Regular Series


Vol. 30 (1999), No. 3, pp. 405 – 838


Neutrino Oscillations and Supersymmetry

abstract

The Super-Kamiokande experiment measured the atmospheric muon and electron neutrinos. The standard model predicts a ratio of 2, while Super-Kamiokande and others measure a much smaller value (\(1.30 \pm 0.02\) for Super-Kamiokande). But Super-Kamiokande can also measure roughly the direction and the energy of the neutrinos. The zenith angle dependence for the muon neutrinos suggest that the muon neutrinos oscillate into a third neutrino species either into the \(\tau \) neutrino or a sterile neutrino. This finding is investigated within the supersymmetric model. The neutrinos mix with the neutralinos, this means the wino, the bino and the two higgsinos. The \(7 \times 7\) mass matrix is calculated on the tree level. One finds that the mass matrix has three linearly dependent rows which means, that two masses are zero. They are identified with the two lightest neutrino masses. The fit of the Super-Kamiokande data to oscillations between three neutrinos yields together with the result of supersymmetry that the third neutrino mass lies between \(2 \cdot 10^{-2} \) and \(10^{-1}\) [eV]. The two lightest neutrino masses are in supersymmetry on the tree level zero. The averaged electron neutrino mass which is the essential parameter in the neutrinoless double beta decay \(\left \lt {m_{\nu e}} \right \gt \simeq {m_{\nu 3}} \cdot P_{3e} \leq 0.8 \cdot 10^{-2}\) [eV] (95 \(\%\) confidence limit). It is derived from the Super-Kamiokande data in this supersymmetric model to be two orders smaller than the best value (1[eV]) from the neutrinoless double beta decay.


NEMO 3 — a Double-Beta Decay Experiment Without Neutrino Emission

abstract

The physics goals of double beta decay experiments are reminded. Various experimental aspects of the NEMO experiment are presented and the expected performances of NEMO 3 compared with previous or forthcoming other experiments.


all authors

V.A. Karnaukhov, S.P. Avdeyev, L.A. Petrov, V.K. Rodionov, H. Oeschler, O.V. Bochkarev, L.V. Chulkov, E.A. Kuzmin, A. Budzanowski, W. Karcz, M. Janicki, E. Norbeck, A.S. Botvina

Thermal and Dynamic Multifragmentation of Hot Nuclei Similarities and Differences

abstract

The experimental data on fragment multiplicities, their energy and charge distributions, the emission times are considered for the nuclear multifragmentation process induced by relativistic light projectiles (protons, helium) and heavy ions. With light projectiles, the multifragmentation is a pure “thermal” process, well described by the statistical models. Heavy-ion-induced multifragmentation is influenced by dynamic effects related first of all to the compression of the system in the collision. But statistical models can also be applied to rendering the partition of the system if the excitation energy is less than 10 MeV/nucleon and compression is modest. For the central collision of heavy ions the statistical approach fails to describe the data.


all authors

B. Zwieglinski, T. Odeh, C. Gross, C. Schwarz, R. Bassini, M. Begemann-Blaich, T. Blaich, H. Emling, A. Ferrero, S. Fritz, S.J. Gaff, G. Immé, I. Iori, U. Kleinevoss, G.J. Kunde, W.D. Kunze, V. Lindenstruth, U. Lynen, M. Mahi, A. Moroni, T. Möhlenkamp, W.F.J. Müller, B. Ocker, J. Pochodzalla, G. Raciti, Th. Rubehn, H. Sann, M. Schnittker, A. Schüttauf, W. Seidel, V. Serfling, J. Stroth, W. Trautmann, A. Trzcinski, G. Verde, A. Wörner, H. Xi, E. Zude

Nonequilibrium Features of the Nuclear Liquid-Gas Phase Transition

abstract

Energy spectra of protons emitted by the target residue in Au + Au collisions at 1 GeV/u were measured for different excitation energy bins. They reveal two components with different slopes attributed to preequilibrium and equilibrium emission. The relative contribution of the latter decreases rapidly with excitation energy, so that its presence becomes not apparent for the highest energy bins. It is argued therefore, that equilibrium may not be reached on the gas branch of the caloric curve.


BRAHMS (Experiment) at RHIC (Collider)

abstract

The RHIC facility of Brookhaven National Laboratory will provide the physicists community with a powerful new tool. For more than five years, it will be the only place in the word for experimental studies of strongly interacting matter in a completely new regime. This accelerator will collide different ions from protons to heavy nuclei at c.m. energies up to 500 GeV for protons and 200 GeV per nucleon pairs for Au nuclei. Theory of strongly interacting matter reveals that at very high temperatures there will be a transition from hadronic matter to a plasma of deconfined quarks and gluons. Such phenomenon is also expected at high baryon density even at zero temperature. It is of special interest to investigate different regions of the phase diagram for expected formation of the quark-gluon plasma. Regardless of whether the quark-gluon state of matter will be convincingly discovered or not, it is important to understand the basic phenomena open for investigation in the RHIC energy domain. The BRAHMS experiment has been designed to gather information on momentum spectra and yields for various emitted hadrons as a function of transverse momenta and rapidity. Early phase of the BRAHMS research concerns several subjects which are crucial for understanding phenomena that occur in heavy ion collisions within this unexplored energy domain. Among them are: (i) reaction dynamics, (ii) mini-jet production, (iii) \({\mit \Phi }\) meson production as quark–gluon plasma creation signature. The BRAHMS experiment will make a unique contribution to research of strongly interacting matter.


Classical Dissipative Function at Finite Mean Free Path

abstract

The dissipative function of slow collective motion in hot nuclei of arbitrary shape is presented in terms of nucleonic trajectories. The expression accounts for finiteness of nucleon mean free path \(\lambda \). The derivation starts from quantum formula for the dissipation rate of collective energy via the dressed particle-hole propagator. The extreme cases of \(\lambda \rightarrow \infty \) and \(\lambda \rightarrow 0\) are studied. As an example, explicit formulas are given for friction coefficients of multipole surface vibrations in spherical leptodermous nuclei.


Can Dissipative Dynamics with Fluctuations Explain Fusion of Heavy Systems?

abstract

A new method of calculating probabilities of rare events in the Langevin dynamics, based on importance sampling, has been used for analysis of the energy dependence of the fusion probability of a heavy nucleus-nucleus system, \(^{86}\)Kr+\(^{136}\)Xe, recently studied experimentally at GSI Darmstadt. The calculations were done applying the importance sampling method to a realistic three dimensional dynamical model based on the concept of one-body dissipation and including shell effects. Comparisons with experimental results show that the fusion processes observed in experiments extend to significantly lower energies than expected theoretically.


all authors

M.A. Bentley, C.D. O'Leary, D.E. Appelbe, R.A. Bark, D.M. Cullen, S. Ertürk, A. Maj, G. Martínez-Pinedo, A. Poves, J.A. Sheikh, D.D. Warner

Gamma-Ray Spectroscopy of High Spin States Near \(N=Z\) in the \(f _{{7}/{2}}\) Shell

abstract

Two pairs of mirror-nuclei, \(^{49}_{25}\)Mn/\(^{49}_{24}\)Cr and \(^{47}_{24}\)Cr/\(^{47}_{23}\)V, and the odd–odd \(N=Z\) nucleus \(^{46}_{23}\)V have been studied up to the \(f _{{7}/{2}}\)-shell band termination states. Differences in energy between isobaric analogue states in these nuclei have been measured and interpreted in terms of Coulomb effects. Through this work, we have shown that Coulomb energies are extremely sensitive to nuclear effects such as particle alignments, band terminations and shape changes. This has allowed us to investigate the extent to which the Coulomb energy can be used as a probe of the nuclear structure.


Nuclear Structure Studies by Direct Reactions with Radioactive Beams

abstract

The investigation of direct reactions with exotic beams in inverse kinematics gives access to a wide field of nuclear structure studies in the region far off stability. The basic concept and the methods involved are briefly discussed. The present contribution will focus on the investigation of light neutron-rich halo nuclei. Such nuclei reveal a new type of nuclear structure, namely an extended neutron distribution surrounding a nuclear core. A brief overview on this phenomenon, and on the various methods which gave first evidence and qualitative confirmation of our present picture of halo nuclei is given. To obtain more quantitative information on the radial shape of halo nuclei elastic proton scattering on neutron-rich light nuclei at intermediate energies was recently investigated for the first time. This method is demonstrated to be an effective means for studying the nuclear matter distributions of such nuclei. The results on the nuclear matter radii of \(^6\)He and \(^8\)He, the deduced nuclear matter density distributions, and the significance of the data on the halo structure is discussed. The present data allow also a sensitive test of theoretical model calculations on the structure of neutron-rich helium isotopes. A few examples are presented.


all authors

A. Bracco, F. Camera, S. Frattini, S. Leoni, B. Million, A. Maj, M. Kmiecik, B. Herskind, M. Bergström

Highly-Excited Normal and Super-Deformed Rotating Nuclei Studied with E1 and E2 \(\gamma \)-Continuum Measurements

abstract

The \(\gamma \)-decay in the continuum region and of both E1 and E2 types is investigated to learn about the properties of hot and warm rotating nuclei. In particular, two topics concerning highly excited nuclei are discussed. The first is the search for the \(\gamma \)-decay of the Giant Dipole Resonance built on superdeformed (SD) nuclear configurations of \(^{143}\)Eu. The available results seem to indicate that the superdeformation survives only few MeV above the yrast line. The second topic concerns the measurement the rotational quadrupole moment of thermally excited high spin states in \(^{168}\)Yb. A new technique, based on fluctuation analysis has been employed which has provided for the first time the value of the quadrupole moment from continuous spectra.


all authors

S. Leoni, A. Bracco, S. Frattini, G. Montingelli, E. Vigezzi, T. Døssing, B. Herskind, M. Matsuo

Nuclear Structure and Selection Rules in the Rotational Quasi-Continuum

abstract

The \(\gamma \)-decay of excited rotating nuclei is studied as function of heat energy through a statistical analysis of the fluctuation of counts in \(\gamma \)-\(\gamma \) coincident spectra. In particular, making use of the covariance technique between spectra gated by different intrinsic configurations, one can find if there are similarities among cascades feeding into different selected bands. This can be used to learn about the transition between order to chaos in the nuclear many-body system, in terms of the validity of selection rules associated with the quantum numbers of the intrinsic structure. Experimental results on the nucleus \(^{164}\)Yb seem to indicate a possible weakening of the selection rules already at the moderate excitation energy \(\geq \) 1 MeV above yrast, probed by the rotational decay-flow.


all authors

S.V. Förtsch, G.F. Steyn, J.J. Lawrie, J.V. Pilcher, A.A. Cowley, W.A. Richter, G.J. Arendse, J.A. Stander, G.C. Hillhouse, S.W. Steyn, J.W. Koen, S. Wyngaardt, R. Lindsay

Multistep Direct Processes in Polarization Phenomena and Composite Particle Emission

abstract

The statistical multistep theory of Feshbach, Kerman and Koonin has established itself in describing proton-induced preequilibrium reactions over a wide angular range up to an incident energy of 200 MeV. Extensions to the theory made it possible to also predict both the continuum cross sections and analysing powers of the (\(\vec {p},p^{\prime }\)), (\(\vec {p},\alpha \)) and (\(\vec {p},^{3}\)He) reactions at incident energies below 100 MeV. These reactions were recently also measured at incident energies above 100 MeV, thus providing further testing grounds of the inferred multistep reaction mechanism.


all authors

G.F. Steyn, A.A. Cowley, S.V. Förtsch, J.J. Lawrie, W.A. Richter, S.W. Steyn

Multistep Direct Processes in Nucleon Knockout Reactions

abstract

The success of statistical multistep direct (MSD) theories in describing continuum cross sections in inclusive (\(p,\,p^{\prime }\)) reactions is important for understanding preequilibrium emission from the continuum in exclusive (\(p,\,p^{\prime }p^{\prime \prime }\)) reactions. This ensures the accurate prediction of the contribution of the rescattering background to other processes, such as deep-lying hole states populated in discrete knockout of nucleons.


Bremsstrahlung \(\gamma \)-Ray Emission in Heavy-Ion Collisions at 6–11 MeV/u

abstract

It is shown that in mass-asymmetric reactions, such as \(^{12}\)C + \(^{24, 26}\)Mg and \(^{12}\)C + \(^{58, 64}\)Ni, the two types of \(\gamma \)-ray radiation, statistical GDR decay and bremsstrahlung emission, may be disentangled by angular distribution measurements. The data are well reproduced when bremsstrahlung spectra are calculated for velocity of the emitting source \(\beta _s = 0.5\cdot \beta _{\mathrm {beam}}\) and an inverse slope parameter \(E_0\) depending on \(\gamma \)-ray energy.


Entrance Channel Effects in the Population of Giant Dipole Resonances in Sn Nuclei

abstract

We have measured the high energy \(\gamma \)-ray spectra from the fusion reactions 130 MeV \(^{16}\)O + \(^{98}\)Mo and 240 MeV \(^{48}\)Ti + \(^{64}\)Ni, populating the \(^{114}\)Sn and \(^{112}\)Sn compound nuclei at the excitation energy of 108 MeV. The comparison of the spectra shows a \(\sim \)38% enhancement of the \(\gamma \)-ray yield in the Giant Dipole Resonance region \((E_{\gamma } \geq \)8 MeV) when the \(^{16}\)O induced reaction is considered. The experimental result is consistent with entrance channel effects related to the \(N/Z\) asymmetry between the target and the projectile.


all authors

G. Surówka, N. Iwasa, F. Boué, K. Sümmerer, T. Baumann, B. Blank, S. Czajkowski, A. Förster, M. Gai, H. Geissel, E. Grosse, M. Hellström, P. Koczon, B. Kohlmeyer, R. Kulessa, F. Laue, C. Marchand, T. Motobayashi, H. Oeschler, A. Ozawa, M.S. Pravikoff, E. Schwab, W. Schwab, P. Senger, J. Speer, C. Sturm, A. Surowiec, T. Teranishi, F. Uhlig, A. Wagner, W. Walus

Coulomb Dissociation of \(^8\)B at 254 MeV/u

abstract

As an alternative method to determine the cross section of \(^7{\rm Be}\,(p,\gamma )^8{\rm B}\), the Coulomb dissociation reaction \(^8{\rm B}\rightarrow ^7{\rm Be}+p\) at \(E_{\rm inc}=254\) MeV/u was measured. Our preliminary results show the dominant role of the dipole excitation in the Coulomb break-up process. The extracted astrophysical \(S_{17}\) factor is consistent with the lower-value results both of the direct-capture studies, and the RIKEN Coulomb-dissociation experiment at \(\sim \) 50 MeV/u.


all authors

C.N. Davids, P.J. Woods, D. Seweryniak, A.A. Sonzogni, J.C. Batchelder, C.R. Bingham, T. Davinson, D.J. Henderson, R.J. Irvine, G.L. Poli, J. Uusitalo, W.B. Walters

Proton Radioactivity — Spherical and Deformed

abstract

The proton drip line defines one of the fundamental limits to nuclear stability. Nuclei lying beyond this line are energetically unbound to the emission of a constituent proton from their ground states. This phenomenon is known as proton radioactivity. For near-spherical nuclei in the region of the drip line between \(Z = 69\) (Tm) and \(Z = 81\) (Tl), proton decay transition rates have been shown to be well reproduced by WKB calculations using spectroscopic factors derived from a low-seniority shell model calculation. Another approach using spectroscopic factors obtained from the independent quasiparticle approximation has also proved successful in this region. These interpretations have allowed the extraction of nuclear structure information from nuclei well beyond the proton drip line. The rare-earth proton emitters \(^{141}\)Ho and \(^{131}\)Eu have recently been observed, and their decay rates can only be explained by assuming large deformation for these nuclei. In addition to providing information on the wavefunctions and deformations of these nuclei, these results offer the opportunity to study the phenomenon of quantum mechanical tunneling through a deformed potential barrier.


all authors

K. Rykaczewski, J.C. Batchelder, C.R. Bingham, T. Davinson, T.N. Ginter, C.J. Gross, R. Grzywacz, Z. Janas, M. Karny, B.D. MacDonald, J.F. Mas, J.W. McConnell, A. Piechaczek, R.C. Slinger, J. Szerypo, K.S. Toth, W.B. Walters, P.J. Woods, E.F. Zganjar, W. Nazarewicz, P.B. Semmes

Studies of Nuclei at and Beyond the Proton Drip-Line with Stable and Radioactive Beams at HRIBF

abstract

Investigations of nuclei in the proton drip-line region performed at the Holifield Radioactive Ion Beam Facility (HRIBF) within the last two years are reviewed. In particular, the discovery of five new proton radioactivities \(^{140}\)Ho, \(^{141m}\)Ho, \(^{145}\)Tm, \(^{150m}\)Lu and \(^{151m}\)Lu is discussed. These proton emitters were produced by means of fusion-evaporation reactions and studied with a Recoil Mass Separator and a Double-sided Silicon Strip Detector. For \(^{113}\)Cs and \(^{151}\)Lu, the studies of level structure were extended beyond the proton-emitting states via the measurements with a clover array CLARION using Recoil Decay Tagging. The plan to use a fusion-evaporation reaction with a radioactive \(^{69}\)As beam developed at HRIBF, in order to study the decay of a new beta-delayed proton emitter \(^{125}\)Nd, is also described.


Probing Excited States in Nuclei at and Beyond the Proton Drip-Line

abstract

The coupling of a Compton-suppressed Ge (CSGe) detector array to a recoil separator has seen limited use in the past due to the low efficiency for measuring recoil-\(\gamma \) ray coincidences (\(\lt 0.1\% )\). With the building of new generation recoil separators and gamma-ray arrays, a substantial increase in detection efficiency has been achieved. This allows for the opportunity to measure excited states in nuclei with cross-sections below 100 nb. In this paper, results from the coupling of a modest array of CSGe detectors (AYE-Ball) and a current generation Ge array (Gammasphere) with a recoil separator (FMA) will be presented.


all authors

M.A. Riley, F.G. Kondev, A.V. Afanasjev, T.B. Brown, M.P. Carpenter, R.M. Clark, M. Devlin, P. Fallon, S.M. Fischer, D.J. Hartley, I.M. Hibbert, R.V.F. Janssens, D.T. Joss, T.L. Khoo, D.R. LaFosse, R.W. Laird, T. Lauritsen, F. Lerma, M. Lively, W.C. Ma, P.J. Nolan, N.J. O'Brien, E.S. Paul, J. Pfohl, I. Ragnarsson, D.G. Sarantites, R.K. Sheline, S.L. Shepherd, J. Simpson, R. Wadsworth

Discrete Line Spectroscopy at the Extremes of Angular Momentum in Normal Deformed \(^{156}\)Dy and Global Differential Lifetime Measurements in the \(A\sim 130\) Highly-Deformed Region

abstract

The highest-spin discrete states (\(I\sim 60\hbar \) and \(E_{x} \sim 30\)MeV) in normal deformed nuclei have been observed in the rare-earth isotope \(^{156}\)Dy using the GAMMASPHERE spectrometer. The quadrupole moments for a variety of configurations, including the \(9/2^{+}[404]\, ({g}_{9/2})\) proton, \(1/2^{+}[660]\,({i}_{13/2})\) and \(1/2^{-}[541]\, ({f}_{7/2},{h}_{9/2})\) neutron orbitals, were measured in a wide range of \(\sim 130\) nuclei.


Collective Exchange Effect in Nuclear Collective Models

abstract

Possible new quantum effect related to quantum exchange force phenomenon is postulated to explain small staggerings observed in superdeformed and ground state rotational bands of nuclei.


The Microscopic Quasiparticle–Phonon Model

abstract

The Microscopic Quasiparticle–Phonon Model (MQPM) is shortly presented. The energies of excited states of odd \(N=82\) isotones calculated using MQPM are compared to results obtained by making large-scale shell-model calculations with microscopic effective interaction. Comparison to experimental spectra shows that MQPM can reproduce the experimental spectra better than shell-model when the number of valence nucleons is large.


all authors

J. Kormicki, H.K. Carter, D.W. Stracener, J.R. Beene, R.F. Welton, P.E. Mueller

Radioactive Ion Beam Development at HRIBF

abstract

At the Holifield Radioactive Ion Beam Facility the hardware to produce and deliver the RIB’s for nuclear physics and nuclear astrophysics experiments is in the initial stage of operation. The \(^{69}\)As and \(^{17}\)F have been delivered for the first experiments. Presently intense research is in progress to improve the intensity of As and F beams. The \(^{63,64}\)Ga beams and the \(^{56}\)Ni beam in batch mode are in development plans.


Experiments with Superheavy Nuclei

abstract

In two series of experiments at SHIP, six new elements (\(Z=107-112\)) were synthesized via fusion reactions using lead or bismuth targets and 1\(n\)-deexcitation channels. The isotopes were unambiguously identified by means of \(\alpha \)-\(\alpha \) correlations. Not fission, but alpha decay is the dominant decay mode. Cross-sections decrease by two orders of magnitude from bohrium (\(Z=107\)) to element 112, for which a cross-section of 1 pb was measured. Based on these results, it is likely that the production of isotopes of element 114 close to the island of spherical SuperHeavy Elements (SHE) could be achieved by fusion reactions using \(^{208}\)Pb targets. Systematic studies of the reaction cross-sections indicate that the transfer of nucleons is an important process for the initiation of fusion. The data allow for the fixing of a narrow energy window for the production of SHE using 1n-emission channels. The likelihood of broadening the energy window by investigation of radiative capture reactions, use of neutron deficient projectile isotopes and use of actinide targets is discussed.


all authors

M. Leino, R.G. Allatt, J.F.C. Cocks, O. Dorvaux, K. Eskola, P.T. Greenlees, K. Helariutta, P.M. Jones, R. Julin, S. Juutinen, H. Kankaanpää, A. Keenan, H. Kettunen, P. Kuusiniemi, M. Muikku, P. Nieminen, R.D. Page, P. Rahkila, A. Savelius, W.H. Trzaska, J. Uusitalo

In-Beam and Decay Studies of Neutron-Deficient Isotopes of Heavy Elements

abstract

An intensive program to study the production, decay properties, and nuclear structure of isotopes of heavy elements is underway at the Department of Physics, University of Jyväskylä, Finland (JYFL). The main tools used in these studies are the gas-filled recoil separator RITU and various germanium detector arrays. Illustrative examples from both decay and in-beam studies will be presented.


Two Applications of the Nuclear Thomas–Fermi Model

abstract

We use the Thomas–Fermi model of macroscopic nuclear properties described in W.D. Myers and W.J. Swiatecki, Nucl. Phys. A601, 141 (1996), to discuss two applications: a) the response of the nuclear energy to changes of the neutron and proton diffusenesses, and b) the equation of state of cold nuclear matter. Under a) formulae are provided which will make it possible to improve existing Microscopic–Macroscopic calculations of nuclear properties by the inclusion of the two degrees of freedom associated with the neutron and proton diffusenesses. The algebraic formulae presented under b) may serve as a reliable baseline estimate of the equation of state. It is argued that the value of the nuclear compressibility coefficient \(K\) as well as its dependence on the relative neutron excess are now fairly well determined.


all authors

Z. Janas, J. Agramunt, A. Algora, L. Batist, B.A. Brown, D. Cano-Ott, R. Collatz, A. Gadea, M. Gierlik, M. Górska, H. Grawe, A. Gulielmetti, M. Hellström, Z. Hu, M. Karny, R. Kirchner, F. Moroz, A. Piechaczek, A. Płochocki, M. Rejmund, E. Roeckl, B. Rubio, K. Rykaczewski, M. Shibata, J. Szeryp, J.L. Tain, V. Wittmann, A. Wöhr

Beta Strength Distribution in the Decays of Neutron–Deficient Nuclei

abstract

The results of recent studies of the Gamow–Teller \(\beta \)-decays of nuclei in the \(^{100}\)Sn region are presented. Measurements performed with the use of the total absorption \(\gamma \)-ray spectrometer and the Cluster Cube array of germanium detectors revealed qualitatively new information on the Gamow–Teller strength distribution in the decays of \(^{97,98}\)Ag and \(^{103-107}\)In. The shape of the measured \(\beta \)-strength distribution and the resulting total \(B_{\rm GT}\) values are compared with the results of shell-model calculations.


all authors

P. Jones, P. Rahkila, J.F.C. Cocks, K. Helariutta, R. Julin, S. Juutinen, H. Kankaanpää, H. Kettunen, P. Kuusiniemi, Y. Le Coz, M. Leino, M. Muikku, P. Nieminen, A. Savelius

Recent Results from the SARI Array with RITU at JYFL

abstract

A compact array of segmented clover detectors has been used in conjunction with a high transmission recoil separator. Prompt gamma-rays are detected by the array, and the subsequent recoiling nucleus by a position sensitive silicon detector at the separator focal plane. Isomeric gamma-ray transitions were also detected by germanium detectors at the focal plane. Transitions from the \(^{166}\)Er(\(^{28}\)Si, \(4n)^{190}\)Pb thin-target reaction at 143 MeV were studied. Both prompt and isomeric states were observed associated with spherical, oblate and prolate configurations.


all authors

S. Hankonen, P. Dendooven, J. Huikari, A. Jokinen, V. Kolhinen, G. Lhersonneau, A. Nieminen, K. Peräjärvi, V. A. Rubchenya, W. H. Trzaska, J.C. Wang, J. Äystö

Production of Neutron-Rich Nuclei with \(A\lt 80\) in Superasymmetric Fission at IGISOL

abstract

Ion guide-based isotope separator has been used in order to study the superasymmetric fission mode at intermediate proton energies. These results, together with the fission fragment mass distributions obtained with HENDES array, indicate that fission at intermediate proton energies is a potential tool in producing nuclei near doubly magic \(^{78}\)Ni. Furthermore, the beta-decay of \(^{69}\)Co has been identified for the first time and its half-life has been measured.


all authors

N. Amzal, P.A. Butler, G.D Jones, D. Hawcroft, R.-D. Herzberg, D.P. Rea, F. Hannachi, C.F. Liang, P. Paris, B. Gall, F. Hoellinger, N. Schulz

Test of Parity Doubling in \(^{223}\)Th

abstract

The level structure of the odd-\(A\) nucleus \(^{223}\)Th has been investigated by means of in beam electron conversion and gamma-ray spectroscopy. Measurements of the \(B\)(M1)/\(B\)(E2) branching ratios for transitions in both positive and negative parity bands in \(^{223}\)Th have been carried out using the GAREL+ facility at IReS Strasbourg.


all authors

P.T. Greenlees, N. Amzal, P.A. Butler, K.J. Cann, J.F.C. Cocks, D. Hawcroft, G.D. Jones, R.D. Page, A. Andreev, T. Enqvist, P. Fallon, B. Gall, M. Guttormsen, K. Helariutta, F.P. Hessberger, F. Hoellinger, P. Jones, R. Julin, S. Juutinen, H. Kankaanpää, H. Kettunen, P. Kuusiniemi, M. Leino, S. Messelt, M. Muikku, A. Savelius, A. Schiller, S. Siem, W.H. Trzaska, T. Tveter, J. Uusitalo

Identification of Excited States in \(^{226}\)U

abstract

Two experiments have been performed at the Accelerator Laboratory of the Department of Physics, University of Jyväskylä, Finland, and are reported here. The first experiment was a recoil-decay tagging study intended to delineate the level scheme of \(^{226}\)U for the first time. The subsequent experiment, the observation of fine structure in the \(\alpha \) decay of \(^{230}\)Pu, was to obtain an improved measurement of the excitation energy of the first excited 2\(^{+}\) state, which was tentatively assigned in the first experiment.


Ground-State Rotational Energies of Deformed Superheavy Nuclei

abstract

Ground-state rotational energies of heavy and superheavy nuclei are calculated in the cranking approximation. Even-even nuclei with proton number \(Z=94-114\) and neutron number \(N=146-168\) are considered. The results are interpreted in terms of the shell structure of these nuclei.


Surface Diffuseness and Properties of Spherical Superheavy Nuclei

abstract

Proton and neutron surface diffusenesses are treated as degrees of freedom in macroscopic-microscopic calculations. Their values are established by minimization of the energy of a nucleus. The effect on nuclear properties such as single-particle spectra and the shell correction to the energy (mass) of a nucleus is studied. Even-even spherical superheavy nuclei with the magic neutron number \(N=184\) and the proton numbers \(Z=110\) to 126 are considered.


Shell Model Analysis of \(N=82\) Isotones Above \(^{132}\)Sn

abstract

Nuclei with up to 6 protons added to \(^{132}\)Sn are described within a truncated shell model basis formed by the proton orbits \(0g_{7/2}\), \(1d_{5/2}\), \(1d_{3/2}\), \(2s_{1/2}\) and \(0h_{11/2}\). Single-particle energies and two-body interaction matrix elements are determined from experimental excitation energies in \(^{133}\)Sb and \(^{134}\)Te. These parameters are then used for calculating levels in \(^{135}\)I, \(^{136}\)Xe, \(^{137}\)Cs and \(^{138}\)Ba. The calculated energies agree well with experimental values in these 4 nuclei.


Present Status of Shell Model Techniques

abstract

The technical problems appearing in Shell Model calculations are discussed. The solutions developped in the codes ANTOINE (\(m\)-scheme) and NATHAN (coupled scheme) are explained with a special focus on the treatment of giant matrices. New possiblities, limitations and possible improvements are presented.


Shell-Model Calculations with Bonn Potential

abstract

We present the results of a shell-model study of nuclei having or lacking few identical nucleons with respect to doubly magic \(^{208}\)Pb. Our calculations have been performed by making use of realistic effective interactions derived from the Bonn A nucleon–nucleon potential. The results are in very good agreement with experimental data showing the ability of these effective interactions to describe with quantitative accuracy the properties of heavy-mass nuclei around closed shells.


all authors

W. Reviol, L.L. Riedinger, B.H. Smith, C.R. Bingham, W. Weintraub, M.P. Carpenter, R.V.F. Janssens, S.M. Fischer, D. Nisius, D. Seweryniak, D. Jenkins, R. Wadsworth, A.N. Wilson, E.F. Moore

Superdeformation and Prolate–Oblate Competition in Tl Nuclei

abstract

Spectroscopic studies of weakly populated proton \(i_{13/2}\) bands in superdeformed Tl nuclei (around mass 190) and in the normally deformed, very light \(^{183}\)Tl nucleus are discussed. Among the results presented, the first measurement of a superdeformed quadrupole moment in an odd-\(Z\) nucleus, \(^{191}\)Tl, is reported. The experiments were conducted with the Gammasphere array as “stand-alone” device and coupled with the Argonne Fragment Mass Analyzer.


all authors

M. Rejmund, K.H. Maier, R. Broda, B. Fornal, M. Lach, J. Wrzesiński, J. Blomqvist, A. Gadea, J. Gerl, M. Górska, H. Grawe, M. Kaspar, H. Schaffner, Ch. Schlegel, R. Schubart, H. J.Wollersheim

Particle-Octupole Vibration Coupling Near \(^{208}\)Pb

abstract

High spin states in nuclei around \(^{208}{\rm Pb}\) were populated in deep inelastic collisions of \(^{136}{\rm Xe}\), and \(^{208}{\rm Pb}\) projectiles with \(^{208}{\rm Pb}\) targets at beam energies about 12% above the Coulomb barrier. New states in nuclei in vicinity of \(^{208}\)Pb have been found that are resulting from coupling of one and two valence quasi-particles to the lowest 3\(^-\) excitation of \(^{208}\)Pb core. The results are presented and discussed in the frame of the Particle-Octupole Vibration Coupling model.


all authors

M. Górska, H. Grawe, D. Kast, G. de Angelis, P.G. Bizzeti, B.A. Brown, A. Dewald, C. Fahlander, A. Gadea, A. Jungclaus, K.P. Lieb, K.H. Maier, D.R. Napoli, Q. Pan, R. Peusquens, M. De Poli, M. Rejmund, H. Tiesler

High Spin Spectroscopy of \(^{104}\)Sn

abstract

High spin states in \(^{104}\)Sn were identified in the reaction \(^{58}\)Ni(\(^{50}\)Cr, \(2p2n\)) at 200 MeV and 205 MeV beam energies. The \(\gamma \)-ray energies, intensities, multipolarities and lifetimes of high spin states were measured with the GASP spectrometer array in combination with a plunger apparatus by means of the recoil distance Doppler shift method. The deduced level scheme and transition probabilities are compared to large scale shell model calculations. The agreement of the level energies is satisfactory, except for a cascade of dipole transitions at high spins. The general good agreement found for \(E2\) transition strengths implies a large effective neutron polarization charge. The measured enhanced \(E3\) transitions cannot be accounted for, which indicates an admixture of a core excited octupole phonon.


all authors

M. Lach, P. Bednarczyk, W. Męczyński, J. Styczeń, K.H. Maier, K. Spohr, M. Rejmund, H. Grawe, G. de Angelis, D. Bazzacco, F. Brandolini, S. Lunardi

High-Spin Structure of \(^{57}\)Ni and Nuclei Nearby

abstract

Nuclei, \(^{57}\)Ni, \(^{58}\)Ni, \(^{57}\)Co, from the closest vicinity of doubly magic \(^{56}\)Ni have been investigated in a series of in-beam \(\gamma \)-spectroscopy measurements. New experimental results concerning the structure of \(^{57}\)Ni are discussed in details. The observed excitations are qualitatively interpreted in the frame of shell model.


Shell Model and Nuclear Structure Far from Stability

abstract

We describe the properties of neutron-rich nuclei around \(N=28\) and \(N=20\) in the shell model framework. The valence space includes the \(sd\) shell for protons and \(pf\) shell for neutrons without any restrictions. Good agreement is found with the available data and the \(N=28\) shell closure is shown to be persisting. Then we perform calculations in the \(N=20\) region where the valence space is enlarged to include intruder states. We are able to account for the vanishing of the \(N=20\) neutron shell and the dominance of the intruders explains the collective features experimentally found in this region.


Nuclei Far from \(\beta \)–Stability within Relativistic Mean Field Theory

abstract

The binding energies, neutron and proton separation energies, shapes and sizes of even-even \(\beta \)–stable nuclei with \(A\geq 40\) and a few chains of isotopes with \(Z=\) 50, 56, 82, 94 protons and isotones with \(N=\) 50, 82, 126 neutrons are studied within the relativistic mean field theory.


Some Questions of the Nuclear Properties Evidence in Simple Photonuclear Reactions

abstract

The results of the study of photonuclear reactions at energies of accelerated electrons ranging up to 40 MeV are presented. Under study were simple \((\gamma , n)\) and \((\gamma , p)\) reaction processing via the excitation of the metastable longlived nuclear states. The data of the isomeric ratio measurements and comparison with results of calculations made in the framework of the statistical models allow one to investigate some characteristics of the excited intermediate nuclei.


Collective Quadrupole Excitations in Even–Even Ru Isotopes

abstract

Quadrupole excitations in Ru isotopes are described within microscopic approach including the effect od pairing dynamics. The observed collective energies and transition probabilities of \(^{104,112}\)Ru are reproduced in the calculation containing no free parameters.


Pseudo-SU(2) Symmetry and a Low Energy Limit of the Dirac Equation with the Woods–Saxon Potentials

abstract

A structure of the Woods–Saxon deformed mean-field Hamiltonian adapted to the nuclear Dirac equation is discussed. The underlying SU(2) symmetries of the Hamiltonian are reviewed together with their consequences for the behavior of the single-nucleon spectra. This brings up a strong motivation for introducing the realistic Woods–Saxon parametrisation in such a way that the position-dependent effective mass, an extra linear momentum potential and other features are directly modeled. It is demonstrated that the relatively low values of the effective mass in the nuclear interior do not cause any incorrect level-density problem close to the Fermi level. Moreover, an over-all correct spreading of the single-particle levels over a large energy scale and a very good single-particle level order can be obtained. The corresponding preliminary calculation results are illustrated.


all authors

D. Hawcroft, R.-D. Herzberg, D.E. Appelbe, P.A. Butler, A.J. Chewter, G.D. Jones, D.P. Rea, D.G. Aschman, B.R.S. Babu, R. Bark, R. Beetge, M. Benatar, G.D. Dracoulis, R. Fearick, S.V. Fortsch, S. Juutinen, H. Kankaanpää, J.J. Lawrie, G.K. Mabala, N. Mhlahlo, S. Murray, S. Naguleswaran, C. Rigollet, J.F. Sharpey-Schafer, B. Simpson, R. Smit, D. Steyn, V.M. Tshivhase, W. Whittaker

Search for Hyperdeformation in U Isotopes

abstract

The \(^{232}\)U nucleus was studied in order to search for a hyperdeformed band built upon the third minimum of the fission barrier. Upper limits for the percentage population of a hypothetical hyperdeformed band relative to the ground state band are given.


all authors

N. Kintz, Ch. Finck, O. Stézowski, J.P. Vivien, A. Nourreddine, K. Zuber, D.E. Appelbe, C.W. Beausang, F.A. Beck, T. Byrski, S. Courtin, D. Curien, G. Duchêne, S. Ertürk, G. de France, B.J.P. Gall, B. Haas, N. Khadiri, A. Lopez-Martens, E. Pachoud, C. Rigollet, M. Smith, P.J. Twin

\(^{149}\)Gd: What’s Confirmed? What’s New?

abstract

A long run performed with EUROGAM II allowed remeasuring the \(^{149}\)Gd superdeformed (SD) band 1. The \(\Delta I = 4\) bifurcation in band 1 is confirmed and two resolved \(\gamma \)-ray transitions linking the SD band 1 and the normal deformed states have been observed.


Towards New Understanding of Nuclear Rotation

abstract

Properties of time evolution of wave packets built up from rotator eigenstates are discussed. The mechanism of perfect cloning of the initial wave packet for circular states at fractional revival times is explained. The smooth transition from circular to linear through intermediate elliptic states is described. Examples of time evolution of a nuclear wave packet created in Coulomb excitation mechanism are presented.


Average Nuclear Potentials from Selfconsistent Semiclassical Calculations

abstract

Using the selfconsistent semiclassical Extended Thomas–Fermi (ETF) method up to 4\(^{\mathrm th}\) order in connection with Skyrme forces it is demonstrated that the neutron and proton average potentials obtained using the semiclassical functionals \(\tau ^{\rm (ETF)}[\rho ]\) and \(\vec {J}^{\rm (ETF)}[\rho ]\) reproduce the corresponding Hartree–Fock fields extremely well, except for shell oscillations in the nuclear center.


Influence of the Initial Spin Distribution on the Decay of Compound Nuclei

abstract

The competition between fission and \(n\), \(p\) and \(\alpha \)-particle emission and fusion process is studied. The calculations are performed for \(^{160}\)Yb and \(^{126}\)Ba nuclei at excitation energies from 80 MeV up to about 300 MeV. The nuclear fission is described by a Langevin equation coupled to the Master equation for particle evaporation. A significant influence of the initial spin distribution of the compound nucleus on the prescission particles multiplicities is found.


The Role of Pairing Correlations for the Description of \(\beta \) Vibrations at Superdeformed Shapes

abstract

In this paper we analyze the possibility of the appearance of quadrupole vibrational states in superdeformed nuclei from the \(A\approx 150\) region. We discuss the role of pairing correlations for a proper description of quadrupole vibrations, especially of the \(\beta \) type.


Rotation of Superdeformed Even–Even Nuclei

abstract

Starting from the microscopic Hamiltonian, we generalized the Bohr–Mottelson equation to describe both the rotation and \(\beta \)-vibrations of superdeformed even-even axially symmetric nuclei.


Microscopic Calculations of Stellar Weak Rates for \(sd\)- and \(fp\)-Shell Nuclei for Astrophysical Applications

abstract

Proton-netron quasiparticle RPA is used for the first time to calculate weak interaction rates for \(\mathit {sd}\)- and \(\mathit {fp}\)-shell nuclei at high temperatures and densities. The calculated rates take into consideration the latest experimental energy levels and \(ft\) value compilations. Particle emission processes from excited states are taken into account. The calculation is done for 700 nuclei with mass number ranging from 18 to 100. The astrophysical applications of the calculated rates are highlighted.


Quantum Mechanics of the Electric Charge

abstract

This is a summary of the talk presented by the Author at the XXXIII Zakopane School of Physics, Zakopane, Poland, September 1–9, 1998.


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