region suggests shape coexistence and competition between pairing correlations in different channels. Recent results concerning the interplay between isospin-mixing and shape-coexistence effects on exotic phenomena in A∼70 nuclei obtained within the beyond-mean-field complex Excited Vampir variational model with symmetry projection before variation using a realistic effective interaction in a relatively large model space are presented. Excited Vampir predictions concerning the Gamow-Teller β decay to the odd-odd N=Z {sup 66}As and {sup 70}Br nuclei correlated with the pair structure analysis in the T=1 and T=0 channel of the involved wave functions are discussed.

  15. Population of isomeric states in fusion and transfer reactions in beams of loosely bound nuclei near the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Skobelev, N. K.

    2015-07-01

    The influence of the mechanisms of nuclear reactions on the population of 195 m Hg and 197 m Hg(7/2-), 198 m Tl and 196 m Tl(7+), and 196 m Au and 198 m Au(12-) isomeric nuclear states obtained in reactions induced by beams of 3He, 6Li, and 6He weakly bound nuclei is studied. The behavior of excitation functions and high values of isomeric ratios ( δ m/ δ g) for products of nuclear reactions proceeding through a compound nucleus and involving neutron evaporation are explained within statistical models. Reactions in which the emission of charged particles occurs have various isomeric ratios depending on the reaction type. The isomeric ratio is lower in direct transfer reactions involving charged-particle emission than in reactions where the evaporation of charged particles occurs. Reactions accompanied by neutron transfer usually have a lower isomeric ratio, which behaves differently for different direct-reaction types (stripping versus pickup reactions).

  16. Sexual excitement.

    PubMed

    Stoller, R J

    1976-08-01

    Sexual excitement depends on a scenario the person to be aroused has been writing since childhood. The story is an adventure, an autobiography disguised as fiction, in which the hero/heroine hides crucial intrapsychic conflicts, mysteries, screen memories of actual traumatic events and the resolution of these elements into a happy ending, best celebrated by orgasm. The function of the fantasy is to take these painful experiences and convert them to pleasure-triumph. In order to sharpen excitement-the vibration between the fear of original traumas repeating and the hope of a pleasurable conclusion this time-one introduces into the story elements of risk (approximations of the trauma) meant to prevent boredom and safety factors (sub-limnal signals to the storyteller that the risk are not truly dangerous). Sexual fantasy can be studied by means of a person's daydreams (including those chosen in magazines, books, plays, television, movies, and outright pornography), masturbatory behavior, object choice, foreplay, techniques of intercourse, or postcoital behavior.

  17. Pre-equilibrium Emission and α-clustering in Nuclei

    NASA Astrophysics Data System (ADS)

    Gramegna, F.; Fabris, D.; Marchi, T.; Degerlier, M.; Fotina, O. V.; Kravchuk, V. L.; D'Agostino, M.; Morelli, L.; Appannababu, S.; Baiocco, G.; Barlini, S.; Bini, M.; Brondi, A.; Bruno, M.; Casini, G.; Cinausero, M.; Gelli, N.; Moro, R.; Olmi, A.; Pasquali, G.; Piantelli, S.; Poggi, G.; Valdrè, S.; Vardaci, E.

    2015-02-01

    The study of nuclear states built on clusters bound by valence neutrons in their molecular configurations is a field of large interest, which is being renewed by the availability of exotic beams: clustering is, in fact, predicted to become very important at the drip-line, where weakly bound systems will prevail. Although for light nuclei at an excitation energy close to the particle separation value there are experimental evidences of such structure effects, this is still not the case for heavier nuclear systems. Many attempts have been done using preformation alpha clustering models, but there is still a lack of experimental data capable to give a direct feedback. In particular, searching for alpha clustering effects in medium mass systems is still a challenge, which can give new hints in this subject. In the past we have studied the reactions 250, 192 and 130 MeV 16O + 116Sn, observing a significant increase in the fast emitted α-particle yield. This effect was ascribed to the presence of preformed a-clusters in the 16O projectile nucleus. In order to investigate these aspects, in a model independent way, a new experimental campaign has been performed with the GARFIELD + RCo set up, to compare results from two different reactions: a double magic a-cluster (16O) and a non-magic α-cluster projectile (19F) at the same beam velocity (16AMeV) have been chosen, impinging respectively on 65Cu and 62Ni targets, thus leading to the same 81Rb* compound nucleus. The angular distributions and the light charged particles emission spectra in coincidence with evaporation residues have been measured and analyzed. The preliminary results of the data analysis and the main features of the theoretical model used for their interpretation are presented.

  18. The nature of comet nuclei

    NASA Technical Reports Server (NTRS)

    Sykes, Mark V.; Walker, Russell G.

    1992-01-01

    The icy-conglomerate model of comet nuclei has dominated all others since its introduction. It provided a basis for understanding the non-gravitational motions of comets which had perplexed dynamicists up to that time, and provided a focus for understanding cometary composition and origin. The image of comets as dirty snowballs was quickly adopted. Comet nuclei including their trail mass loss rates and refractory to volatile mass ratios are described.

  19. Generalized parton distributions in nuclei

    SciTech Connect

    Vadim Guzey

    2009-12-01

    Generalized parton distributions (GPDs) of nuclei describe the distribution of quarks and gluons in nuclei probed in hard exclusive reactions, such as e.g. deeply virtual Compton scattering (DVCS). Nuclear GPDs and nuclear DVCS allow us to study new aspects of many traditional nuclear effects (nuclear shadowing, EMC effect, medium modifications of the bound nucleons) as well as to access novel nuclear effects. In my talk, I review recent theoretical progress in the area of nuclear GPDs.

  20. Excitation of nuclear isomers by X rays from laser plasma

    SciTech Connect

    Andreev, Aleksandr A; Karpeshin, F; Trzhaskovskaya, M B; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V

    2010-06-23

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer {sup 93}Mo upon irradiation of a niobium {sup 93}Nb target by {approx}50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma. (interaction of laser radiation with matter. laser plasma)

  1. Alternative method for evaluating the pair energy of nucleons in nuclei

    SciTech Connect

    Nurmukhamedov, A. M.

    2015-12-15

    An alternative method for determining the odd–even effect parameter related to special features of the Casimir operator in Wigner’s mass formula for nuclei is proposed. A procedure for calculating this parameter is presented. The proposed method relies on a geometric interpretation of the Casimir operator, experimental data concerning the contribution of spin–orbit interaction to the nuclear mass for even–even and odd–odd nuclei, and systematics of energy gaps in the spectra of excited states of even–even nuclei.

  2. Isotopic Dependence of the Shape of Se Nuclei in the Collective-Model Representation

    SciTech Connect

    Davidovskaya, O.I.; Kashuba, I.E.; Porodzinsky, Yu.V.

    2005-06-01

    The energy structure of low-lying excited states in the nuclei of even selenium isotopes is considered on the basis of a soft-nucleus model. The nuclei are treated as nonaxial rotors, longitudinal and transverse vibrations of their surface being taken into account in the quadrupole-deformation approximation featuring an admixture of an octupole deformation. The parameters of a phenomenological collective model for the {sup 72,74,76,78,80,82}Se nuclei are found both in the case of {beta} vibrations (longitudinal vibrations) and in the presence of additional {gamma} vibrations (transverse vibrations) of the nuclear surface.

  3. Fission decay of N=Z nuclei at high angular momentum: {sup 60}Zn

    SciTech Connect

    Oertzen, W. von; Zherebchevsky, V.; Gebauer, B.; Schulz, Ch.; Thummerer, S.; Wilpert, Th.; Kamanin, D.; Royer, G.

    2008-10-15

    Using a unique two-arm detector system for heavy ions (the BRS, binary reaction spectrometer), coincident fission events have been measured from the decay of {sup 60}Zn compound nuclei formed at 88 MeV excitation energy in the reactions with {sup 36}Ar beams on a {sup 24}Mg target at E{sub lab}({sup 36}Ar)=195 MeV. The detectors consisted of two large-area position-sensitive (x,y) gas telescopes with Bragg-ionization chambers. From the binary coincidences in the two detectors, inclusive and exclusive cross sections for fission channels with differing losses of charge were obtained. Narrow out-of-plane correlations corresponding to coplanar decay are observed for two fragments emitted in binary events, and in the data for ternary decay with missing charges from 4 up to 8. After subtraction of broad components, these narrow correlations are interpreted as a ternary fission process at high angular momentum through an elongated shape. The lighter mass in the neck region consists dominantly of two or three {alpha} particles. Differential cross sections for the different mass splits for binary and ternary fission are presented. The relative yields of the binary and ternary events are explained using the statistical model based on the extended Hauser-Feshbach formalism for compound nucleus decay. The ternary fission process can be described by the decay of hyper-deformed states with angular momenta around 4552({Dirac_h}/2{pi})

  4. Hybrid configuration mixing model for odd nuclei

    NASA Astrophysics Data System (ADS)

    Colò, G.; Bortignon, P. F.; Bocchi, G.

    2017-03-01

    In this work, we introduce a new approach which is meant to be a first step towards complete self-consistent low-lying spectroscopy of odd nuclei. So far, we essentially limit ourselves to the description of a double-magic core plus an extra nucleon. The model does not contain any free adjustable parameter and is instead based on a Hartree-Fock (HF) description of the particle states in the core, together with self-consistent random-phase approximation (RPA) calculations for the core excitations. We include both collective and noncollective excitations, with proper care of the corrections due to the overlap between them (i.e., due to the nonorthonormality of the basis). As a consequence, with respect to traditional particle-vibration coupling calculations in which one can only address single-nucleon states and particle-vibration multiplets, we can also describe states of shell-model types like 2 particle-1 hole. We will report results for 49Ca and 133Sb and discuss future perspectives.

  5. Coulomb excitation of radioactive {sup 79}Pb

    SciTech Connect

    Lister, C.J.; Blumenthal, D.; Davids, C.N.

    1995-08-01

    The technical challenges expected in experiments with radioactive beams can already be explored by using ions produced in primary reactions. In addition, the re-excitation of these ions by Coulomb excitation allows a sensitive search for collective states that are well above the yrast line. We are building an experiment to study Coulomb excitation of radioactive ions which are separated from beam particles by the Fragment Mass Analyzer. An array of gamma detectors will be mounted at the focal plane to measure the gamma radiation following re-excitation. Five Compton-suppressed Ge detectors and five planar LEPS detectors will be used. The optimum experiment of this type appears to be the study of {sup 79}Rb following the {sup 24}Mg ({sup 58}Ni,3p) reaction. We calculate that about 5 x 10{sup 5} {sup 79}Rb nuclei/second will reach the excitation foil. This rubidium isotope was selected for study as it is strongly produced and is highly deformed, so easily re-excited. The use of a {sup 58}Ni re-excitation foil offers the best yields. After re-excitation the ions will be subsequently transported into a shielded beamdump to prevent the accumulation of activity.

  6. Toward open-shell nuclei with coupled-cluster theory

    SciTech Connect

    Jansen, G. R.; Hjorth-Jensen, M.; Hagen, G.; Papenbrock, T.

    2011-05-15

    We develop a method based on equation-of-motion coupled-cluster theory to describe properties of open-shell nuclei with A{+-}2 nucleons outside a closed shell. We perform proof-of-principle calculations for the ground states of the helium isotopes {sup 3-6}He and the first excited 2{sup +} state in {sup 6}He. The comparison with exact results from matrix diagonalization in small model spaces demonstrates the accuracy of the coupled-cluster methods. Three-particle-one-hole excitations of {sup 4}He play an important role for the accurate description of {sup 6}He. For the open-shell nucleus {sup 6}He, the computational cost of the method is comparable with the coupled-cluster singles-and-doubles approximation while its accuracy is similar to the coupled-cluster with singles, doubles, and triples excitations.

  7. Tunneling from super- to normal-deformed minima in nuclei.

    SciTech Connect

    Khoo, T. L.

    1998-01-08

    An excited minimum, or false vacuum, gives rise to a highly elongated superdeformed (SD) nucleus. A brief review of superdeformation is given, with emphasis on the tunneling from the false to the true vacuum, which occurs in the feeding and decay of SD bands. During the feeding process the tunneling is between hot states, while in the decay it is from a cold to a hot state. The {gamma} spectra connecting SD and normal-deformed (ND) states provide information on several physics issues: the decay mechanism; the spin/parity quantum numbers, energies and microscopic structures of SD bands; the origin of identical SD bands; the quenching of pairing with excitation energy; and the chaoticity of excited ND states at 2.5-5 MeV. Other examples of tunneling in nuclei, which are briefly described, include the possible role of tunneling in {Delta}I = 4 bifurcation in SD bands, sub-barrier fusion and proton emitters.

  8. Studies of Heavy-Ion Reactions and Transuranic Nuclei

    SciTech Connect

    Schroeder, W. Udo

    2016-07-28

    Studies of heavy-ion reactions and transuranic nuclei performed by the University of Rochester Nuclear Science Research Group have been successful in furthering experimental systematics and theoretical understanding of the behavior of nuclear systems excited to their limits of stability. The theoretical results explain specifically the “boiling” and “vaporization” of atomic nuclei, but are more generally applicable to isolated, quantal many-particle systems which, under thermal or mechanical stresses, all disintegrate by evaporation, via surface cluster emission, or via fission-like processes. Accompanying experimental investigations by the group have demonstrated several new types of dynamical instability of nuclei: In central, “head-on” collisions, target nuclei exhibit limited ability to stop energetic projectile nuclei and to dissipate the imparted linear momentum. Substantial matter overlap (“neck”) between projectile and target nuclei, which is observed at elevated collision energies, can be stretched considerably and break at several places simultaneously. These results provide new testing grounds for microscopic theory of the cohesion of nuclear matter. This property has remained elusive, even though the elementary nucleon-nucleon forces are well known since some time. Technical R&D has resulted in a detailed characterization of a novel plastic material, which can now be used in the design of sensitive diagnostic systems for various types of radio-activity. Innovative application of powerful laser systems has produced intense, controllable sources of exotic particle radioactivity for nuclear investigations. Several students have received their Ph.D. degree in experimental nuclear science for their work on basic nuclear research or R&D projects.

  9. Cavitation inception from bubble nuclei

    PubMed Central

    Mørch, K. A.

    2015-01-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure–time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes. PMID:26442138

  10. Reflection asymmetric shapes in nuclei

    SciTech Connect

    Ahmad, I.; Carpenter, M.P.; Emling, H.; Holzmann, R.; Janssens, R.V.F.; Khoo, T.L.; Moore, E.F.; Morss, L.R.; Durell, J.L.; Fitzgerald, J.B.; Mowbary, A.S.; Hotchkiss, M.A.; Phillips, W.R.; Drigert, M.W.; Ye, D.; Benet, P.; Manchester Univ. . Dept. of Physics; EG and G Idaho, Inc., Idaho Falls, ID; Notre Dame Univ., IN; Purdue Univ., Lafayette, IN )

    1989-01-01

    Experimental data show that there is no even-even nucleus with a reflection asymmetric shape in its ground state. Maximum octupole- octupole correlations occur in nuclei in the mass 224 (N{approximately}134, Z{approximately}88) region. Parity doublets, which are the characteristic signature of octupole deformation, have been observed in several odd mass Ra, Ac and Pa nuclei. Intertwined negative and positive parity levels have been observed in several even-even Ra and Th nuclei above spin {approximately}8{Dirac h}. In both cases, the opposite parity states are connected by fast El transitions. In some medium-mass nuclei intertwined negative and positive parity levels have also been observed above spin {approximately}7{Dirac h}. The nuclei which exhibit octupole deformation in this mass region are {sup 144}Ba, {sup 146}Ba and {sub 146}Ce; {sup 142}Ba, {sup 148}Ce, {sup 150}Ce and {sup 142}Xe do not show these characteristics. No case of parity doublet has been observed in the mass 144 region. 32 refs., 16 figs., 1 tab.

  11. Cavitation inception from bubble nuclei.

    PubMed

    Mørch, K A

    2015-10-06

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years, and experimental investigations of bubbles and cavitation inception have been presented. These results suggest that cavitation nuclei in equilibrium are gaseous voids in the water, stabilized by a skin which allows diffusion balance between gas inside the void and gas in solution in the surrounding liquid. The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes.

  12. NUCLEI SEGMENTATION VIA SPARSITY CONSTRAINED CONVOLUTIONAL REGRESSION

    PubMed Central

    Zhou, Yin; Chang, Hang; Barner, Kenneth E.; Parvin, Bahram

    2017-01-01

    Automated profiling of nuclear architecture, in histology sections, can potentially help predict the clinical outcomes. However, the task is challenging as a result of nuclear pleomorphism and cellular states (e.g., cell fate, cell cycle), which are compounded by the batch effect (e.g., variations in fixation and staining). Present methods, for nuclear segmentation, are based on human-designed features that may not effectively capture intrinsic nuclear architecture. In this paper, we propose a novel approach, called sparsity constrained convolutional regression (SCCR), for nuclei segmentation. Specifically, given raw image patches and the corresponding annotated binary masks, our algorithm jointly learns a bank of convolutional filters and a sparse linear regressor, where the former is used for feature extraction, and the latter aims to produce a likelihood for each pixel being nuclear region or background. During classification, the pixel label is simply determined by a thresholding operation applied on the likelihood map. The method has been evaluated using the benchmark dataset collected from The Cancer Genome Atlas (TCGA). Experimental results demonstrate that our method outperforms traditional nuclei segmentation algorithms and is able to achieve competitive performance compared to the state-of-the-art algorithm built upon human-designed features with biological prior knowledge. PMID:28101301

  13. New results on the structure of exotic nuclei

    NASA Astrophysics Data System (ADS)

    Sakurai, Hiroyoshi

    2015-04-01

    `Exotic nuclei' far from the stability line are unique objects of many-body quantum system, where ratios of neutron number to proton number are much larger or much smaller than those of nuclei found in nature. Their exotic properties and phenomena emerge from their large isospin asymmetry, and even affect scenarios of nucleosynthesis in universe. One of the exotic emergences is shell evolution. The magic numbers of stable nuclei are known; 2, 8, 20, 28, 50, 82 and 126. However the numbers 8, 20 and 28 have been found no more magic in a neutron-rich region, and new magic numbers such as 6, 16, 32 and 34 have been discovered. To access nuclei far from the stability line, especially neutron-rich nuclei, a large heavy-ion accelerator facility `Radioactive Isotope Beam Factory (RIBF)' was constructed at RIKEN, Japan in 2007. The facility is highly optimized for inflight production of fission fragments via a U beam. The accelerator complex delivers an intense 345 MeV/u U beam. The U nuclide is converted at a target to fission fragments. The fragments of interest are collected and separated at an inflight separator, and are delivered to several experimental devices. The shell evolution programs at RIBF have been conducted with two methods; in-beam gamma spectroscopy and decay spectroscopy. A standard setup of in-beam gamma spectroscopy is combination of a NaI gamma detector array `DALI2' and a beam line spectrometer `ZeroDegree Spectrometer (ZDS)'. Coincidence measurements of de-excitation gamma rays at DALI2 and of reaction products at ZDS make it possible to select reaction channels event-by-event and to observe excited states of exotic nuclei in a specific reaction channel. Recently, a French-made thick liquid hydrogen target system `MINOS' has been introduced to access more neutron-rich nuclei. Isomer and beta-delayed gamma spectroscopy is organized with a Euroball germanium cluster array system `EURICA' and an active silicon stopper In this talk, I would like to

  14. Spectroscopy of Actinide Nuclei - Perspectives with Position Sensitive HPGe Detectors

    NASA Astrophysics Data System (ADS)

    Reiter, P.; Birkenbach, B.; Kotthaus, T.

    Recent advances in in-beam gamma-ray spectroscopy of actinide nuclei are based on highly efficient arrays of escape-suppressed spectrometers. The sensitivity of these detector arrays is greatly enhanced by the combination with powerful mass separators or particle detector systems. This technique is demonstrated by an experiment to investigate excited states in 234U after the one-neutron-transfer reaction 235U(d,t). In coincidence with the outgoing tritons, γ-rays were detected with the highly efficient MINIBALL spectrometer. In the near future an even enhanced sensitivity will be achieved by utilizing position sensitive HPGe detectors which will exploit the novel detection method of gamma-ray energy tracking in electrically segmented germanium detectors. An example for this novel approach is the investigation neutron-rich actinide Th and U nuclei after multi nucleon transfer reactions employing the AGATA demonstrator and PRISMA setup at LNL, Italy. A primary 136Xe beam hitting a 238U target was used to produce the nuclei of interest. Beam-like reaction products after neutron transfer were selected by the PRISMA spectrometer. Coincident γ-rays from excited states in beam and target like particles were measured with the position sensitive AGATA HPGe detectors. Improved Doppler correction and quality of the γ-spectra is based on the novel γ-ray tracking technique, which was successfully exploited in this region.

  15. Microscopic structure of high-spin vibrational states in superdeformed A=190 nuclei

    SciTech Connect

    Nakatsukasa, Takashi; Matsuyanagi, Kenichi; Mizutori, Shoujirou

    1996-12-31

    Microscopic RPA calculations based on the cranked shell model are performed to investigate the quadrupole and octupole correlations for excited superdeformed (SD) bands in even-even A=190 nuclei. The K = 2 octupole vibrations are predicted to be the lowest excitation modes at zero rotational frequency. The Coriolis coupling at finite frequency produces different effects depending on the neutron and proton number of nucleus. The calculations also indicate that some collective excitations may produce moments of inertia almost identical to those of the yrast SD band. An interpretation of the observed excited bands invoking the octupole vibrations is proposed, which suggests those octupole vibrations may be prevalent in even-even SD A=190 nuclei.

  16. Chromatin structure in barley nuclei.

    PubMed

    Mithieux, G; Roux, B

    1983-10-03

    In order to study the chromatin structure of a higher plant we used a high-yield method, which allows one to obtain up to 10(9) nuclei/kg fresh barley leaves. Significant amounts of low-ionic-strength-soluble chromatin can be extracted from these nuclei. Physicochemical properties were examined and discussed. Electric birefringence allowed us to observe the same transition in electro-optical properties as has been observed for animal chromatin, and suggested the existence of a symetrical structure occurring for approximately six nucleosomes. Circular dichroism showed that barley oligonucleosomes exhibit a higher molar ellipticity at 282 nm than total soluble chromatin and than their animal counterparts.

  17. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  18. Unstable nuclei in dissociation of light stable and radioactive nuclei in nuclear track emulsion

    NASA Astrophysics Data System (ADS)

    Artemenkov, D. A.; Zaitsev, A. A.; Zarubin, P. I.

    2017-01-01

    A role of the unstable nuclei 6Be, 8Be and 9B in the dissociation of relativistic nuclei 7,9Be, 10B and 10,11C is under study on the basis of nuclear track emulsion exposed to secondary beams of the JINR Nuclotron. Contribution of the configuration 6Be + n to the 7Be nucleus structure is 8 ± 1% which is near the value for the configuration 6Li + p. Distributions over the opening angle of α-particle pairs indicate to a simultaneous presence of virtual 8Beg.s. and 8Be2+ states in the ground states of the 9Be and 10C nuclei. The core 9B is manifested in the 10C nucleus with a probability of 30 ± 4%. Selection of the 10C "white" stars accompanied by 8Beg.s. (9B) leads to appearance in the excitation energy distribution of 2α2 p "quartets" of the distinct peak with a maximum at 4.1 ± 0.3 MeV. 8Beg.s. decays are presented in 24 ± 7% of 2He + 2H events of the 11C coherent dissociation and 27 ± 11% of the 3He ones. The channel 9B + H amounts 14 ± 3%. The 8Bg.s. nucleus is manifested in the coherent dissociation 10B → 2He + H with a probability of 25 ± 5% including 13 ± 3% of 9B decays. A probability ratio of the mirror channels 9B + n and 9Be + p is estimated to be 10 ± 1.

  19. Four-Quasiparticle High-K States in Neutron-Deficient Lead and Polonium Nuclei

    NASA Astrophysics Data System (ADS)

    Shi, Yue; Xu, Furong

    2012-06-01

    Configuration-constrained potential energy surface calculations have been performed to investigate four-quasiparticle high-K configurations in neutron-deficient lead and polonium isotopes. A good agreement between the calculations and the experimental data has been found for the excitation energy of the observed Kπ = 19- state in 188Pb. Several lowly excited high-K states are predicted, and the large oblate deformation and low energy indicate high-K isomerism in these nuclei.

  20. Excitation energies of superdeformed states in the Pb isotopes

    SciTech Connect

    Wilson, A. N.; Byrne, A. P.; Dracoulis, G. D.; Davidson, P. M.; Lane, G. J.; Huebel, H.; Rossbach, D.; Schonwasser, G.; Korichi, A.; Hannachi, F.; Lopez-Martens, A.; Clark, R. M.; Fallon, P.; Macchiavelli, A. O.; Ward, D.

    2006-04-26

    Measurements of the excitation energies of superdeformed states via the observation of single-step linking transitions have now been made in three even-A Pb nuclei, with a quasicontinuum analysis providing a limit in a fourth, odd-A case. These results allow us to take the first steps towards establishing systematic trends in excitation energies and binding energies in the second minimum in Pb isotopes.

  1. Ultra-High Spin Spectroscopy In Er Nuclei

    SciTech Connect

    Simpson, J.

    2008-11-11

    The discoveries observed in the ongoing conflict between collective and single-particle nuclear behaviour with increasing angular momentum have driven the field of nuclear spectroscopy for many decades and have given rise to new nuclear phenomena. Recently a new frontier of {gamma} spectroscopy at ultra-high spin has been opened in the rare-earth region with rotational bands that bypass the classic band-terminating states that appear at spin 45({Dirac_h}/2{pi}) in the N 90 Er nuclei. These weakly populated rotational structures have characteristics of triaxial strongly-deformed bands. Such structures have been observed in {sup 157,158,160}Er, following a series of experiments using the Gammasphere spectrometer. These observations herald a return to collective excitations at spins of about 50 to 65({Dirac_h}/2{pi}). This talk reviews the status of the spectroscopy and understanding of the observed structures in these Er and neighbouring nuclei.

  2. Probing the Evolution of the Shell Structures in Exotic Nuclei

    SciTech Connect

    De Angelis, Giacomo

    2008-11-11

    Magic numbers are a key feature in finite Fermion systems since they are strongly related to the underlying mean field. The size of the shell gaps and their evolution far from stability can be linked to the shape and symmetry of the nuclear mean field. Moreover the study of nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Changes of the nuclear density and size in nuclei with increasing N/Z ratios are expected to lead to different nuclear symmetries and excitations. In this contribution I will discuss some selected examples which show the big potential of stable beams and of binary reactions for the study of the properties of the neutron-rich nuclear many body systems.

  3. Studies of the Shapes of Heavy Nuclei at ISOLDE

    NASA Astrophysics Data System (ADS)

    Butler, Peter A.

    For certain combinations of protons and neutrons there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a "pear-shape" in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation). In this talk I will briefly review the historic evidence for reflection asymmetry in nuclei and describe how recent experiments carried out at REX-ISOLDE have constrained nuclear theory and how they contribute to tests of extensions of the Standard Model. I will also discuss future prospects for measuring nuclear shapes from Coulomb Excitation: experiments are being planned that will exploit beams from HIE-ISOLDE that are cooled in the TSR storage ring and injected into a solenoidal spectrometer similar to the HELIOS device developed at the Argonne National Laboratory.

  4. Perspectives of Physics of Exotic Nuclei Beyond the Shell Evolution

    NASA Astrophysics Data System (ADS)

    Otsuka, Takaharu

    2015-11-01

    I present one of the possible paradigm shifts with exotic nuclei. This is the shell evolution due to nuclear forces, such as tensor, central and three-nucleon forces. I shall present major points with the N=34 magic number confirmed in 54Ca by RIBF of RIKEN very recently, after the theoretical prediction made in 2001. The shell evolution has been generalized to phenomena caused by massive particle-hole excitations, being referred to as Type II Shell Evolution. This can be found in 68,70Ni. In particular, the shape coexistence of spherical, oblate and prolate shapes is suggested theoretically. Thus, the perspectives of physics with exotic nuclei is being expanded further from single-particle aspects to shapes/deformation, changing the landscape of nuclear structure.

  5. Coulomb Excitation of 78,80Se and the radioactive 84Se (N = 50) isotopes

    NASA Astrophysics Data System (ADS)

    Galindo-Uribarri, A.; Padilla-Rodal, E.; Garcia-Ruiz, R. F.; Allmond, J. M.; Batchelder, J. C.; Beene, J. R.; Lagergren, K. B.; Mueller, P. E.; Radford, D. C.; Stracener, D. W.; Urrego-Blanco, J. P.; Varner, R. L.; Yu, C.-H.

    2011-10-01

    Coulomb excitation is a purely electromagnetic excitation process of nuclear states due to the Coulomb field of two colliding nuclei. It is a very precise tool to measure excitation probabilities and provide insight on the collectivity of nuclear excitations and in particular on nuclear shapes. We have measured the B(E2) value of various nuclei in the mass A ~ 80 region using particle-gamma coincidences with the HyBall and Clarion arrays at HRIBF. The Coulomb excitation of various projectile-target combinations (ASe on 12C, 24Mg, 27Al and 50Ti) allow the use of consistency cross checks and the systematic study of isotopic and isotonic chains using both stable and radioactive nuclei under almost identical experimental conditions.We present new results for 78Se, 80Se and the radioactive nucleus 84Se (N = 50). Research sponsored by the Office of Nuclear Physics, U.S. Department of Energy and CONACyT Grant 103366.

  6. Chiral electroweak currents in nuclei

    DOE PAGES

    Riska, D. O.; Schiavilla, R.

    2017-01-10

    Here, the development of the chiral dynamics based description of nuclear electroweak currents is reviewed. Gerald E. (Gerry) Brown’s role in basing theoretical nuclear physics on chiral Lagrangians is emphasized. Illustrative examples of the successful description of electroweak observables of light nuclei obtained from chiral effective field theory are presented.

  7. Electromagnetic structure of light nuclei

    SciTech Connect

    Pastore, Saori

    2016-03-25

    Here, the present understanding of nuclear electromagnetic properties including electromagnetic moments, form factors and transitions in nuclei with A ≤ 10 is reviewed. Emphasis is on calculations based on nuclear Hamiltonians that include two- and three-nucleon realistic potentials, along with one- and two-body electromagnetic currents derived from a chiral effective field theory with pions and nucleons.

  8. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-01-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  9. Octupole correlation effects in nuclei

    SciTech Connect

    Chasman, R.R.

    1992-08-01

    Octupole correlation effects in nuclei are discussed from the point of view of many-body wavefunctions as well as mean-field methods. The light actinides, where octupole effects are largest, are considered in detail. Comparisons of theory and experiment are made for energy splittings of parity doublets; E1 transition matrix elements and one-nucleon transfer reactions.

  10. Proton Distribution in Heavy Nuclei

    DOE R&D Accomplishments Database

    Johnson, M. H; Teller, E.

    1953-11-13

    It is reasoned that, from considerations connected with beta-decay stability and Coulomb repulsion forces, a neutron excess is developed on the surface of heavy nuclei. Several consequences of this qualitative analysis in nucleon interactions are briefly noted. (K.S.)

  11. Nuclei and propeller cavitation inception

    SciTech Connect

    Gindroz, B.; Billet, M.L.

    1994-12-31

    Propeller cavitation inception tests were conducted in the Grand Tunnel Hydrodynamique (GTH) of the Bassin d`Essaid des Carenes. Both acoustic and visual cavitation inception were determined for leading-edge sheet, travelling bubble, and tip vortex. These data were obtained for specific water quality conditions. The water quality was determined from cavitation susceptibility meter measurements for degassed water (maximum liquid tension, few nuclei), low injection rate of microbubbles (medium liquid tension, low nuclei concentration), medium injection rate of microbubbles (medium liquid tension, high nuclei concentration) and high injection rate of microbubbles (minimum liquid tension, high nuclei concentration). Results clearly demonstrate a different influence of water quality for each type of cavitation. Little variation in cavitation inception index for a significant increase in liquid tension and microbubble size distribution was found for leading-edge sheet; however, tip vortex cavitation inception index decreased significantly for an increase in liquid tension. In addition, a dependency on event rate was determined for tip vortex cavitation inception.

  12. Parity-projected shell model Monte Carlo level densities for medium-mass nuclei

    SciTech Connect

    Oezen, C.; Langanke, K.; Martinez-Pinedo, G.; Dean, D. J.

    2008-11-11

    We investigate the effects of single-particle structure and pairing on the equilibration of positive and negative-parity level densities for the even-even nuclei {sup 58,62,66}Fe and {sup 58}Ni and the odd-A nuclei {sup 59}Ni and {sup 65}Fe. Calculations are performed using the shell model Monte Carlo method in the complete fp-gds shell-model space using a pairing+quadrupole type residual interaction. We find for the even-even nuclei that the positive-parity states dominate at low excitation energies due to strong pairing correlations. At excitation energies at which pairs are broken, single-particle structure of these nuclei is seen to play the decisive role for the energy dependence of the ratio of negative-to-positive parity level densities. We also find that equilibration energies are noticeably lower for the odd-A nuclei {sup 59}Ni and {sup 65}Fe than for the neighboring even-even nuclei {sup 58}Ni and {sup 66}Fe.

  13. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    SciTech Connect

    Nishio, K.; Andreyev, A. N.; Chapman, R.; Derkx, X.; Düllmann, Ch. E.; Ghys, L.; Heßberger, F. P.; Hirose, K.; Ikezoe, H.; Khuyagbaatar, J.; Kindler, B.; Lommel, B.; Makii, H.; Nishinaka, I.; Ohtsuki, T.; Pain, S. D.; Sagaidak, R.; Tsekhanovich, I.; Venhart, M.; Wakabayashi, Y.; Yan, S.

    2015-06-30

    Mass distributions of fission fragments from the compound nuclei 180Hg and 190 Hg formed in fusion reactions 36Ar + 144 Smand 36Ar + 154Sm, respectively, were measured at initial excitation energies of E*(180Hg) = 33-66 MeV and E*(190Hg) = 48-71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses $\\overline{A}_L$/$\\overline{A}_H$ = 79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of$\\overline{A}_L$/$\\overline{A}_H$ = 83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. In conclusion, this behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  14. Towards Superheavies: Spectroscopy of 94 < Z < 98, 150 < N < 154 Nuclei

    NASA Astrophysics Data System (ADS)

    Chowdhury, P.; Hota, S. S.; Qiu, Y.; Ahmad, I.; Carpenter, M. P.; Greene, J. P.; Janssens, R. V. F.; Khoo, T. L.; Kondev, F. G.; Lauritsen, T.; Lister, C. J.; Seweryniak, D.; Zhu, S.

    2016-09-01

    The heaviest nuclei where excitations above the ground state can be studied lie near Z ~ 100. These nuclear structure studies are important testing grounds for theoretical models that aim to describe superheavy nuclei. To study the highest neutron orbitals (150 ≤ N ≤ 154), we have populated high angular momentum states in a series of Pu (Z = 94), Cm (Z = 96) and Cf (Z = 98) nuclei, via inelastic and transfer reactions, with heavy beams on long-lived radioactive actinide targets. Multiple collective excitation modes and structures were identified, and their configurations deduced. Quasiparticle alignments are mapped, with odd-A band structures helping identify specific orbital contributions via blocking arguments. Higher-order multipole shapes are observed to play a significant role in disentangling competing neutron and proton alignments. The N > 152 data provide new perspectives on physics beyond the N = 152 sub-shell gap.

  15. Exact diagonalization of the Bohr Hamiltonian for rotational nuclei: Dynamical {gamma} softness and triaxiality

    SciTech Connect

    Caprio, M. A.

    2011-06-15

    Detailed quantitative predictions are obtained for phonon and multiphonon excitations in well-deformed rotor nuclei within the geometric framework, by exact numerical diagonalization of the Bohr Hamiltonian in an SO(5) basis. Dynamical {gamma} deformation is found to significantly influence the predictions through its coupling to the rotational motion. Basic signatures for the onset of rigid triaxial deformation are also obtained.

  16. Bands and Isomers in Neutron-Rich Rare-Earth Nuclei in PHF Model

    NASA Astrophysics Data System (ADS)

    Praharaj, C. R.; Ghorui, S. K.; Naik, Z.; Sahu, B. B.

    Rotational structures of neutron-rich Gd and Dy nuclei in the REE peak region are studied with deformed Hartee-Fock (HF) and angular momentum (J) projection model. Spectra of ground band and a few more excited, positive and negative parity bands have been studied up to high spin values. Some 4-quasiparticle K-isomeric bands and their electromagnetic properties are predicted.

  17. Precision investigations of nuclei and nucleons with the (e, e'. gamma. ) reaction

    SciTech Connect

    Papanicolas, C.N.; Ammons, E.A.; Cardman, L.S.; Deininger, J.R.; Dolfini, S.M.; Mandeville, J.B.; Mueller, P.E.; Williamson, S.E.

    1988-11-20

    Recent theoretical and experimental investigations of the (e, e'..gamma..) reaction show that it provides a probe of unparalleled precision and selectivity. Experiments aimed towards the isolation of multipole form factors in mixed transitions, the study of continuum excitations in nuclei, and the measurement of the response of the proton are underway at several laboratories.

  18. Favored configurations for four-quasiparticle K isomerism in the heaviest nuclei

    NASA Astrophysics Data System (ADS)

    Liu, H. L.; Walker, P. M.; Xu, F. R.

    2014-04-01

    Configuration-constrained potential-energy-surface calculations are performed including β6 deformation to investigate high-K isomeric states in nuclei around 254No and 270Ds, the heaviest nuclei where there have been some observations of two-quasiparticle isomers, while data for four-quasiparticle isomers are scarce. We predict the prevalent occurrence of four-quasiparticle isomeric states in these nuclei, together with their favored configurations. The most notable examples, among others, are Kπ=20+ states in 266,268Ds and 268,270Cn having very high K value, relatively low excitation energy, and well-deformed axially symmetric shape. The predicted isomeric states, with hindered spontaneous fission and α decay, could play a significant role in the future study of superheavy nuclei.

  19. MCNP6 Simulation of Light and Medium Nuclei Fragmentation at Intermediate Energies

    SciTech Connect

    Mashnik, Stepan Georgievich; Kerby, Leslie Marie

    2015-08-24

    Fragmentation reactions induced on light and medium nuclei by protons and light nuclei of energies around 1 GeV/nucleon and below are studied with the Los Alamos transport code MCNP6 and with its CEM03.03 and LAQGSM03.03 event generators. CEM and LAQGSM assume that intermediate-energy fragmentation reactions on light nuclei occur generally in two stages. The first stage is the intranuclear cascade (INC), followed by the second, Fermi breakup disintegration of light excited residual nuclei produced after the INC. CEM and LAQGSM account also for coalescence of light fragments (complex particles) up to sup>4He from energetic nucleons emitted during INC. We investigate the validity and performance of MCNP6, CEM, and LAQGSM in simulating fragmentation reactions at intermediate energies and discuss possible ways of further improving these codes.

  20. From Homochiral Clusters to Racemate Crystals: Viable Nuclei in 2D Chiral Crystallization.

    PubMed

    Seibel, Johannes; Parschau, Manfred; Ernst, Karl-Heinz

    2015-07-01

    The quest for enantiopure compounds raises the question of which factors favor conglomerate crystallization over racemate crystallization. Studying nucleation and crystal growth at surfaces with submolecular-resolution scanning tunneling microscopy is a suitable approach to better understand intermolecular chiral recognition. Racemic heptahelicene on the Ag(100) surface shows a transition from homochiral nuclei to larger racemic motifs, although the extended homochiral phase exhibits higher density. The homochiral-heterochiral transition is explained by the higher stability of growing nuclei due to a better match of the molecular lattice to the substrate surface. Our observations are direct visual proof of viable nuclei.

  1. Probing collectivity in the vicinity of neutron deficient Pb nuclei

    SciTech Connect

    Grahn, T.; Page, R. D.; Petts, A.; Dewald, A.; Jolie, J.; Melon, B.; Pissulla, Th.; Hornillos, M. B. Gomez; Greenlees, P. T.; Jones, P.; Julin, R.; Juutinen, S.; Ketelhut, S.; Leino, M.; Nyman, M.; Rahkila, P.; Saren, J.; Scholey, C.; Sorri, J.; Uusitalo, J.

    2008-05-12

    A series of recoil distance Doppler-shift lifetime measurements have been carried out to probe collectivity and configuration mixing of different shapes in the vicinity of neutron mid-shell Pb nuclei. Lifetime measurements of {sup 186}Pb and {sup 194}Po, the first ever utilizing the recoil-decay tagging method, probed the collectivity of coexisting prolate and oblate shapes in this region. Futher lifetime measurements of excited states in {sup 180}Hg, {sup 182}Hg and {sup 196}Po have been carried out.

  2. Evolution of pre-collective nuclei: Structural signatures near the drip lines

    SciTech Connect

    Casten, R.F.; Zamfir, N.V. ||

    1994-10-01

    Recent studies have shown that the phenomenology of single-magic and near-magic nuclei has universal characteristics analogous to those of collective nuclei and that, moreover, this phenomenology attaches smoothly to that describing collective nuclei. This has led to a number of new signatures of structure as well as to a new, tripartite, classification of nuclear structure that embraces the gamut of structures from magic, through pre-collective, to fully collective and rotational nuclei. Aside from the natural appeal of simple global correlations of collective observables, these results have particular significance for soon-to-be accessible exotic nuclei near the drip lines since they rely on only the simplest-to-obtain data, in particular, the energies of just the first two excited states, E(4{sub 1}{sup +}) and E(2{sub 1}{sup +}), of even-even nuclei, and the B(E2:2{sub 1}{sup +}{yields}0{sub 1}{sup +}) value. Indeed, without the need for more extensive level schemes, these basic data alone can reveal information about the goodness of seniority, about the validity of pair-addition mode relationships of adjacent even-even nuclei, about underlying shell structure (validity of magic numbers) and even about the shell model potential itself (e.g., the strengths of the l{center_dot} and l{sup 2} terms).

  3. Radio characteristics of galactic nuclei

    NASA Astrophysics Data System (ADS)

    Condon, J. J.

    1986-02-01

    Radio characteristics of galactic nuclei, providing such unique information as spectral data on source variability, and the long-term history of the central engine and its duration of activity and total energy, are reviewed. The compact radio source characteristics are complicated by orientation-dependent relativistic beaming and by refractive focusing in the interstellar medium. Incoherent synchrotron radiation is thought to be the emission mechanism, with the result that synchrotron self-absorption in compact sources hides the central engine from direct radio observation. However, the history revealed by the extended jets and lobes of radio galaxies and quasars favors a single massive object not supported by radiation pressure, either a spinar or a black hole, as the energy source in radio-galaxy nuclei.

  4. Nuclear structure/nuclei far from stability

    SciTech Connect

    Casten, R.F.; Garrett, J.D.; Moller, P.; Bauer, W.W.; Brenner, D.S.; Butler, G.W.; Crawford, J.E.; Davids, C.N.; Dyer, P.L.; Gregorich, K.; Hagbert, E.G.; Hamilton, W.D.; Harar, S.; Haustein, P.E.; Hayes, A.C.; Hoffman, D.C.; Hsu, H.H.; Madland, D.G.; Myers, W.D.; Penttila, H.T.; Ragnarsson, I.; Reeder, P.L.; Robertson, G.H.; Rowley, N.; Schreiber, F.; Seifert, H.L.; Sherrill, B.M.; Siciliano, E.R.; Sprouse, G.D.; Stephens, F

    1990-01-01

    This report outlines some of the nuclear structure topics discussed at the Los Alamos Workshop on the Science of Intense Radioactive Ion Beams (RIB). In it we also tried to convey some of the excitement of the participants for utilizing RIBs in their future research. The introduction of radioactive beams promises to be a major milestone for nuclear structure perhaps even more important than the last such advance in beams based on the advent of heavy-ion accelerators in the 1960's. RIBs not only will allow a vast number of new nuclei to be studies at the extremes of isospin, but the variety of combinations of exotic proton and neutron configurations should lead to entirely new phenomena. A number of these intriguing new studies and the profound consequences that they promise for understanding the structure of the atomic nucleus, nature's only many-body, strongly-inteacting quantum system, are discussed in the preceeding sections. However, as with any scientific frontier, the most interesting phenomena probably will be those that are not anticipated--they will be truly new.

  5. Direct Reactions with Exotic Nuclei

    SciTech Connect

    Baur, G.; Typel, S.

    2005-10-14

    We discuss recent work on Coulomb dissociation and an effective-range theory of low-lying electromagnetic strength of halo nuclei. We propose to study Coulomb dissociation of a halo nucleus bound by a zero-range potential as a homework problem. We study the transition from stripping to bound and unbound states and point out in this context that the Trojan-Horse method is a suitable tool to investigate subthreshold resonances.

  6. Simultaneous two-photon excitation of photodynamic therapy agents

    SciTech Connect

    Wachter, E.A.; Fisher, W.G. |; Partridge, W.P.; Dees, H.C.; Petersen, M.G.

    1998-01-01

    The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type 1 and type 2 photodynamic therapy (PDT) agents are examined.

  7. RESONANT CAVITY EXCITATION SYSTEM

    DOEpatents

    Baker, W.R.; Kerns, Q.A.; Riedel, J.

    1959-01-13

    An apparatus is presented for exciting a cavity resonator with a minimum of difficulty and, more specifically describes a sub-exciter and an amplifier type pre-exciter for the high-frequency cxcitation of large cavities. Instead of applying full voltage to the main oscillator, a sub-excitation voltage is initially used to establish a base level of oscillation in the cavity. A portion of the cavity encrgy is coupled to the input of the pre-exciter where it is amplified and fed back into the cavity when the pre-exciter is energized. After the voltage in the cavity resonator has reached maximum value under excitation by the pre-exciter, full voltage is applied to the oscillator and the pre-exciter is tunned off. The cavity is then excited to the maximum high voltage value of radio frequency by the oscillator.

  8. Separation of U-238 and Np-237 nuclei by gamma-quanta intermediate energies

    NASA Astrophysics Data System (ADS)

    Kazakov, A. A.; Kezerashvili, G. Y.; Lazareva, T. Y.; Nedorezov, V. G.; Skrinskiy, A. N.; Sudov, A. S.; Tumaykin, G. M.; Shatunov, Y. M.

    1986-01-01

    A system employing a beam of backscattered Compton quanta based on the e(+)e(-) accumulating complex and an LTI-701 solid state laser is employed to measure the average photoseparation and separability cross sections of U234 and Np237 nuclei at energies ranging from 150 to 170 MeV. The findings contradict the predictions of existing models based on photon-meson nuclear excitation, and suggest that one of the most probable mechanisms underlying the excitation of nuclei by gamma quanta with intermediate energies, in addition to the photogeneration of pions, is the generation of e(+)e(-) pairs in the field of the nucleus: the gamma quanta wavelength energies in this region becomes comparable to the nucleon dimension, so that collective nuclear excitations are generally suppressed.

  9. Predicting the growth of nanoscale nuclei by histotripsy pulses

    PubMed Central

    Bader, Kenneth B; Holland, Christy K

    2016-01-01

    Histotripsy is a focused ultrasound therapy that ablates tissue through the mechanical action of cavitation. Histotripsy-initiated cavitation activity is generated from shocked ultrasound pulses that scatter from incidental nuclei (shock scattering histotripsy), or purely tensile ultrasound pulses (microtripsy). The Yang/Church model was numerically integrated to predict the behavior of the cavitation nuclei exposed to measured shock scattering histotripsy pulses. The bubble motion exhibited expansion only behavior, suggesting that the ablative action of a histotripsy pulse is related to the maximum size of the bubble. The analytic model of Holland and Apfel was extended to predict the maximum size of cavitation nuclei for both shock scattering histotripsy and microtripsy excitations. The predictions of the analytic model and the numerical model agree within 2% for fully developed shock scattering histotripsy pulses (>72 MPa peak positive pressure). For shock scattering histotripsy pulses that are not fully developed (<72 MPa), the analytic model underestimated the maximum size by less than 5%. The analytic model was also used to predict bubble growth nucleated from microtripsy insonations, and was found to be consistent with experimental observations. Based on the extended analytic model, metrics were developed to predict the extent of the treatment zone from histotripsy pulses. PMID:26988374

  10. Note on spin orbit interactions in nuclei and hypernuclei

    NASA Astrophysics Data System (ADS)

    Kaiser, N.; Weise, W.

    2008-05-01

    A detailed comparison is made between the spin-orbit interactions in Λ hypernuclei and ordinary nuclei. We argue that there are three major contributions to the spin-orbit interaction: (1) a short-range component involving scalar and vector mean fields; (2) a "wrong-sign" spin-orbit term generated by the pion exchange tensor force in second order; and (3) a three-body term induced by two-pion exchange with excitation of virtual Δ (1232)-isobars (à la Fujita-Miyazawa). For nucleons in nuclei the long-range pieces related to the pion-exchange dynamics tend to cancel, leaving room dominantly for spin-orbit mechanisms of short-range origin (parametrized, e.g., in terms of relativistic scalar and vector mean fields terms). In contrast, the absence of an analogous 2π-exchange three-body contribution for Λ hyperons in hypernuclei leads to an almost complete cancellation between the short-range (relativistic mean-field) component and the "wrong-sign" spin-orbit interaction generated by second order π-exchange with an intermediate Σ hyperon. These different balancing mechanisms between short- and long-range components are able to explain simultaneously the very strong spin-orbit interaction in ordinary nuclei and the remarkably weak spin-orbit splitting in Λ hypernuclei.

  11. Cosmochemical implications of the physical processing of cometary nuclei

    SciTech Connect

    McSween, H.Y. Jr. ); Weissman, P.R. )

    1989-12-01

    Comets are not necessarily pristine nebular and interstellar material, despite a common perception to that effect. Alteration processes may occur during comet formation in the outer planet region, during their dispersal to or residence within the Oort cloud, and after their return to the planetary region. Processes that may have significantly modified cometary nuclei include heating, impacts, and irradiation. Possible consequences include phase changes in ices, hydration reactions in silicates, synthesis of organic compounds, collisional disruption and re-accretion, shock and irradiation effects in minerals and ices, cosmogenic nuclide formation, redistribution or loss of volatiles, and formation of a refractory veneer. A model of cometary nuclei that emerges from these considerations provides a framework for understanding observations of comets and future samples.

  12. Ground states of larger nuclei

    SciTech Connect

    Pieper, S.C.; Wiringa, R.B.; Pandharipande, V.R.

    1995-08-01

    The methods used for the few-body nuclei require operations on the complete spin-isospin vector; the size of this vector makes such methods impractical for nuclei with A > 8. During the last few years we developed cluster expansion methods that do not require operations on the complete vector. We use the same Hamiltonians as for the few-body nuclei and variational wave functions of form similar to the few-body wave functions. The cluster expansions are made for the noncentral parts of the wave functions and for the operators whose expectation values are being evaluated. The central pair correlations in the wave functions are treated exactly and this requires the evaluation of 3A-dimensional integrals which are done with Monte Carlo techniques. Most of our effort was on {sup 16}O, other p-shell nuclei, and {sup 40}Ca. In 1993 the Mathematics and Computer Science Division acquired a 128-processor IBM SP which has a theoretical peak speed of 16 Gigaflops (GFLOPS). We converted our program to run on this machine. Because of the large memory on each node of the SP, it was easy to convert the program to parallel form with very low communication overhead. Considerably more effort was needed to restructure the program from one oriented towards long vectors for the Cray computers at NERSC to one that makes efficient use of the cache of the RS6000 architecture. The SP made possible complete five-body cluster calculations of {sup 16}O for the first time; previously we could only do four-body cluster calculations. These calculations show that the expectation value of the two-body potential is converging less rapidly than we had thought, while that of the three-body potential is more rapidly convergent; the net result is no significant change to our predicted binding energy for {sup 16}O using the new Argonne v{sub 18} potential and the Urbana IX three-nucleon potential. This result is in good agreement with experiment.

  13. "Fast Excitation" CID in Quadrupole Ion Trap Mass Spectrometer

    SciTech Connect

    Murrell, J.; Despeyroux, D.; Lammert, Stephen {Steve} A; Stephenson Jr, James {Jim} L; Goeringer, Doug

    2003-01-01

    Collision-induced dissociation (CID) in a quadrupole ion trap mass spectrometer is usually performed by applying a small amplitude excitation voltage at the same secular frequency as the ion of interest. Here we disclose studies examining the use of large amplitude voltage excitations (applied for short periods of time) to cause fragmentation of the ions of interest. This process has been examined using leucine enkephalin as the model compound and the motion of the ions within the ion trap simulated using ITSIM. The resulting fragmentation information obtained is identical with that observed by conventional resonance excitation CID. ''Fast excitation'' CID deposits (as determined by the intensity ratio of the a{sub 4}/b{sub 4} ion of leucine enkephalin) approximately the same amount of internal energy into an ion as conventional resonance excitation CID where the excitation signal is applied for much longer periods of time. The major difference between the two excitation techniques is the higher rate of excitation (gain in kinetic energy) between successive collisions with helium atoms with ''fast excitation'' CID as opposed to the conventional resonance excitation CID. With conventional resonance excitation CID ions fragment while the excitation voltage is still being applied whereas for ''fast excitation'' CID a higher proportion of the ions fragment in the ion cooling time following the excitation pulse. The fragmentation of the (M + 17H){sup 17+} of horse heart myoglobin is also shown to illustrate the application of ''fast excitation'' CID to proteins.

  14. Threshold photoneutron angular distribution and polarization studies of nuclei

    SciTech Connect

    Holt, R.J.

    1980-01-01

    The photoneutron method was applied to the study of: (1) deuteron photodisintegration; (2) giant magnetic dipole resonances in heavy nuclei; (3) mechanism of radiative capture in light nuclei; and (4) isospin splitting of the giant dipole resonance in /sup 60/Ni. These studies were performed with the pulsed bremsstrahlung beam and high-resolution spectrometer available at the Argonne high-current electron linac. A threshold photoneutron polarization method was developed in order to search for the giant M1 resonance in heavy nuclei. A surprisingly small amount of M1 strength was found in /sup 208/Pb. Furthermore, the M1 strength for the 5.08-MeV excitation in /sup 17/O, the best example of a single-particle M1 resonance in nuclei, was found to be strongly quenched. In addition, the /sup 17/O(..gamma..,n/sub 0/)/sup 16/O reaction was found to provide an ideal example of the Lane-Lynn theory of radiative capture. The interplay among the three components of the theory, internal, channel and potential capture, were evident from the data. An electron beam transport system was developed which allows the bremsstrahlung to impinge on the photoneutron target on an axis perpendicular to the usual reaction plane. This system provides an accurate method for the measurement of relative angular distributions in (..gamma..,n) reactions. This system was applied to a high-accuracy measurement of the relative angular distribution for the D(..gamma..,n)H reaction. The question of isospin-splitting of the giant dipole resonance in /sup 60/Ni was studied by using the unique pico-pulse from the accelerator and the newly installed 25-m, neutron flight paths. The results provide clear evidence for the effect of isospin splitting.

  15. Model-space approach to parity violation in heavy nuclei

    SciTech Connect

    Johnson, M.B.

    1996-06-01

    The model-space approach is the basis of both shell model and statistical spectroscopy analyses of nuclear phenomena. The goal of this session is to bring out the main theoretical issues involved in its application to parity violation in the compound nucleus. Section 1 of the current paper sets the stage for the session, and Sect. 2 introduces and explores the model-space formulation as it underlies quantitative connections that are being made between the mean-square matrix element M{sup 2} measured in polarized neutron scattering from compound nuclei and the underlying parity violating interaction. This is followed in the paper by Tomsovic by a description of how statistical spectroscopy is applied to this problem, and in the paper by Hayes by a discussion of shell-model aspects of parity violation in the compound nucleus.

  16. Excited charmed mesons

    SciTech Connect

    Butler, J.N.; Shukla, S.

    1995-05-01

    The experimental status of excited charmed mesons is reviewed and is compared to theoretical expectations. Six states have been observed and their properties are consistent with those predicted for excited charmed states with orbital angular momentum equal to one.

  17. Portable vibration exciter

    NASA Technical Reports Server (NTRS)

    Beecher, L. C.; Williams, F. T.

    1970-01-01

    Gas-driven vibration exciter produces a sinusoidal excitation function controllable in frequency and in amplitude. It allows direct vibration testing of components under normal loads, removing the possibility of component damage due to high static pressure.

  18. Crossings in alternating-parity bands of neutron-rich Ba nuclei

    SciTech Connect

    Urban, W.; Jones, M.A.; Durell, J.L.

    1995-07-22

    {sup 144}Ba and {sup 146}Ba nuclei produced in the spontaneous fission of {sup 248}Cm have been studied using the EUROGRAM II array. Spins and parities of excited levels have been deduced from triple-{gamma} angular correlation and direction-polarization correlation measurements, which is the first use of these techniques in studies of fission product nuclei. Ground-state, alternating-parity bands have been extended significantly and crossing in these bands has been found in both isotopes. For the first time alternating-parity band termination by particle alignment has been observed.

  19. Time-dependent Hartree-Fock Study of Octupole Vibrations in doubly magic nuclei

    NASA Astrophysics Data System (ADS)

    Simenel, C.; Buete, J.; Vo-Phuoc, K.

    2016-09-01

    Octupole vibrations are studied in some doubly magic nuclei using the time-dependent Hartree-Fock (TDHF) theory with a Skyrme energy density functional. Through the use of the linear response theory, the energies and transition amplitudes of the low-lying vibrational modes for each of the nuclei were determined. Energies were found to be close to experimental results. However, transition amplitudes, quantified by the deformation parameter β3, are underestimated by TDHF. A comparison with single-particle excitations on the Hartree-Fock ground-state shows that the collective octupole vibrations have their energy lowered due to attractive RPA residual interaction.

  20. Entropy Driven Excitation Energy Sorting in Superfluid Fission Dynamics

    SciTech Connect

    Schmidt, Karl-Heinz; Jurado, Beatriz

    2010-05-28

    It is shown that the constant-temperature behavior of nuclei in the superfluid regime leads to an energy-sorting process if two nuclei are in thermal contact, as is the case in the fission process. This effect explains why an increase of the initial excitation energy leads an increase of the number of emitted neutrons from the heavy fission fragment, only. The observed essentially complete energy sorting may be seen as a new counterintuitive manifestation of quantum-mechanical properties of microscopic systems.

  1. Transcription in Isolated Wheat Nuclei

    PubMed Central

    Luthe, Dawn Sywassink; Quatrano, Ralph S.

    1980-01-01

    Nuclei free of RNase activity were isolated from 3-hour-imbibed wheat (var. Yamhill) embryos by centrifugation through a discontinuous gradient of Percoll. The maximum rate of RNA synthesis observed in these nuclei was approximately 5 picomoles [3H]UTP per milligram DNA per minute. Two monovalent cation optima were found when measured in the presence of 15 millimolar MgCl2 or 2 millimolar MnCl2; 15 and 75 millimolar (NH4)2SO4. At the high monovalent cation optimum, the rate of RNA synthesis was linear for the first 10 to 15 minutes of incubation and still increasing after 3 hours. RNA synthesized in vitro (30-minute pulse followed by a 30-minute chase) showed distinct 18 and 26S RNA peaks comprising 13 and 17% of the total radioactivity, respectively. The over-all pattern of RNA synthesized in vitro was similar to the in vivo pattern. Approximately 40 to 50% of the RNA synthesized was inhibited by α-amanitin at 4 micrograms per milliliter. The newly synthesized 6 to 10S RNA appeared to be selectively inhibited by α-amanitin. PMID:16661179

  2. Selfconsistent calculations for hyperdeformed nuclei

    SciTech Connect

    Molique, H.; Dobaczewski, J.; Dudek, J.; Luo, W.D.

    1996-12-31

    Properties of the hyperdeformed nuclei in the A {approximately} 170 mass range are re-examined using the self-consistent Hartree-Fock method with the SOP parametrization. A comparison with the previous predictions that were based on a non-selfconsistent approach is made. The existence of the {open_quotes}hyper-deformed shell closures{close_quotes} at the proton and neutron numbers Z=70 and N=100 and their very weak dependence on the rotational frequency is suggested; the corresponding single-particle energy gaps are predicted to play a role similar to that of the Z=66 and N=86 gaps in the super-deformed nuclei of the A {approximately} 150 mass range. Selfconsistent calculations suggest also that the A {approximately} 170 hyperdeformed structures have neglegible mass asymmetry in their shapes. Very importantly for the experimental studies, both the fission barriers and the {open_quotes}inner{close_quotes} barriers (that separate the hyperdeformed structures from those with smaller deformations) are predicted to be relatively high, up to the factor of {approximately}2 higher than the corresponding ones in the {sup 152}Dy superdeformed nucleus used as a reference.

  3. Physical Processing of Cometary Nuclei

    NASA Astrophysics Data System (ADS)

    Weissman, Paul R.; Stern, S. Alan

    1997-12-01

    Cometary nuclei preserve a cosmo-chemical record of conditions and processes in the primordial solar nebula, and possibly even the interstellar medium. However, that record is not perfectly preserved over the age of the solar system due to a variety of physical processes which act to modify cometary surfaces and interiors. Possible structural and/or internal processes include: collisional accretion, disruption, and reassembly during formation; internal heating by long and short-lived radionuclides; amorphous to crystalline phase transitions, and thermal stresses. Identified surface modification processes include: irradiation by galactic cosmic rays, solar protons, UV photons, and the Sun's T Tauri stage mass outflow; heating by passing stars and nearby supernovae; gardening by debris impacts; the accretion of interstellar dust and gas and accompanying erosion by hypervelocity dust impacts and sputtering; and solar heating with accompanying crust formation. These modification processes must be taken into account in both the planning and the interpretation of the results of a Comet Nucleus Sample Return Mission. Sampling of nuclei should be done at as great a depth below the surface crust as technically feasible, and at vents or fissures leading to exposed volatiles at depth. Samples of the expected cometary crust and near-surface layers also need to be returned for analysis to achieve a better understanding of the effects of these physical processes. We stress that comets are still likely less modified dm any other solar system bodies, but the degree of modification can vary greatly from one comet to the next.

  4. Physical Processing of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Weissman, Paul R.; Stern, S. Alan

    1997-01-01

    Cometary nuclei preserve a cosmo-chemical record of conditions and processes in the primordial solar nebula, and possibly even the interstellar medium. However, that record is not perfectly preserved over the age of the solar system due to a variety of physical processes which act to modify cometary surfaces and interiors. Possible structural and/or internal processes include: collisional accretion, disruption, and reassembly during formation; internal heating by long and short-lived radionuclides; amorphous to crystalline phase transitions, and thermal stresses. Identified surface modification processes include: irradiation by galactic cosmic rays, solar protons, UV photons, and the Sun's T Tauri stage mass outflow; heating by passing stars and nearby supernovae; gardening by debris impacts; the accretion of interstellar dust and gas and accompanying erosion by hypervelocity dust impacts and sputtering; and solar heating with accompanying crust formation. These modification processes must be taken into account in both the planning and the interpretation of the results of a Comet Nucleus Sample Return Mission. Sampling of nuclei should be done at as great a depth below the surface crust as technically feasible, and at vents or fissures leading to exposed volatiles at depth. Samples of the expected cometary crust and near-surface layers also need to be returned for analysis to achieve a better understanding of the effects of these physical processes. We stress that comets are still likely less modified dm any other solar system bodies, but the degree of modification can vary greatly from one comet to the next.

  5. Mass-23 nuclei in astrophysics

    NASA Astrophysics Data System (ADS)

    Fraser, P. R.; Amos, K.; Canton, L.; Karataglidis, S.; Svenne, J. P.; van der Kniff, D.

    2015-09-01

    The formation of mass-23 nuclei by radiative capture is of great interest in astrophysics. A topical problem associated with these isobars is the so-called 22Na puzzle of ONe white dwarf novae, where the abundance of 22Na observed is not as is predicted by current stellar models, indicating there is more to learn about how the distribution of elements in the universe occurred. Another concerns unexplained variations in elements abundance on the surface of aging red giant stars. One method for theoretically studying nuclear scattering is the Multi-Channel Algebraic Scattering (MCAS) formalism. Studies to date have used a simple collective-rotor prescription to model the target states which couple to projectile nucleons. While, in general, the target states considered all belong to the ground state rotor band, for some systems it is necessary to include coupling to states outside of this band. Herein we discuss an extension of MCAS to allow coupling of different strengths between such states and the ground state band. This consideration is essential when studying the scattering of neutrons from 22Ne, a necessary step in studying the mass-23 nuclei mentioned above.

  6. α -decay spectra of odd nuclei using the effective Skyrme interaction

    NASA Astrophysics Data System (ADS)

    Ward, D. E.; Carlsson, B. G.; Åberg, S.

    2015-07-01

    Background: For nuclei heavier than 208Pb α decay is a dominating decay mode. α decay of odd nuclei can give spectroscopic information because different states in the daughter nucleus can be populated in the decay. Purpose: To explore and test microscopic descriptions of α decay of odd nuclei based on self-consistent models with effective nuclear interactions. To predict the hindrance of α decay of odd-A superheavy nuclei. Methods: We apply the method of our previous work [15e D. E. Ward, B. G. Carlsson, and S. Åberg, Phys. Rev. C 88, 064316 (2013), 10.1103/PhysRevC.88.064316] to the case of odd-A near-spherical nuclei. The Skyrme effective interaction SLy4 is used. Starting from the obtained Hartree-Fock-Bogoliubov vacuum and quasiparticle excitations, the α -particle formation amplitude is calculated giving the decay rates and hindrance of different α -decay channels. Result: The calculated relative decay rates show good agreement with available data. The hindrance of decay channels where the odd nucleon changes orbital is reasonably described by the microscopic calculation. Several hindered ground-state decays of superheavy nuclei are predicted, implying possible α -γ coincidences. Conclusions: The approach offers a practical method of making quantitative predictions for the relative hindrance of different α -decay channels.

  7. PHYSICAL STUDIES OF ISOLATED EUCARYOTIC NUCLEI

    PubMed Central

    Olins, Donald E.; Olins, Ada L.

    1972-01-01

    The degree of chromatin condensation in isolated rat liver nuclei and chicken erythrocyte nuclei was studied by phase-contrast microscopy as a function of solvent pH, K+ and Mg++ concentrations Data were represented as "phase" maps, and standard solvent conditions selected that reproducibly yield granular, slightly granular, and homogeneous nuclei Nuclei in these various states were examined by ultraviolet absorption and circular dichroism (CD) spectroscopy, low-angle X-ray diffraction, electron microscopy, and binding capacity for ethidium bromide Homogeneous nuclei exhibited absorption and CD spectra resembling those of isolated nucleohistone. Suspensions of granular nuclei showed marked turbidity and absorption flattening, and a characteristic blue-shift of a crossover wavelength in the CD spectra. In all solvent conditions studied, except pH < 2 3, low-angle X-ray reflections characteristic of the native, presumably superhelical, nucleohistone were observed from pellets of intact nuclei. Threads (100–200 A diameter) were present in the condensed and dispersed phases of nuclei fixed under the standard solvent conditions, and examined in the electron microscope after thin sectioning and staining Nuclei at neutral pH, with different degrees of chromatin condensation, exhibited similar binding capacities for ethidium bromide. These data suggest a model that views chromatin condensation as a close packing of superhelical nucleohistone threads but still permits condensed chromatin to respond rapidly to alterations in solvent environment. PMID:4554987

  8. Review of metastable states in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Dracoulis, G. D.; Walker, P. M.; Kondev, F. G.

    2016-07-01

    The structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with A≳ 150 . The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances.

  9. Review of metastable states in heavy nuclei

    DOE PAGES

    Dracoulis, G. D.; Walker, P. M.; Kondev, F. G.

    2016-05-31

    Here, the structure of nuclear isomeric states is reviewed in the context of their role in contemporary nuclear physics research. Emphasis is given to high-spin isomers in heavy nuclei, with A ≳ 150. The possibility to exploit isomers to study some of the most exotic nuclei is a recurring theme. In spherical nuclei, the role of octupole collectivity is discussed in detail, while in deformed nuclei the limitations of the K quantum number are addressed. Isomer targets and isomer beams are considered, along with applications related to energy storage, astrophysics, medicine, and experimental advances.

  10. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation.

    PubMed

    Isegawa, Miho; Truhlar, Donald G

    2013-04-07

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel

  11. Valence excitation energies of alkenes, carbonyl compounds, and azabenzenes by time-dependent density functional theory: Linear response of the ground state compared to collinear and noncollinear spin-flip TDDFT with the Tamm-Dancoff approximation

    NASA Astrophysics Data System (ADS)

    Isegawa, Miho; Truhlar, Donald G.

    2013-04-01

    Time-dependent density functional theory (TDDFT) holds great promise for studying photochemistry because of its affordable cost for large systems and for repeated calculations as required for direct dynamics. The chief obstacle is uncertain accuracy. There have been many validation studies, but there are also many formulations, and there have been few studies where several formulations were applied systematically to the same problems. Another issue, when TDDFT is applied with only a single exchange-correlation functional, is that errors in the functional may mask successes or failures of the formulation. Here, to try to sort out some of the issues, we apply eight formulations of adiabatic TDDFT to the first valence excitations of ten molecules with 18 density functionals of diverse types. The formulations examined are linear response from the ground state (LR-TDDFT), linear response from the ground state with the Tamm-Dancoff approximation (TDDFT-TDA), the original collinear spin-flip approximation with the Tamm-Dancoff (TD) approximation (SF1-TDDFT-TDA), the original noncollinear spin-flip approximation with the TDA approximation (SF1-NC-TDDFT-TDA), combined self-consistent-field (SCF) and collinear spin-flip calculations in the original spin-projected form (SF2-TDDFT-TDA) or non-spin-projected (NSF2-TDDFT-TDA), and combined SCF and noncollinear spin-flip calculations (SF2-NC-TDDFT-TDA and NSF2-NC-TDDFT-TDA). Comparing LR-TDDFT to TDDFT-TDA, we observed that the excitation energy is raised by the TDA; this brings the excitation energies underestimated by full linear response closer to experiment, but sometimes it makes the results worse. For ethylene and butadiene, the excitation energies are underestimated by LR-TDDFT, and the error becomes smaller making the TDA. Neither SF1-TDDFT-TDA nor SF2-TDDFT-TDA provides a lower mean unsigned error than LR-TDDFT or TDDFT-TDA. The comparison between collinear and noncollinear kernels shows that the noncollinear kernel

  12. Anomalous Neutron Capture and Plastic Deformation of cu and pd Cathodes during Electrolysis in a Weak Thermalized Neutron Field:. Evidence of Nuclei-Lattice Exchange

    NASA Astrophysics Data System (ADS)

    Lipson, A. G.; Miley, G. H.; Lipson, A. G.

    2006-02-01

    Anomalous neutron capture and plastic deformation in the hardened Cu and Pd cathodes has been established under combined action of electrolysis and a weak thermalized neutron field (WTNF) with a flux in the range of 180-400 n/s cm2. Experiments with these cathodes showed ~7.0% decrease in the 2224 keV n-D gamma peak accompanying thermalized neutron capture inside the PE cavity during electrolysis vs. experiments with annealed Cu and Pd as well as with the background runs (i.e., no electrolysis). The anomalous neutron capture and plastic deformation of Cu and Pd cathodes under combined action of electrolysis and WTNF may be explained energetically by assuming a selective radiationless thermalized neutron capture at high-internal strain concentration sites in the hardened cathodes. The results of these experiments provide straightforward (avoids the Coulomb barrier penetration issue) evidence that nuclei-lattice energy exchange can result in an increase in neutron capture probability and radiationless de-excitation of the resulting compound nuclei.

  13. Acoustically excited heated jets. 1: Internal excitation

    NASA Technical Reports Server (NTRS)

    Lepicovsky, J.; Ahuja, K. K.; Brown, W. H.; Salikuddin, M.; Morris, P. J.

    1988-01-01

    The effects of relatively strong upstream acoustic excitation on the mixing of heated jets with the surrounding air are investigated. To determine the extent of the available information on experiments and theories dealing with acoustically excited heated jets, an extensive literature survey was carried out. The experimental program consisted of flow visualization and flowfield velocity and temperature measurements for a broad range of jet operating and flow excitation conditions. A 50.8-mm-diam nozzle was used for this purpose. Parallel to the experimental study, an existing theoretical model of excited jets was refined to include the region downstream of the jet potential core. Excellent agreement was found between theory and experiment in moderately heated jets. However, the theory has not yet been confirmed for highly heated jets. It was found that the sensitivity of heated jets to upstream acoustic excitation varies strongly with the jet operating conditions and that the threshold excitation level increases with increasing jet temperature. Furthermore, the preferential Strouhal number is found not to change significantly with a change of the jet operating conditions. Finally, the effects of the nozzle exit boundary layer thickness appear to be similar for both heated and unheated jets at low Mach numbers.

  14. Determination of the compound nucleus survival probability Psurv for various "hot" fusion reactions based on the dynamical cluster-decay model

    NASA Astrophysics Data System (ADS)

    Chopra, Sahila; Kaur, Arshdeep; Gupta, Raj K.

    2015-03-01

    After a successful attempt to define and determine recently the compound nucleus (CN) fusion/ formation probability PCN within the dynamical cluster-decay model (DCM), we introduce and estimate here for the first time the survival probability Psurv of CN against fission, again within the DCM. Calculated as the dynamical fragmentation process, Psurv is defined as the ratio of the evaporation residue (ER) cross section σER and the sum of σER and fusion-fission (ff) cross section σff, the CN formation cross section σCN, where each contributing fragmentation cross section is determined in terms of its formation and barrier penetration probabilities P0 and P . In DCM, the deformations up to hexadecapole and "compact" orientations for both in-plane (coplanar) and out-of-plane (noncoplanar) configurations are allowed. Some 16 "hot" fusion reactions, forming a CN of mass number ACN˜100 to superheavy nuclei, are analyzed for various different nuclear interaction potentials, and the variation of Psurv on CN excitation energy E*, fissility parameter χ , CN mass ACN, and Coulomb parameter Z1Z2 is investigated. Interesting results are that three groups, namely, weakly fissioning, radioactive, and strongly fissioning superheavy nuclei, are identified with Psurv, respectively, ˜1 ,˜10-6 , and ˜10-10 . For the weakly fissioning group (100 nuclei also Psurv is a decreasing function of E*. Furthermore, of particular interest are the cases of 105Ag* , isotopes of Pt*, and 213 ,215 ,217Fr

  15. Quasifree kaon photoproduction on nuclei

    SciTech Connect

    Frank Lee; T. MART; Cornelius Bennhold; Lester Wright

    2001-12-01

    Investigations of the quasifree reaction A({gamma}, K Y)B are presented in the distorted wave impulse approximation (DWIA). For this purpose, we present a revised tree-level model of elementary kaon photoproduction that incorporates hadronic form factors consistent with gauge invariance, uses SU(3) values for the Born couplings and uses resonances consistent with multi-channel analyses. The potential of exclusive quasifree kaon photoproduction on nuclei to reveal details of the hyperon-nucleus interaction is examined. Detailed predictions for the coincidence cross section, the photon asymmetry, and the hyperon polarization and their sensitivities to the ingredients of the model are obtained for all six production channels. Under selected kinematics these observables are found to be sensitive to the hyperon-nucleus final state interaction. Some polarization observables are found to be insensitive to distortion effects, making them ideal tools to search for possible medium modifications of the elementary amplitude.

  16. The Physics of Cometary Nuclei

    NASA Technical Reports Server (NTRS)

    Whipple, Fred L.

    1997-01-01

    The recent developments in cometary studies suggest rather low mean densities and weak structures for the nuclei. They appear to be accumulations of fairly discrete units loosely bound together, as deduced from the observations of Comet Shoemaker-Levy 9 during its encounter with Jupiter. The compressive strengths deduced from comet splitting by Opik and Sekanina are extremely low. These values are confirmed by theory developed here. assuming that Comet P/Holmes had a companion that collided with it in 1892. There follows a short discussion that suggests that the mean densities of comets should increase with comet dimensions. The place of origin of short-period comets may relate to these properties.

  17. Reaction theory for exotic nuclei

    SciTech Connect

    Bonaccorso, Angela

    2014-05-09

    Exotic nuclei are usually defined as those with unusual N/Z ratios. They can be found in the crust of neutron stars enbedded in a sea of electrons or created in laboratory by fragmentation of a primary beam (in-flight method) or of the target (ISOL method). They are extremely important for nuclear astrophysics, see for example Ref.[1]. Furthermore by studying them we can check the limits of validity of nuclear reaction and structure models. This contribution will be devoted to the understanding of how by using reaction theory and comparing to the data we can extract structure information. We shall discuss the differences between the mechanisms of transfer and breakup reactions, an we will try to explain how nowadays it is possible to do accurate spectroscopy in extreme conditions.

  18. Proton emission from triaxial nuclei

    SciTech Connect

    Delion, D.S.; Wyss, R.; Karlgren, D.; Liotta, R.J.

    2004-12-01

    Proton decay from triaxially deformed nuclei is investigated. The deformation parameters corresponding to the mother nucleus are determined microscopically and the calculated decay widths are used to probe the mean-field wave function. The proton wave function in the mother nucleus is described as a resonant state in a coupled-channel formalism. The decay width, as well as the angular distribution of the decaying particle, are evaluated and their dependence upon the triaxial deformation parameters is studied in the decay of {sup 161}Re and {sup 185}Bi. It is found that the decay width is very sensitive to the parameters defining the triaxial deformation while the angular distribution is a universal function which does not depend upon details of the nuclear structure.

  19. Towards the exact calculation of medium nuclei

    SciTech Connect

    Gandolfi, Stefano; Carlson, Joseph Allen; Lonardoni, Diego; Wang, Xiaobao

    2016-12-19

    The prediction of the structure of light and medium nuclei is crucial to test our knowledge of nuclear interactions. The calculation of the nuclei from two- and three-nucleon interactions obtained from rst principle is, however, one of the most challenging problems for many-body nuclear physics.

  20. High spin spectroscopy of near spherical nuclei: Role of intruder orbitals

    SciTech Connect

    Bhattacharyya, S.; Bhattacharjee, T.; Mukherjee, G.; Banerjee, D.; Das, S. K.; Guin, R.; Gupta, S. Das

    2014-08-14

    High spin states of nuclei in the vicinity of neutron shell closure N = 82 and proton shell closure Z = 82 have been studied using the Clovere Ge detectors of Indian National Gamma Array. The shape driving effects of proton and neutron unique parity intruder orbitals for the structure of nuclei around the above shell closures have been investigated using light and heavy ion beams. Lifetime measurements of excited states in {sup 139}Pr have been done using pulsed-beam-γ coincidence technique. The prompt spectroscopy of {sup 207}Rn has been extended beyond the 181μs 13/2{sup +} isomer. Neutron-rich nuclei around {sup 132}Sn have been produced from proton induced fission of {sup 235}U and lifetime measurement of low-lying states of odd-odd {sup 132}I have been performed from offline decay.

  1. Systematics of Scissors Mode in Gd Nuclei from Experiments with the DANCE Detector

    NASA Astrophysics Data System (ADS)

    Kroll, J.; Agvaanluvsan, U.; Baramsai, B.; Becker, J. A.; Bečvář, F.; Bredeweg, T. A.; Chyzh, A.; Couture, A.; Dashdorj, D.; Haight, R. C.; Jandel, M.; Keksis, A. L.; Krtička, M.; Mitchell, G. E.; O'Donnell, J. M.; Parker, W.; Rundberg, R. S.; Ullmann, J. L.; Valenta, S.; Vieira, D. J.; Walker, C. L.; Wilhelmy, J. B.; Wouters, J. M.; Wu, C. Y.

    2014-05-01

    Multi-step cascade γ-ray spectra from neutron capture at isolated resonances of 152,154-158Gd nuclei were measured at the LANSCE/DANCE time-of-flight facility in Los Alamos National Laboratory. The main objective of these experiments was to obtain new information on photon strength functions with emphasis on the role of the M1 scissors mode vibration. An analysis of the data obtained shows that the scissors mode plays a significant role in the ground state transitions, as well as in the transitions populating all excited states of the studied nuclei. The estimates of the scissors mode strength indicate that for 157,159Gd this strength is significantly higher than in neighboring even-even nuclei 156,158Gd. The results are compared with the (γ,γ‧) data for the ground-state scissors mode and the results from 3He-induced reactions.

  2. Coupled cluster calculation for ground state properties of closed-shell nuclei and single hole states.

    NASA Astrophysics Data System (ADS)

    Mihaila, Bogdan; Heisenberg, Jochen

    2000-04-01

    We continue the investigations of ground state properties of closed-shell nuclei using the Argonne v18 realistic NN potential, together with the Urbana IX three-nucleon interaction. The ground state wave function is used to calculate the charge form factor and charge density. Starting with the ground state wave function of the closed-shell nucleus, we use the equation of motion technique to calculate the ground state and excited states of a neighboring nucleus. We then generate the corresponding magnetic form factor. We correct for distortions due to the interaction between the electron probe and the nuclear Coulomb field using the DWBA picture. We compare our results with the available experimental data. Even though our presentation will focus mainly on the ^16O and ^15N nuclei, results for other nuclei in the p and s-d shell will also be presented.

  3. Nuclear structure studies of medium-mass nuclei using large Ge arrays

    SciTech Connect

    Baktash, C.

    1996-12-31

    The advent of large Ge arrays and their ancillary detectors has greatly advanced spectroscopic studies of the medium-mass nuclei. These nuclei undergo rapid shape changes as a function of spin, excitation energy and particle number and, thus, provide a unique laboratory to test and refine a variety of theoretical models. Following a brief review of the physics motivation, some of the highlights of the experimental results obtained with the help of these powerful detector systems will be discussed. Among results presented here are the newly-discovered island of superdeformation in the A{approximately}80 mass region, and the high-spin band structures in the N{approximately}Z nuclei. These band structures may be understood in the framework of the conventional cranking models, without the introduction of additional T=0 neutron-proton pairing correlations.

  4. Bridging the nuclear structure gap between stable and super heavy nuclei.

    SciTech Connect

    Seweryniak, D.; Khoo, T. L.; Ahmad, I.; Kondev, F. G.; Robinson, A.; Back, B. B.; Carpenter, M. P.; Davids, C. N.; Greene, J. P.; Gros, S.; Janssens, R. V. F.; Lauritsen, T.; Lister, C. J.; McCutchan, E. A.; Peterson, D.; Zhu, S. F.; Physics; Univ. of York; Univ. of Massachusetts at Lowell; Japan Atomic Energy Agency; Univ. of Jyvaskyla; CSNSM Orsay; Yale Univ.; Univ. of Liverpool; RIKEN; Univ. of Maryland; Univ. of Notre Dame

    2010-01-01

    Due to recent advances in detection techniques, excited states in several trans-fermium nuclei were studied in many laboratories worldwide, shedding light on the evolution of nuclear structure between stable nuclei and the predicted island of stability centered around spherical magic numbers. In particular, studies of K-isomers around the Z=100 and N=152 deformed shell closures extended information on the energies of Nilsson orbitals at the Fermi surface. Some of these orbitals originate from spherical states, which are relevant to the magic gaps in super-heavy nuclei. The single-particle energies can be used to test various theoretical predictions and aid in extrapolations towards heavier systems. So far, the Woods-Saxon potential reproduces the data best, while self-consistent approaches miss some of the observed features, indicating a need to modify the underlying effective nucleon-nucleon interactions.

  5. Bridging the nuclear structure gap between stable and super heavy nuclei

    NASA Astrophysics Data System (ADS)

    Seweryniak, D.; Khoo, T. L.; Ahmad, I.; Kondev, F. G.; Robinson, A.; Tandel, S. K.; Asai, M.; Back, B. B.; Carpenter, M. P.; Chowdhury, P.; Davids, C. N.; Eeckhaudt, S.; Greene, J. P.; Greenlees, P. T.; Gros, S.; Hauschild, K.; Heinz, A.; Herzberg, R.-D.; Janssens, R. V. F.; Jenkins, D. G.; Jones, G. D.; Ketelhut, S.; Lauritsen, T.; Lister, C. J.; Lopez-Martens, A.; Marley, P.; McCutchan, E. A.; Nakatsukasa, T.; Papadakis, P.; Peterson, D.; Qian, J.; Rostron, D.; Stefanescu, I.; Tandel, U. S.; Wang, X. F.; Zhu, S. F.

    2010-03-01

    Due to recent advances in detection techniques, excited states in several trans-fermium nuclei were studied in many laboratories worldwide, shedding light on the evolution of nuclear structure between stable nuclei and the predicted island of stability centered around spherical magic numbers. In particular, studies of K-isomers around the Z=100 and N=152 deformed shell closures extended information on the energies of Nilsson orbitals at the Fermi surface. Some of these orbitals originate from spherical states, which are relevant to the magic gaps in super-heavy nuclei. The single-particle energies can be used to test various theoretical predictions and aid in extrapolations towards heavier systems. So far, the Woods-Saxon potential reproduces the data best, while self-consistent approaches miss some of the observed features, indicating a need to modify the underlying effective nucleon-nucleon interactions.

  6. Odd-Z Transactinide Compound Nucleus Reactions Including the Discovery of 260Bh

    SciTech Connect

    Nelson, Sarah L.

    2008-01-01

    Several reactions producing odd-Z transactinide compound nuclei were studiedwith the 88-Inch Cyclotron and the Berkeley Gas-Filled Separator at the Lawrence Berkeley National Laboratory. The goal was to produce the same compound nucleus ator near the same excitation energy with similar values of angular momentum via differentnuclear reactions. In doing so, it can be determined if there is a preference in entrancechannel, because under these experimental conditions the survival portion of Swiatecki, Siwek-Wilcznska, and Wilczynski's"Fusion By Diffusion" model is nearly identical forthe two reactions. Additionally, because the same compound nucleus is produced, theexit channel is the same. Four compound nuclei were examined in this study: 258Db, 262Bh, 266Mt, and 272Rg. These nuclei were produced by using very similar heavy-ion induced-fusion reactions which differ only by one proton in the projectile or target nucleus (e.g.: 50Ti + 209Bi vs. 51V + 208Pb). Peak 1n exit channel cross sections were determined for each reaction in each pair, and three of the four pairs' cross sections were identical within statistical uncertainties. This indicates there is not an obvious preference of entrancechannel in these paired reactions. Charge equilibration immediately prior to fusionleading to a decreased fusion barrier is the likely cause of this phenomenon. In addition to this systematic study, the lightest isotope of element 107, bohrium, was discovered in the 209Bi(52Cr,n) reaction. 260Bh was found to decay by emission of a 10.16 MeV alpha particle with a half-life of 35$+19\\atop{-9}$ ms. The cross section is 59 pb at an excitation energy of 15.0 MeV. The effect of the N = 152 shell is also seen in this isotope's alpha particle energy, the first evidence of such an effect in Bh. All reactions studied are also compared to model predictions by Swiatecki

  7. Excitation of interstellar hydrogen chloride

    NASA Technical Reports Server (NTRS)

    Neufild, David A.; Green, Sheldon

    1994-01-01

    We have computed new rate coefficients for the collisional excitation of HCl by He, in the close-coupled formalism and using an interaction potential determined recently by Willey, Choong, & DeLucia. Results have been obtained for temperatures between 10 K and 300 K. With the use of the infinite order sudden approximation, we have derived approximate expressions of general applicability which may be used to estimate how the rate constant for a transition (J to J prime) is apportioned among the various hyperfine states F prime of the final state J prime. Using these new rate coefficients, we have obtained predictions for the HCl rotational line strengths expected from a dense clump of interstellar gas, as a function of the HCl fractional abundance. Over a wide range of HCl abundances, we have found that the line luminosities are proportional to abundance(exp 2/3), a general result which can be explained using a simple analytical approximation. Our model for the excitation of HCl within a dense molecular cloud core indicates that the J = 1 goes to 0 line strengths measured by Blake, Keene, & Phillips toward the Orion Molecular Cloud (OMC-1) imply a fractional abundance n(HCl)/n(H2) approximately 2 x 10(exp -9), a value which amounts to only approximately 0.3% of the cosmic abundance of chlorine nuclei. Given a fractional abundance of 2 x 10(exp -9), the contribution of HCl emission to the total radiative cooling of a dense clump is small. For Orion, we predict a flux approximately 10(exp -19) W/sq cm for the HCl J = 3 goes to 2 line near 159.8 micrometers, suggesting that the strength of this line could be measured using the Infrared Space Observatory.

  8. 76 FR 63702 - In the Matter of the Designation of Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-13

    ... Conspiracy of Fire Nuclei, aka Conspiracy of the Nuclei of Fire, aka Conspiracy of Cells of Fire, aka Synomosia of Pyrinon Tis Fotias, aka Thessaloniki-Athens Fire Nuclei Conspiracy, as a Specially Designated... that the organization known as Conspiracy of Fire Nuclei, also known as Conspiracy of the Nuclei...

  9. Production of actinide nuclei by multi-nucleon transfer

    SciTech Connect

    Lauritsen, T.; Ahmad, I.; Carpenter, M.P.

    1995-08-01

    Multi-nucleon transfers have increasingly allowed us to reach parts of the nuclear chart where regular compound nuclear reactions are prohibited. The interesting region of Ra and Rn, where a rich tapestry of nuclear structure manifests itself, is now accessible using this technique of deep inelastic scattering. In particular, these nuclei are predicted to lie at the onset of octupole deformation and the region is rich in examples of shape coexistence. There are several theoretical predictions of nuclear structure of these nuclei that have not been experimentally tested. Moreover, there is serious disagreement among these theories. We used a beam of {sup 136}Xe at 720 MeV from ATLAS on a target of {sup 232}Th to produce a range of Rn isotopes, with a mass from 220 to 224, and Ra isotopes with masses greater than 222. The beam energy, target and beam were selected carefully to enhance the cross-section for production of these nuclei and reduce the Doppler broadening of the gamma rays that were observed in the Argonne Notre Dame gamma-ray facility. The 12 germanium detectors of this array allowed the observation of gamma-gamma coincidences. The inner ball of 50 BGO detectors allowed us to record the multiplicity and sum-energy information for each event. The latter should permit us to determine the entry region in the products of the transfer reaction. We had four successful days of beam-time, when we collected in excess of 8 x 10{sup 7} events. Data analysis is in progress at the University of Liverpool. A complete set of spectroscopic information on the yrast structure of the many nuclei produced in this reaction is being extracted.

  10. Dynamical coupling of electrons and nuclei for Coulomb explosion of argon trimers in intense laser fields

    NASA Astrophysics Data System (ADS)

    Xie, Xiguo; Wu, Chengyin; Yuan, Zongqiang; Ye, Difa; Wang, Peng; Deng, Yongkai; Fu, Libin; Liu, Jie; Liu, Yunquan; Gong, Qihuang

    2015-08-01

    We have experimentally and theoretically studied the fragmentation dynamics of argon trimer (A r3) in intense laser fields. By coincidently measuring the momentum vectors, we obtained the emission geometry of the three fragmental ions produced in the three-body fragmentation process. In addition to the direct Coulomb explosion channels, we observed the indirect Coulomb explosion channels with Rydberg excitation. We have further developed a classical polyatomic molecular ensemble model, in which all interactions among electrons and nuclei are fully included, to simulate the fragmentation dynamics of argon trimer in intense laser fields. The experimental observations have been reproduced by the model calculation. The simulations show that the Rydberg excitation modifies the kinetic energy release as well as the emission geometry of fragmental ions during the explosion process. The study provides insight into the correlation dynamics of electrons and nuclei of many-body physics driven by intense laser fields.

  11. Emergence of rotational bands in ab initio no-core configuration interaction calculations of light nuclei

    NASA Astrophysics Data System (ADS)

    Caprio, Mark A.; Maris, Pieter; Vary, James P.

    2014-03-01

    The emergence of rotational bands has recently been observed in no-core configuration interaction (NCCI) calculations for p-shell nuclei, as evidenced by rotational patterns for excitation energies, electromagnetic moments, and electromagnetic transitions. Yrast and low-lying excited bands are found. The results demonstrate the possibility of well-developed rotational structure in NCCI calculations, using realistic nucleon-nucleon interactions, and within finite, computationally-accessible configuration spaces. This talk will focus on results for rotation in both the even-mass and odd-mass Be isotopes (7 <= A <= 12). Supported by US DOE (DE-FG02-95ER-40934, DESC0008485 SciDAC/NUCLEI, DE-FG02-87ER40371), US NSF (0904782), and Research Corporation for Science Advancement (Cottrell Scholar Award). Computational resources provided by NERSC (US DOE DE-AC02-05CH11231).

  12. Results for p-shell nuclei at LO, NLO, and N2LO in chiral EFT

    NASA Astrophysics Data System (ADS)

    Maris, Pieter; Vary, James

    2016-09-01

    We present results for p-shell nuclei using interactions derived from chiral effective field theory up to N2LO. The many-body calculations are performed order-by-order in the chiral expansion. We show the dependence of the ground state energies on the chiral order; we also present excitation energies of narrow excited states and other observables such as magnetic and quadrupole moments of selected ground states. We discuss both the theoretical uncertainties due to the truncation of the chiral expansion, as well as the numerical uncertainties associated with the many-body method. Supported by the US DOE Grants DESC0008485 (SciDAC/NUCLEI) and DE-FG02-87ER40371. Computational resources provided by NERSC, supported under US DOE Contract DE-AC02-05CH11231, and by the ALCF, supported under US DOE Contract DE-AC02-06CH11357.

  13. Diverse precerebellar neurons share similar intrinsic excitability

    PubMed Central

    Kolkman, Kristine E.; McElvain, Lauren E.; du Lac, Sascha

    2011-01-01

    The cerebellum dedicates a majority of the brain’s neurons to processing a wide range of sensory, motor, and cognitive signals. Stereotyped circuitry within the cerebellar cortex suggests that similar computations are performed throughout the cerebellum, but little is known about whether diverse precerebellar neurons are specialized for the nature of the information they convey. In vivo recordings indicate that firing responses to sensory or motor stimuli vary dramatically across different precerebellar nuclei, but whether this reflects diverse synaptic inputs or differentially tuned intrinsic excitability has not been determined. We targeted whole-cell patch clamp recordings to neurons in 8 precerebellar nuclei which were retrogradely labeled from different regions of the cerebellum in mice. Intrinsic physiology was compared across neurons in the medial vestibular, external cuneate, lateral reticular, prepositus hypoglossi, supragenual, Roller/intercalatus, reticularis tegmenti pontis (NRTP), and pontine nuclei. Within the firing domain, precerebellar neurons were remarkably similar. Firing faithfully followed temporally modulated inputs, could be sustained at high rates, and was a linear function of input current over a wide range of inputs and firing rates. Pharmacological analyses revealed common expression of Kv3 currents, which were essential for a wide linear firing range, and of SK currents, which were essential for a wide linear input range. In contrast, membrane properties below spike threshold varied considerably within and across precerebellar nuclei, as evidenced by variability in postinhibitory rebound firing. Our findings indicate that diverse precerebellar neurons perfom similar scaling computations on their inputs but may be differentially tuned to synaptic inhibition. PMID:22090493

  14. Survivability and Fusability in Reactions Leading to Heavy Nuclei in the Vicinity of the N = 126 Closed Shell

    SciTech Connect

    Sagaidak, Roman N.

    2009-08-26

    The macroscopic component of fission barriers for Po to Th nuclei around the N = 126 closed neutron shell has been derived within the framework of the analysis of available fission and evaporation residues excitation functions using the conventional barrier passing (fusion) model coupled with the standard statistical model and compared with the predictions of various theoretical models.

  15. Applications of Energy Density Functional Theory to Skin Nuclei and Astrophysical Reactions

    NASA Astrophysics Data System (ADS)

    Tsoneva, N.; Lenske, H.

    2013-03-01

    A theoretical method based on energy-density-functional theory and quasiparticle-phonon model is applied for investigations of low-energy excitations of different multipolarities in stable and exotic nuclei. Of special interest is the possible relation of these modes to neutron or proton skins. From investigations of low-energy dipole and quadrupole states new modes of excitations related to pygmy dipole and pygmy quadrupole resonances of neutron or proton character are identified. The astrophysical relevance of the pygmy resonances is discussed.

  16. Fragmentation of two-phonon {gamma}-vibrational strength in deformed nuclei

    SciTech Connect

    Wu, C.Y.; Cline, D.

    1996-12-31

    Rotational and vibrational modes of collective motion. are very useful in classifying the low-lying excited states in deformed nuclei. The rotational mode of collective motion is characterized by rotational bands having correlated level energies and strongly-enhanced E2 matrix elements. The lowest intrinsic excitation with I,K{sup {pi}} = 2,2{sup +} in even-even deformed nuclei, typically occurring at {approx}1 MeV, is classified as a one-phonon {gamma}-vibration state. In a pure harmonic vibration limit, the expected two-phonon {gamma}-vibration states with I,K{sup {pi}} = 0,0{sup +} and 4,4{sup +} should have excitation energies at twice that of the I,K{sup {pi}} = 2,2{sup +} excitation, i.e. {approx}2 MeV, which usually is above the pairing gap leading to possible mixing with two-quasiparticle configurations. Therefore, the question of the localization of two-phonon {gamma}-vibration strength has been raised because mixing may lead to fragmentation of the two-phonon strength over a range of excitation energy. For several well-deformed nuclei, an assignment of I,K{sup {pi}}=4,4{sup +} states as being two-phonon vibrational excitations has been suggested based on the excitation energies and the predominant {gamma}-ray decay to the I,K{sup {pi}}=2,2{sup +} state. However, absolute B(E2) values connecting the presumed two- and one-phonon states are the only unambiguous measure of double phonon excitation. Such B(E2) data are available for {sup 156}Gd, {sup 160}Dy, {sup 168}Er, {sup 232}Th, and {sup 186,188,190,192}Os. Except for {sup 160}Dy, the measured B(E2) values range from 2-3 Weisskopf units in {sup 156}Gd to 10-20 Weisskopf units in osmium nuclei; enhancement that is consistent with collective modes of motion.

  17. Coulomb excitation of states in 238U

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1994-05-01

    Twenty-two states in 238U have been observed with 18 MeV 4He ions on a thick target. Eight 2 + states between 966 and 1782 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and /or populated by the γ-ray decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.10 to 3.0 W.u. (281 W.u. for the first 2 + state). For the 3 states, the B(E3, 0 → 3 -) values are 7.1, 7.8, and 24.2 W.u. Several of the 2 + states have decay branches to the one-phonon states with B(E2) values between 27 and 56 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if these 2 + states are considered to be collective two-phonon excitations. However, the excitation energies of these 2 + states with respect to the one-phonon states are only 1.3 to 1.6. The B(E1) values for 17 transitions between the positive- and negative-parity states range between 10 -3 and 10 -7 W.u. The B(E1) branching ratios for many of these transitions have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the one-phonon octupole quadruplet in deformed nuclei. The general features of the experimental results for the B(E3) values are reproduced by the microscopic calculations of Neergård and Vogel when the Coriolis coupling between the states of the octupole quadruplet is included.

  18. Coulomb excitation of states in 232Th

    NASA Astrophysics Data System (ADS)

    McGowan, F. K.; Milner, W. T.

    1993-09-01

    Twenty-five states in 232Th have been observed with 18 MeV 4He ions on a thick target. Eleven 2 + states between 774 and 1554 keV and three 3 - states are populated by direct E2 and E3, respectively. The remaining states are either weakly excited by multiple Coulomb excitation and/or populated by the decay of the directly excited states. Spin assignments are based on γ-ray angular distributions. Reduced transition probabilities have been deduced from the γ-ray yields. The B(E2) values for excitation of the 2 + states range from 0.024 to 3.5 W.u. (222 W.u. for the first 2 + state). For the 3 - states, the B(E3,0 → 3 -) values are 1.7, 11, and 24 W.u. A possible two-phonon state at 1554 keV, which is nearly harmonic, decays to four members of the one-phonon states, to the ground-state band, and to the K = 0 - octupole band. The B(E2) value for excitation of this state is 0.66 ± 0.05 W.u. and the B(E1) values for decay of this state are (2 and 6)×10 -4 W.u. The B(E2) values between two- and one-phonon vibrational states range between 16 and 53 W.u. which are an order of magnitude larger than the B(E2) values between the one- and zero-phonon states. This disagrees with our present understanding of collectivity in nuclei if this 2 + state is considered to be a collective two-phonon excitation. The 2 + states at 1477 and 1387 keV, which are also nearly harmonic, are possible candidates with two-phonon structure. The agreement between the experimental results and the microscopic calculations by Neergård and Vogel of the B(E3,0 → 3) for the 3 - members of the one-phonon octupole quadruplet is satisfactory when the Coriolis coupling between the states with K and K ± 1 is included. The B(E1) branching ratios for transitions from the 3 - and 1 - states to the ground-state band have large deviations from the Alaga-rule predictions. These deviations can be understood by the strong Coriolis coupling between the states of the octupole quadruplet in deformed nuclei.

  19. Synthesis of the lightest nuclei

    NASA Astrophysics Data System (ADS)

    Kneller, James Patrick

    The lightest nuclei are principally synthesized either during the first moments of the Universe or as fragments from the spallation of heavier nuclei when Cosmic Rays interact with the Interstellar Medium and this dissertation investigates each in turn. In the first half the predictions from Big Bang Nucleosynthesis are studied when the requirements of only three relativistic neutrino flavors and a small electron neutrino chemical potential are relaxed. The hope that a small, acceptable region for each can be identified is shown to be unfounded because of a degeneracy amongst the parameters. Additional information is required and this may be obtained from the anisotropies in the Cosmic Microwave Background. The estimates of the baryon to photon ratio are shown to be consistent and a relatively well identified value for the number of relativistic neutrino species can be found but with a variance that exhibits a dependency upon the prior assumptions. By imposing a constraint upon the age of the Universe the number of relativistic neutrino species is shown to be <=6 which then yields an limit to the electron neutrino chemical potential of <=0.3. The second is concerned with the kinetics and evolution of Galactic Cosmic Ray Nucleosynthesis. Two approximations are frequently employed in calculations of the production rates: the termination of the reaction expansion at the `One-Step' term and the Straight-Ahead Approximation for the fragment energies. Relaxing the Straight-Ahead Approximation produces minor differences of order 5% but changes of order 10-50% are found when the Two-Step terms in the reaction expansion are included. The two proposed solutions capable of reconciling the theoretical predictions of the evolution of the abundances of these elements with the observations: the possibility of an enriched cosmic ray composition and a modified Oxygen to Iron relation. From the analysis of a simple model it is found that an enriched component greater than >~ 70% is

  20. Effect of nuclear-reaction mechanisms on the population of excited nuclear states and isomeric ratios

    NASA Astrophysics Data System (ADS)

    Skobelev, N. K.

    2016-07-01

    Experimental data on the cross sections for channels of fusion and transfer reactions induced by beams of radioactive halo nuclei and clustered and stable loosely bound nuclei were analyzed, and the results of this analysis were summarized. The interplay of the excitation of single-particle states in reaction-product nuclei and direct reaction channels was established for transfer reactions. Respective experiments were performed in stable (6Li) and radioactive (6He) beams of the DRIBs accelerator complex at the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, and in deuteron and 3He beams of the U-120M cyclotron at the Nuclear Physics Institute, Academy Sciences of Czech Republic (Řež and Prague, Czech Republic). Data on subbarrier and near-barrier fusion reactions involving clustered and loosely bound light nuclei (6Li and 3He) can be described quite reliably within simple evaporation models with allowance for different reaction Q-values and couple channels. In reactions involving halo nuclei, their structure manifests itself most strongly in the region of energies below the Coulomb barrier. Neutron transfer occurs with a high probability in the interactions of all loosely bound nuclei with light and heavy stable nuclei at positive Q-values. The cross sections for such reactions and the respective isomeric ratios differ drastically for nucleon stripping and nucleon pickup mechanisms. This is due to the difference in the population probabilities for excited single-particle states.

  1. Quasielastic knockout of light fragments from {sup 12}C and {sup 16}O nuclei by intermediate-energy pions

    SciTech Connect

    Abramov, B. M.; Borodin, Yu. A.; Bulychjov, S. A.; Dukhovskoy, I. A.; Krutenkova, A. P.; Kulikov, V. V. Martemianov, M. A.; Matsuk, M. A.; Tarasov, V. E.; Turdakina, E. N.; Khanov, A. I.

    2007-07-15

    Quasielastic deuteron and triton knockout from {sup 12}C and {sup 16}O nuclei has been studied infull kinematics using a 0.72-GeV/c pion beam. The momentum distributions of the intranuclear quasideuteron motion, excitation-energy spectra of the residual nuclei, and the effective numbers N{sub d}{sup eff} of quasideuterons are determined. The parameters of the quasideuteron intranuclear motion are in reasonable agreement with the results obtained in other beams. The N{sub d}{sup eff} in the nuclei from {sup 6}Li to {sup 16}O measured in full kinematics are virtually independent of the atomic number in contrast to the analogous values in the inclusive deuteron-knockout reaction induced by protons. The phenomenon of triton knockout from these nuclei is observed, which makes possible estimation of the cross section of backward pion-triton elastic scattering in yet unexplored regions of energy and momentum transfer.

  2. Excitation Energy Deposition and the Fission Process in the Reactions COPPER-63 + MOLYBDENUM-92, 100 AT 10, 17, 25 and 35 Amev and NEON-20 + SAMARIUM-144, 148, 154 AT 20 Amev.

    NASA Astrophysics Data System (ADS)

    Lou, Yunian

    Excitation energy deposition and light particle emission for fissioning nuclei with excitation energies from 2 to 6 MeV/nucleon are studied for the reaction of 20 AMeV ^{20}Ne with ^{144,148,154}Sm and 10, 17, 25 and 35 AMeV ^{63}Cu with ^{92,100}Mo using the Texas A&M Neutron Ball detector. Linear momentum transfers (LMT) are determined from fission fragment folding angle measurements and used to estimate excitation energies. The associated multiplicities of neutrons, protons and alpha particles are obtained, together with their average energies. These data are used to reconstruct the initial excitation energies of the compound nucleus. With increasing beam energy, an increasing discrepancy between the excitation energy derived from the LMT measurements and the reconstructed one is observed attributed to intermediate mass fragment (IMF) emission. The measured neutron multiplicities show a strong increase with increasing neutron to proton ratio of composite system, as well as increasing beam energy. The experimental data for particle multiplicities are compared with calculations using the statistical model GEMINI. The effect of the dynamic fission delay on the light particle multiplicities is explored. The neutron multiplicities are relatively insensitive to the dynamic fission delay. The calculated charged particle multiplicities are more sensitive, but the comparisons between the calculation and experiment indicate that the light charged particle multiplicity data are not a good measure of dynamic fission delay.

  3. Photoconversion of DAPI following UV or violet excitation can cause DAPI to fluoresce with blue or cyan excitation.

    PubMed

    Piterburg, M; Panet, H; Weiss, A

    2012-04-01

    4'-6-Diamidino-2-phenylindole is a fluorescent dye commonly used to visualize deoxyribonucleic acid or cell nuclei in fixed cell preparations, and is often used together with fluorescein or green fluorescent protein, which can be excited without exciting 4'-6-Diamidino-2-phenylindole. It is assumed that when using typical fluorescein or green fluorescent protein filter cubes, 4'-6-Diamidino-2-phenylindole will not be observed. In this paper, we show that following observation of 4'-6-Diamidino-2-phenylindole using UV or violet excitation, it may become sensitive to the blue/cyan excitation used in fluorescein/green fluorescent protein filter cubes. This has serious implications for the use of 4'-6-Diamidino-2-phenylindole together with widely used green fluorophores in double labelling experiments.

  4. Molecular outflows in starburst nuclei

    NASA Astrophysics Data System (ADS)

    Roy, Arpita; Nath, Biman B.; Sharma, Prateek; Shchekinov, Yuri

    2016-12-01

    Recent observations have detected molecular outflows in a few nearby starburst nuclei. We discuss the physical processes at work in such an environment in order to outline a scenario that can explain the observed parameters of the phenomenon, such as the molecular mass, speed and size of the outflows. We show that outflows triggered by OB associations, with NOB ≥ 105 (corresponding to a star formation rate (SFR)≥1 M⊙ yr-1 in the nuclear region), in a stratified disc with mid-plane density n0 ˜ 200-1000 cm-3 and scaleheight z0 ≥ 200(n0/102 cm-3)-3/5 pc, can form molecules in a cool dense and expanding shell. The associated molecular mass is ≥107 M⊙ at a distance of a few hundred pc, with a speed of several tens of km s-1. We show that an SFR surface density of 10 ≤ ΣSFR ≤ 50 M⊙ yr-1 kpc-2 favours the production of molecular outflows, consistent with observed values.

  5. Neurotransmitters of the suprachiasmatic nuclei

    PubMed Central

    Reghunandanan, Vallath; Reghunandanan, Rajalaxmy

    2006-01-01

    There has been extensive research in the recent past looking into the molecular basis and mechanisms of the biological clock, situated in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. Neurotransmitters are a very important component of SCN function. Thorough knowledge of neurotransmitters is not only essential for the understanding of the clock but also for the successful manipulation of the clock with experimental chemicals and therapeutical drugs. This article reviews the current knowledge about neurotransmitters in the SCN, including neurotransmitters that have been identified only recently. An attempt was made to describe the neurotransmitters and hormonal/diffusible signals of the SCN efference, which are necessary for the master clock to exert its overt function. The expression of robust circadian rhythms depends on the integrity of the biological clock and on the integration of thousands of individual cellular clocks found in the clock. Neurotransmitters are required at all levels, at the input, in the clock itself, and in its efferent output for the normal function of the clock. The relationship between neurotransmitter function and gene expression is also discussed because clock gene transcription forms the molecular basis of the clock and its working. PMID:16480518

  6. The morphology of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Keller, H. U.; Jorda, L.

    comets display residual activity or clouds of dust grains around their nuclei. Taking the residual signal into account (mostly using simple models for the brightness distribution) the size estimates of the nuclei could be improved. The (nuclear) magnitude of a comet depends on the product of its albedo and cross-section. Only in a few cases could the albedo and size of a cometary nucleus be separated by additional observation of its thermal emission at infrared wavelengths. By comparison with outer Solar System asteroids Cruikshank et al. (1985) derived a surprisingly low albedo of about 0.04. A value in clear contradiction to the perception of an icy surface but fully confirmed by the first resolved images of a cometary nucleus during the flybys of the Vega and Giotto spacecraft of comet Halley (Sagdeev et al. 1986, Keller et al. 1986). The improvements of radar techniques led to the detection of reflected signals and finally to the derivation of nuclear dimensions and rotation rates. The observations, however, are also model dependent (rotation and size are similarly interwoven as are albedo and size) and sensitive to large dust grains in the vicinity of a nucleus. As an example, Kamoun et al. (1982) determined the radius of comet Encke to 1.5 (2.3, 1.0) km using the spin axis determination of Whipple and Sekanina (1979). The superb spatial resolution of the Hubble Space Telescope (HST) is not quite sufficient to resolve a cometary nucleus. The intensity distribution of the inner coma, however, can be observed and extrapolated toward the nucleus based on models of the dust distribution. If this contribution is subtracted from the central brightness the signal of the nucleus can be derived and hence its product of albedo times cross-section (Lamy and Toth 1995, Rembor 1998, Keller and Rembor 1998; Section 4.3). It has become clear that cometary nuclei are dark, small, often irregular bodies with dimensions ranging from about a kilometre (comet Wirtanen, the target of

  7. The low-energy dipole structure of 232Th , 236U and 238U actinide nuclei

    NASA Astrophysics Data System (ADS)

    Kuliev, A. A.; Guliyev, E.; Ertugral, F.; Özkan, S.

    2010-03-01

    In this study, ensuremath I^{π} = 1+ and ensuremath I^{π} = 1- dipole mode excitations are systematically investigated within the rotational and translational + Galilean invariant quasiparticle random-phase approximation for 232Th , 236U , and 238U actinide nuclei. It is shown that the investigated nuclei reach a B( M1) strength structure, which corresponds to the scissors mode. The calculated mean excitation energies as well as the summed B( M1) value of the scissors mode excitations are consistent with the available experimental data. The results of calculations indicate large differences to the rare-earth nuclei as is the case for the experiment: a doubling of the observed dipole strengths and a shift of the energy centroid to the lower energies by about 800keV. The calculations indicate the presence of a few prominent negative-parity ensuremath K^{π} = 1- states in the 2.0-4.0MeV energy interval. The occurrence of the negative-parity dipole states with the rather high B( E1) value less than 4MeV shows the necessity of explicit parity measurements for the correct determination of the scissors mode strength in 232Th , 236U , and 238U isotopes.

  8. Low-energy dipole modes in unstable nuclei

    NASA Astrophysics Data System (ADS)

    Suzuki, T.; Sagawa, H.

    2001-01-01

    Enhancement of electric dipole (E1) strength at low energy is investigated in light neutron and proton drip-line nuclei with halo or skin by large scale shell model calculations. Large E1 strength are found in low excitation energy region below 5 MeV in 11Li, 12Be and 13O. Both the effects of extended halo or skin wave functions and the coherence in the transition amplitudes are important to enhance the E1 strength. The particle (hole)- vibration coupling model is shown to explain the splitting of the low energy E1 strength in 11Li and 13O. Melting of the shell magicity at N=8 and Z=8 is pointed out. Pigmy resonances in oxygen isotopes are also studied. The pigmy strength below E x = 15 MeV are shown to have about 10 % of the Thomas- Reiche-Kuhn (TRK) sum rule and more than 40 % of the cluster sum rule.

  9. Deformed Brueckner-Hartree-Fock calculation for light nuclei

    NASA Technical Reports Server (NTRS)

    Braley, R. C.; Ford, W. F.; Becker, R. L.; Patterson, M. R.

    1971-01-01

    For the first time the Brueckner-Hartree-Fock (BHF) method was applied to nuclei whose intrinsic structure is nonspherical. One aim was to investigate whether the energy dependent reaction matrix calculated from a realistic nucleon-nucleon interaction leads to deformations similar to, or different from, those obtained from energy independent interactions in Hartree-Fock (HF) calculations. Reaction matrix elements were calculated as a function of starting energy for the Hamada-Johnston interaction, using a Pauli operator appropriate to O-16 and a shifted oscillator spectrum for virtual excited states. Binding energies, single-particle energies, radii, and shape deformations of the intrinsic state in unrenormalized as well as renormalized BHF are discussed and compared with previous HF studies. Results are presented for C-12, O-16, and Ne-20.

  10. Antagonistic otolith-visual units in cat vestibular nuclei

    NASA Technical Reports Server (NTRS)

    Daunton, Nancy G.; Christensen, Carol A.

    1992-01-01

    The nature of neural coding of visual (Vis) and vestibular (Vst) information on translational motion in the region of the vestibular nuclei was investigated using extracellular single-unit recordings in alert adult cats. Responses were recorded and averaged over 60 cycles of stimulation in the vertical and horizontal planes, which included the Vst (movement of the animal in the dark), Vis (movement within lighted visual surround), and combined Vis and Vst (movement of the animal within the lighted stationary visual surround). Data are reported on responses to stimulations along the axis showing maximal sensitivity. A small number of units were identified that showed an antagonistic relationship between their Vis and Vst responses (since they were maximally excited by Vis and by Vst stimulations in the same direction). Results suggest that antagonistic units may belong to an infrequently encountered, but functionally distinct, class of neurons.

  11. Systematic study of iodine nuclei in A∼125 mass region

    SciTech Connect

    Sharma, H. P.; Chakraborty, S.; Kumar, A.; Banerjee, P.; Ganguly, S.; Muralithar, S.; Singh, R. P.; Kumar, A.; Kaur, N.; Kumar, S.; Chaturvedi, L.; Jain, A. K.; Laxminarayan, S.

    2014-08-14

    Excited states of {sup 127}I were populated via {sup 124}Sn({sup 7}Li,{sup 4}nγ){sup 127}I fusion-evaporation reaction at beam energy of 33 MeV. Multipolarities of several transitions were determined and spins of corresponding states have been confirmed. The band-head spin and parity of an already reported band at 2901.2 keV has been confirmed. Based on the observed characteristic features and by comparing with the systematics of odd mass iodine nuclei, a πg{sub 7/2}⊗νh{sub 11/2}{sup 2} configuration has been proposed for this band. The experimental B(M1)/B(E2) values for πg{sub 7/2} band were compared with the theoretical results of semi classical model of Frauendorf and Donau and found in well agreement.

  12. Systematic study of iodine nuclei in A˜125 mass region

    NASA Astrophysics Data System (ADS)

    Sharma, H. P.; Chakraborty, S.; Banerjee, P.; Ganguly, S.; Muralithar, S.; Singh, R. P.; Kumar, A.; Kaur, N.; Kumar, S.; Kumar, A.; Chaturvedi, L.; Jain, A. K.; Laxminarayan, S.

    2014-08-01

    Excited states of 127I were populated via 124Sn(7Li,4nγ)127I fusion-evaporation reaction at beam energy of 33 MeV. Multipolarities of several transitions were determined and spins of corresponding states have been confirmed. The band-head spin and parity of an already reported band at 2901.2 keV has been confirmed. Based on the observed characteristic features and by comparing with the systematics of odd mass iodine nuclei, a πg7/2⊗νh11/22 configuration has been proposed for this band. The experimental B(M1)/B(E2) values for πg7/2 band were compared with the theoretical results of semi classical model of Frauendorf and Donau and found in well agreement.

  13. New high spin states and isomers in the {sup 208}Pb and {sup 207}Pb nuclei

    SciTech Connect

    Broda, R.; Wrzesinski, J.; Pawlat, T.

    1996-12-31

    The two most prominent examples of the heavy doubly closed shell (DCS) nuclei, {sup 208}Pb and {sup 132}Sn, are not accessible by conventional heavy-ion fusion processes populating high-spin states. This experimental difficulty obscured for a long time the investigation of yrast high-spin states in both DCS and neighboring nuclei and consequently restricted the study of the shell model in its most attractive regions. Recent technical development of multidetector gamma arrays opened new ways to exploit more complex nuclear processes which populate the nuclei of interest with suitable yields for gamma spectroscopy and involve population of moderately high spin states. This new possibility extended the range of accessible spin values and is a promising way to reach new yrast states. Some of these states are expected to be of high configurational purity and can be a source of important shell model parameters which possibly can be used later to check the validity of the spherical shell model description at yet higher spin and higher excitation energy. The nuclei in the closest vicinity of {sup 132}Sn are produced in spontaneous fission and states with spin values up to I=14 can be reached in fission gamma spectroscopy studies with the presently achieved sensitivity of gamma arrays. New results on yrast states in the {sup 134}Te and {sup 135}I nuclei populated in fission of the {sup 248}Cm presented at this conference illustrate such application of the resolving power offered by modern gamma techniques.

  14. Theory of two-step two-proton decays of nuclei

    SciTech Connect

    Kadmensky, S. G. Ivankov, Yu. V.

    2014-12-15

    A general theory of many-body diagonal and nondiagonal one-proton decays of spherical and deformed nuclei is developed on the basis of an approach not employing R-matrix theory in describing deep-subbarrier alpha and one-proton decays of nuclei but relying on integral formulas for the widths with respect to these decays. With the aid of this theory and by means of a diagram technique, a formalism is developed for describing two-step two-proton decays of a (Z, A) parent nucleus, which proceed as two successive time-separated one-proton decays of the parent and intermediate [(Z − 1, A − 1)] nuclei, these decays being related by the Green’s function for the intermediate nucleus, G(Z − 1, A − 1). It is shown that, upon taking into account, in this Green’s function, intermediate-nucleus states that are on- and off-shell states for the decaying system, there arise, respectively, sequential and virtual two-proton decays of parent nuclei. Expressions for the widths with respect to sequential and virtual two-proton decays from the ground and excited states of spherical and deformed nuclei and for the angular and energy distributions of emitted protons are obtained.

  15. Separating Cloud Forming Nuclei from Interstitial Aerosol

    SciTech Connect

    Kulkarni, Gourihar R.

    2012-09-12

    It has become important to characterize the physicochemical properties of aerosol that have initiated the warm and ice clouds. The data is urgently needed to better represent the aerosol-cloud interaction mechanisms in the climate models. The laboratory and in-situ techniques to separate precisely the aerosol particles that act as cloud condensation nuclei (CCN) and ice nuclei (IN), termed as cloud nuclei (CN) henceforth, have become imperative in studying aerosol effects on clouds and the environment. This review summarizes these techniques, design considerations, associated artifacts and challenges, and briefly discusses the need for improved designs to expand the CN measurement database.

  16. Empirical moments of inertia of axially asymmetric nuclei

    NASA Astrophysics Data System (ADS)

    Allmond, J. M.; Wood, J. L.

    2017-04-01

    Empirical moments of inertia, J1, J2, J3, of atomic nuclei with E (41+) / E (21+) > 2.7 are extracted from experimental 2g,γ+ energies and electric quadrupole matrix elements, determined from multi-step Coulomb excitation data, and the results are compared to expectations based on rigid and irrotational inertial flow. Only by having the signs of the E2 matrix elements, i.e., <2g+ ‖ M ˆ (E 2) ‖2g+ > and < 0g+ ‖ M ˆ (E 2) ‖2g+ > < 2g+ ‖ M ˆ (E 2) ‖ 2γ+ > <2γ+ ‖ M ˆ (E 2) ‖ 0g+ >, can a unique solution to all three components of the inertia tensor of an asymmetric top be obtained. While the absolute moments of inertia fall between the rigid and irrotational values as expected, the relative moments of inertia appear to be qualitatively consistent with the β2sin2 ⁡ (γ) dependence of the Bohr Hamiltonian which originates from a SO(5) invariance. A better understanding of inertial flow is central to improving collective models, particularly hydrodynamic-based collective models. The results suggest that a better description of collective dynamics and inertial flow for atomic nuclei is needed. The inclusion of vorticity degrees of freedom may provide a path forward. This is the first report of empirical moments of inertia for all three axes and the results should challenge both collective and microscopic descriptions of inertial flow.

  17. Automated seeding-based nuclei segmentation in nonlinear optical microscopy.

    PubMed

    Medyukhina, Anna; Meyer, Tobias; Heuke, Sandro; Vogler, Nadine; Dietzek, Benjamin; Popp, Jürgen

    2013-10-01

    Nonlinear optical (NLO) microscopy based, e.g., on coherent anti-Stokes Raman scattering (CARS) or two-photon-excited fluorescence (TPEF) is a fast label-free imaging technique, with a great potential for biomedical applications. However, NLO microscopy as a diagnostic tool is still in its infancy; there is a lack of robust and durable nuclei segmentation methods capable of accurate image processing in cases of variable image contrast, nuclear density, and type of investigated tissue. Nonetheless, such algorithms specifically adapted to NLO microscopy present one prerequisite for the technology to be routinely used, e.g., in pathology or intraoperatively for surgical guidance. In this paper, we compare the applicability of different seeding and boundary detection methods to NLO microscopic images in order to develop an optimal seeding-based approach capable of accurate segmentation of both TPEF and CARS images. Among different methods, the Laplacian of Gaussian filter showed the best accuracy for the seeding of the image, while a modified seeded watershed segmentation was the most accurate in the task of boundary detection. The resulting combination of these methods followed by the verification of the detected nuclei performs high average sensitivity and specificity when applied to various types of NLO microscopy images.

  18. Mean-field studies of time reversal breaking states in super-heavy nuclei with the Gogny force

    SciTech Connect

    Robledo, L. M.

    2015-10-15

    Recent progress on the description of time reversal breaking (odd mass and multi-quasiparticle excitation) states in super-heavy nuclei within a mean field framework and using several flavors of the Gogny interaction is reported. The study includes ground and excited states in selected odd mass isotopes of nobelium and mendelevium as well as high K isomeric states in {sup 254}No. These are two and four-quasiparticle excitations that are treated in the same self-consistent HFB plus blocking framework as the odd mass states.

  19. Mean-field studies of time reversal breaking states in super-heavy nuclei with the Gogny force

    NASA Astrophysics Data System (ADS)

    Robledo, L. M.

    2015-10-01

    Recent progress on the description of time reversal breaking (odd mass and multi-quasiparticle excitation) states in super-heavy nuclei within a mean field framework and using several flavors of the Gogny interaction is reported. The study includes ground and excited states in selected odd mass isotopes of nobelium and mendelevium as well as high K isomeric states in 254No. These are two and four-quasiparticle excitations that are treated in the same self-consistent HFB plus blocking framework as the odd mass states.

  20. Population of isomeric states in fusion and transfer reactions in beams of loosely bound nuclei near the Coulomb barrier

    SciTech Connect

    Skobelev, N. K.

    2015-07-15

    The influence of the mechanisms of nuclear reactions on the population of {sup 195m}Hg and {sup 197m}Hg(7/2{sup −}), {sup 198m}Tl and {sup 196m}Tl(7{sup +}), and {sup 196m}Au and {sub 198m}Au(12{sup −}) isomeric nuclear states obtained in reactions induced by beams of {sup 3}He, {sup 6}Li, and {sup 6}He weakly bound nuclei is studied. The behavior of excitation functions and high values of isomeric ratios (δ{sub m}/δ{sub g}) for products of nuclear reactions proceeding through a compound nucleus and involving neutron evaporation are explained within statistical models. Reactions in which the emission of charged particles occurs have various isomeric ratios depending on the reaction type. The isomeric ratio is lower in direct transfer reactions involving charged-particle emission than in reactions where the evaporation of charged particles occurs. Reactions accompanied by neutron transfer usually have a lower isomeric ratio, which behaves differently for different direct-reaction types (stripping versus pickup reactions)

  1. Bench-top endomicroscope for visualization and imaging of nuclei using ultraviolet autofluorescence

    NASA Astrophysics Data System (ADS)

    Lin, Bevin

    The long range goal of this research was to develop autofluorescence technology and instrumentation for transition towards an in vivo endomicroscopy imaging system. This approach would provide resolution sufficient to image nuclei for real-time categorization of normal and abnormal tissue implicative of disease progression. Esophageal adenocarcinoma was the chosen model to develop this diagnostic imaging system because the heterogeneous and multifocal nature of this disease makes early diagnosis extremely challenging during the window of time when the prognosis for survival is high. The asymptomatic character of this disease generally presents at a malignant stage when removal of the esophagus has become the standard treatment. The traditional gold standard of histologic diagnosis suffers from a slow turn-around-time from tissue removal to microscopic observation, compounded by error in random biopsy sampling and tissue-processing artifacts, in addition to significant variation in pathologist diagnosis. Optical biopsy has thus been developed to alleviate the problems associated with current standard video endoscopy and histopathology. Following tremendous research in the realm of optical biopsy, some traction has been gained using confocal endomicroscopy. However, current confocal methods require contrast agents and optical sectioning in order to provide images at a cellular level. We have developed a minimally invasive imaging system using autofluorescence that highlights the short photon penetration depth of ultraviolet excitation. This approach provides cellular level resolution with a clinically relevant field of view without requiring contrast agents or optical sectioning. Optical histopathology has been demonstrated using unprocessed ex vivo human gastrointestinal tissues providing diagnostic assessment in real-time, a function imperative for improved patient care and quality of life. This robust bench-top prototype endomicroscopy system is capable of rapid

  2. 8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. POWERHOUSE INTERIOR SHOWING EXCITER No. 1 IN FOREGROUND, EXCITER No. 2., AND GENERATOR UNITS BEHIND EXCITER No. 2 IN BACKGROUND. EXCITER No. 1 GENERATOR HAS A COVER OVER TOP HALF OF COMMUTATOR ELEMENT. VIEW TO NORTHWEST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  3. Fission and Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Hamilton, Joseph H.; Ramayya, A. V.; Carter, H. K.

    2008-08-01

    . Fission-fragment spectroscopy with STEFF / A. G. Smith ... [et al.]. Gamma ray multiplicity of [symbol]Cf spontaneous fission using LiBerACE / D. L. Bleuel ... [et al.]. Excitation energy dependence of fragment mass and total kinetic energy distributions in proton-induced fission of light actinides / I. Nishinaka ... [et al.]. A dynamical calculation of multi-modal nuclear fission / T. Wada and T. Asano. Structure of fission potential energy surfaces in ten-dimensional spaces / V. V. Pashkevich, Y. K Pyatkov and A. V. Unzhakova. A possible enhancement of nuclear fission in scattering with low energy charged particles / V. Gudkov. Dynamical multi-break processes in the [symbol]Sn + [symbol]Ni system at 35 MeV/Nucleon / M. Papa and ISOSPIN-RE VERSE collaboration -- New experimental techniques. MTOF - a high resolution isobar separator for studies of exotic decays / A. Piechaczek ... [et al.]. Development of ORRUBA: a silicon array for the measurement of transfer reactions in inverse kinematics / S. D. Pain ... [et al.]. Indian national gamma array: present & future / R. K. Bhowmik. Absolute intensities of [symbol] rays emitted in the decay of [symbol]U / H. C. Griffin -- Superheavy elements theory and experiments / M. G. Itkis ... [et al.]. Study of superheavy elements at SHIP / S. Hofinann. Heaviest nuclei from [symbol]Ca-induced reactions / Yu. Ts. Oaanessian. Superheavy nuclei and giant nuclear systems / W. Greiner and V. Zagrebaev. Fission approach to alpha-decay of superheavy nuclei / D.N. Poenaru and W. Greiner. Superheavy elements in the Magic Islands / C. Samanta. Relativistic mean field studies of superheavy nuclei / A. V. Afanas jev. Understanding the synthesis of the heaviest nuclei / W. Loveland -- Mass measurements and g-factors. G factor measurements in neutron-rich [symbol]Cf fission fragments, measured using the gammasphere array / R. Orlandi ... [et al.]. Technique for measuring angular correlations and g-factors in neutron rich nuclei produced by the

  4. Where Should the Nuclei Be Located?

    ERIC Educational Resources Information Center

    Ying Liu; Yue Liu; Drew, Michael G. B.

    2005-01-01

    The approach of determining the nature of the electron wave function via orbital representations qualitatively and via numerical calculations quantitatively is demonstrated. The angular part of the wave function provides suitable representation of the positions of the nuclei.

  5. Infrared Observations of Cometary Dust and Nuclei

    NASA Technical Reports Server (NTRS)

    Lisse, Carey

    2004-01-01

    This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

  6. From nucleons to nuclei to fusion reactions

    NASA Astrophysics Data System (ADS)

    Quaglioni, S.; Navrátil, P.; Roth, R.; Horiuchi, W.

    2012-12-01

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  7. A focus on shape coexistence in nuclei

    NASA Astrophysics Data System (ADS)

    Wood, J. L.; Heyde, K.

    2016-02-01

    The present collection of articles focuses on new directions and developments under the title of shape coexistence in nuclei, following our 2011 Reviews of Modern Physics article (K Heyde and J L Wood).

  8. Clusterization and quadrupole deformation in nuclei

    SciTech Connect

    Cseh, J.; Algora, A.; Antonenko, N. V.; Jolos, R. V.; Scheid, W.; Darai, J.; Hess, P. O.

    2006-04-26

    We study the interrelation of the clusterization and quadrupole deformation of atomic nuclei, by applying cluster models. Both the energetic stability and the exclusion principle is investigated. Special attention is paid to the relative orientations of deformed clusters.

  9. ULTRA-RELATIVISTIC NUCLEI: A NEW FRONTIER

    SciTech Connect

    MCLERRAN,L.

    1999-10-29

    The collisions of ultra-relativistic nuclei provide a window on the behavior of strong interactions at asymptotically high energies. They also will allow the authors to study the bulk properties of hadronic matter at very high densities.

  10. From Nucleons To Nuclei To Fusion Reactions

    SciTech Connect

    Quaglioni, S; Navratil, P; Roth, R; Horiuchi, W

    2012-02-15

    Nuclei are prototypes of many-body open quantum systems. Complex aggregates of protons and neutrons that interact through forces arising from quantum chromo-dynamics, nuclei exhibit both bound and unbound states, which can be strongly coupled. In this respect, one of the major challenges for computational nuclear physics, is to provide a unified description of structural and reaction properties of nuclei that is based on the fundamental underlying physics: the constituent nucleons and the realistic interactions among them. This requires a combination of innovative theoretical approaches and high-performance computing. In this contribution, we present one of such promising techniques, the ab initio no-core shell model/resonating-group method, and discuss applications to light nuclei scattering and fusion reactions that power stars and Earth-base fusion facilities.

  11. Parton distributions in nuclei: Quagma or quagmire

    SciTech Connect

    Close, F.E.

    1988-01-01

    The emerging information on the way quark, antiquark, and gluon distributions are modified in nuclei relative to free nucleons is reviewed. Particular emphasis is placed on Drell-Yan and /psi/ production on nuclei and caution against premature use of these as signals for quagma in heavy-ion collisions. If we are to identify the formation of quark-gluon plasma in heavy-ion collisions by changes in the production rates for /psi/ relative to Drell-Yan lepton pairs, then it is important that we first understand the ''intrinsic'' changes in parton distributions in nuclei relative to free nucleons. So, emerging knowledge on how quark, antiquark, and gluon distributions are modified in nuclei relative to free nucleons is reviewed, and the emerging theoretical concensus is briefly summarized.

  12. Possibilities of synthesis of unknown isotopes of superheavy nuclei with charge numbers Z > 108 in asymmetric actinide-based complete fusion reactions

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Adamian, G. G.; Antonenko, N. V.

    2016-10-01

    The possibilities of production of new isotopes of superheavy nuclei with charge numbers Z = 109-114 in various asymmetric hot fusion reactions are studied for the first time. The excitation functions of the formation of these isotopes in the xn evaporation channels are predicted and the optimal conditions for the synthesis are proposed. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of the heaviest nuclei obtained in cold and hot complete fusion reactions.

  13. Fission fragment angular distributions in pre-actinide nuclei

    NASA Astrophysics Data System (ADS)

    Banerjee, Tathagata; Nath, S.; Jhingan, A.; Kaur, Gurpreet; Dubey, R.; Yadav, Abhishek; Laveen, P. V.; Shamlath, A.; Shareef, M.; Gehlot, J.; Saneesh, N.; Prasad, E.; Sugathan, P.; Pal, Santanu

    2016-10-01

    Background: Complete fusion of two nuclei leading to formation of a heavy compound nucleus (CN) is known to be hindered by various fission-like processes, in which the composite system reseparates after capture of the target and the projectile inside the potential barrier. As a consequence of these non-CN fission (NCNF) processes, fusion probability (PCN) starts deviating from unity. Despite substantial progress in understanding, the onset and the experimental signatures of NCNF and the degree of its influence on fusion have not yet been unambiguously identified. Purpose: This work aims to investigate the presence of NCNF, if any, in pre-actinide nuclei by systematic study of fission angular anisotropies and fission cross sections (σfis) in a number of nuclear reactions carried out at and above the Coulomb barrier (VB) . Method: Fission fragment angular distributions were measured for six 28Si-induced reactions involving isotopically enriched targets of 169Tm,176Yb,175Lu,180Hf,181Ta, and 182W leading to probable formation of CN in the pre-actinide region, at a laboratory energy (Elab) range of 129-146 MeV. Measurements were performed with large angular coverage (θlab=41∘ -170∘) in which fission fragments (FFs) were detected by nine hybrid telescope (E -Δ E ) detectors. Extracted fission angular anisotropies and σfis were compared with statistical model (SM) predictions. Results: Barring two reactions involving targets with large non-zero ground state spin (J ) , viz., 175Lu(7/2+) and 181Ta(7/2+) , experimental fission angular anisotropies were found to be higher in comparison with predictions of the statistical saddle point model (SSPM), at Ec .m . near VB. Comparison of present results with those from neighboring systems revealed that experimental anisotropies increasingly deviated from SSPM predictions as one moved from pre-actinide to actinide nuclei. For reactions involving targets with large nonzero J , this deviation was subdued. Comparison between

  14. Study of M1 and E1 excitations by high-resolution proton inelastic scattering measurement at forward angles

    SciTech Connect

    Tamii, A.; Adachi, T.; Hatanaka, K.; Hashimoto, H.; Kaneda, T.; Matsubara, H.; Okamura, H.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Yosoi, M.; Carter, J.; Dozono, M.; Fujita, H.; Fujita, Y.; Itoh, M.; Kawabata, T.; Nakanishi, K.; Sasamoto, Y.; Neumann-Cosel, P. von

    2007-06-13

    Experimental technique for measuring proton inelastic scattering with high-resolution at 295 MeV and at forward angles including zero degrees is described. The method is useful for extracting spin part of the M1 strength via nuclear excitation as well as E1 strength via Coulomb excitation. An excitation energy resolution of 20 keV, good scattering angle resolution, and low background condition have been achieved. The experimental technique was applied for several sd and pf shell nuclei.

  15. Organization of projections from the raphe nuclei to the vestibular nuclei in rats

    NASA Technical Reports Server (NTRS)

    Halberstadt, A. L.; Balaban, C. D.

    2003-01-01

    Previous anatomic and electrophysiological evidence suggests that serotonin modulates processing in the vestibular nuclei. This study examined the organization of projections from serotonergic raphe nuclei to the vestibular nuclei in rats. The distribution of serotonergic axons in the vestibular nuclei was visualized immunohistochemically in rat brain slices using antisera directed against the serotonin transporter. The density of serotonin transporter-immunopositive fibers is greatest in the superior vestibular nucleus and the medial vestibular nucleus, especially along the border of the fourth ventricle; it declines in more lateral and caudal regions of the vestibular nuclear complex. After unilateral iontophoretic injections of Fluoro-Gold into the vestibular nuclei, retrogradely labeled neurons were found in the dorsal raphe nucleus (including the dorsomedial, ventromedial and lateral subdivisions) and nucleus raphe obscurus, and to a minor extent in nucleus raphe pallidus and nucleus raphe magnus. The combination of retrograde tracing with serotonin immunohistofluorescence in additional experiments revealed that the vestibular nuclei receive both serotonergic and non-serotonergic projections from raphe nuclei. Tracer injections in densely innervated regions (especially the medial and superior vestibular nuclei) were associated with the largest numbers of Fluoro-Gold-labeled cells. Differences were observed in the termination patterns of projections from the individual raphe nuclei. Thus, the dorsal raphe nucleus sends projections that terminate predominantly in the rostral and medial aspects of the vestibular nuclear complex, while nucleus raphe obscurus projects relatively uniformly throughout the vestibular nuclei. Based on the topographical organization of raphe input to the vestibular nuclei, it appears that dense projections from raphe nuclei are colocalized with terminal fields of flocculo-nodular lobe and uvula Purkinje cells. It is hypothesized that

  16. Isobar analog states (IAS), double isobar analog states (DIAS), configuration states (CS), and double configuration states (DCS) in halo nuclei. Halo isomers

    NASA Astrophysics Data System (ADS)

    Izosimov, I. N.

    2015-10-01

    It has been shown that IAS, DIAS, CS, and DCS can simultaneously have n-n, n-p, and p-p halo components in their wave functions. Differences in halo structure of the excited and ground states can result in the formation of isomers (halo-isomers). Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei. The structure of the ground and excited states with different isospin quantum number in halo like nuclei is discussed. B(Mλ) and B(Eλ) for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei whose ground state does not exhibit halo structure but the excited state may have one.

  17. Excitability dependent pattern formation

    NASA Astrophysics Data System (ADS)

    Prabhakara, Kaumudi; Gholami, Azam; Bodenschatz, Eberhard

    2014-03-01

    On starvation, the amoebae Dictyostelium discoideum emit the chemo-attractant cyclic adenosine monophosphate (cAMP) at specific frequencies. The neighboring amoebae sense cAMP through membrane receptors and produce their own cAMP. Soon the cells synchronize and move via chemotaxis along the gradient of cAMP. The response of the amoebae to the emission of cAMP is seen as spiral waves or target patterns under a dark field microscope. The causal reasons for the selection of one or the other patterns are still unclear. Here we present a possible explanation based on excitability. The excitability of the amoebae depends on the starvation time because the gene expression changes with starvation. Cells starved for longer times are more excitable. In this work, we mix cells of different excitabilities to study the dependence of the emergent patterns on the excitability. Preliminary results show a transition from spirals to target patterns for specific excitabilities. A phase map of the patterns for different combinations of excitability and number densities is obtained. We compare our findings with numerical simulations of existing theoretical models.

  18. The anatomy of the vestibular nuclei.

    PubMed

    Highstein, Stephen M; Holstein, Gay R

    2006-01-01

    The vestibular portion of the eighth cranial nerve informs the brain about the linear and angular movements of the head in space and the position of the head with respect to gravity. The termination sites of these eighth nerve afferents define the territory of the vestibular nuclei in the brainstem. (There is also a subset of afferents that project directly to the cerebellum.) This chapter reviews the anatomical organization of the vestibular nuclei, and the anatomy of the pathways from the nuclei to various target areas in the brain. The cytoarchitectonics of the vestibular brainstem are discussed, since these features have been used to distinguish the individual nuclei. The neurochemical phenotype of vestibular neurons and pathways are also summarized because the chemical anatomy of the system contributes to its signal-processing capabilities. Similarly, the morphologic features of short-axon local circuit neurons and long-axon cells with extrinsic projections are described in detail, since these structural attributes of the neurons are critical to their functional potential. Finally, the composition and hodology of the afferent and efferent pathways of the vestibular nuclei are discussed. In sum, this chapter reviews the morphology, chemoanatomy, connectivity, and synaptology of the vestibular nuclei.

  19. Major new sources of biological ice nuclei

    NASA Astrophysics Data System (ADS)

    Moffett, B. F.; Hill, T.; Henderson-Begg, S. K.

    2009-12-01

    Almost all research on biological ice nucleation has focussed on a limited number of bacteria. Here we characterise several major new sources of biogenic ice nuclei. These include mosses, hornworts, liverworts and cyanobacteria. Ice nucleation in the eukaryotic bryophytes appears to be ubiquitous. The temperature at which these organisms nucleate is that at which the difference in vapour pressure over ice and water is at or close to its maximum. At these temperatures (-8 to -18 degrees C) ice will grow at the expense of supercooled water. These organisms are dependent for their water on occult precipitation - fog, dew and cloudwater which by its nature is not collected in conventional rain gauges. Therefore we suggest that these organism produce ice nuclei as a water harvesting mechanism. Since the same mechanism would also drive the Bergeron-Findeisen process, and as moss is known to become airborne, these nuclei may have a role in the initiation of precipitation. The properties of these ice nuclei are very different from the well characterised bacterial nuclei. We will also present DNA sequence data showing that, although related, the proteins responsible are only very distantly related to the classical bacterial ice nuclei.

  20. Characteristics of Symmetric and Asymmetric Fission Modes as a Function of the Compound Nucleus Excitation in the Proton-Induced Fission of 233Pa, 239Np and 243Am

    SciTech Connect

    Beresova, M.; Kliman, J.; Krupa, L.; Bogatchev, A. A.; Itkis, I. M.; Itkis, M. G.; Kniajeva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Pokrovsky, I. V.; Dorvaux, O.; Khlebnikov, S.; Lyapin, V.; Rubchenia, W.; Stuttge, L.; Trzaska, W.; Vakhtin, D.

    2007-05-22

    Average preequilibrium average statistical prescission and postscission neutron multiplicities as well as average {gamma}-ray multiplicity , average energy emitted by {gamma}-rays and average energy per one gamma quantum <{epsilon}{gamma}> as a function of mass and total kinetic energy (TKE) of fission fragments were measured in the proton-induced reactions p+232Th{yields}233Pa, p+238U{yields}239Np and p+242Pu{yields}243Am (at proton energy Ep=13, 20, 40 and 55 MeV). The fragment mass and energy distributions (MEDs) have been analyzed in terms of the multimodal fission. The decomposition of the experimental MEDs onto the MEDs of the distinct modes has been fulfilled in the framework of a method that is free from any parameterization of the distinct fission mode mass distribution shapes. The main characteristics for symmetric and asymmetric modes have been studied in their dependence on the compound nucleus composition and proton energy. The manifestation of multimodal fission in average {gamma}-ray multiplicities of fission fragments was also studied in this work.

  1. 15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. POWERHOUSE INTERIOR SHOWING EXCITER No. 2 WITH EXCITER No. 1 BEHIND. OVERHEAD CRANE DANGLES AT TOP OF PHOTO. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Powerhouse Exciters, Rush Creek, June Lake, Mono County, CA

  2. Relativistic mean field models for finite nuclei and neutron stars

    NASA Astrophysics Data System (ADS)

    Chen, Wei-Chia

    In this dissertation we have created theoretical models for finite nuclei, nuclear matter, and neutron stars within the framework of relativistic mean field (RMF) theory, and we have used these models to investigate the elusive isovector sector and related physics, in particular, the neutron-skin thickness of heavy nuclei, the nuclear symmetry energy, and the properties of neutron stars. To build RMF models that incorporate collective excitations in finite nuclei in addition to their ground-state properties, we have extended the non-relativistic sum rule approach to the relativistic domain. This allows an efficient estimate of giant monopole energies. Moreover, we have combined an exact shell-model-like approach with the mean-field calculation to describe pairing correlations in open-shell nuclei. All the ingredients were then put together to establish the calibration scheme. We have also extended the transformation between model parameters and pseudo data of nuclear matter within the RMF context. Performing calibration in this pseudo data space can not only facilitate the searching algorithm but also make the pseudo data genuine model predictions. This calibration scheme is also supplemented by a covariance analysis enabling us to extract the information content of a model, including theoretical uncertainties and correlation coefficients. A series of RMF models subject to the same isoscalar constraints but one differing isovector assumption were then created using this calibration scheme. By comparing their predictions of the nuclear matter equation of state to both experimental and theoretical constraints, we found that a small neutron skin of about 0.16 fm in Pb208 is favored, indicating that the symmetry energy should be soft. To obtain stronger evidence, we proceeded to examine the evolution of the isotopic chains in both oxygen and calcium. Again, it was found that the model with such small neutron skin and soft symmetry energy can best describe both isotopic

  3. Gamma-ray spectroscopy of proton drip-line nuclei

    NASA Astrophysics Data System (ADS)

    Seweryniak, Dariusz

    1998-10-01

    Spectroscopy of nuclei far from the line of stability extends our knowledge of nuclear systems characterized by extreme values of nuclear isospin. The collapse and appearance of magic numbers, the onset of new regions of deformation, new decay modes are predicted for nuclei with exotic isospin composition. Despite continuous progress, the neutron drip-line has not been reached experimentally, but for the light elements. However, modern experimental techniques have made studies of nuclei at the limits of proton stability possible. For example, thanks to recent proton-decay studies, the proton drip-line was almost completely delineated for elements between Z=51 and Z=83(P.J. Woods and C. Davids, Ann. Rev. Nucl. and Part. Sci. 47), 541 (1997). Large arrays of Ge detectors combined with ancillary detectors facilitating reaction channel selection have provided a vast amount of in-beam spectroscopic data across the nuclidic chart. The Recoil-Decay Tagging (RDT) method(R.S. Simon et al., Z. Phys. A325) 197 (1986) and E.S. Paul, P.J. Woods et al., Phys. Rev. C51, 78 (1995), which takes advantage of the high selectivity of alpha- and proton-decay studies, has been particularly successful. GAMMASPHERE coupled with the Fragment Mass Analyzer at the Argonne National Laboratory represents the state-of-the-art system for RDT experiments. Since its commissioning in the beginning of 1998, excited states in many nuclei situated at or even beyond the proton drip-line (ranging from the ^100Sn region through actinide nuclides) were observed. Among others, transitions feeding the ground-state and the isomeric state in the deformed proton emitter ^141Ho(C.N. Davids et al., Phys. Rev. Lett. 80), 1849 (1998) were selected(P.J. Woods et al., private communication). The cross section for populating the isomer is about 50 nb and it represents the weakest channel ever observed in an in-beam experiment. During this talk the Recoil Decay Tagging Method will be introduced and the results

  4. Pure-Phase Selective Excitation in Fast-Relaxing Systems

    NASA Astrophysics Data System (ADS)

    Zangger, Klaus; Oberer, Monika; Sterk, Heinz

    2001-09-01

    Selective pulses have been used frequently for small molecules. However, their application to proteins and other macromolecules has been limited. The long duration of shaped-selective pulses and the short T2 relaxation times in proteins often prohibited the use of highly selective pulses especially on larger biomolecules. A very selective excitation can be obtained within a short time by using the selective excitation sequence presented in this paper. Instead of using a shaped low-intensity radiofrequency pulse, a cluster of hard 90° pulses, delays of free precession, and pulsed field gradients can be used to selectively excite a narrow chemical shift range within a relatively short time. Thereby, off-resonance magnetization, which is allowed to evolve freely during the free precession intervals, is destroyed by the gradient pulses. Off-resonance excitation artifacts can be removed by random variation of the interpulse delays. This leads to an excitation profile with selectivity as well as phase and relaxation behavior superior to that of commonly used shaped-selective pulses. Since the evolution of scalar coupling is inherently suppressed during the double-selective excitation of two different scalar-coupled nuclei, the presented pulse cluster is especially suited for simultaneous highly selective excitation of N-H and C-H fragments. Experimental examples are demonstrated on hen egg white lysozyme (14 kD) and the bacterial antidote ParD (19 kD).

  5. Characterization of biological ice nuclei from a lichen.

    PubMed Central

    Kieft, T L; Ruscetti, T

    1990-01-01

    Biological ice nuclei (active at approximately -4 degrees C) were extracted from cells of the lichen Rhizoplaca chrysoleuca by sonication. Sensitivity to proteases, guanidine hydrochloride, and urea showed these nuclei to be proteinaceous. The nuclei were relatively heat stable, active from pH 1.5 to 12, and active without lipids, thereby demonstrating significant differences from bacterial ice nuclei. PMID:2188965

  6. Geomagnetic excitation of nutation

    NASA Astrophysics Data System (ADS)

    Ron, C.; Vondrák, J.

    2015-08-01

    We tested the hypothesis of Malkin (2013), who demonstrated that the observed changes of Free Core Nutation parameters (phase, amplitude) occur near the epochs of geomagnetic jerks. We found that if the numerical integration of Brzeziński broad-band Liouville equations of atmospheric/oceanic excitations is re-initialized at the epochs of geomagnetic jerks, the agreement between the integrated and observed celestial pole offsets is improved (Vondrák & Ron, 2014). Nevertheless, this approach assumes that the influence of geomagnetic jerks leads to a stepwise change in the position of celestial pole, which is physically not acceptable. Therefore we introduce a simple continuous excitation function that hypothetically describes the influence of geomagnetic jerks, and leads to rapid but continuous changes of pole position. The results of numerical integration of atmospheric/oceanic excitations and this newly introduced excitation are then compared with the observed celestial pole offsets, and prove that the agreement is improved significantly.

  7. Cell and nuclei separation from tissue and from various phases of the cell cycle. Final report

    SciTech Connect

    Pipkin, J.

    1982-05-01

    The Cell Biology laboratory has developed practical methods for routine electrostatic separation of nuclei. Specially designed collection chambers facilitate the capture of sufficient numbers of cells and/or nuclei from precise areas of the cell cycle for biochemical analysis. These analyses include: one- and two-dimensional gel electrophoresis, isoelectric focusing, amino acid analysis and capillary isotachophoretic techniques that are used to demonstrate nuclear regulatory protein synthesis during the in vivo cell cycle after administration of various compounds. Separation of nuclei into homogeneous populations simplifies the detection of biochemical events that transpire in both cycling and non-cycling tissue into more discrete stages for analysis, thus uncluttering the more complex overall picture seen so commonly in generalized proliferating tissue.

  8. TRIFLUOROMETHYL COMPOUNDS OF GERMANIUM

    DTIC Science & Technology

    FLUORIDES, *GERMANIUM COMPOUNDS, *HALIDES, *ORGANOMETALLIC COMPOUNDS, ALKYL RADICALS, ARSENIC COMPOUNDS, CHEMICAL BONDS, CHEMICAL REACTIONS ...CHLORIDES, CHLORINE COMPOUNDS, HYDROLYSIS, IODIDES, METHYL RADICALS, POTASSIUM COMPOUNDS, PYROLYSIS, STABILITY, SYNTHESIS, TIN COMPOUNDS.

  9. The composition of cometary nuclei

    NASA Astrophysics Data System (ADS)

    Brownlee, D. E.

    1989-12-01

    The most detailed information on the elemental and molecular composition of comets was obtained during the 1986 apparition of comet Halley. Although there are uncertainties in the dust/gas ratio and the abundances of several gaseous species, there is a reasonably good understanding of the major composition of the comet. The ice component is dominated by water, and the abundances of CO, H2CO, NH3 and other carbon and nitrogen bearing species are sufficiently low that the carbon and nitrogen are underabundant in the ice relative to solar proportions. These elements are abundant in the dust and it is likely that the cumulative composition of dust plus ice is a reasonably close match to solar abundances for those elements that are carried in compounds that condense at temperatures above 30K.

  10. Search for η' mesic nuclei by missing-mass spectroscopy of the 12C(p,d) reaction

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshiki K.; Ayyad, Yassid; Benlliure, Jose; Brinkmann, Kai-Thomas; Friedrich, Stefan; Fujioka, Hiroyuki; Geissel, Hans; Gellanki, Jnaneswari; Guo, Chenlei; Gutz, Eric; Haettner, Emma; Harakeh, Muhsin N.; Hayano, Ryugo S.; Higashi, Yuko; Hirenzaki, Satoru; Hornung, Christine; Igarashi, Yoichi; Ikeno, Natsumi; Itahashi, Kenta; Iwasaki, Masahiko; Jido, Daisuke; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Knoebel, Ronja; Kurz, Nikolaus; Metag, Volker; Mukha, Ivan; Nagae, Tomofumi; Nagahiro, Hideko; Nanova, Mariana; Nishi, Takahiro; Ong, Hooi Jin; Pietri, Stephane; Prochazka, Andrej; Rappold, Christophe; Reiter, Moritz P.; Rodríguez Sánchez, Jose Luis; Scheidenberger, Christoph; Simon, Haik; Sitar, Branislav; Strmen, Peter; Sun, Baohua; Suzuki, Ken; Szarka, Imrich; Takechi, Maya; Tanihata, Isao; Terashima, Satoru; Watanabe, Yuni N.; Weick, Helmut; Widmann, Eberhard; Winfield, John S.; Xu, Xiaodong; Yamakami, Hiroki; Zhao, Jianwei

    2016-11-01

    We performed a missing-mass spectroscopy experiment of the 12C(p, d) reaction at 2.5 GeV proton energy in order to search for η' mesic nuclei. An excitation-energy spectrum of 11C was obtained around the η' production threshold. As no significant peak structure was observed in the spectrum, upper limits of the formation cross section of η' mesic nuclei have been determined. Preliminary results of the experiment as well as future prospects are given.

  11. Excited State Quantum-Classical Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Krstic, Predrag

    2005-05-01

    The development of a new theoretical, algorithmic, and computational framework is reported describing the corresponding excited state many-body dynamics by applying multiphysics described by classical equations of motion for nuclei and Hartree-Fock/Multi-Configuration Hartree-Fock and multiresolution techniques for solving the quantum part of the problem (i.e. the motion of the electrons). We primarily have in mind reactive and electron-transition dynamics which involves molecular clusters, containing hundreds of atoms, perturbed by a slow ionic/atomic/molecular projectile, with possible applications in plasma-surface interactions, cluster physics, chemistry and biotechnology. The validation of the developed technique is performed at three-body systems. Application to the transition dynamics in small carbon clusters and hydrocarbons perturbed by slow carbon ions resolves some long-standing issues in the ion-surface interactions in fusion tokamaks.

  12. A comparison of {sup 252}Cf and 14-MeV neutron excitation to identify chemical warfare agents by PGNAA

    SciTech Connect

    Caffrey, A.J.; Harlow, B.D.; Edwards, A.J.; Krebs, K.M.; Jones, J.L.; Yoon, W.; Zabriskie, J.M.; Dougan, A.D.

    2000-07-01

    Since 1992, Idaho National Engineering and Environmental Laboratory's portable isotopic neutron spectrometry (PINS) system has been widely used for the nondestructive assessment of munitions suspected to contain chemical warfare agents, such as the nerve agent sarin. PINS is a {sup 252}Cf-based prompt gamma-ray neutron activation analysis (PGNAA) system. The standard PINS system employs a partially moderated 5-{micro}g {sup 252}Cf source emitting 10{sup 7} n/s to excite the atomic nuclei inside the item under test. The chemical elements inside the item are revealed by their characteristic gamma-ray spectrum, measured by a high-resolution high-purity germanium gamma-ray spectrometer. The system computer then infers the fill compound or mixture from the elemental data extracted from the gamma-ray spectrum. Reliable PINS assessments can be completed in as little as 100 s for favorable cases such as white phosphorus smoke munitions, but normally, a 1000 to 3000 live-second counting interval is required. To improve PINS throughput when hundreds or more munitions must be assessed, they are evaluating the possible advantages of 14-MeV neutron excitation over their current radioisotopic source.

  13. Flavanol binding of nuclei from tree species.

    PubMed

    Feucht, W; Treutter, D; Polster, J

    2004-01-01

    Light microscopy was used to examine the nuclei of five tree species with respect to the presence of flavanols. Flavanols develop a blue colouration in the presence of a special p-dimethylaminocinnamaldehyde (DMACA) reagent that enables those nuclei loaded with flavanols to be recognized. Staining of the nuclei was most pronounced in both Tsuga canadensis and Taxus baccata, variable in Metasequoia glyptostroboides, faint in Coffea arabica and minimal in Prunus avium. HPLC analysis showed that the five species contained substantial amounts of different flavanols such as catechin, epicatechin and proanthocyanidins. Quantitatively, total flavanols were quite different among the species. The nuclei themselves, as studied in Tsuga seed wings, were found to contain mainly catechin, much lower amounts of epicatechin and traces of proanthocyanidins. Blue-coloured nuclei located centrally in small cells were often found to maximally occupy up to 90% of a cell's radius, and the surrounding small rim of cytoplasm was visibly free of flavanols. A survey of 34 gymnosperm and angiosperm species indicated that the first group has much higher nuclear binding capacities for flavanols than the second group.

  14. Role of the "window" component of the friction tensor in the formation of superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Liang, Yu-Jie; Zhu, Min; Liu, Zu-Hua; Wang, Wen-Zhong

    2014-03-01

    Formation of superheavy nuclei is greatly hindered by the inner barrier and strong dissipation on the way from the contact point of two colliding nuclei to the compound nucleus configuration. One of the dissipation mechanisms is related to the exchange of particles across the window between two nuclei in relative motion, which is the "window" term in the "wall-plus-window" formula. By means of the dynamic analysis for the symmetric systems Xe132 + Xe132 and Xe136 + Xe136, we have shown that the window component of friction tensor retards the elongation of the fusing composite nucleus, decreases the height of the inner barrier, and hence increases the fusion probability. Therefore, the friction associated with "window" term enhances the formation cross sections of superheavy nuclei. Besides, we have shown the mass difference (in units of the temperature) of the fission and neutron emission saddle points as a function of mass number of the hassium isotopes, which may provide a useful reference for synthesis and study of the nuclei adjacent to the doubly magic nucleus Hs270.

  15. Effects of Ultrasound Pulsing on Neural Excitability

    DTIC Science & Technology

    1988-06-30

    to alter the - excitability of myelinated fibers within the frog sciatic nerve. The magnitude and direction of these changes are critically dependent...on the timing of the burst relative to the electrical stimulus and are different for various fiber types and frog species. These effects cannot be...the ganglion-microelectrode approach in favor of using a compound nerve trunk (the frog sciatic nerve) which cold be stimulated and recorded from

  16. Inclusive breakup of three-fragment weakly bound nuclei

    NASA Astrophysics Data System (ADS)

    Carlson, B. V.; Frederico, T.; Hussein, M. S.

    2017-04-01

    The inclusive breakup of three-fragment projectiles is discussed within a four-body spectator model. Both the elastic breakup and the non-elastic breakup are obtained in a unified framework. Originally developed in the 80's for two-fragment projectiles such as the deuteron, in this paper the theory is successfully generalized to three-fragment projectiles. The expression obtained for the inclusive cross section allows the extraction of the incomplete fusion cross section, and accordingly generalizes the surrogate method to cases such as (t, p) and (t, n) reactions. It is found that two-fragment correlations inside the projectile affect in a conspicuous way the elastic breakup cross section. The inclusive non-elastic breakup cross section is calculated and is found to contain the contribution of a three-body absorption term that is also strongly influenced by the two-fragment correlations. This latter cross section contains the so-called incomplete fusion where more than one compound nuclei are formed. Our theory describes both stable weakly bound three-fragment projectiles and unstable ones such as the Borromean nuclei.

  17. Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the 18O + 232Th reaction

    NASA Astrophysics Data System (ADS)

    Léguillon, R.; Nishio, K.; Hirose, K.; Makii, H.; Nishinaka, I.; Orlandi, R.; Tsukada, K.; Smallcombe, J.; Chiba, S.; Aritomo, Y.; Ohtsuki, T.; Tatsuzawa, R.; Takaki, N.; Tamura, N.; Goto, S.; Tsekhanovich, I.; Petrache, C. M.; Andreyev, A. N.

    2016-10-01

    It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O + 232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation-dissipation model.

  18. Collective and non-collective structures in nuclei of mass region A ≈ 125

    SciTech Connect

    Singh, A. K.; Collaboration: INGA Collaboration; Gammasphere Collaboration

    2014-08-14

    Generation of angular momentum in nuclei is a key question in nuclear structure studies. In single particle model, it is due to alignment of spin of individual nucleon available in the valence space, whereas coherent motion of nucleons are assumed in the collective model. The nuclei near the closed shell at Z = 50 with mass number A ≈ 120-125 represent ideal cases to explore the interplay between these competing mechanisms and the transition from non-collective to collective behavior or vice versa. Recent spectroscopic studies of nuclei in this region reveal several non-collective maximally aligned states representing the first kind of excitation mechanism, where 8-12 particles above the {sup 114}Sn align their spins to generate these states. Deformed rotational bands feeding the non-collective states in the spin range I=20-25 and excitation energies around 10 MeV have also been observed. Structure of the collective and non-collective states are discussed in the framework of Cranked-Nilsson-Strutinsky model.

  19. In-medium similarity renormalization group for closed and open-shell nuclei

    NASA Astrophysics Data System (ADS)

    Hergert, H.

    2017-02-01

    We present a pedagogical introduction to the in-medium similarity renormalization group (IMSRG) framework for ab initio calculations of nuclei. The IMSRG performs continuous unitary transformations of the nuclear many-body Hamiltonian in second-quantized form, which can be implemented with polynomial computational effort. Through suitably chosen generators, it is possible to extract eigenvalues of the Hamiltonian in a given nucleus, or drive the Hamiltonian matrix in configuration space to specific structures, e.g., band- or block-diagonal form. Exploiting this flexibility, we describe two complementary approaches for the description of closed- and open-shell nuclei: the first is the multireference IMSRG (MR-IMSRG), which is designed for the efficient calculation of nuclear ground-state properties. The second is the derivation of non-empirical valence-space interactions that can be used as input for nuclear shell model (i.e., configuration interaction (CI)) calculations. This IMSRG+shell model approach provides immediate access to excitation spectra, transitions, etc, but is limited in applicability by the factorial cost of the CI calculations. We review applications of the MR-IMSRG and IMSRG+shell model approaches to the calculation of ground-state properties for the oxygen, calcium, and nickel isotopic chains or the spectroscopy of nuclei in the lower sd shell, respectively, and present selected new results, e.g., for the ground- and excited state properties of neon isotopes.

  20. Structure and spectroscopy of transcurium nuclei.

    SciTech Connect

    Ahmad, I.

    2001-11-09

    The stability of the superheavy elements depends on the shell corrections which are governed by the single-particle spectra. Ideally one would like to experimentally determine the single-particle levels in the superheavy nuclei but the production of only a few atoms of these nuclides precludes such measurements. One therefore has to identify single-particle levels in the heaviest nuclei which are available in at least nanoCurie amounts. They have studied the structure of such heavy nuclei in the Z=98 region and identified many single-particle states. In particular, they have studied the structure of {sup 251}Cf and {sup 249}Bk by measuring the radiations emitted in the {alpha} decay of {sup 255}Fm and {sup 253}Es. These single-particle spectra can be used to test theoretical models for superheavy elements.

  1. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Excitation of nuclear isomers by X rays from laser plasma

    NASA Astrophysics Data System (ADS)

    Andreev, Aleksandr A.; Platonov, Konstantin Yu; Rozhdestvenskii, Yu V.; Karpeshin, F.; Trzhaskovskaya, M. B.

    2010-06-01

    The possibility of obtaining isomer nuclei is studied by the example of the molybdenum isomer 93Mo upon irradiation of a niobium 93Nb target by ~50-J, 100-fs laser pulses. It is shown that the modern laser technique allows production of isomer nuclei by accelerated protons and radiative de-excitation of isomer nuclear states by thermal or line X-rays from laser plasma.

  2. Adiabatic fission barriers in superheavy nuclei

    NASA Astrophysics Data System (ADS)

    Jachimowicz, P.; Kowal, M.; Skalski, J.

    2017-01-01

    Using the microscopic-macroscopic model based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy, we calculated static fission barriers Bf for 1305 heavy and superheavy nuclei 98 ≤Z ≤126 , including even-even, odd-even, even-odd and odd-odd systems. For odd and odd-odd nuclei, adiabatic potential-energy surfaces were calculated by a minimization over configurations with one blocked neutron or/and proton on a level from the 10th below to the 10th above the Fermi level. The parameters of the model that have been fixed previously by a fit to masses of even-even heavy nuclei were kept unchanged. A search for saddle points has been performed by the "imaginary water flow" method on a basic five-dimensional deformation grid, including triaxiality. Two auxiliary grids were used for checking the effects of the mass asymmetry and hexadecapole nonaxiality. The ground states (g.s.) were found by energy minimization over configurations and deformations. We find that the nonaxiality significantly changes first and second fission saddle in many nuclei. The effect of the mass asymmetry, known to lower the second, very deformed saddles in actinides, in the heaviest nuclei appears at the less deformed saddles in more than 100 nuclei. It happens for those saddles in which the triaxiality does not play any role, which suggests a decoupling between effects of the mass asymmetry and triaxiality. We studied also the influence of the pairing interaction strength on the staggering of Bf for odd- and even-particle numbers. Finally, we provide a comparison of our results with other theoretical fission barrier evaluations and with available experimental estimates.

  3. Towards automated segmentation of cells and cell nuclei in nonlinear optical microscopy.

    PubMed

    Medyukhina, Anna; Meyer, Tobias; Schmitt, Michael; Romeike, Bernd F M; Dietzek, Benjamin; Popp, Jürgen

    2012-11-01

    Nonlinear optical (NLO) imaging techniques based e.g. on coherent anti-Stokes Raman scattering (CARS) or two photon excited fluorescence (TPEF) show great potential for biomedical imaging. In order to facilitate the diagnostic process based on NLO imaging, there is need for an automated calculation of quantitative values such as cell density, nucleus-to-cytoplasm ratio, average nuclear size. Extraction of these parameters is helpful for the histological assessment in general and specifically e.g. for the determination of tumor grades. This requires an accurate image segmentation and detection of locations and boundaries of cells and nuclei. Here we present an image processing approach for the detection of nuclei and cells in co-registered TPEF and CARS images. The algorithm developed utilizes the gray-scale information for the detection of the nuclei locations and the gradient information for the delineation of the nuclear and cellular boundaries. The approach reported is capable for an automated segmentation of cells and nuclei in multimodal TPEF-CARS images of human brain tumor samples. The results are important for the development of NLO microscopy into a clinically relevant diagnostic tool.

  4. VIBRATIONALLY EXCITED HCN IN THE LUMINOUS INFRARED GALAXY NGC 4418

    SciTech Connect

    Sakamoto, Kazushi; Aalto, Susanne; Evans, Aaron S.; Wiedner, Martina C.; Wilner, David J.

    2010-12-20

    Infrared pumping and its effect on the excitation of HCN molecules can be important when using rotational lines of HCN to probe dense molecular gas in galaxy nuclei. We report the first extragalactic detection of (sub)millimeter rotational lines of vibrationally excited HCN, in the dust-enshrouded nucleus of the luminous infrared galaxy NGC 4418. We estimate the excitation temperature of T{sub vib} {approx} 230 K between the vibrational ground and excited (v{sub 2} = 1) states. This excitation is most likely due to infrared radiation. At this high vibrational temperature the path through the v{sub 2} = 1 state must have a strong impact on the rotational excitation in the vibrational ground level, although it may not be dominant for all rotational levels. Our observations also revealed nearly confusion-limited lines of CO, HCN, HCO{sup +}, H{sup 13}CN, HC{sup 15}N, CS, N{sub 2}H{sup +}, and HC{sub 3}N at {lambda} {approx} 1 mm. Their relative intensities may also be affected by the infrared pumping.

  5. Constraining nucleon high momentum in nuclei

    NASA Astrophysics Data System (ADS)

    Yong, Gao-Chan

    2017-02-01

    Recent studies at Jefferson Lab show that there are a certain proportion of nucleons in nuclei have momenta greater than the so-called nuclear Fermi momentum pF. Based on the transport model of nucleus-nucleus collisions at intermediate energies, nucleon high momentum caused by the neutron-proton short-range correlations in nuclei is constrained by comparing with π and photon experimental data and considering some uncertainties. The high momentum cutoff value pmax ≤ 2pF is obtained.

  6. Structure of neutron-rich nuclei

    SciTech Connect

    Nazarewicz, W. ||

    1997-11-01

    One of the frontiers of today`s nuclear science is the ``journey to the limits``: of atomic charge and nuclear mass, of neutron-to-proton ratio, and of angular momentum. The new data on exotic nuclei are expected to bring qualitatively new information about the fundamental properties of the nucleonic many-body system, the nature of the nuclear interaction, and nucleonic correlations at various energy-distance scales. In this talk, current developments in nuclear structure of neutron-rich nuclei are discussed from a theoretical perspective.

  7. Clathrate hydrates in cometary nuclei and porosity

    NASA Technical Reports Server (NTRS)

    Smoluchowski, R.

    1988-01-01

    Possible mechanisms of formation and decomposition of CO2-clathrate hydrate in cometary nuclei are discussed. As far as it is known, this is the only clathrate hydrate which is unstable at low temperatures. Calculation shows that, in accord with other evidence, neither volume nor grain boundary diffusion in the clathrate lattice can be responsible for the rate of these reactions and that a surface mechanism with the attendant sensitivity to pressure must play a crucial role. Density changes accompanying CO2-clathrate decomposition and formation can lead to microporosity and enhanced brittleness or even to fracture of cometary nuclei at low temperatures. Other clathrate hydrates and mixed clathrates are also discussed.

  8. Computer Model Of Fragmentation Of Atomic Nuclei

    NASA Technical Reports Server (NTRS)

    Wilson, John W.; Townsend, Lawrence W.; Tripathi, Ram K.; Norbury, John W.; KHAN FERDOUS; Badavi, Francis F.

    1995-01-01

    High Charge and Energy Semiempirical Nuclear Fragmentation Model (HZEFRG1) computer program developed to be computationally efficient, user-friendly, physics-based program for generating data bases on fragmentation of atomic nuclei. Data bases generated used in calculations pertaining to such radiation-transport applications as shielding against radiation in outer space, radiation dosimetry in outer space, cancer therapy in laboratories with beams of heavy ions, and simulation studies for designing detectors for experiments in nuclear physics. Provides cross sections for production of individual elements and isotopes in breakups of high-energy heavy ions by combined nuclear and Coulomb fields of interacting nuclei. Written in ANSI FORTRAN 77.

  9. African Dust Aerosols as Atmospheric Ice Nuclei

    NASA Technical Reports Server (NTRS)

    DeMott, Paul J.; Brooks, Sarah D.; Prenni, Anthony J.; Kreidenweis, Sonia M.; Sassen, Kenneth; Poellot, Michael; Rogers, David C.; Baumgardner, Darrel

    2003-01-01

    Measurements of the ice nucleating ability of aerosol particles in air masses over Florida having sources from North Africa support the potential importance of dust aerosols for indirectly affecting cloud properties and climate. The concentrations of ice nuclei within dust layers at particle sizes below 1 pn exceeded 1/cu cm; the highest ever reported with our device at temperatures warmer than homogeneous freezing conditions. These measurements add to previous direct and indirect evidence of the ice nucleation efficiency of desert dust aerosols, but also confirm their contribution to ice nuclei populations at great distances from source regions.

  10. Light nuclei from chiral EFT interactions

    NASA Astrophysics Data System (ADS)

    Navrátil, P.; Gueorguiev, V. G.; Vary, J. P.; Ormand, W. E.; Nogga, A.; Quaglioni, S.

    2008-12-01

    Recent developments in nuclear theory allow us to make a connection between quantum chromodynamics (QCD) and low-energy nuclear physics. First, chiral effective field theory (χEFT) provides a natural hierarchy to define two-nucleon ( NN), three-nucleon ( NNN), and even four-nucleon interactions. Second, ab-initio methods have been developed capable to test these interactions for light nuclei. In this contribution, we discuss ab-initio no-core shell-model (NCSM) calculations for s-shell and p-shell nuclei with NN and NNN interactions derived within χEFT.

  11. Photochemical transformations of diazocarbonyl compounds: expected and novel reactions

    NASA Astrophysics Data System (ADS)

    Galkina, O. S.; Rodina, L. L.

    2016-05-01

    Photochemical reactions of diazocarbonyl compounds are well positioned in synthetic practice as an efficient method for ring contraction and homologation of carboxylic acids and as a carbene generation method. However, interpretation of the observed transformations of diazo compounds in electronically excited states is incomplete and requires a careful study of the fine mechanisms of these processes specific to different excited states of diazo compounds resorting to modern methods of investigation, including laser technology. The review is devoted to analysis of new data in the chemistry of excited states of diazocarbonyl compounds. The bibliography includes 155 references.

  12. Excitation Methods for Bridge Structures

    SciTech Connect

    Farrar, C.R.; Duffy, T.A.; Cornwell, P.J.; Doebling, S.W.

    1999-02-08

    This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.

  13. Fission and Properties of Neutron-Rich Nuclei - Proceedings of the Second International Conference

    NASA Astrophysics Data System (ADS)

    Hamilton, J. H.; Phillips, W. R.; Carter, H. K.

    Long Range Alpha Emission Probabilities in the Thermal and Resonance for 239Pu * Spectroscopy of Selected Fission Fragments * Gamma-Ray Spectra of Individual Fission Products * Gamma Spectroscopy of the Transfermium Nucleus Nobelium-254 * Summary of the Yield Values from Fast Fission of 233U Measured of Studsvik * Decay Studies of Neutron-Rich Isotopes Produced in Proton-Induced Fission of Actinides * Understanding of the Fission Process From the Deformation Properties of Fissioning Nuclei * Heavy Clusterization in 252Cf: An Application of the U(3) Selection Rule * Synthesis of Superheavy Elements with Three-Dimensional Fluctuation-Dissipation Dynamical Model * Asymmetric Fission Along Nuclear Lattice Planes * Experimental Study of Correlations Between Fission Neutron Multiplicity, Mass and Kinetic Energy of Fission Fragments From Spontaneous Fission of 252Cf, 244Cm and 248Cm * Super- and Hyper-Deformed Isomeric States and Long-Lived Superheavy Elements * Systematic Investigation of the Neutron Induced Fission Reaction 235, 238U and 237Np below 6 MeV * Studying Iso-chains with RNBs * Cold Fission Studies with Large Detector Arrays * Single-Particle States in Transcurium Nuclei * Shell Effects and Fission of Superheavy Nuclei at Low Excitation Energies * Experiments on the Synthesis of Superheavy Nuclei in 48Ca-Induced Reactions * GSI Experiments on the Synthesis of Superheavy Elements - Results and Plans for the Future * Spectroscopy of Refractory Fission Products at IGISOL * Ternary Fission Induced by Polarized Neutrons * Neutron Decay of Ternary Particles in Spontaneous Fission of 252Cf * New Fission Modes * Alpha Clustering and Ternary Fission * Interplay of Fusion and Fission Dynamics * Applications of the Hartree Bogoliubov Model to Nuclei with Large Isospin Values * Structure of Neutron-Rich Pd Isotopes * Systematic Studies of Fission Saddle-Point Shapes and Their Relation to the Maxima of the Fission-Fragment Mass and Kinetic-Energy Distributions * Limits of

  14. Correlations in Nuclei: Recent Progress on an Old Problem

    NASA Astrophysics Data System (ADS)

    Schiavilla, Rocco

    2007-10-01

    The two preeminent features of the nucleon-nucleon (NN) interaction are its short-range repulsion and intermediate- to long-range tensor character. These induce strong spatial-spin-isospin NN correlations, which leave their imprint on the structure of ground- and excited-state wave functions. In the present talk I will review how these features influence a variety of nuclear properties---from energy spectra of low-lying states to two-nucleon density distributions to nuclear response functions---as well as the experimental evidence in support of their presence. In particular, I will show [R. Schiavilla, R.B. Wiringa, S.C. Pieper, and J.Carlson, Phys. Rev. Lett. 98, 132501 (2007)] how tensor correlations impact the momentum distribution of np pairs in the ground state of nuclei and make it orders of magnitude larger than that of pp pairs for values of the relative momentum in the range (300--600) MeV/c and vanishing total momentum. This order-of-magnitude difference is seen in all nuclei considered, and has a universal character originating from the tensor components present in any realistic NN interaction. It should be easily observable in two-nucleon knock-out processes. Indeed, a preliminary analysis of (e,e^'np) and (e,e^'pp) reactions in ^12C finds [R. Subedi et al., in preparation] that the pp cross section is suppressed relative to the np by a factor ˜10 in kinematics close to back-to-back emission of the two nucleons.

  15. Spin waves and magnetic excitations

    SciTech Connect

    Borovik-Romanov, A.S.; Sinha, S.K.

    1988-01-01

    This book describes both simple spin waves (magnons) and complicated excitations in magnetic systems. The following subjects are covered: - various methods of magnetic excitation investigations such as neutron scattering on magnetic excitations, spin-wave excitation by radio-frequency, power light scattering on magnons and magnetic excitation observation within the light-absorption spectrum; - oscillations of magnetic electron systems coupled with phonons, nuclear spin systems and localized impurity modes: - low-dimensional magnetics, amorphous magnetics and spin glasses.

  16. A primer on rotational collective enhancements in even-even nuclei

    SciTech Connect

    Younes, W

    2004-07-15

    The enhancement of the level density for deformed nuclei relative to the level density in spherical nuclei is calculated. The qualitative behavior of the enhancement factor as a function of excitation energy is explained, and a prescription for a more quantitative description of this behavior is suggested. The results presented here can be found elsewhere in the literature, however the treatments of this topic are dispersed in the literature, are often terse, and require some familiarity with disparate branches of physics. The emphasis of this paper is on step-by-step derivations of the physics and mathematics used in the calculation of level densities and rotational enhancement factors. Pertinent techniques from thermodynamics and group theory are introduced. Appendices provide detailed introductions to the principal mathematical tools.

  17. Study of neutron-rich nuclei near doubly magic 132Sn

    NASA Astrophysics Data System (ADS)

    Sarkar, M. Saha; Sarkar, S.

    2012-06-01

    Large basis untruncated shell-model (SM) calculations have been done for nuclei with 50 ≤Z ≤56 and 82 ≤ N ≤ 88 in the π(gdsh) ⊗ ν (hf pi) valence space above the 132Sn core using both realistic CWG and empirical SMPN (1+2)-body Hamiltonians. These neutronrich nuclei lie on or close to the path of astrophysical r-process flow. Reasons behind the similarity and dissimilarity between the results using these two interactions have been discussed. The observation and prediction of unusually depressed first excited 2+1 states in even-A semi-magic Sn isotopes having N =84-88 and the possibility of a new magic number at N = 90 above 132Sn provide motivations for reviewing the problems related to the nuclear astrophysics in general.

  18. Effective field theory of emergent symmetry breaking in deformed atomic nuclei

    SciTech Connect

    Papenbrock, Thomas F.; Weidenmüller, H. A.

    2015-09-03

    Spontaneous symmetry breaking in non-relativistic quantum systems has previously been addressed in the framework of effective field theory. Low-lying excitations are constructed from Nambu–Goldstone modes using symmetry arguments only. In this study, we extend that approach to finite systems. The approach is very general. To be specific, however, we consider atomic nuclei with intrinsically deformed ground states. The emergent symmetry breaking in such systems requires the introduction of additional degrees of freedom on top of the Nambu–Goldstone modes. Symmetry arguments suffice to construct the low-lying states of the system. Lastly, in deformed nuclei these are vibrational modes each of which serves as band head of a rotational band.

  19. Effective field theory of emergent symmetry breaking in deformed atomic nuclei

    DOE PAGES

    Papenbrock, Thomas F.; Weidenmüller, H. A.

    2015-09-03

    Spontaneous symmetry breaking in non-relativistic quantum systems has previously been addressed in the framework of effective field theory. Low-lying excitations are constructed from Nambu–Goldstone modes using symmetry arguments only. In this study, we extend that approach to finite systems. The approach is very general. To be specific, however, we consider atomic nuclei with intrinsically deformed ground states. The emergent symmetry breaking in such systems requires the introduction of additional degrees of freedom on top of the Nambu–Goldstone modes. Symmetry arguments suffice to construct the low-lying states of the system. Lastly, in deformed nuclei these are vibrational modes each of whichmore » serves as band head of a rotational band.« less

  20. Gamow-Teller Transitions in Stable and Unstable pf-shell Nuclei

    SciTech Connect

    Fujita, Y.; Rubio, B.; Gelletly, W.

    2008-11-11

    Gamow-Teller (GT) transitions starting from stable as well as unstable pf-shell nuclei are of interest not only in nuclear physics, but also in astrophysics, e.g. in violent neutrino-induced reactions at the core-collapse stage of type II supernovae. In the {beta}-decay study of these pf-shell nuclei, half-lives can be measured rather accurately. On the other hand, in high-resolution ({sup 3}He,t) charge-exchange reactions at 0 deg., individual GT transitions up to high excitations can be studied. Assuming the isospin symmetry for the strengths of T{sub z} = {+-}1{yields}0 analogous GT transitions, we present a unique 'merged analysis' for the determination of absolute B(GT) values. This method can be applied not only to T = 1 systems, but also to higher T systems.

  1. A Lane consistent optical model potential for nucleon scattering on actinide nuclei with extended coupling

    NASA Astrophysics Data System (ADS)

    Quesada, José Manuel; Capote, Roberto; Soukhovitski, Efrem S.; Chiba, Satoshi

    2016-03-01

    An extension for odd-A actinides of a previously derived dispersive coupledchannel optical model potential (OMP) for 238U and 232Th nuclei is presented. It is used to fit simultaneously all the available experimental databases including neutron strength functions for nucleon scattering on 232Th, 233,235,238U and 239Pu nuclei. Quasi-elastic (p,n) scattering data on 232Th and 238U to the isobaric analogue states of the target nucleus are also used to constrain the isovector part of the optical potential. For even-even (odd) actinides almost all low-lying collective levels below 1 MeV (0.5 MeV) of excitation energy are coupled. OMP parameters show a smooth energy dependence and energy independent geometry.

  2. Variational and Green`s function Monte Carlo calculations of few-body nuclei

    SciTech Connect

    Wiringa, R.B.; Carlson, J.; Pandharipande, V.R.; Pudliner, B.S.

    1995-08-01

    We performed an extensive series of variational Monte Carlo (VMC) and Green`s Function Monte Carlo (GFMC) calculations for few-body nuclei using a Hamiltonian, H, containing the new Argonne v{sub 18} NN interaction supplemented by a model three-nucleon (3N) potential. These calculations include the ground state binding energy of {sup 3}H, {sup 3}He, {sup 4}He, {sup 6}He, {sup 6}Li and {sup 6}Be, low-lying excited states in the A = 6 nuclei, and scattering states of {sup 5}He. The variational wave functions, {Psi}{sub v}(R), include central, spin, isospin, tensor, and spin-orbit two- and three-body correlations. These trial functions give upper bounds to the ground-state binding energy {approximately}2% above exact GFMC calculations in {sup 3}H and {sup 4}He.

  3. Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach

    SciTech Connect

    Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E.; Tretyakova, T. Yu.

    2015-12-15

    Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.

  4. Possibilities of production of transfermium nuclei in charged-particle evaporation channels

    NASA Astrophysics Data System (ADS)

    Hong, Juhee; Adamian, G. G.; Antonenko, N. V.

    2016-10-01

    The possibilities of direct production of the isotopes of transfermium nuclei Md,260259, No,261260, Lr-264261, Rf,265264, Db-268264, Sg-269266, Bh-271266, Hs-274267, and Mt-274270 in various asymmetric hot fusion-evaporation reactions are studied. The excitation functions of the formation of these isotopes in the α x n and p x n evaporation channels are predicted for the first time. The optimal reaction partners and conditions for the synthesis of new isotopes are suggested. The products of the suggested reactions can fill a gap of unknown isotopes between the isotopes of heaviest nuclei obtained in the x n evaporation channels of the cold and hot complete fusion reactions.

  5. Studies of the shapes of heavy pear-shaped nuclei at ISOLDE

    NASA Astrophysics Data System (ADS)

    Butler, P. A.

    2016-07-01

    For certain combinations of protons and neutrons there is a theoretical expectation that the shape of nuclei can assume octupole deformation, which would give rise to reflection asymmetry or a "pear-shape" in the intrinsic frame, either dynamically (octupole vibrations) or statically (permanent octupole deformation). I will briefly review the historic evidence for reflection asymmetry in nuclei and describe how recent experiments carried out at REX-ISOLDE have constrained nuclear theory and how they contribute to tests of extensions of the Standard Model. I will also discuss future prospects for measuring nuclear shapes from Coulomb Excitation: experiments are being planned that will exploit beams from HIE-ISOLDE that are cooled in the TSR storage ring and injected into a solenoidal spectrometer similar to the HELIOS device developed at the Argonne National Laboratory.

  6. Proteins of Excitable Membranes

    PubMed Central

    Nachmansohn, David

    1969-01-01

    Excitable membranes have the special ability of changing rapidly and reversibly their permeability to ions, thereby controlling the ion movements that carry the electric currents propagating nerve impulses. Acetylcholine (ACh) is the specific signal which is released by excitation and is recognized by a specific protein, the ACh-receptor; it induces a conformational change, triggering off a sequence of reactions resulting in increased permeability. The hydrolysis of ACh by ACh-esterase restores the barrier to ions. The enzymes hydrolyzing and forming ACh and the receptor protein are present in the various types of excitable membranes. Properties of the two proteins directly associated with electrical activity, receptor and esterase, will be described in this and subsequent lectures. ACh-esterase has been shown to be located within the excitable membranes. Potent enzyme inhibitors block electrical activity demonstrating the essential role in this function. The enzyme has been recently crystallized and some protein properties will be described. The monocellular electroplax preparation offers a uniquely favorable material for analyzing the properties of the ACh-receptor and its relation to function. The essential role of the receptor in electrical activity has been demonstrated with specific receptor inhibitors. Recent data show the basically similar role of ACh in the axonal and junctional membranes; the differences of electrical events and pharmacological actions are due to variations of shape, structural organization, and environment. PMID:19873642

  7. Positron excitation of neon

    NASA Technical Reports Server (NTRS)

    Parcell, L. A.; Mceachran, R. P.; Stauffer, A. D.

    1990-01-01

    The differential and total cross section for the excitation of the 3s1P10 and 3p1P1 states of neon by positron impact were calculated using a distorted-wave approximation. The results agree well with experimental conclusions.

  8. Neutron-antineutron oscillations in nuclei

    SciTech Connect

    Dover, C.B.; Gal, A.; Richard, J.M.; Hebrew Univ., Jerusalem . Racah Inst. of Physics; Grenoble-1 Univ., 38 . Inst. des Sciences Nucleaires)

    1989-01-01

    We briefly review the state of the art for extracting the period of neutron-antineutron oscillations from the lifetime of nuclei. The most recent data on nuclear stability provide a limit of 10{sup 8} s for the oscillation period. 13 refs.

  9. Four-Body Correlations in Nuclei

    NASA Astrophysics Data System (ADS)

    Sambataro, M.; Sandulescu, N.

    2015-09-01

    Low-energy spectra of 4 n nuclei are described with high accuracy in terms of four-body correlated structures ("quartets"). The states of all N ≥Z nuclei belonging to the A =24 isobaric chain are represented as a superposition of two-quartet states, with quartets being characterized by isospin T and angular momentum J . These quartets are assumed to be those describing the lowest states in 20Ne (Tz=0 ), 20F (Tz=1 ), and 20O (Tz=2 ). We find that the spectrum of the self-conjugate nucleus 24Mg can be well reproduced in terms of T =0 quartets only and that, among these, the J =0 quartet plays by far the leading role in the structure of the ground state. The same conclusion is drawn in the case of the three-quartet N =Z nucleus 28Si. As an application of the quartet formalism to nuclei not confined to the s d shell, we provide a description of the low-lying spectrum of the proton-rich 92Pd. The results achieved indicate that, in 4 n nuclei, four-body degrees of freedom are more important and more general than usually expected.

  10. Precision lifetime measurements in light exotic nuclei

    NASA Astrophysics Data System (ADS)

    McCutchan, Elizabeth

    2017-01-01

    A new generation of ab-initio calculations, based on realistic two- and three-body forces have had a profound impact on our understanding of nuclei. They have shed light on topics such as the origin of effective forces (like spin-orbit and tensor interactions) and the mechanisms behind cluster and pairing correlations. New precise data are required to both better parameterize the three body forces and to improve numerical methods. A sensitive probe of the structure of light nuclei comes from their electromagnetic transition rates. A refined Doppler Shift Attenuation Method (DSAM) will be outlined which is used to precisely measure lifetimes in light nuclei and helps to reduce and quantity systematic uncertainties in the measurement. Using this careful DSAM, we have made a series of precise measurements of electromagnetic transition strengths in Li isotopes, A =10 nuclei, and the exotic halo nucleus, 12Be. Various phenomena, such as alpha clustering and meson-exchange currents, can be investigated in these seemingly simple systems, while the collection of data spanning stable to neutron-rich, allows us to probe the influence of additional valence neutrons. This talk will report on what has been learned, and the challenges that lie in the future, both in experiment and theory, as we push to describing and measuring even more exotic systems. Work supported by the Office of Nuclear Physics, Office of Science of the U.S. Department of Energy under contract No. DE-AC02-98CH10886.

  11. Quasars: Active nuclei of young galaxies

    NASA Technical Reports Server (NTRS)

    Komberg, B. V.

    1980-01-01

    The hypothetical properties of 'young' galaxies and possible methods of observing them are discussed. It is proposed that star formation first takes place in the central regions of protogalaxies which may appear as quasar-like objects. An evolutionary scheme is outlined in which the radio quasars are transformed in time into the nuclei of radio galaxies.

  12. Form Factors and Radii of Light Nuclei

    SciTech Connect

    Sick, Ingo

    2015-09-15

    We discuss the determination of electromagnetic form factors from the world data on electron–nucleus scattering for nuclei Z ≤ 3, with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.

  13. Transfer-induced fission of superheavy nuclei

    SciTech Connect

    Adamian, G. G.; Antonenko, N. V.; Zubov, A. S.; Sargsyan, V. V.; Scheid, W.

    2010-07-15

    Possibilities of transfer-induced fission of new isotopes of superheavy nuclei with charge numbers 103-108 are studied for the first time in the reactions {sup 48}Ca+{sup 244,246,248}Cm at energies near the corresponding Coulomb barriers. The predicted cross sections are found to be measurable with the detection of three-body final states.

  14. Nucleon compositeness and nucleon-nuclei scattering

    NASA Astrophysics Data System (ADS)

    Li, Ming

    1990-04-01

    Large N QCD arguments are used to distinguish phenomenology of nucleon-nuclei scattering based on the Dirac equation with point nucleons and on quark based models with composite nucleons. The Friedberg-Lee soliton model is used as an explicit example.

  15. Ab initio Bogoliubov coupled cluster theory for open-shell nuclei

    DOE PAGES

    Signoracci, Angelo J.; Duguet, Thomas; Hagen, Gaute; ...

    2015-06-29

    Background: Ab initio many-body methods have been developed over the past 10 yr to address closed-shell nuclei up to mass A≈130 on the basis of realistic two- and three-nucleon interactions. A current frontier relates to the extension of those many-body methods to the description of open-shell nuclei. Several routes to address open-shell nuclei are currently under investigation, including ideas that exploit spontaneous symmetry breaking. Purpose: Singly open-shell nuclei can be efficiently described via the sole breaking of U(1) gauge symmetry associated with particle-number conservation as a way to account for their superfluid character. While this route was recently followed withinmore » the framework of self-consistent Green's function theory, the goal of the present work is to formulate a similar extension within the framework of coupled cluster theory. Methods: We formulate and apply Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wave function of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and the cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCC code is implemented in m scheme, which will permit the treatment of doubly open-shell nuclei via the further breaking of SU(2) symmetry associated with angular momentum conservation. Results: Proof-of-principle calculations in an Nmax=6 spherical harmonic oscillator basis for 16,18O and 18Ne in the BCCD approximation are in good agreement with standard coupled cluster results with the same chiral two-nucleon interaction, while 20O and 20Mg display underbinding relative to experiment. The breaking of U(1) symmetry, monitored by computing the variance associated with the particle-number operator, is

  16. Ab initio Bogoliubov coupled cluster theory for open-shell nuclei

    SciTech Connect

    Signoracci, Angelo J.; Duguet, Thomas; Hagen, Gaute; Jansen, G. R.

    2015-06-29

    Background: Ab initio many-body methods have been developed over the past 10 yr to address closed-shell nuclei up to mass A≈130 on the basis of realistic two- and three-nucleon interactions. A current frontier relates to the extension of those many-body methods to the description of open-shell nuclei. Several routes to address open-shell nuclei are currently under investigation, including ideas that exploit spontaneous symmetry breaking. Purpose: Singly open-shell nuclei can be efficiently described via the sole breaking of U(1) gauge symmetry associated with particle-number conservation as a way to account for their superfluid character. While this route was recently followed within the framework of self-consistent Green's function theory, the goal of the present work is to formulate a similar extension within the framework of coupled cluster theory. Methods: We formulate and apply Bogoliubov coupled cluster (BCC) theory, which consists of representing the exact ground-state wave function of the system as the exponential of a quasiparticle excitation cluster operator acting on a Bogoliubov reference state. Equations for the ground-state energy and the cluster amplitudes are derived at the singles and doubles level (BCCSD) both algebraically and diagrammatically. The formalism includes three-nucleon forces at the normal-ordered two-body level. The first BCC code is implemented in m scheme, which will permit the treatment of doubly open-shell nuclei via the further breaking of SU(2) symmetry associated with angular momentum conservation. Results: Proof-of-principle calculations in an Nmax=6 spherical harmonic oscillator basis for 16,18O and 18Ne in the BCCD approximation are in good agreement with standard coupled cluster results with the same chiral two-nucleon interaction, while 20O and 20Mg display underbinding relative to experiment. The breaking of U(1) symmetry, monitored by computing the variance

  17. Physics of Exotic Nuclei at RIBF

    NASA Astrophysics Data System (ADS)

    Sakurai, Hiroyoshi

    2014-09-01

    ``Exotic nuclei'' far from the stability line are unique objects of many-body quantum system, where ratios of neutron number to proton number are much larger or much smaller than those of nuclei found in nature. Their exotic properties and phenomena emerge from their large isospin asymmetry, and even affect scenarios of nucleosynthesis in the universe. Efforts have been made to produce and investigate such exotic nuclei at the accelerator facilities in the world. One of the facilities, the Radioactive Isotope Beam Factory (RIBF) facility at RIKEN, Japan has delivered intense radioactive isotope (RI) beams since 2007. In US, the Facility for Rare Isotope Beams is being constructed to start around 2020. To access nuclei far from the stability line, especially neutron-rich nuclei, the RIBF facility is highly optimized for inflight production of fission fragments via a U beam. The Super-conducting Ring Cyclotron delivers a 345 MeV/u U beam. The U nuclide is converted at a target to fission fragments. An inflight separator BigRIPS was designed to collect about 50% of fission fragments produced at the target and separate nuclei of interest. The RI beams produced at BigRIPS are then delivered to several experimental devices. Large-scale international collaborations have been formed at three spectrometers to conduct unique programs for the investigation of decay properties single particle orbits, collective motions, nucleon correlation, and the equation-of-state of asymmetric nuclear matter. Nuclear binding energy will be measured at a newly constructed ring for the r-process path, and charge distribution of exotic nuclei will be examined at a unique setup of an RI target section in an electron storage ring. Ultra slow RI beams available at a gas catcher system will be utilized for table-top and high precision measurements. In this talk, I would give a facility overview of RIBF, and introduce objectives at RIBF. Special emphasis would be given to selected recent highlights

  18. Megamaser Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Kartje, John F.; Königl, Arieh; Elitzur, Moshe

    1999-03-01

    Recent spectroscopic and VLBI-imaging observations of bright extragalactic H2O maser sources have revealed that the megamaser emission often originates in thin circumnuclear disks near the centers of active galactic nuclei (AGNs). Using general radiative and kinematic considerations and taking account of the observed flux variability, we argue that the maser emission regions are clumpy, a conclusion that is independent of the detailed mechanism (X-ray heating, shocks, etc.) driving the collisionally pumped masers. We examine scenarios in which the clumps represent discrete gas condensations (i.e., clouds) and do not merely correspond to velocity irregularities in the disk. We show that even two clouds that overlap within the velocity-coherence length along the line of sight could account (through self-amplification) for the entire maser flux of a high-velocity ``satellite'' feature in sources like NGC 4258 and NGC 1068, and we suggest that cloud self-amplification likely contributes also to the flux of the background-amplifying ``systemic'' features in these objects. Analogous interpretations have previously been proposed for water maser sources in Galactic star-forming regions. We argue that this picture provides a natural explanation of the time-variability characteristics of extragalactic megamaser sources and of their apparent association with Seyfert 2-like galaxies. We also show that the requisite cloud space densities and internal densities are consistent with the typical values of nuclear (broad emission line region type) clouds. We examine two scenarios of clumpy disks in which the maser emission is excited by a central continuum source. This excitation mechanism was first considered in the context of megamaser disks by Neufeld & Maloney, but our proposed models are clearly distinct from their warped, homogeneous disk interpretation. In our first scenario we consider an annular disk (or ``ring'') whose inner edge corresponds to the innermost radius of the

  19. Binary and multifragment decay of very hot nuclei

    SciTech Connect

    Moretto, L.G.; Blumenfeld, Y.; Charity, R.J.; Wozniak, G.J.

    1990-05-01

    Compound binary emission of complex fragments is illustrated for a variety of reactions. Complex fragment emission from 35 and 40 MeV/N {sup 139}La + {sup 12}C, {sup 27}Al, {sup 40}Ca and {sup 51}V reactions has been studied. Multifragment events from these reactions were assigned to sources characterized by their energy and mass through the incomplete-fusion-model kinematics. Excitation functions for the various multifragment channels appear to be nearly independent of the system and bombarding energy. Preliminary comparisons of the data with sequential-statistical-decay calculations are discussed. 14 refs., 7 figs.

  20. Observation of mass-asymmetric fission of mercury nuclei in heavy ion fusion

    NASA Astrophysics Data System (ADS)

    Prasad, E.; Hinde, D. J.; Ramachandran, K.; Williams, E.; Dasgupta, M.; Carter, I. P.; Cook, K. J.; Jeung, D. Y.; Luong, D. H.; McNeil, S.; Palshetkar, C. S.; Rafferty, D. C.; Simenel, C.; Wakhle, A.; Khuyagbaatar, J.; Düllmann, Ch. E.; Lommel, B.; Kindler, B.

    2015-06-01

    Background: Mass-asymmetric fission has been observed in low energy fission of 180Hg . Calculations predicted the persistence of asymmetric fission in this region even at excitation energies of 30-40 MeV. Purpose: To investigate fission mass distributions by populating different isotopes of Hg using heavy ion fusion reactions. Methods: Fission fragment mass-angle distributions have been measured for two reactions, 40Ca+142Nd and 13C+182W , populating 182Hg and 195Hg , respectively, using the Heavy Ion Accelerator Facility and CUBE spectrometer at the Australian National University. Measurements were made at beam energies around the capture barrier for the two reactions and mass ratio distributions were obtained using the kinematic reconstruction method. Results: Asymmetric fission has been observed following the population of 182Hg at an excitation energy of 22.8 MeV above the saddle point. A symmetric peaked mass ratio distribution was observed for 195Hg nuclei at a similar excitation energy above the saddle point. Conclusions: Mass-asymmetric fission has been observed in neutron deficient Hg nuclei populated via heavy ion fusion for the first time. The results are consistent with observations from beta-delayed fission measurements and provide a proof-of-principle for expanding experimental studies of the influence of shell effects on the fission processes.

  1. On the spin excitation energy of the nucleon in the Skyrme model

    NASA Astrophysics Data System (ADS)

    Adam, C.; Sanchez-Guillen, J.; Wereszczynski, A.

    2016-11-01

    In the Skyrme model of nucleons and nuclei, the spin excitation energy of the nucleon is traditionally calculated by a fit of the rigid rotor quantization of spin/isospin of the fundamental Skyrmion (the hedgehog) to the masses of the nucleon and the Delta resonance. The resulting, quite large spin excitation energy of the nucleon of about 73MeV is, however, rather difficult to reconcile with the small binding energies of physical nuclei, among other problems. Here, we argue that a more reliable interval of values for the spin excitation energy of the nucleon, compatible with many physical constraints is between 15MeV and 30MeV. The fit of the rigid rotor to the Delta, on the other hand, is problematic in any case, because it implies the use of a nonrelativistic method for a highly relativistic system.

  2. Binary cluster model calculations for 20Ne and 44Ti nuclei

    NASA Astrophysics Data System (ADS)

    Koyuncu, F.; Soylu, A.; Bayrak, O.

    2017-03-01

    The elastic scattering data of α+16O and α+40Ca systems at Elab = 32.2-146 MeV and Elab = 24.1-49.5 MeV energies have been analyzed with double-folding (DF) potential in optical model formalism in order to investigate the cluster structures of 20Ne and 44Ti nuclei. The deduced DF potentials between α and 16O as well as α and 40Ca have been used for obtaining the excitation energies and α-decay widths of 20Ne and 44Ti in Gamow code, but the reasonable results could not be obtained. Thus, the real parts of DF potentials which are in the best agreement with experimental data have been fitted with the squared-Woods-Saxon (WS2) potential parameters to calculate the α-decay widths of 20Ne and 44Ti with Wentzel-Kramers-Brillouin (WKB) approach. The nuclear potential sets obtained in WKB calculations are also used for Gamow code calculations. We take into account the deformation and orientation of 40Ca nucleus to examine their influence on both the excitation energies and decay widths of 44Ti. Besides, by using the binary cluster model the rotational band energies and electromagnetic transition probabilities (BE2)s according to angles are also reproduced for both nuclei. The obtained results showed that the binary cluster model is very useful to understand the observables of 20Ne and 44Ti nuclei. Although only spherical calculations are made for 20Ne (α + 16O), the deformation in 40Ca would be important for the understanding of 44Ti (α + 40Ca) cluster structure. The mechanism presented here would also be applied to understand the cluster structures in heavy nuclei.

  3. RNA-sequencing from single nuclei

    PubMed Central

    Grindberg, Rashel V.; Yee-Greenbaum, Joyclyn L.; McConnell, Michael J.; Novotny, Mark; O’Shaughnessy, Andy L.; Lambert, Georgina M.; Araúzo-Bravo, Marcos J.; Lee, Jun; Fishman, Max; Robbins, Gillian E.; Lin, Xiaoying; Venepally, Pratap; Badger, Jonathan H.; Galbraith, David W.; Gage, Fred H.; Lasken, Roger S.

    2013-01-01

    It has recently been established that synthesis of double-stranded cDNA can be done from a single cell for use in DNA sequencing. Global gene expression can be quantified from the number of reads mapping to each gene, and mutations and mRNA splicing variants determined from the sequence reads. Here we demonstrate that this method of transcriptomic analysis can be done using the extremely low levels of mRNA in a single nucleus, isolated from a mouse neural progenitor cell line and from dissected hippocampal tissue. This method is characterized by excellent coverage and technical reproducibility. On average, more than 16,000 of the 24,057 mouse protein-coding genes were detected from single nuclei, and the amount of gene-expression variation was similar when measured between single nuclei and single cells. Several major advantages of the method exist: first, nuclei, compared with whole cells, have the advantage of being easily isolated from complex tissues and organs, such as those in the CNS. Second, the method can be widely applied to eukaryotic species, including those of different kingdoms. The method also provides insight into regulatory mechanisms specific to the nucleus. Finally, the method enables dissection of regulatory events at the single-cell level; pooling of 10 nuclei or 10 cells obscures some of the variability measured in transcript levels, implying that single nuclei and cells will be extremely useful in revealing the physiological state and interconnectedness of gene regulation in a manner that avoids the masking inherent to conventional transcriptomics using bulk cells or tissues. PMID:24248345

  4. RNA-sequencing from single nuclei.

    PubMed

    Grindberg, Rashel V; Yee-Greenbaum, Joyclyn L; McConnell, Michael J; Novotny, Mark; O'Shaughnessy, Andy L; Lambert, Georgina M; Araúzo-Bravo, Marcos J; Lee, Jun; Fishman, Max; Robbins, Gillian E; Lin, Xiaoying; Venepally, Pratap; Badger, Jonathan H; Galbraith, David W; Gage, Fred H; Lasken, Roger S

    2013-12-03

    It has recently been established that synthesis of double-stranded cDNA can be done from a single cell for use in DNA sequencing. Global gene expression can be quantified from the number of reads mapping to each gene, and mutations and mRNA splicing variants determined from the sequence reads. Here we demonstrate that this method of transcriptomic analysis can be done using the extremely low levels of mRNA in a single nucleus, isolated from a mouse neural progenitor cell line and from dissected hippocampal tissue. This method is characterized by excellent coverage and technical reproducibility. On average, more than 16,000 of the 24,057 mouse protein-coding genes were detected from single nuclei, and the amount of gene-expression variation was similar when measured between single nuclei and single cells. Several major advantages of the method exist: first, nuclei, compared with whole cells, have the advantage of being easily isolated from complex tissues and organs, such as those in the CNS. Second, the method can be widely applied to eukaryotic species, including those of different kingdoms. The method also provides insight into regulatory mechanisms specific to the nucleus. Finally, the method enables dissection of regulatory events at the single-cell level; pooling of 10 nuclei or 10 cells obscures some of the variability measured in transcript levels, implying that single nuclei and cells will be extremely useful in revealing the physiological state and interconnectedness of gene regulation in a manner that avoids the masking inherent to conventional transcriptomics using bulk cells or tissues.

  5. Ice Nuclei Production in Volcanic Clouds

    NASA Astrophysics Data System (ADS)

    Few, A. A.

    2012-12-01

    The paper [Durant et al., 2008] includes a review of research on ice nucleation in explosive volcanic clouds in addition to reporting their own research on laboratory measurements focused on single-particle ice nucleation. Their research as well as the research they reviewed were concerned with the freezing of supercooled water drops (250 to 260 K) by volcanic ash particles acting as ice freezing nuclei. Among their conclusions are: Fine volcanic ash particles are very efficient ice freezing nuclei. Volcanic clouds likely contain fine ash concentrations 104 to 105 times greater than found in meteorological clouds. This overabundance of ice nuclei will produce a cloud with many small ice crystals that will not grow larger as they do in meteorological clouds because the cloud water content is widely distributed among the numerous small ice crystals. The small ice crystals have a small fall velocity, thus volcanic clouds are very stable. The small ice crystals are easily lofted into the stratosphere transporting water and adsorbed trace gasses. In this paper we examine the mechanism for the production of the small ice nuclei and develop a simple model for calculating the size of the ice nuclei based upon the distribution of magma around imbedded bubbles. We also have acquired a volcanic bomb that exhibits bubble remnants on its entire surface. The naturally occurring fragments from the volcanic bomb reveal a size distribution consistent with that predicted by the simple model. Durant, A. J., R. A. Shaw, W. I. Rose, Y. Mi, and G. G. J. Ernst (2008), Ice nucleation and overseeding of ice in volcanic clouds, J. Geophys. Res., 113, D09206, doi:10.1029/2007JD009064.

  6. Electron-driven excitation and dissociation of molecules

    NASA Astrophysics Data System (ADS)

    Orel, Ann

    2009-10-01

    Due to the large difference in mass between the electron and the nuclei, when an electron collides with a molecule or molecular ion, there is inefficient transfer of energy from the electron into the motion of the nuclei, leading to little vibrational excitation or dissociation. However, in certain special cases, the electron can temporarily attach to the molecule and change the forces felt between its atoms for a period of time comparable to a vibrational period. This can lead to resonant vibrational excitation and dissociative attachment, for neutral targets, or dissociative recombination in the case of ions. Studies of dissociative recombination and attachment in several polyatomic systems have shown that simple one-dimensional models can fail to capture the correct dissociation dynamics. In our treatment of these processes we first carry out ab initio electron scattering calculations at fixed internuclear geometries to determine the resonant energy surfaces and the corresponding surface of autoionization widths using the Complex Kohn variational method. These resonance positions and widths are then used as input to a dynamics study to determine the cross-section and product distributions for the dissociation or excitation process. We will present results on a number of systems, including HCCH, HCN/HNC and HCCCN as examples of dissociative attachment and N2H^+ and H2O^+ for dissociative recombination.

  7. Nuclear Shell Structure and Beta Decay I. Odd A Nuclei II. Even A Nuclei

    DOE R&D Accomplishments Database

    Mayer, M.G.; Moszkowski, S.A.; Nordheim, L.W.

    1951-05-01

    In Part I a systematics is given of all transitions for odd A nuclei for which sufficiently reliable data are available. The allowed or forbidden characters of the transitions are correlated with the positions of the initial and final odd nucleon groups in the nuclear shell scheme. The nuclear shells show definite characteristics with respect to parity of the ground states. The latter is the same as the one obtained from known spins and magnetic moments in a one-particle interpretation. In Part II a systematics of the beta transitions of even-A nuclei is given. An interpretation of the character of the transitions in terms of nuclear shell structure is achieved on the hypothesis that the odd nucleon groups have the same structure as in odd-A nuclei, together with a simple coupling rule between the neutron and proton groups in odd-odd nuclei.

  8. Near and sub-barrier fusion of neutron-rich oxygen and carbon nuclei using low-intensity beams

    NASA Astrophysics Data System (ADS)

    Steinbach, Tracy K.

    Fusion between neutron-rich light nuclei in the crust of an accreting neutron star has been proposed as a heat source that triggers an X-ray superburst. To explore the probability with which such fusion events occur and examine their decay characteristics, an experimental program using beams of neutron-rich light nuclei has been established. Evaporation residues resulting from the fusion of oxygen and 12C nuclei, are directly measured and distinguished from unreacted beam particles on the basis of their energy and time-of-flight. Using an experimental setup developed for measurements utilizing low-intensity (< 105 ions/s) radioactive beams, the fusion excitation functions for 16O + 12C and 18O + 12C have been measured. The fusion excitation function for 18O + 12C has been measured in the sub-barrier domain down to the 820 mub level, a factor of 30 lower than previous direct measurements. This measured fusion excitation function is compared to the predictions of a density constrained time-dependent Hartree-Fock model. This comparison reveals a shape difference in the fusion excitation functions, indicating a larger tunneling probability for the experimental data as compared to the theoretical calculations. In addition to the measured cross-section, the measured angular distribution of the evaporation residues provides insight into the relative importance of the different de-excitation channels. These evaporation residue angular distributions are compared to the predictions of a statistical model code, evapOR, revealing an under-prediction of the de-excitation channels associated with alpha particle emission.

  9. Excitation of Nuclei and Atoms Trapping in Optical Fields of High Intensity

    DTIC Science & Technology

    2006-11-01

    absorption rate of γ-quanta will be evaluated by taking into account the last achievements in synchrotron-radiation sources. 8. Development in...or absorption of a gamma photon with a relatively large momentum. Thus, in any radiative transition a nucleus acquires a recoil kinetic energy equal...approximately to 1 meV. In an emission process, this kinetic energy is drawn from the energy of a nuclear state and, in absorption , from the photon

  10. Multi-quasiparticle excitation: Extending shape coexistence in A~190 neutron-deficient nuclei

    NASA Astrophysics Data System (ADS)

    Shi, Yue; Xu, F. R.; Liu, H. L.; Walker, P. M.

    2010-10-01

    Multi-quasiparticle high-K states in neutron-deficient mercury, lead, and polonium isotopes have been investigated systematically by means of configuration-constrained potential-energy-surface calculations. An abundance of high-K states is predicted with both prolate and oblate shapes, which extends the shape coexistence of the mass region. Well-deformed shapes provide good conditions for the formation of isomers, as exemplified in Pb188. Of particular interest is the prediction of low-lying 10- states in polonium isotopes, which indicate long-lived isomers.

  11. Multi-quasiparticle excitation: Extending shape coexistence in A{approx}190 neutron-deficient nuclei

    SciTech Connect

    Shi Yue; Liu, H. L.; Xu, F. R.; Walker, P. M.

    2010-10-15

    Multi-quasiparticle high-K states in neutron-deficient mercury, lead, and polonium isotopes have been investigated systematically by means of configuration-constrained potential-energy-surface calculations. An abundance of high-K states is predicted with both prolate and oblate shapes, which extends the shape coexistence of the mass region. Well-deformed shapes provide good conditions for the formation of isomers, as exemplified in {sup 188}Pb. Of particular interest is the prediction of low-lying 10{sup -} states in polonium isotopes, which indicate long-lived isomers.

  12. Recent searches for double-electron capture of nuclei to excited states

    SciTech Connect

    Povinec, P. P.; Frekers, D.; Šimkovic, F.

    2015-10-28

    Double electron capture has been of interest of many theoretical and experimental works as a possible extension of double beta-decay investigations. The neutrinoless double-electron capture, similarly as the neutrinoless double beta-decay may help to clarify if neutrinos are Majorana or Dirac particles. Results obtained in several double electron capture experiments are reviewed and new experiments to be carried out in deep underground laboratories using enriched sources and multidimensional HPGe-HPGe gamma-ray spectrometry with a few years of counting time are proposed, which should be able to improve half-lives limits by at least an order of magnitude.

  13. Polybenzimidazole compounds

    DOEpatents

    Klaehn, John R [Idaho Falls, ID; Peterson, Eric S [Idaho Falls, ID; Orme, Christopher J [Shelley, ID; Jones, Michael G [Chubbuck, ID; Wertsching, Alan K [Idaho Falls, ID; Luther, Thomas A [Idaho Falls, ID; Trowbridge, Tammy L [Idaho Falls, ID

    2011-11-22

    A PBI compound includes imidazole nitrogens at least a portion of which are substituted with a moiety containing a carbonyl group, the substituted imidazole nitrogens being bonded to carbon of the carbonyl group. At least 85% of the nitrogens may be substituted. The carbonyl-containing moiety may include RCO--, where R is alkoxy or haloalkyl. The PBI compound may exhibit a first temperature marking an onset of weight loss corresponding to reversion of the substituted PBI that is less than a second temperature marking an onset of decomposition of an otherwise identical PBI compound without the substituted moiety. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may use more than 5 equivalents in relation to the imidazole nitrogens to be substituted.

  14. Polybenzimidazole compounds

    DOEpatents

    Klaehn, John R.; Peterson, Eric S.; Wertsching, Alan K.; Orme, Christopher J.; Luther, Thomas A.; Jones, Michael G.

    2010-08-10

    A PBI compound that includes imidazole nitrogens, at least a portion of which are substituted with an organic-inorganic hybrid moiety. At least 85% of the imidazole nitrogens may be substituted. The organic-inorganic hybrid moiety may be an organosilane moiety, for example, (R)Me.sub.2SiCH.sub.2--, where R is selected from among methyl, phenyl, vinyl, and allyl. The PBI compound may exhibit similar thermal properties in comparison to the unsubstituted PBI. The PBI compound may exhibit a solubility in an organic solvent greater than the solubility of the unsubstituted PBI. The PBI compound may be included in separatory media. A substituted PBI synthesis method may include providing a parent PBI in a less than 5 wt % solvent solution. Substituting may occur at about room temperature and/or at about atmospheric pressure. Substituting may use at least five equivalents in relation to the imidazole nitrogens to be substituted or, preferably, about fifteen equivalents.

  15. Theoretical resonant electron-impact vibrational excitation, dissociative recombination and dissociative excitation cross sections of ro-vibrationally excited BeH+ ion

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Chakrabarti, K.; Celiberto, R.; Janev, R. K.; Mezei, J. Zs; Niyonzima, S.; Tennyson, J.; Schneider, I. F.

    2017-02-01

    A theoretical study of resonant vibrational excitation, dissociative recombination and dissociative excitation processes of the beryllium monohydride cation, BeH+, induced by electron impact, is reported. Full sets of ro-vibrationally-resolved cross sections and of the corresponding Maxwellian rate coefficients are presented for the three processes. Particular emphasis is given to the high-energy behaviour. Potential curves of {}2{{{Σ }}}+, {}2{{\\Pi }} and {}2{{Δ }} symmetries and the corresponding resonance widths, obtained from R-matrix calculations, provide the input for calculations which use a local complex-potential model for resonant collisions in each of the three symmetries. Rotational motion of nuclei and isotopic effects are also discussed. The relevant results are compared with those obtained using a multichannel quantum defect theory method. Full results are available from the Phys4Entry database.

  16. Anharmonicity of the excited octupole band in actinides using supersymmetric quantum mechanics

    NASA Astrophysics Data System (ADS)

    Jolos, R. V.; von Brentano, P.; Casten, R. F.

    2013-09-01

    Background: Low-lying octupole collective excitations play an important role in the description of the structure of nuclei in the actinide region. Ground state alternating parity rotational bands combining both positive and negative parity states are known in several nuclei. However, only recently it has been discovered in 240Pu an excited positive parity rotational band having an octupole nature and demonstrating strong anharmonicity of the octupole motion in the band head energies.Purpose: To suggest a model describing both ground state and excited alternating parity bands, which includes a description of the anharmonic effects in the bandhead excitation energies and can be used to predict the energies of the excited rotational bands of octupole nature and the E1 transition probabilities.Methods: The mathematical technique of the supersymmetric quantum mechanics with a collective Hamiltonian depending only on the octupole collective variable which keeps axial symmetry is used to describe the ground state and excited alternating parity rotational bands.Results: The excitation energies of the states belonging to the lowest negative parity and the excited positive parity bands are calculated for 232Th, 238U, and 240Pu. The E1 transition matrix elements are also calculated for 240Pu.Conclusions: It is shown that the suggested model describes the excitation energies of the states of the lowest negative parity band with the accuracy around 10 keV. The anharmonicity in the bandhead energy of the excited positive parity band is described also. The bandhead energy of the excited positive parity band is described with the accuracy around 100 keV.

  17. Evaporation residue cross sections for the {sup 64}Ni + {sup 144,154}Sm reaction -- Energy dissipation in hot nuclei

    SciTech Connect

    Back, B.B.; Blumenthal, D.J.; Davids, C.N.

    1995-08-01

    The fission hindrance of hot nuclei was deduced recently from an enhanced emission of GDR {gamma} rays, neutrons and charged particles prior to scission of heavy nuclei. In the most recent experiments addressing this topic, namely new measurements of the pre-scission {gamma} rays and evaporation residues from the {sup 32}S + {sup 184}W reaction, a rather sharp transition from negligible to full one-body dissipation occurs over the excitation energy region E{sub exc} = 60-100 MeV. However, the cross section does not appear to level out or start to decline again at the upper end of the energy range as expected in this interpretation. It is therefore clearly desirable to extend the excitation energy range to look for such an effect in order to either corroborate or refute this interpretation.

  18. Simultaneous two-photon excitation of photodynamic therapy agents

    NASA Astrophysics Data System (ADS)

    Wachter, Eric A.; Partridge, W. P., Jr.; Fisher, Walter G.; Dees, Craig; Petersen, Mark G.

    1998-07-01

    The spectroscopic and photochemical properties of several photosensitive compounds are compared using conventional single-photon excitation (SPE) and simultaneous two-photon excitation (TPE). TPE is achieved using a mode-locked titanium:sapphire laser, the near infrared output of which allows direct promotion of non-resonant TPE. Excitation spectra and excited state properties of both type I and type II photodynamic therapy (PDT) agents are examined. In general, while SPE and TPE selection rules may be somewhat different, the excited state photochemical properties are equivalent for both modes of excitation. In vitro promotion of a two-photon photodynamic effect is demonstrated using bacterial and human breast cancer models. These results suggest that use of TPE may be beneficial for PDT, since the technique allows replacement of visible or ultraviolet excitation with non- damaging near infrared light. Further, a comparison of possible excitation sources for TPE indicates that the titanium:sapphire laser is exceptionally well suited for non- linear excitation of PDT agents in biological systems due to its extremely short pulse width and high repetition rate; these features combine to effect efficient PDT activation with minimal potential for non-specific biological damage.

  19. Different mechanism of two-proton emission from proton-rich nuclei 23Al and 22Mg

    NASA Astrophysics Data System (ADS)

    Ma, Y. G.; Fang, D. Q.; Sun, X. Y.; Zhou, P.; Togano, Y.; Aoi, N.; Baba, H.; Cai, X. Z.; Cao, X. G.; Chen, J. G.; Fu, Y.; Guo, W.; Hara, Y.; Honda, T.; Hu, Z. G.; Ieki, K.; Ishibashi, Y.; Ito, Y.; Iwasa, N.; Kanno, S.; Kawabata, T.; Kimura, H.; Kondo, Y.; Kurita, K.; Kurokawa, M.; Moriguchi, T.; Murakami, H.; Ooishi, H.; Okada, K.; Ota, S.; Ozawa, A.; Sakurai, H.; Shimoura, S.; Shioda, R.; Takeshita, E.; Takeuchi, S.; Tian, W. D.; Wang, H. W.; Wang, J. S.; Wang, M.; Yamada, K.; Yamada, Y.; Yasuda, Y.; Yoneda, K.; Zhang, G. Q.; Motobayashi, T.

    2015-04-01

    Two-proton relative momentum (qpp) and opening angle (θpp) distributions from the three-body decay of two excited proton-rich nuclei, namely 23Al → p + p +21Na and 22Mg → p + p +20Ne, have been measured with the projectile fragment separator (RIPS) at the RIKEN RI Beam Factory. An evident peak at qpp ∼ 20 MeV / c as well as a peak in θpp around 30° are seen in the two-proton break-up channel from a highly-excited 22Mg. In contrast, such peaks are absent for the 23Al case. It is concluded that the two-proton emission mechanism of excited 22Mg is quite different from the 23Al case, with the former having a favorable diproton emission component at a highly excited state and the latter dominated by the sequential decay process.

  20. Derivation of an optical potential for statically deformed rare-earth nuclei from a global spherical potential

    SciTech Connect

    Nobre, G. P. A.; Palumbo, A.; Herman, M.; Brown, D.; Hoblit, S.; Dietrich, F. S.

    2015-02-25

    The coupled-channel theory is a natural way of treating nonelastic channels, in particular those arising from collective excitations characterized by nuclear deformations. A proper treatment of such excitations is often essential to the accurate description of experimental nuclear-reaction data and to the prediction of a wide variety of scattering observables. Stimulated by recent work substantiating the near validity of the adiabatic approximation in coupled-channel calculations for scattering on statically deformed nuclei, we explore the possibility of generalizing a global spherical optical model potential (OMP) to make it usable in coupled-channel calculations on this class of nuclei. To do this, we have deformed the Koning-Delaroche global spherical potential for neutrons, coupling a sufficient number of states of the ground state band to ensure convergence. We present an extensive study of the effects of collective couplings and nuclear deformations on integrated cross sections as well as on angular distributions for neutron-induced reactions on statically deformed nuclei in the rare-earth region. We choose isotopes of three rare-earth elements (Gd, Ho, W), which are known to be nearly perfect rotors, to exemplify the results of the proposed method. Predictions from our model for total, elastic and inelastic cross sections, as well as for elastic and inelastic angular distributions, are in reasonable agreement with measured experimental data. In conclusion, these results suggest that the deformed Koning-Delaroche potential provides a useful regional neutron optical potential for the statically deformed rare earth nuclei.

  1. Rotational-vibrational Description of Nucleon Scattering on Actinide Nuclei Using a Dispersive Coupled-channel Optical Model

    NASA Astrophysics Data System (ADS)

    Quesada, J. M.; Capote, R.; Soukhovitskiı˜, E. Sh.; Chiba, S.

    2014-04-01

    Tamura's coupling formalism has been extended to consider low-lying rotational bands built on vibrational (single-particle) band heads in well-deformed even-even (odd) actinides. These additional excitations are introduced as a perturbation to the underlying rigid rotor structure that is known to describe well the ground state rotational band of major actinides. Coupling matrix elements needed in extended Tamura's formalism are derived for both even-even and odd actinides. Employed dispersive optical model (DCCOMP) replaces the incident proton energy Ep (for proton induced reactions) by the equivalent Coulomb subtracted energy in all potential terms including both the imaginary and real potentials with the corresponding dispersive corrections. Therefore, the optical potential becomes fully symmetric for protons and neutrons. This potential is used to fit simultaneously all the available optical experimental databases (including neutron strength functions) for nucleon scattering on 238U and 232Th (even even) nuclei. Quasi-elastic (p,n) scattering data to the isobaric analogue states of the target nuclei are also used to constrain the isovector part of the optical potential. Derived Lane-consistent DCCOMP is based on coupling of almost all levels below 1 MeV of excitation energy. The ground state, octupole, beta, gamma and non-axial rotational bands are considered for even nuclei, and rotational bands built on single-particle levels - for odd nuclei. Application of derived potential to odd targets based on a new coupling scheme is foreseen.

  2. IBA for novice experimentalists. I. Introduction to IBA: mostly symmetries. II. Tests in even-even nuclei: mostly transitional systems. III. Supersymmetries: theory and experiment

    SciTech Connect

    Cizewski, J.A.

    1982-08-01

    The report contains the notes from a series of lectures on the Interacting Boson Approximation (IBA) model. The lectures were presented at Lawrence Livermore National Laboratory on July 28, 30 and August 1, 1982 by Jolie A. Cizewski from Yale University. The IBA was developed by F. Iachello and A. Arima starting about seven years ago to understand collective quadrupole excitations in medium and heavy mass nuclei away from closed shells. Since then the formalism has been extended to odd-mass nuclei and considerable work has gone into understanding the microscopic construction of the bosons in this model. The IBA has been applied to nuclei as light as Zn and Ge and as heavy as U and Pu; to nuclei near closed shells, such as Mo and Hg; to stable nuclei and nuclei far from stability. The present lectures were designed to give the experimentalist an introduction to the IBA and to give specific examples of how it could be applied to understand the structure of heavy even and odd mass nuclei. Much of the emphasis was on the symmetries (and supersymmetries) of the model and how the use of symmetries enabled the relatively straightforward understanding of empirical systems as deviations from these symmetries. The richness of possible applications of the IBA to understanding collective phenomena in nuclei was not fully explored, but rather a few illustrative examples were selected and described in detail. The references, accumulated at the end of this report, provide a more comprehensive, although not complete, list of tests of the IBA in even mass nuclei and the new symmetries in odd mass nuclei. The references also list the main theoretical papers which provide the details of the IBA formalism.

  3. Study of Nuclei far From Stability by Using the CHIMERA 4{pi} Detector and Radioactive Beams at LNS

    SciTech Connect

    Cardella, G.; De Filippo, E.; Pagano, A.; Papa, M.; Pirrone, S.; Verde, G.; Amorini, F.; Anzalone, A.; Maiolino, C.; Auditore, L.; Loria, D.; Trifiro, A.; Trimarchi, M.; Cavallaro, S.; Lombardo, I.; Porto, F.; Rizzo, F.; Russotto, P.; Chatterjee, M. B.; Geraci, E.

    2009-08-26

    At LNS are available radioactive beams at tandem and intermediate energies provided respectively by the EXCYT and by the fragmentation FRIBS facilities. Using these beams, and the 4{pi} detector CHIMERA, we want to study excitation and decay of resonances in light exotic nuclei populated with pick-up stripping and other reaction mechanisms. Some preliminary results obtained with stable and unstable beams are reported.

  4. Presence of magnetic excitations in SmFeAsO

    NASA Astrophysics Data System (ADS)

    Pelliciari, Jonathan; Dantz, Marcus; Huang, Yaobo; Strocov, Vladimir N.; Xing, Lingyi; Wang, Xiancheng; Jin, Changqing; Schmitt, Thorsten

    2016-09-01

    We measured dispersive spin excitations in SmFeAsO, a parent compound of SmFeAsO1 -xFx and one of the highest temperature superconductors of Fe pnictides (TC ≈ 55 K). We determine the magnetic excitations to disperse with a bandwidth energy of ca 170 meV at (0.47, 0) and (0.34, 0.34), which merges into the elastic line approaching the Γ point. Comparing our results with other parent Fe pnictides, we show the importance of structural parameters for the magnetic excitation spectrum, with small modifications of the tetrahedron angles and As height strongly affecting the magnetism.

  5. Spectroscopy of Neutron-rich Nuclei of the A{approx_equal}60 region populated through binary heavy-ion collisions

    SciTech Connect

    Lunardi, S.

    2008-11-11

    Neutron-rich nuclei of the mass A = 60 region (from V to Fe) have been studied through multi-nucleon transfer reactions by bombarding a {sup 238}U target with beams of {sup 64}Ni and {sup 70}Zn. Unambiguous identification of prompt {gamma} rays belonging to each nucleus has been achieved by using the efficient gamma-array CLARA coupled to the large-acceptance magnetic spectrometer PRISMA installed at the Legnaro National Laboratories. With the new data, the existence of the N = 32 sub-shell closure has been corroborated through the study of odd V isotopes, whereas a new region of deformation appears for neutron-rich Fe nuclei close to N = 40. The results obtained for all these nuclei are compared with shell model calculations which reproduces quite well the experimental data also for the most neutron-rich nuclei when excitations from the fp shell into the upper g{sub 9/2} orbital are allowed.

  6. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $$(n,\\gamma )$$ reaction rates

    DOE PAGES

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; ...

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  7. Upbend and M1 scissors mode in neutron-rich nuclei - consequences for r-process $(n,\\gamma )$ reaction rates

    SciTech Connect

    Larsen, A. C.; Goriely, S.; Bernstein, L. A.; Bleuel, D. L.; Bracco, A.; Brown, B. A.; Camera, F.; Eriksen, T. K.; Frauendorf, S.; Giacoppo, F.; Guttormsen, M.; Gorgen, A.; Harissopulos, S.; Leoni, S.; Liddick, S. N.; Naqvi, F.; Nyhus, H. T.; Rose, S. J.; Renstrom, T.; Schwengner, R.; Siem, S.; Spyrou, A.; Tveten, G. M.; Voinov, A. V.; Wiedeking, M.

    2015-01-01

    An enhanced probability for low-energy γ-emission (upbend, Eγ < 3 MeV) at high excitation energies has been observed for several light and medium-mass nuclei close to the valley of stability. Also the M1 scissors mode seen in deformed nuclei increases the γ-decay probability for low-energy γ-rays (Eγ ≈ 2–3 MeV). These phenomena, if present in neutron-rich nuclei, have the potential to increase radiative neutron-capture rates relevant for the r-process. Furthermore, the experimental and theoretical status of the upbend is discussed, and preliminary calculations of (n,γ) reaction rates for neutron-rich, mid-mass nuclei including the scissors mode are shown.

  8. Magnetostrictive resonance excitation

    DOEpatents

    Schwarz, Ricardo B.; Kuokkala, Veli-Tapani

    1992-01-01

    The resonance frequency spectrum of a magnetostrictive sample is remotely determined by exciting the magnetostrictive property with an oscillating magnetic field. The permeability of a magnetostrictive material and concomitant coupling with a detection coil varies with the strain in the material whereby resonance responses of the sample can be readily detected. A suitable sample may be a magnetostrictive material or some other material having at least one side coated with a magnetostrictive material. When the sample is a suitable shape, i.e., a cube, rectangular parallelepiped, solid sphere or spherical shell, the elastic moduli or the material can be analytically determined from the measured resonance frequency spectrum. No mechanical transducers are required and the sample excitation is obtained without contact with the sample, leading to highly reproducible results and a measurement capability over a wide temperature range, e.g. from liquid nitrogen temperature to the Curie temperature of the magnetostrictive material.

  9. Experiments on excitation waves

    NASA Astrophysics Data System (ADS)

    Müller, S. C.

    Recent trends in the experimentation on chemical and biochemical excitation waves are presented. In the Belousov-Zhabotinsky reaction, which is the most suitable chemical laboratory system for the study of wave propagation in excitable medium, the efficient control of wave dynamics by electrical fields and by light illumination is illustrated. In particular, the effects of a feedback control are shown. Further new experiments in this system are concerned with three-dimensional topologies and boundary effects. Important biological applications are found in the aggregation of slime mould amoebae, in proton waves during oscillatory glycolysis, and in waves of spreading depression in neuronal tissue as studied by experiments in chicken retina. Numerical simulations with appropriate reaction-diffusion models complement a large number of these experimental findings.

  10. Few-nucleon transfer reactions on deformed nuclei

    SciTech Connect

    van den Berg, A.M.

    1985-01-01

    Recent developments discussed include: alpha-transfer reactions on deformed nuclei, quasi-elastic neutron transfer reactions induced by /sup 58/Ni beams on spherical and deformed samarium nuclei, and the population of low-lying states in neutron rich nuclei using (particle,..gamma..) or (particle,e) coincidence methods. 37 refs., 10 figs. (LEW)

  11. Excitable scale free networks

    NASA Astrophysics Data System (ADS)

    Copelli, M.; Campos, P. R. A.

    2007-04-01

    When a simple excitable system is continuously stimulated by a Poissonian external source, the response function (mean activity versus stimulus rate) generally shows a linear saturating shape. This is experimentally verified in some classes of sensory neurons, which accordingly present a small dynamic range (defined as the interval of stimulus intensity which can be appropriately coded by the mean activity of the excitable element), usually about one or two decades only. The brain, on the other hand, can handle a significantly broader range of stimulus intensity, and a collective phenomenon involving the interaction among excitable neurons has been suggested to account for the enhancement of the dynamic range. Since the role of the pattern of such interactions is still unclear, here we investigate the performance of a scale-free (SF) network topology in this dynamic range problem. Specifically, we study the transfer function of disordered SF networks of excitable Greenberg-Hastings cellular automata. We observe that the dynamic range is maximum when the coupling among the elements is critical, corroborating a general reasoning recently proposed. Although the maximum dynamic range yielded by general SF networks is slightly worse than that of random networks, for special SF networks which lack loops the enhancement of the dynamic range can be dramatic, reaching nearly five decades. In order to understand the role of loops on the transfer function we propose a simple model in which the density of loops in the network can be gradually increased, and show that this is accompanied by a gradual decrease of dynamic range.

  12. Measurement of the fusion excitation function for 19O + 12C at near barrier energies

    NASA Astrophysics Data System (ADS)

    Singh, Varinderjit; Steinbach, T. K.; Vadas, J.; Wiggins, B. B.; Hudan, S.; Desouza, R. T.; Baby, L. T.; Tripathi, V.; Kuvin, S. A.; Wiedenhover, I.

    2015-10-01

    Fusion of neutron-rich light nuclei in the outer crust of an accreting neutron star has been proposed as responsible for triggering X-ray super-bursts. The underlying hypothesis in this proposition is that the fusion of neutron-rich nuclei is enhanced as compared to stable nuclei. To investigate this hypothesis, an experiment has been performed to measure the fusion excitation function for 18O and 19O nuclei incident on a 12C target. A beam of 19O was produced by the 18O(d,p) reaction at Florida State University and separated using the RESOLUT mass spectrometer. The resulting 19O beam bombarded a 100 μg/cm2 12C target at an intensity of 2-4 × 103 p/s. Evaporation residues resulting from the de-excitation of the fusion product were distinguished by measuring their energy and time-of-flight. Using silicon detectors, micro-channel plate detectors, and an ionization chamber, evaporation residues were detected in the angular range θlab <= 23° with high efficiency. Initial experimental results including measurement of the fusion cross-section to approximately the 100 mb level will be presented. The measured excitation function will be compared to theoretical predictions. Supported by the US DOE under Grand No. DEFG02-88ER-40404.

  13. Low-energy fusion dynamics of weakly bound nuclei: A time dependent perspective

    NASA Astrophysics Data System (ADS)

    Diaz-Torres, A.; Boselli, M.

    2016-05-01

    Recent dynamical fusion models for weakly bound nuclei at low incident energies, based on a time-dependent perspective, are briefly presented. The main features of both the PLATYPUS model and a new quantum approach are highlighted. In contrast to existing timedependent quantum models, the present quantum approach separates the complete and incomplete fusion from the total fusion. Calculations performed within a toy model for 6Li + 209Bi at near-barrier energies show that converged excitation functions for total, complete and incomplete fusion can be determined with the time-dependent wavepacket dynamics.

  14. Thermal effects on the Fission Barrier of neutron-rich nuclei

    SciTech Connect

    Minato, Futoshi; Hagino, Kouichi

    2008-11-11

    We discuss the fission barrier height of neutron-rich nuclei in a r-process site at highly excited state, which is resulted from the beta-decay or the neutron-capture processes. We particularly investigate the sensitivity of the fission barrier height to the temperature, including the effect of pairing phase transition from superfluid to normal fluid phases. To this end, we use the finite-temperature Skyrme-Hartree-Fock-Bogolubov method with a zero-range pairing interaction. We also discuss the temperature dependence of the fission decay rate.

  15. Sensitivity enhancement of MQMAS NMR spectra of spin 3/2 nuclei using hyperbolic secant pulses

    NASA Astrophysics Data System (ADS)

    Siegel, Renée; Nakashima, Thomas T.; Wasylishen, Roderick E.

    2005-02-01

    The use of hyperbolic secant (HS) pulses to enhance the intensity of the central transition in MQMAS experiments for spin 3/2 quadrupolar nuclei is investigated by examining 87Rb NMR spectra of a powder sample of RbNO 3. The application of HS pulses prior to the triple-quantum (3Q) excitation provides sensitivity enhancements in MQMAS spectra that are superior to those previously reported. For the conversion of 3Q to single-quantum (1Q) observables, the HS pulses have an efficiency similar to that reported for double frequency sweeps (DFS) but greater than that of the fast amplitude modulation (FAM) technique.

  16. The stellar seismology of hot white dwarfs and planetary nebula nuclei

    NASA Technical Reports Server (NTRS)

    Kawaler, Steven D.

    1987-01-01

    The pulsation properties of hot white dwarfs make it possible to determine their mass, surface composition, rotation, and rate of evolution, and provide constraints on their internal structure. Period spacings are sensitive measures of stellar mass and indicate surface layer structure. Measurement of the rate of period change for these stars provide a way to determine their cooling rates. Attention is also given to how well (or poorly) models of excitation of the pulsations fit within current models of planetary nebula nuclei and hot white dwarfs.

  17. Simple empirical order parameter for a first-order quantum phase transition in atomic nuclei.

    PubMed

    Bonatsos, Dennis; McCutchan, E A; Casten, R F; Casperson, R J

    2008-04-11

    A simple, empirical, easy-to-measure effective order parameter of a first-order phase transition in atomic nuclei is presented, namely, the ratio of the energies of the first excited 6+ and 0+ states, distinguishing between first- and second-order transitions, and taking on a special value in the critical region, as data in Nd-Dy show. In the large NB limit of the interacting boson approximation model, a repeating degeneracy between alternate yrast and successive 0+ states is found in the critical region around the line of a first-order phase transition, pointing to a possible underlying symmetry.

  18. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2004-01-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  19. Biocompound detection through fluorescence excitation-emission matrix analysis

    NASA Astrophysics Data System (ADS)

    Twede, David R.; Sanders, Lee C.; Wagner, Michael L.

    2003-12-01

    The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.

  20. Harmonically excited orbital variations

    SciTech Connect

    Morgan, T.

    1985-08-06

    Rephrasing the equations of motion for orbital maneuvers in terms of Lagrangian generalized coordinates instead of Newtonian rectangular cartesian coordinates can make certain harmonic terms in the orbital angular momentum vector more readily apparent. In this formulation the equations of motion adopt the form of a damped harmonic oscillator when torques are applied to the orbit in a variationally prescribed manner. The frequencies of the oscillator equation are in some ways unexpected but can nonetheless be exploited through resonant forcing functions to achieve large secular variations in the orbital elements. Two cases are discussed using a circular orbit as the control case: (1) large changes in orbital inclination achieved by harmonic excitation rather than one impulsive velocity change, and (2) periodic and secular changes to the longitude of the ascending node using both stable and unstable excitation strategies. The implications of these equations are also discussed for both artificial satellites and natural satellites. For the former, two utilitarian orbits are suggested, each exploiting a form of harmonic excitation. 5 refs.

  1. Magnetic Excitations from Stripes in Cuprate Superconductors

    NASA Astrophysics Data System (ADS)

    Tranquada, J. M.; Woo, H.; Perring, T. G.; Goka, H.; Gu, G. D.; Xu, G.; Fujita, M.; Yamada, K.

    2004-03-01

    While it is generally believed that antiferromagnetic spin excitations play a significant role in the pairing mechanism of copper-oxide superconductors [1], the nature of the magnetic excitations themselves remains a matter of controversy. Recent measurements of the dispersion of spin excitations in superconducting YBa_2Cu_3O_6+x (YBCO) have attracted much attention. Here we present the results of comprehensive inelastic neutron scattering measurements of the momentum- and energy-dependent spectra of the magnetic fluctuations in La_0.875Ba_0.125CuO_4, which exhibits inhomogeneous, charge-stripe order. We will also point out universalities and differences in the magnetic excitation spectra compared to related charge-stripe ordered compounds and high-temperature superconductors, including La_2-xSr_xNiO4 and YBCO. JMT, HW, GDG and GX are supported by U.S. Department of Energy contract # DE-AC02-98CH1088 [1] J. Orenstein and A. J. Millis, Science 288, 468 (2000).

  2. Detection of chlorinated aromatic compounds

    DOEpatents

    Ekechukwu, Amy A.

    1996-01-01

    A method for making a composition for measuring the concentration of chloated aromatic compounds in aqueous fluids, and an optical probe for use with the method. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis.

  3. Detection of chlorinated aromatic compounds

    DOEpatents

    Ekechukwu, A.A.

    1996-02-06

    A method for making a composition for measuring the concentration of chlorinated aromatic compounds in aqueous fluids, and an optical probe for use with the method are disclosed. The composition comprises a hydrophobic polymer matrix, preferably polyamide, with a fluorescent indicator uniformly dispersed therein. The indicator fluoresces in the presence of the chlorinated aromatic compounds with an intensity dependent on the concentration of these compounds in the fluid of interest, such as 8-amino-2-naphthalene sulfonate. The probe includes a hollow cylindrical housing that contains the composition in its distal end. The probe admits an aqueous fluid to the probe interior for exposure to the composition. An optical fiber transmits excitation light from a remote source to the composition while the indicator reacts with chlorinated aromatic compounds present in the fluid. The resulting fluorescence light signal is reflected to a second optical fiber that transmits the light to a spectrophotometer for analysis. 5 figs.

  4. Decay branching ratios of excited 24Mg

    NASA Astrophysics Data System (ADS)

    Munson, J. M.; Norman, E. B.; Burke, J. T.; Casperson, R. J.; Phair, L. W.; McCleskey, E.; McCleskey, M.; Lee, D.; Hughes, R. O.; Ota, S.; Czeszumska, A.; Chodash, P. A.; Saastamoinen, A. J.; Austin, R. A. E.; Spiridon, A. E.; Dag, M.; Chyzh, R.; Basunia, M. S.; Ressler, J. J.; Ross, T. J.

    2017-01-01

    The nuclear reactions 12C(12C,α )20Ne , 12C(12C,p )23Na , and 12C(12C,n )23Mg are the primary reactions in carbon burning, which occurs as part of several stellar processes. The Gamow window, which describes the energy range where most of these reactions take place, is typically around 1.5 MeV in the center-of-mass frame. Direct measurements of the cross sections at this energy are difficult due to the large Coulomb barrier present between the carbon nuclei; however, a successful surrogate measurement can provide the branching ratios between these reactions while avoiding the 12C+12C Coulomb barrier. An experiment was performed using inelastic scattering of 40 MeV α particles on 24Mg as a possible surrogate for the 12C+12C compound nucleus.

  5. A cell line with decreased sensitivity to the methyl mercury-induced stimulation of alpha-amanitin sensitive RNA synthesis in isolated nuclei.

    PubMed

    Frenkel, G D; Ducote, J; Reboulleau, C P; Gierthy, J

    1988-01-01

    1. In nuclei isolated from cells of the B50 rat neuroblastoma line the stimulatory effect of methyl mercury on alpha-amanitin-sensitive RNA synthesis is very much reduced compared to the stimulatory effect in HeLa nuclei (see: Frenkel G. D. and Randles K. (1982) Specific stimulation of alpha-amanitin-sensitive RNA synthesis in isolated HeLa nuclei by methyl mercury. J. biol. Chem. 257, 6275-6279). 2. The stimulatory effect of another mercury compound, p-hydroxymercuribenzoate, was also much less pronounced in the B50 nuclei. 3. Similar results were obtained with nuclei isolated from B50 cells which had been induced to differentiate by exposure to dibutaryl cyclic AMP. 4. Nuclei isolated from cells of another rat neuroblastoma line (B35), and nuclei from cells of a human neuroblastoma line both exhibited levels of stimulation similar to that of HeLa nuclei. 5. The B50 and HeLa cells were also compared as to their sensitivity to other effects of methyl mercury.

  6. Pulse excitation of bolometer bridges

    NASA Technical Reports Server (NTRS)

    Rusk, S. J.

    1972-01-01

    Driving bolometer bridge by appropriately phased excitation pulses increases signal-to-noise ratio of bolometer sensor which operates on a chopped light beam. Method allows higher applied voltage than is possible by conventional ac or dc excitation.

  7. Apparatus for photon excited catalysis

    NASA Technical Reports Server (NTRS)

    Saffren, M. M. (Inventor)

    1977-01-01

    An apparatus is described for increasing the yield of photonically excited gas phase reactions by extracting excess energy from unstable, excited species by contacting the species with the surface of a finely divided solid.

  8. Antiproton Production by CR on Air Nuclei

    NASA Technical Reports Server (NTRS)

    Maskalenko, I. V.; Mashnik, S. G.

    2003-01-01

    Recent measurements of the cosmic ray (CR) antiproton flux have been shown to challenge existing CR propagation models. In particular, the conventional reacceleration model designed to match secondary/primary nuclei ratios produces too few antiprotons. Recently there appear some indications that the atmospheric contribution to antiproton production is considerably underestimated, which implies that antiproton CR flux might be lower. This may be the primary reason of the discrepancy discovered in CR propagation. We use the Los Alamos version of the Quark-Gluon String Model code LAQGSM together with available data on antiproton production on nuclei to analyse the accuracy of existing parameterizations of antiproton production cross section. The LAQGSM model has been shown to reproduce well nuclear reactions and hadronic data in the range 0.01-800 GeV/nucleon.

  9. Nuclei at HERA and heavy ion physics

    SciTech Connect

    Gavin, S.; Strikman, M.

    1995-12-31

    Copies of 16 viewgraph sets from a workshop held at Brookhaven National Laboratory, 17-18 November, 1995. Titles of talks: HERA: The Present; HERA: Potential with Nuclei; Review of Hadron-Lepton Nucleus Data; Fermilab E665: results in muon scattering; Interactions of Quarks and Gluons with Nuclear Matter; Rescattering in Nuclear Targets for Photoproduction and DIS; Structure Functions and Nuclear Effect at PHENIX; Probing Spin-Averaged and Spin-Dependent Parton Distributions Using the Solenoidal Tracker at RHIC (STAR); Jet Quenching in eA, pA, AA; Nuclear Gluon Shadowing via Continuum Lepton Pairs; What can we learn from HERA with a colliding heavy ion beam? The limiting curve of leading particles at infinite A; Coherent Production of Vector Mesons off Light Nuclei in DIS; A Model of High Parton Densities in PQCD; Gluon Production for Weizaecker-Williams Field in Nucleus-Nucleus Collisions; Summary Talk.

  10. Collective properties of drip-line nuclei

    SciTech Connect

    Hamamoto, I.; Sagawa, H.

    1996-12-31

    Performing the spherical Hartree-Fock (HF) calculations with Skyrme interactions and, then, using RPA solved in the coordinate space with the Green`s function method, the authors have studied the effect of the unique shell structure as well as the very low particle threshold on collective modes in drip line nuclei. In this method a proper strength function in the continuum is obtained, though the spreading width of collective modes is not included. They have examined also one-particle resonant states in the obtained HF potential. Unperturbed particle-hole (p-h) response functions are carefully studied, which contain all basic information on the exotic behaviour of the RPA strength function in drip line nuclei.

  11. Shell model for warm rotating nuclei

    SciTech Connect

    Matsuo, M.; Yoshida, K.; Dossing, T.

    1996-12-31

    Utilizing a shell model which combines the cranked Nilsson mean-field and the residual surface and volume delta two-body forces, the authors discuss the onset of rotational damping in normal- and super-deformed nuclei. Calculation for a typical normal deformed nucleus {sup 168}Yb indicates that the rotational damping sets in at around 0.8 MeV above the yrast line, and about 30 rotational bands of various length exists at a given rotational frequency, in overall agreement with experimental findings. It is predicted that the onset of rotational damping changes significantly in different superdeformed nuclei due to the variety of the shell gaps and single-particle orbits associated with the superdeformed mean-field.

  12. DAPI fluorescence in nuclei isolated from tumors.

    PubMed

    Krishan, Awtar; Dandekar, Payal D

    2005-08-01

    In DNA histograms of some human solid tumors stained with nuclear isolation medium--4,6-diamidino-2-phenylindole dihydrochloride (NIM-DAPI), the coefficient of variation (CV) of the G0/G1 peak was broad, and in nuclear volume vs DNA scattergrams, a prominent slope was seen. To determine the cause for this, nuclei from frozen breast tumors were stained with NIM-DAPI and analyzed after dilution or resuspension in PBS. In two-color (blue vs red) analysis, most of the slope and broad CV was due to red fluorescence of nuclei stained with NIM-DAPI, which was reduced on dilution or resuspension in PBS, resulting in elimination of the slope and tightening of the CV.

  13. Isobar giant resonance formation in self-conjugate nuclei

    NASA Astrophysics Data System (ADS)

    Townsend, L. W.; Deutchman, P. A.

    1981-03-01

    The production of isobars with concomitant giant resonance excitations due to peripheral collisions of relativistic heavy ions is investigated. The interaction is described by a modified form of the central term in the one-pion-exchange potential (OPEP) where the projectile ordinary spin operator is replaced by a transition spin operator which describes the creation of an isobar from a nucleon. The scattering is analyzed using time-dependent harmonic perturbation theory to determine the reaction total cross sections. The results obtained, which are valid for reactions involving self-conjugate nuclei, are applied to the specific collison of 2.1 {GeV}/{nucleon}16O projectiles with 12C targets at rest. Cross sections are investigated using two different models for the nuclear spin states. In the first model, the many-body nuclear spin state is reduced, in the spirit of a particle-hole state, to an equivalent two-body state called a particle-core state. In the second model, the many-body spin states are described by unsymmetrized products of individual particle spins. Properties of the spin giant resonance and isobar giant resonance states are investigated. Finally, isobar decay and isobar/pion absorption effects are discussed.

  14. Octupole response and stability of spherical shape in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Abrosimov, V. I.; Davidovskaya, O. I.; Dellafiore, A.; Matera, F.

    2003-11-01

    The isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized Vlasov equation. The octupole strength function is evaluated with different degrees of approximation. The zero-order fixed-surface response displays a remarkable concentration of strength in the 1ℏ ω and 3ℏ ω regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole resonances, but not the low-lying 3 - collective states, while the moving-surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei. The role of triangular nucleon orbits, that have been related to a possible instability of the spherical shape with respect to octupole-type deformations, is discussed within this model. It is found that, rather than creating instability, the triangular trajectories are the only classical orbits contributing to the damping of low-energy octupole excitations.

  15. Signatures of shape phase transitions in odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Nomura, K.; Nikšić, T.; Vretenar, D.

    2016-12-01

    Quantum phase transitions between competing ground-state shapes of atomic nuclei with an odd number of protons or neutrons are investigated in a microscopic framework based on nuclear energy density functional theory and the particle-plus-boson-core coupling scheme. The boson-core Hamiltonian, as well as the single-particle energies and occupation probabilities of the unpaired nucleon, are completely determined by constrained self-consistent mean-field calculations for a specific choice of the energy density functional and paring interaction, and only the strength parameters of the particle-core coupling are adjusted to reproduce selected spectroscopic properties of the odd-mass system. We apply this method to odd-A Eu and Sm isotopes with neutron number N ≈90 , and explore the influence of the single unpaired fermion on the occurrence of a shape phase transition. Collective wave functions of low-energy states are used to compute quantities that can be related to quantum order parameters: deformations, excitation energies, E 2 transition rates, and separation energies, and their evolution with the control parameter (neutron number) is analyzed.

  16. Green's function calculations of light nuclei

    NASA Astrophysics Data System (ADS)

    Sun, ZhongHao; Wu, Qiang; Xu, FuRong

    2016-09-01

    The influence of short-range correlations in nuclei was investigated with realistic nuclear force. The nucleon-nucleon interaction was renormalized with V lowk technique and applied to the Green's function calculations. The Dyson equation was reformulated with algebraic diagrammatic constructions. We also analyzed the binding energy of 4He, calculated with chiral potential and CD-Bonn potential. The properties of Green's function with realistic nuclear forces are also discussed.

  17. On Closed Shells in Nuclei. II

    DOE R&D Accomplishments Database

    Mayer, M. G.

    1949-04-01

    Discussion on the use of spins and magnetic moments of the even-odd nuclei by Feenberg and Nordheim to determine the angular momentum of the eigenfunction of the odd particle; discussion of prevalence of isomerism in certain regions of the isotope chart; tabulated data on levels of square well potential, spectroscopic levels, spin term, number of states, shells and known spins and orbital assignments.

  18. How do nuclei really vibrate or rotate

    SciTech Connect

    Andresen, H.G.; Kunz, J.; Mosel, U.; Mueller, M.; Schuh, A.; Wust, U.

    1983-01-01

    By means of the adiabatic cranking model the properties of the current and velocity fields of nuclear quadrupole vibrations for even-even nuclei in the rare-earth region are investigated. BCS correlated wave functions based on the Nilsson single particle Hamiltonian have been used. The current fields are analyzed in terms of vector spherical harmonics. The realistic microscopic currents show a vortex structure not present in the classical irrotational flow. The microscopic origin of the vortex structure is investigated.

  19. Accretion disk thermal instability in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Mineshige, S.; Shields, G. A.

    1990-03-01

    The nonlinear evolution and spatial propagation of the thermal instability in accretion disks in galactic nuclei are investigated. Integrations of the vertical structure of the disks are described for different alpha prescriptions, and the thermal stability is examined. Global time-dependent calculations of the unstable disks are performed which show that there are two distinct types of behavior according to the assumed prescription for the viscosity parameter: the 'purr' type and the 'roar' type. The roar type is analyzed in some detail.

  20. Deeply virtual Compton scattering off nuclei

    SciTech Connect

    Voutier, Eric

    2009-01-01

    Deeply virtual Compton scattering (DVCS) is the golden exclusive channel for the study of the partonic structure of hadrons, within the universal framework of generalized parton distributions (GPDs). This paper presents the aim and general ideas of the DVCS experimental program off nuclei at the Jefferson Laboratory. The benefits of the study of the coherent and incoherent channels to the understanding of the EMC (European Muon Collaboration) effect are discussed, along with the case of nuclear targets to access neutron GPDs.