共查询到20条相似文献,搜索用时 448 毫秒
1.
I. Hamamoto 《The European physical journal. Special topics》2007,150(1):123-126
Both
positive-energy and weakly-bound one-particle levels for neutrons in
Y20 deformed Woods-Saxon potentials are examined in comparison with those
in spherical Woods-Saxon potentials.
While s1/2 levels play a unique role in spherical drip-line nuclei,
the Ωπ = 1/2+ levels in Y20 deformed potentials,
which always contain some amount of s1/2 component, exhibit an
important role in deformed drip-line nuclei.
As the potential strength becomes weaker, some weakly-bound
Ωπ = 1/2+ levels continue to the positive-energy region as
one-particle resonant levels, while others have no such continuation.
Among an infinite number of one-particle levels at a given positive-energy
and in a given deformed potential, only some selected levels expressed
in terms of eigenphase
are found to be important in the pair-correlated ground state of
neutron-drip-line nuclei. 相似文献
2.
M. Bender T. Cornelius G.A. Lalazissis J.A. Maruhn W. Nazarewicz P.-G. Reinhard 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):23-28
Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms
of deformed ground states of Hg and Po isotopes.
Received: 25 October 2001 / Accepted: 28 February 2002 相似文献
3.
H. Röpke J. Brenneisen M. Lickert 《The European Physical Journal A - Hadrons and Nuclei》2002,14(2):159-167
Eight high-spin states in 36Ar below 10MeV excitation energy, among them a prospective J
π = 8- state at 9408keV and the J? 8 levels of the recently discovered superdeformed rotational band, have been observed by n-γ coincidence measurements with
the 33S(α, nγ) reaction at E
α = 14.4 and 13.4MeV. High-spin assignments of, respectively, J
π = 6+ and 5- were obtained for the E
p = 1209 and 1462keV (E
x = 9682 and 9927keV) resonances of the 35Cl (p,γ) reaction by a measurement of γ-ray angular distributions. The spectrum of the high-spin and of the E
x? 7.4MeV levels is decomposed according to the underlying shell model configurations with n = 0, 1, 2, 4 particles excited from the N = 2 into the N = 3 major shell. The role of four-particle excitations, all connected with large prolate distortions, is elucidated for the
entire A = 36-40 mass region.
Received: 21 December 2001 / Accepted: 25 March 2002 相似文献
4.
H.A. Roth S.E. Arnell D. Foltescu Ö. Skeppstedt J. Blomqvist G. de Angelis D. Bazzacco S. Lunardi 《The European Physical Journal A - Hadrons and Nuclei》2001,10(3):275-287
High-spin level schemes of the N = 80 isotones 146Dy, 147Ho and 148Er have been investigated by in-beam γ-ray spectroscopic methods using the NORDBALL Compton-suppressed multidetector array
including proton and neutron selection. The projectile-target system 58Ni + 92Mo at 260 MeV beam energy has been used to produce the neutron-deficient N = 80 isotones. The previously known schemes have been extended to considerably higher spin and exitation energy, up to I = 23?, E
x≈ 8.9 MeV in 146Dy, I = 53/2?, E
x≈ 8.7 MeV in 147Ho and I = 23?, E
x≈ 9.6 MeV in 148Er. The results are discussed in terms of the spherical shell model. Many of the levels can be described within this framework.
Received: 12 January 2001 / Accepted: 11 April 2001 相似文献
5.
T. Kautzsch W.B. Walters M. Hannawald K.-L. Kratz V.I. Mishin V.N. Fedoseyev W. Böhmer Y. Jading P. Van Duppen B. Pfeiffer A. Wöhr P. Möller I. Klöckl V. Sebastian U. Köster M. Koizumi J. Lettry H.L. Ravn the ISOLDE Collaboration 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):201-206
A chemically selective laser ion source has been used in a β-decay study of heavy Ag isotopes into even-even Cd nuclides.
Gamma-spectroscopic techniques in time-resolving event-by-event and multiscaling modes have permitted the identification of
the first 2+ and 4+ levels in 126Cd78, 128Cd80, and tentatively the 2+ state in 130Cd82. From a comparison of these new states in 48Cd with the E(2+) and E(4+)/E(2+) level systematics of 46Pd and 52Te isotopes and several recent model predictions, possible evidence for a weakening of the spherical N = 82 neutron-shell below double-magic 132Sn is obtained.
Received: 13 July 2000 / Accepted: 12 October 2000 相似文献
6.
Zs. Podolyák P.G. Bizzeti A.M. Bizzeti-Sona S. Lunardi D. Bazzacco A. Dewald A. Algora G. de Angelis E. Farnea A. Gadea D.R. Kasemann T. Klug Th. Kröll S. Lenzi D.R. Napoli C.M. Petrache R. Peusquens C. Rossi Alvarez T. Martinez C.A. Ur 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):29-36
Lifetimes of excited states in 148Gd were measured using the recoil distance method with a plunger device coupled to the EUROBALL Ge detector array. The differential
decay curve method in coincidence mode allowed the unambiguous determination of lifetimes of more than 20 excited states.
The obtained transition strengths are in good agreement with the shell model calculations. The effect of the Z = 64 subshell closure on the B(E2 : 2+ → 0+) reduced strengths above the N = 82 magic number is discussed.-1
Received: 14 November 2002 / Accepted: 4 February 2003 / Published online: 29 April 2003 相似文献
7.
Strengths of Gamow-Teller decays of Tz = ±1 nuclei to Tz = 0 odd-odd nuclei have been calculated by using spherical shell model and deformed Nilsson wave functions. The role and
competition of the microscopic direct and spin-flip mechanisms generating Gamow-Teller transitions are analyzed. Analytical
expressions derived for the B(GT) values give useful insight into the regularities of B(GT) values along the N = Z line. The crucial role of configuration mixing is discussed. 相似文献
8.
W. von Oertzen 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):133-139
The systematics for binding energies per α-particle in N = Z nuclei, E
Bα/N
α, are studied up to 164Pb. It is shown that, although a geometrical model can be used to explain the systematics for light nuclei, the binding energy
per α-particle exhibits structures which are due to the well-known shells of the mean field of nucleons in nuclei. The overall
dependence of E
Bα/N
α on N
α in N = Z nuclei (for the ground-state masses) can be described in a liquid-drop model of α-particles. Conditions for a phase change
with the formation of an α-particle condensate, a dilute Bose gas in excited compound nuclei are discussed for E
Bα/N
α = 0, at the thresholds. This is achieved when the binding energy per nucleon in nuclei is equal to or smaller than in the
α-cluster. At somewhat smaller excitation energies the appearance of a Bose gas with a closed-shell core (N = Z, e.g. of 40Ca) is proposed within the same concept. The experimental observation of the decay of such condensed α-particle states is
proposed with the coherent emission of several correlated α-particles not described by the Hauser-Feshbach approach for compound-nucleus
decay. This decay will be observed by the emission of unbound resonances in the form of 8Be and 12C * (0+
2) clusters. 相似文献
9.
S.W. Ødegård B. Herskind T. Døssing G.B. Hagemann D.R. Jensen G. Sletten J.N. Wilson S. Leoni P.O. Tjøm P. Bednarczyk D. Curien 《The European Physical Journal A - Hadrons and Nuclei》2002,14(3):309-316
High-spin properties of the triaxial strongly deformed potential well in 163Lu at excitation energies above resolvable bands have been investigated. Gated E
γ-E
γ spectra display clear ridges with moments of inertia corresponding to those observed for the discrete strongly deformed bands.
A fluctuation analysis of the ridges yields a number of two-step paths of ≈ 40 and ≈ 20, when gating on triaxial strongly
or normally deformed bands, respectively. These results show that a potential well at large deformation coexists with the
normally deformed well, and indicate a mixing between states in the two wells at higher excitation energy.
Received: 4 January 2002 / Accepted: 6 May 2002 相似文献
10.
Y. Toh T. Czosnyka M. Oshima T. Hayakawa H. Kusakari M. Sugawara Y. Hatsukawa J. Katakura N. Shinohara M. Matsuda 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):353-356
74Ge beam was Coulomb-excited on a natPb target. Ten E2 matrix elements including diagonal matrix elements for 5 low-lying states have been determined using the least-squares search
code GOSIA. The expectation values of the rotational invariants 〈Q
2〉 and 〈cos3δ〉 show the small and triaxial deformation of the two lowest members of the ground-state band , while the 02
+ and 22
+ states are found to be almost spherical.
Received: 31 August 2000 / Accepted: 4 December 2000 相似文献
11.
Y. Gono A. Odahara T. Fukuchi E. Ideguchi T. Kishida T. Kubo H. Watanabe S. Motomura K. Saito O. Kashiyama T. Morikawa B. Cederwall Y.H. Zhang X.H. Zhou M. Ishihara H. Sagawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):5-8
Isomers in N = 83 isotones of Z = 60-66, were studied systematically. Their spins and parities are 49/2+ and 27+ for odd and odd-odd nuclei, respectively. Nearly constant excitation energies of these isomers indicated a decrease of a
Z = 64 shell gap energy as Z decreases from 64 to 60 within the framework of a deformed independent-particle model (DIPM). Their configurations are [ν(f
7/2
h
9/2
i
13/2),π(h
11/2)2]49/2+ and [ν(f
7/2
h
9/2
i
13/2),π(h
11/2)2(d
5/2)-1]27+ for odd and odd-odd nuclei, respectively. The shape of the yrast states changes suddenly at spin 49/2(odd) and 27(odd-odd)
from a near spherical to an oblate shape. Transitions from isomers are highly hindered because of the shape changes. They
may be categorized to be shape isomers. The development of a secondary beam produced by using these high-spin isomers is also
described.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
12.
E. Caurier F. Nowacki A. Poves 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):145-150
Recent shell model calculations for the neutron-rich nuclei around the magic numbers N = 20, N = 28 and N = 40 are reviewed. We stress two points: i) The crucial role played by the monopole part of the effective interaction that
determines the evolution of the spherical mean field. In particular, the reduction in the quasiparticle gaps at the magic
numbers can erode or even erase the shell closures. ii) The rich variety of structures that can be found in these situations,
with coexisting deformed and spherical states, rapid changes of behaviour with N or Z, and the massive occurrence of intruder states as ground states.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: alfredo.poves@uam.es 相似文献
13.
J. Ekman D. Rudolph C. Fahlander R.J. Charity W. Reviol D.G. Sarantites V. Tomov R.M. Clark M. Cromaz P. Fallon A.O. Macchiavelli M. Carpenter D. Seweryniak 《The European Physical Journal A - Hadrons and Nuclei》2000,9(1):13-17
Eighteen previously unknown γ-ray transitions were identified in the T
z = - 1/2 nucleus 51Fe following the fusion-evaporation reaction 32S(28Si,2α1n)51Fe. The level scheme reaches the fully aligned I
π = 27/2- terminating state of the five holes in the f
7/2 shell. The 17/2- state was found to be isomeric, and the lifetime was measured to be 2.87 ns. The mirror symmetry of 51Fe and 51Mn is discussed, and the level scheme of 51Fe is compared to shell-model calculations.
Received: 20 July 2000 / Accepted: 1 August 2000 相似文献
14.
A. Johnson 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):9-14
Neutron-deficient nuclei in the mass region A≈ 90-100 exhibit a large variety of phenomena. In this region the heaviest N = Z nuclei are identified and enhanced neutron-proton correlations are expected when protons and neutrons occupy identical orbitals.
A variety of nuclear shapes are predicted and observed for A? 91, including superdeformed shapes. The nucleus 100Sn is the heaviest N = Z doubly magic nucleus believed to be bound. Knowledge of the shell structure around 100Sn is of utmost importance for understanding the nuclear shell model. New results on both the N = Z nucleus 88Ru, superdeformed structures in A≈ 90 nuclei as well as the first result on the level structure in 103Sn, and an extended level structure in 102In are presented. The limitations of using stable beams and targets and the possibilities with new radioactive beams are briefly
outlined.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
15.
T. Hayakawa M. Oshima Y. Hatsukawa J. Katakura H. Iimura M. Matsuda N. Shinohara Y. Toh S. Mitarai T. Shizuma M. Sugawara H. Kusakari 《The European Physical Journal A - Hadrons and Nuclei》2000,9(2):153-156
The in-beam spectroscopy on N = 91 isotones has been carried out using the 12C + 150Nd reaction. The νi
13/2 and νh
11/2 bands of 153Sm have been extended up to 33/2+ and 31/2-, respectively. Two new γ-rays have been located on the top of the unfavored band with νi
13/2 configuration in 157Dy. Two identical relationships have been established in the low-spin region of the yrast νi
13/2 configuration between 153Sm and 155Gd, and between unfavored bands of 155Gd and 157Dy. Here all these nuclei have the same neutron number N = 91.
Received: 28 June 2000 / Accepted: 20 October 2000 相似文献
16.
A. Prévost N. Buforn A. Astier R. Duffait M. Meyer S. Perriès N. Redon O. Stézowski A. Bauchet I. Deloncle M.G. Porquet A. Görgen H. Hübel E. Mergel S. Neumann D. Roßbach N. Nenoff G. Schönwaßer A.N. Wilson R. Lucas F.A. Beck D. Curien G. Duchêne B.J.P. Gall N. Kintz J.P. Vivien D.M. Cullen 《The European Physical Journal A - Hadrons and Nuclei》2001,10(1):13-19
We report the identification of six new superdeformed (SD) bands in 197,198Pb observed with the EUROBALL IV spectrometer. The results are interpreted in the framework of cranked Hartree-Fock calculations
with approximate projection on the particle number by means of the Lipkin-Nogami method. A mixing between quasi-particle excitations
and an octupole vibration is suggested in the two SD isotopes. We have estimated the ordering of the neutron valence orbitals
and confirm indirectly a N = 118 SD gap.
Received: 20 December 2000 / Accepted: 24 January 2001 相似文献
17.
E. Galindo A. Jungclaus K.P. Lieb 《The European Physical Journal A - Hadrons and Nuclei》2000,9(4):439-451
The known level energies, electromagnetic moments and decay probabilities of high-spin states in the N = 46 isotones 86Zr, 87Nb, 88Mo, 89Tc, and 90Ru are interpreted within the shell model. The single-particle space was truncated to the p
1/2 and g
9/2 orbits (relative to the 88Sr core) and the single-particle energies and empirical two-body matrix elements derived by Gross and Frenkel were used in
the calculations. Based on the generally good success of this approach, energies and decay properties of the yrast spectra
in 90Ru and 91Rh are predicted.
Received: 31 July 2000 / Accepted: 18 December 2000 相似文献
18.
I. Piqueras M.J.G. Borge Ph. Dessagne J. Giovinazzo A. Huck A. Jokinen A. Knipper C. Longour G. Marguier M. Ramdhane V. Rauch O. Tengblad G. Walter Ch. Miehé 《The European Physical Journal A - Hadrons and Nuclei》2003,16(3):313-329
The beta-decay of the N = Z, even-even nucleus 72Kr has been studied at the ISOLDE PSB facility at CERN. Measurements of βγ and βγγ coincidences have enriched the decay scheme
of the daughter nucleus 72Br with 27 new low spin levels. A more precise half-life of T
1/2 = 17.1(2) s has been determined. Strong feeding to the 72Br ground state is established yielding an unambiguous J
π = 1+ assignment for this state. Candidates for the 72Br g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme
force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10-6 for this decay branch obtained. The cumulated experimental level density of 1+ states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1+ levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not
follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different
calculations made in the framework of the quasiparticle random phase approximation.
Received: 7 February 2002 / Accepted: 31 October 2002 / Published online: 6 March 2003
RID="a"
ID="a"e-mail: borge@pinar2.csic.es
RID="b"
ID="b"Present address: Centre d' Etudes Nucléaires de Bordeaux-Gradignan, Le Haut Vigneau, F-33175 Gradignan Cedex, France.
RID="c"
ID="c"Present address: University Mentouri, 25000 Constantine, Algeria.
Communicated by J. ?yst? 相似文献
19.
D. T. Khoa 《The European physical journal. Special topics》2007,150(1):31-34
DWBA analysis of the inelastic 30-40S(p,p') and
18-22O(p,p') scattering data measured in the inverse kinematics has been
performed to determine the isoscalar (δ0) and isovector (δ1)
deformation lengths of the 2+1 excitations in the Sulfur and Oxygen isotopes
using a compact folding approach. A systematic N-dependence of δ0 and
δ1 has been established which shows a link between δ1 and the
neutron-shell closure. Strong isovector deformations were found in several
cases, e.g., the 2+1 state in 20O where δ1 is nearly three
times larger than δ0. These results confirm the relation
δ1>δ0 anticipated from the core polarization by the valence
neutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell
closure at N=14 or 16 has been discussed based on the folding model analysis
of the inelastic 22O+p scattering data at 46.6 MeV/u measured recently at
GANIL. 相似文献
20.
R.R. Rodríguez-Guzmán J.L. Egido L.M. Robledo 《The European Physical Journal A - Hadrons and Nuclei》2003,17(1):37-47
The Angular Momentum Projected Generator Coordinate Method, with the quadrupole moment as collective coordinate and the Gogny
force (D1S) as the effective interaction, is used to describe the properties of the ground state and low-lying excited states
of the even-even neon isotopes 20-34Ne, that is, from the stability valley up to the drip line. It is found that the ground state of the N = 20 nucleus 30Ne is deformed but to a lesser extent than the N = 20 isotope of the magnesium. In the calculations, the isotope 32Ne is at the drip line in good agreement with other theoretical predictions. On the other hand, rather good agreement with
experimental data for many observables is obtained.
Received: 19 Novemeber 2002 / Accepted: 24 January 2003 / Published online: 8 April 2003 相似文献