共查询到20条相似文献,搜索用时 15 毫秒
1.
J. J. Cuenca-Garcıa G. Martınez-Pinedo K. Langanke F. Nowacki I. N. Borzov 《The European Physical Journal A - Hadrons and Nuclei》2007,34(1):99-105
We have performed shell model calculations of the half-lives and neutron-branching probabilities of the r-process waiting-point
nuclei at the magic neutron number N = 82 . These new calculations use a larger model space than previous shell model studies and an improved residual interaction
which is adjusted to recent spectroscopic data around A = 130 . Our shell model results give a good account of all experimentally known half-lives and Q
β -values for the N = 82 r-process waiting-point nuclei. Our half-life predictions for the N = 82 nuclei with Z = 42-46 agree well with recent estimates based in the energy-density functional method. 相似文献
2.
For r-process nucleosynthesis the β-decay rates for a number of neutron-rich intermediate heavy nuclei are calculated. The model for the β-strength function is able to reproduce the observed half-lives quite well. 相似文献
3.
Ritesh Kumar Dubey V. J. Menon Madhukar Mishra Mukesh Kumar Pandey B. K. Patra 《Pramana》2007,68(3):423-433
The half-lives are calculated for the β
− decay process for nuclei in the mass range ∼65–75 relevant for the core of a massive star at the late burning stage of stellar
evolution and the collapse that leads to supernova explosion. These half-lives and rates are calculated by expressing the
β
− Gamow-Teller decay strengths in terms of smoothed bivariate strength densities. These strength densities are constructed
in the framework of spectral averaging theory for two-body nuclear Hamiltonian in a large nuclear shell model space. The method
has a natural extension to electron captures as well as weak interaction rates for r and rp-processes.
相似文献
4.
Taking Coulomb and proximity potentials as the interacting barrier we have studied the cold valley in the radioactive decay
of 244–260Fm isotopes. It is found that in addition to alpha particle minima, other minima occur at S, Ar and Ca clusters. We have computed
the half-lives and other characteristics of different clusters emitted from these parents treating parent, daughter and emitted
cluster as spheres. Our study reveals that most of these parents are unstable against alpha and heavy cluster (46Ar, 48,50Ca) emissions and stable against light cluster emission, except 8Be from 244–248Fm isotopes. The most probable clusters from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters (Z = 20, N = 28) and also stress the role of doubly magic 208Pb daughter. The computed half-lives for alpha decay are in good agreement with the experimental data. It is found that the
presence of neutron excess in the parent nuclei slows down the cluster decay process. The effect of quadrupole (β
2) and hexadecapole (β
4) deformations of parent and fragments on half-lives are also studied. It is found that inclusion of β
2 and β
4 reduces the height and shape of the barrier (increases barrier penetrability) and hence the half-life decreases. 相似文献
5.
Yu. E. Penionzhkevich 《Hyperfine Interactions》2006,171(1-3):157-166
The present work reviews the properties of the neutron-rich isotopes near the closed shells N = 20 and N = 28. The changes in nuclear structure appearing as one goes away from the β-stability line are discussed. The location of
the neutron drip line and questions about the stability of nuclides with Z ≥ 8 are considered in connection with the weakening or even vanishing of the shell effects at the magic numbers 20 and 28,
and the discovery of the new neutron magic numbers at N = 16 and N = 32. These properties are extremely interesting from the point of view of laser experiments as well as for all other experimental
methods giving access to this region. 相似文献
6.
K. V. Stepanyantz 《Physics of Particles and Nuclei Letters》2011,8(3):321-324
Using the higher covariant derivative regularization we calculate a two-loop β-function for the N = 1 supersymmetric Yang-Mills theory with the matter superfields, containing the cubic superpotential. It is found that all
integrals, defining this function, are integrals of total derivatives. 相似文献
7.
Based on the concept of cold valley in fission and fusion, the radioactive decay of superheavy280–314116 nuclei was studied taking Coulomb and proximity potentials as the interacting barrier. It is found that the inclusion
of proximity potential does not change the position of minima but minima become deeper which agrees with the earlier findings
of Gupta and co-workers. In addition to alpha particle minima, the other deepest minima occur for 8Be, 12,14C clusters. In the fission region two deep regions are found each consisting of several comparable minima, the first region
centred on 208Pb and the second is around 132Sn. The cluster decay half-lives and other characteristics are computed for various clusters ranging from alpha particle to
70Ni. The computed half-lives for alpha decay match with the experimental values and with the values calculated using Viola-Seaborg-Sobiczewski
(VSS) systematic. The plots connecting computed Q values and half-lives against neutron number of daughter nuclei were studied for different clusters and it is found that
the next neutron shell closures occur at N = 162, 172 and 184. Isotopic and isobaric mass parabolas are studied for various cluster emissions and minima of parabola
indicate neutron shell closure at N = 162, 184 and proton shell closure at Z = 114. Our study shows that 162276114 is the deformed doubly magic and 184298114 is the spherical doubly magic nuclei.
相似文献
8.
A. S. Rinat M. F. Taragin M. Viviani 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):415-416
We use the relation between Structure Functions (SFs) of nuclei A and nucleons N in order to fomulate a criterion which isolates the QE part out of the total inclusive cross-section. From data points around
the QEP we extract the reduced neutron magnetic form factor 〈α
n = G
M
n/μ
n
G
d〉. The latter shows an unexpected decrease up to Q
2 = 10GeV^2, the largest measured. 相似文献
9.
W. Zuo A. Lejeune U. Lombardo J.F. Mathiot 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):469-475
Brueckner calculations including a microscopic three-body force have been extended to isospin-asymmetric nuclear matter. The
effects of the three-body force on the equation of state and on the single-particle properties of nuclear matter are discussed
with a view to possible applications in nuclear physics and astrophysics. It is shown that, even in the presence of the three-body
force, the empirical parabolic law of the energy per nucleon vs. isospin asymmetry β = (N - Z)/A is fulfilled in the whole asymmetry range 0≤β≤1 up to high densities. The three-body force provides a strong enhancement
of the symmetry energy which increases with density in good agreement with the predictions of relativistic approaches. The
Lane's assumption that proton and neutron mean fields linearly vary vs. the isospin parameter is violated at high density due to the three-body force, while the momentum dependence of the mean
fields turns out to be only weakly affected. Consequently, a linear isospin split of the neutron and proton effective masses
is found for both cases with and without the three-body force. The isospin effects on multifragmentation events and collective
flows in heavy-ion collisions are briefly discussed along with the conditions for direct URCA processes to occur in the neutron
star cooling.
Received: 18 February 2002 / Accepted: 16 May 2002 相似文献
10.
M. Karny L. Batist A. Banu F. Becker A. Blazhev B. A. Brown W. Brüchle J. Döring T. Faestermann M. Górska H. Grawe Z. Janas A. Jungclaus M. Kavatsyuk O. Kavatsyuk R. Kirchner M. La Commara S. Mandal C. Mazzocchi K. Miernik I. Mukha S. Muralithar C. Plettner A. Płochocki E. Roeckl M. Romoli K. Rykaczewski M. Schädel K. Schmidt R. Schwengner J. Żylicz 《The European Physical Journal A - Hadrons and Nuclei》2006,27(2):129-136
The β decays of 102Sn and 104Sn were studied by using high-resolution germanium detectors as well as a Total Absorption Spectrometer (TAS). For 104Sn, with three new β-delayed γ-rays identified, the total Gamow-Teller strength (BGT) value of 2.7(3) was obtained. For 102Sn, the γ-γ coincidence data were collected for the first time, allowing us to considerably extend the decay scheme. This
scheme was used to unfold the TAS data and to deduce a BGT value of 4.2(8) for this decay. This result is compared to shell model predictions, yielding a hindrance factor of 3.6(7)
in agreement with those obtained previously for 98Cd and 100In. Together with the latter two, 102Sn completes the triplet of Z ⩽ 50, N ≥ 50 nuclei with two proton holes, one proton hole and one neutron particle, and two neutron particles with respect to the
doubly magic 100Sn core. 相似文献
11.
I. N. Boboshin V. V. Varlamov B. S. Ishkhanov E. A. Romanovsky 《Physics of Atomic Nuclei》2007,70(8):1363-1368
New information about energies and occupation probabilities of neutron and proton single-particle (hole) subshells in even—even
nuclei was obtained in previous studies applying the method of putting into correspondence all available data on one-nucleon
pickup and stripping reactions. The most important and interesting resultwas identification of several nuclei as new magic
ones. Namely, itwas found that a filling of the neutron 2d
5/2 subshell in 96Zr makes this nuclide a magic one. Moreover, changes in proton subshell energies with increasing neutron number N are accompanied by an increasing energy gap between closed 2p
1/2 and empty 1g
9/2 subshells. Thus, the neutron number N = 56 appears to be a magic one if the proton number Z is equal to 40. The proton number Z = 40 manifests properties of the magic number in 96Zr. Therefore, 96Zr was identified as a new double-magic nucleus. Further investigations revealed that the energy of the first 2+ state E(2
1
+
) in 96Zr is much higher than that in the neighboring isotopes and isotones, whereas the ratio E(4
1
+
)/E(2
1
+
) and the quadrupole deformation parameter β2 are, vice versa, clearly lower. Moreover, the A dependence of the neutron separation energy B(n) in Zr isotopes has an irregularity at N = 56 which is typical of magic nuclei. As a result of these investigations, it was found that, near the Fermi energy, there
are two closed subshells with the same (and large) angular momentum j = 5/2 (viz. π1f
5/2 and ν2d
5/2). We call this situation the jj connection. The magic numbers under discussion (Z = 40 and N = 56) are achieved at the points where both subshells are closed, and in addition, the closed subshell with j = 1/2, π2p
1/2, occurs above the proton π1f
5/2 subshell. This looks like a result of some additional attractive proton-neutron interaction. It was found that application
of this scheme (jj connection) to other subshells reveals several other new magic nuclei: 54Ca (closed π1d
3/2 and ν2p
3/2 together with closed ν2p
1/2), 30S and 30Si (closed π1d
5/2 and ν1d
5/2 together with closed (π/ν)2s
1/2), and 14O and 14C (closed π1p
3/2 and ν1p
3/2 together with closed ν2p
1/2).
The text was submitted by the authors in English. 相似文献
12.
S. Singh R. Chandra P. K. Rath P. K. Raina J. G. Hirsch 《The European Physical Journal A - Hadrons and Nuclei》2007,33(4):375-388
The two-neutrino double-beta decay of 124, 126Xe , 128, 130Te , 130, 132Ba and 150Nd isotopes is studied in the Projected Hartree-Fock-Bogoliubov (PHFB) model. Theoretical 2ν β-β- half-lives of 128, 130Te , and 150Nd isotopes, and 2ν β+β+ , 2ν β+
EC and 2ν ECEC for 124, 126Xe and 130, 132Ba nuclei are presented. Calculated quadrupolar transition probabilities B(E2 : 0+ → 2+) , static quadrupole moments and g -factors in the parent and daughter nuclei reproduce the experimental information, validating the reliability of the model
wave functions. The anticorrelation between nuclear deformation and the nuclear transition matrix element M
2ν is confirmed. 相似文献
13.
I. Dillmann M. Hannawald U. Köster V.N. Fedoseyev A. Wöhr B. Pfeiffer D. Fedorov J. Shergur L. Weissman W.B. Walters K.-L. Kratz 《The European Physical Journal A - Hadrons and Nuclei》2002,13(3):281-284
Production yields and β-decay half-lives (T
1/2) of very neutron-rich indium isotopes were determined at CERN/ISOLDE using isobaric selectivity of a resonance-ionization
laser ion-source. Beta-delayed neutron (βdn) multiscaling measurements have yielded improved T
1/2 for 206(6) ms 132In, 165(3) ms 133In and 141(5) ms 134In. With 92(10) ms 135In, a new r-process nuclide has been identified which acts as an important “waiting point” in the In isotopic chain for neutron
densities in the range n
n≃ 1024-1026 n/cm3, where the r-matter flow has already passed the A≃ 130 abundance peak region.
Received: 17 January 2002 / Accepted: 30 January 2002 相似文献
14.
15.
T. Faestermann R. Schneider A. Stolz K. Sümmerer E. Wefers J. Friese H. Geissel M. Hellström P. Kienle H.-J. Körner M. Mineva M. Münch G. Münzenberg C. Schlegel K. Schmidt P. Thirolf H. Weick K. Zeitelhack 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):185-188
Neutron deficient nuclei near 100Sn have been produced by fragmentation of a 1 .
AGeV 112Sn beam. The fragments were separated, identified and stopped in a highly segmented silicon strip detector stack. This detector
measured the total energy of emitted β+-particles. γ-radiation was measured with surrounding detectors. The half-lives for many nuclides have been determined for
the first time and give important information for the following topics: For the heaviest particle-stable odd-odd nuclei 90Rh, 94Ag and 98In we observed for the first time fast β-decays, compatible with superallowed Fermi transitions and confirmed such decays
for 78Y, 82Nb and 86Tc. We have also observed long-lived T = 0 states in some of these nuclei. We measured the half-lives of all rp-process waiting-point nuclei from 80Zr up to 92, 93Pd. In addition we find the proton drip line nucleus 77Y to decay dominantly via β-decay. To study the Gamov-Teller strength in the β-decay near the doubly magic 100Sn we measured the half-life, β- and γ-spectrum of 102Sn. We propose a level scheme for the daughter nuclide 102In and deduce the Gamov-Teller strength (B
GT = 4.0±0.6). This is one of the largest values known.
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"e-mail: thomas.faestermann@ph.tum.de 相似文献
16.
K. V. Stepanyantz 《International Journal of Theoretical Physics》2012,51(1):276-291
Some calculations in supersymmetric theories, made with the higher derivative regularization, show that the β-function is given by integrals of total derivatives. This is qualitatively explained for the N=1 supersymmetric electrodynamics in all orders. 相似文献
17.
D. D. Dzhappuev Yu. V. Balabin E. V. Vashenyuk B. B. Gvozdevsky N. F. Klimenko A. U. Kudzhaev A. M. Kuchmezov O. I. Mikhailova V. B. Petkov 《Bulletin of the Russian Academy of Sciences: Physics》2011,75(3):360-363
Characteristics of the hadronic component of EASes with hadron energies E
h
> 50 MeV were measured on the CARPET-2 complex shower array at the Baksan Neutrino Observatory of the Institute for Nuclear
Research, Russian Academy of Sciences. Hadrons were registered using a 6-NM-64 neutron monitor; the data collection system
of this array enables us to register the time intervals between pulses of neutron monitor counters with an error of up to
1 μs. For EASes with N
e
= 105–107 whose axes are located in CARPET, we obtain the dependence of the mean neutron multiplicity in the neutron monitor on the
total number of charged particles in the EAS. 相似文献
18.
D. P. Kozlenko N. T. Dang Z. Jirák S. E. Kichanov E. V. Lukin B. N. Savenko L. S. Dubrovinsky C. Lathe C. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):407-411
The crystal and magnetic structures of Pr0.15Sr0.85MnO3
manganite have been studied by means of powder X-ray and neutron diffraction
in the temperature range 10–400 K at high external pressures up to 55 and 4 GPa, respectively. A structural phase transition
from cubic to tetragonal
phase upon compression was observed, with large positive pressure
coefficient of transition temperature dT
ct
/dP = 28(2) K/GPa. The C-type
antiferromagnetic (AFM) ground state is formed below T
N
≈ 260 K
at ambient pressure. While at ambient pressure the structural and magnetic
transition temperatures are close, T
ct
~ T
N
, upon compression
they become decoupled with T
N
≪ T
ct
due to much weaker
T
N
pressure dependence with coefficient dT
N
/dP = 3.8(1) K/GPa. 相似文献
19.
M. Oinonen U. Köster J. Äystö V. Fedoseyev V. Mishin J. Huikari A. Jokinen A. Nieminen K. Peräjärvi A. Knipper G. Walter 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):123-127
Beta-decay of 59Mn has been studied at PSB-ISOLDE, CERN. The intense and pure Mn beam was produced using the Resonance Ionization Laser Ion
Source (RILIS). Based on the measured β-decay rates the ground-state spin and parity are proposed to be J
π = 5/2-. This result is consistent with the systematic trend of the odd-A Mn nuclei and extends the systematics one step further towards the neutron drip line.
Received: 17 November 2000 / Accepted: 16 February 2001 相似文献
20.
L. Batist A. Blazhev J. Döring H. Grawe M. Kavatsyuk O. Kavatsyuk R. Kirchner M. La Commara C. Mazzocchi I. Mukha C. Plettner E. Roeckl M. Romoli 《The European Physical Journal A - Hadrons and Nuclei》2006,29(2):175-182
The β decay of 94Pd and of the 71s isomer of 94Rh was investigated by using total γ-ray absorption techniques. Several levels in 94Rh are established, including a new low-lying isomer characterized by a half-life of 0.48(3)μs and a de-exciting transition
of 55keV. E2 multipolarity is determined for this transition by measuring the intensities of its γ-rays and the characteristic X-rays
from its electron conversion. On the basis of the measured reduced β-decay transition rates to known 94Ru levels and shell model considerations, the spin-parity of the 71s and the 0.48μs isomers of 94Rh is assigned to be (4+) and (2+), respectively. The β-decay strength distributions measured for 94Pd and the 71s isomer of 94Rh yield Q
EC values of 6700(320) and 9750(320)keV for these decays and give evidence for the population of those states below and above
the magic N = 50 gap that belong to both components of the 0g spin-orbit doublet. 相似文献