共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
E. Hammarén K.W. Schmid A. Faessler 《The European Physical Journal A - Hadrons and Nuclei》1998,2(4):371-377
Abstact: The solution of the Hartree–Fock–Bogoliubov problem with restoration of the broken symmetries before the variation has been
generalized for the use of totally unrestricted quasi–particle determinants. With this method doubly–even, doubly–odd and
odd nuclei can be treated on the same footing. Comparison with the results of complete shell–model diagonalizations shows
that already one–determinant representations yield a very good approximation to the exact solutions even in the middle of
the 1s0d shell. The problem is especially suited for numerical implementation on parallel computers. First tests show a linear
dependence of the inverse CPU time with the number of processors used.
Received: 26 February 1998 / Revised version: 8 May 1998 相似文献
3.
R. Bernabei P. Belli F. Cappella F. Montecchia F. Nozzoli A. d’Angelo A. Incicchitti D. Prosperi R. Cerulli C. J. Dai H. H. Kuang J. M. Ma Z. P. Ye 《The European Physical Journal A - Hadrons and Nuclei》2005,23(1):7-10
We report the results of an experimental search for spontaneous transition of nuclei from ordinary to superdense state in NaI(Tl). New limits on the superdense-state parameters are presented. 相似文献
4.
D. Savran W. Bayer D. Galaviz S. Müller K. Sonnabend A. Zilges 《The European Physical Journal A - Hadrons and Nuclei》2008,36(1):17-20
High-resolution photon scattering experiments have been performed on the nucleus 45Sc at the Darmstadt superconducting electron accelerator S-DALINAC using bremsstrahlung beams with end point energies of 5.0
and 7.0MeV. Energies, absolute cross-sections and decay widths of 50 states, most of them previously unknown, have been determined.
The results are compared to (γ,
) experiments on the neighbouring closed proton shell isotope 44Ca . 相似文献
5.
D. Guillemaud-Mueller 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):63-67
The structure of neutron-rich light nuclei around N = 20, 28 has been investigated at GANIL by means of in-beam gamma spectroscopy using fragmentation reactions of 36S and 48Ca beams on a Be target. Gamma decay of relatively high-lying excited states have been measured for the first time in nuclei
around 32Mg and 44S. Level schemes are proposed and discussed for a large number of these neutron-rich nuclei around N = 20 and N = 28.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
6.
J. Enders O. Karg P. von Neumann-Cosel V. Yu. Ponomarev 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):15-22
A comparison between the electric quadrupole (E2) strength distributions in 40, 48Ca with new results from 52Cr is presented. The deduced E2 strength distributions and the exhaustion of the isoscalar energy-weighted E2 sum rule are very different. Microscopic approaches fail to reproduce these differences. A survey of the available data
shows that the exhaustion of the energy-weighted isoscalar E2 sum rule in doubly magic nuclei below the isoscalar giant quadrupole resonance is typically more than two times larger than
in semi-magic nuclei. On the other hand, the E2 strength in this energy region exhausts about 50% of the total E2 strength, independent from shell closures. 相似文献
7.
N. Itagaki S. Okabe K. Ikeda I. Tanihata 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):43-47
The structure of Be and C isotopes are investigated based on the molecular-orbit (MO) model. The low-lying states are characterized
by several configurations of valence neutrons, which are constructed as combinations of basic orbits. In 10Be, all of the observed positive-parity bands and the negative-parity bands are described within the model. The second 0+ state of 10Be has a large α-α cluster structure, and this is characterized by a (1/2+
σ)2 configuration. An enlargement of the α-α distance due to two-valence neutrons along the α-α axis makes their wave function
smooth and reduces the kinetic energy drastically. Furthermore, the contribution of the spin-orbit interaction due to coupling
between the S
z = 0 and the S
z = 1 configurations, is important. In the ground state of 12Be, the calculated energy exhibits similar characteristics, that the remarkable α clustering and the contribution of the spin-orbit
interaction make the binding of the state with (3/2-
π)2(1/2+
σ)2 configuration properly stronger in comparison with the closed p-shell (3/2-
π)2(1/2-
π)2 configuration. This is related to the breaking of the N = 8 (closed p-shell) neutron magic number. Also, the molecule-like structure of the C isotopes is investigated using a microscopic α+α+α+n+n+ . . . model. The combination of the valence neutrons in the π- and the σ-orbit is promising to stabilize the linear-chain state
against the breathing and bending modes, and it is found that the excited states of 16C are the most promising candidates for such structure.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
8.
A. Bürger M. Stanoiu F. Azaiez Zs. Dombrádi A. Algora A. Al-Khatib B. Bastin G. Benzoni R. Borcea Ch. Bourgeois P. Bringel E. Clément J.-C. Dalouzy Z. Dlouhý A. Drouart C. Engelhardt S. Franchoo Zs. Fülöp A. Görgen S. Grévy H. Hübel F. Ibrahim W. Korten J. Mrázek A. Navin F. Rotaru P. Roussel-Chomaz M.-G. Saint-Laurent G. Sletten D. Sohler O. Sorlin Ch. Theisen C. Timis D. Verney S. Williams 《The European physical journal. Special topics》2007,150(1):89-91
An experiment was performed to extend the knowledge of excited
states in neutron-deficient Ca isotopes.
In particular, the first excited state in 36Ca was searched for
to obtain information on the isospin dependence of the
nucleon-nucleon interaction near the proton drip line from a
comparison with its stable mirror nucleus, 36S.
The 36Ca ions were produced using a two-step fragmentation
technique with a 37Ca secondary beam, and in-beam γ-rays
were measured.
First results are the energy of the first 2+ state in 36Ca,
E(2+)=3036(11) keV, and the cross section for the reaction
37Ca → 36Ca at 61.A MeV.
In addition, the de-excitaion of the first 2+ state in 28S
has been observed. 相似文献
9.
10.
In a systematic search through experimental results for transfer reactions, inelastic excitations and other data for 13C we identify states which have no simple structure related to the low-lying states of 12C. We propose that these states have strong α-clustering and that they are related to chain states expected in 13-14C. The properties of these states are discussed on the basis of a molecular orbital model.
Received: 12 December 2001 / Accepted: 3 April 2002 相似文献
11.
G. Schönwaßer H. Hübel G.B. Hagemann J. Domscheit A. Görgen B. Herskind G. Sletten J.N. Wilson D.R. Napoli C. Rossi-Alvarez D. Bazzacco R. Bengtsson H. Ryde P.O. Tjøm S.W. Ødegård 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):291-296
Lifetimes of states in the yrast superdeformed bands of 163Lu and 164Lu were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average
transition quadrupole moments, Q
t = 8.2-0.6
+1.0 b and 7.1-0.6
+0.5 b, were deduced for one of the bands in 163Lu and 164Lu, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in 163Yb, Q
t = 4.9-0.4
+1.3 b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands
correspond to a local potential energy minimum with a pronounced triaxiality, γ∼ 20°.
Received: 8 November 2001 / Accepted: 9 January 2002 相似文献
12.
W. von Oertzen 《The European Physical Journal A - Hadrons and Nuclei》2001,11(4):403-411
Using the concept of covalent molecular orbitals for neutrons and the known properties of the local α + 16O potential the formation of asymmetric molecular structures in neon isotopes is discussed. Experimental evidence for parity doublets in 21Ne is reviewed and a corresponding band structure for the states in 21Ne at moderate excitation energy of E
x = 0-8 MeV is proposed. The structure of some bands can be interpreted as consisting of an instrinsic asymmetric ( 4He + 16O) structure bound by a covalent neutron in σ and π orbitals. An extension of the observed structures to symmetric molecular structures in isotopes of Mg and heavier nuclei is suggested. In particular shape isomers in isotopes of magnesium, namely (He)2O molecules, can be predicted and an extended Ikeda diagram is proposed.
Received: 11 July 2001 / Accepted: 22 August 2001 相似文献
13.
Production and studies of neutron-rich nuclei produced in fission are reviewed. Some recent experiments performed with the
ISOL technique at the IGISOL and the ISOLDE facilities are reviewed. The manipulation of neutron-rich nuclei is discussed
with a special focus on radioactive ion cooling and trapping techniques under construction worldwide. Perspectives of obtaining
intense post accelarated beams of fission products are discussed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
14.
K.P. Rykaczewski 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):81-84
A review of experimental data obtained recently on proton-radioactive nuclei is presented. The highlights include the observation
of fine structure in proton emission, for the decays of 131Eu, 145Tm and 146Tm, and the studies of the excited states in proton-emitting nuclei. The observation limits are extended to few nanobarns
cross-sections ( 140Ho, 164Ir and 130Eu) and few microsecond half-lives (e.g., 145Tm). Measured decay properties for thirty-nine proton-emitting ground and isomeric states contributed to the understanding
of nuclear masses and evolution of single-particle states at and beyond the proton drip line. Experimental results have stimulated
new theoretical approaches to proton emission and the structure of unbound narrow resonance states.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: rykaczew@phy.ornl.gov 相似文献
15.
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
16.
The evolution of shape from the spherical to the axially deformed shapes in the Sm isotopes is investigated microscopically in relativistic mean-field theory. The microscopic and self-consistent quadrupole deformation constrained relativistic mean-field calculations show a clear shape change for the even-even Sm isotopes with N = 82-96. The potential surfaces for 148Sm, 150Sm and 152Sm are found to be relatively flat, which may be the possible critical-point nuclei. By examining the single-particle spectra and nearest-neighbor spacing distribution of the single-particle levels, one finds that the single-particle levels in 148Sm , 150Sm, and 152Sm distribute more uniformly. 相似文献
17.
S. Kamerdzhiev E. E. Saperstein 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):333-341
A method of consistent treatment of phonon contributions to the self-energy and gap terms in non-magic nuclei is developed
in so-called g
2 approximation, where g is the creation amplitude of a low-lying phonon. The method simultaneously takes into account both usual non-local and local
phonon tadpole terms. Relations that allow the tadpoles to be calculated without introduction of new parameters are derived.
As an application of the method, the effect of the phonon tadpoles on the single-particle strength distribution, single-particle
energies and gap values is considered. Hypothesis of the surface nature of pairing correlations is discussed in the light
of the tadpole effect. 相似文献
18.
Inspired by the Bertlmann-Martin inequality relating the rms radius of the ground state wave function to the lowest dipole
transition energy, we have proposed a dimensional relationship to be used in weakly bound two-body systems. In the present
work, it is applied to halo nuclei. Lower and upper bounds to the size of halo nuclei are compared to values obtained from
reaction cross sections. The case of the deuteron is also presented.
Received: 18 September 1998 相似文献
19.
Y. Utsuno T. Otsuka T. Mizusaki M. Honma 《The European physical journal. Special topics》2007,150(1):187-188
Focusing on the importance of the tensor force in the effective
interaction, we investigate the structure of unstable nuclei
around N=28 with large-scale shell-model calculations.
From the analysis of the spin-tensor decomposition for
some interactions, the tensor force in the effective interaction
should be close to the π+ ρ force, whereas it is
much weaker in the Millener-Kurath (MK) interaction which is often used as the
cross-shell interaction. The significance of the tensor force
appears in the structure around 42Si: the proper tensor force
predicts that it is deformed contrary to the result from MK. 相似文献
20.
G. Schönwaßer H. Hübel G.B. Hagemann H. Amro R.M. Clark M. Cromaz R.M. Diamond P. Fallon B. Herskind G. Lane W.C. Ma A.O. Macchiavelli S.W. Ødegård G. Sletten D. Ward J.N. Wilson 《The European Physical Journal A - Hadrons and Nuclei》2002,15(4):435-437
Average transition quadrupole moments in the yrast triaxial superdeformed bands of 163Lu, 164Lu and 165Lu were determined in a Doppler-shift attenuation-method experiment. Fractional Doppler shifts were determined in γ-ray coincidence
spectra measured with the Gammasphere array. The transition quadrupole moments derived from these data show a decrease from
163Lu to 165Lu which is not predicted by total-energy surface calculations.
Received: 12 August 2002 / Accepted: 23 October 2002 / Published online: 10 December 2002
RID="a"
ID="a"e-mail: schoenwa@iskp.uni-bonn.de
Communicated by D. Schwalm 相似文献