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1.
A.?A.?Kuliev E.?Guliyev F.?Ertugral S.??zkan 《The European Physical Journal A - Hadrons and Nuclei》2010,43(3):313-321
In this study, Ip = 1+\ensuremath I^{\pi} = 1^{+} and Ip = 1-\ensuremath I^{\pi} = 1^{-} dipole mode excitations are systematically investigated within the rotational and translational + Galilean invariant quasiparticle
random-phase approximation for 232Th , 236U , and 238U actinide nuclei. It is shown that the investigated nuclei reach a B(M1) strength structure, which corresponds to the scissors mode. The calculated mean excitation energies as well as the summed
B(M1) value of the scissors mode excitations are consistent with the available experimental data. The results of calculations
indicate large differences to the rare-earth nuclei as is the case for the experiment: a doubling of the observed dipole strengths
and a shift of the energy centroid to the lower energies by about 800keV. The calculations indicate the presence of a few
prominent negative-parity Kp = 1-\ensuremath K^{\pi} = 1^{-} states in the 2.0-4.0MeV energy interval. The occurrence of the negative-parity dipole states with the rather high B(E1) value less than 4MeV shows the necessity of explicit parity measurements for the correct determination of the scissors
mode strength in 232Th , 236U , and 238U isotopes. 相似文献
2.
L. A. Vaishnene V. G. Vovchenko Yu. A. Gavrikov V. I. Murzin V. V. Polyakov M. G. Tverskoi O. Ya. Fedorov Yu. A. Chestnov A. V. Shvedchikov A. I. Shchetkovskii 《Physics of Atomic Nuclei》2011,74(1):115-121
The total cross sections for 197Au and 203Tl fission induced by protons of energy varied from about 200 to 1000 MeV with a step of about 100 MeV are measured. New approximations
to the energy dependences of the cross sections for the proton-induced fission of 197Au, 203Tl, natPb, and 209Bi nuclei are presented and discussed. For all of these nuclei, exponential functions are used as approximations. 相似文献
3.
E.?Ruchowska W.?A.?P?óciennik H.?Mach K.?Gulda B.?Fogelberg H.?Gausemel L.?M.?Fraile W.?Kurcewicz K.?Mezilev M.?Sanchez-Vega 《The European Physical Journal A - Hadrons and Nuclei》2010,45(1):1-10
Lifetime measurements of excited states in 149Nd have been performed using the advanced time-delayed b \beta
g \gamma
g \gamma(t) method. Half-lives of 14 excited states in 149Nd have been determined for the first time or measured with higher precision. Twelve new g \gamma -lines and 5 new levels have been introduced into the decay scheme of 149Pr based on results of the g \gamma
g \gamma coincidence measurements. Reduced transition probabilities have been determined for 40 g \gamma -transitions in 149Nd . Configuration assignments for 6 rotational bands in 149Nd are proposed. Enhanced E1 transitions indicate that the ground-state band and the band built on the 332.9keV level constitute a pair of the Kp = 5/2±\ensuremath K^{\pi} = 5/2^{\pm} parity doublet bands. Potential energy surfaces on the (b2,b3)\ensuremath (\beta_{2},\beta_{3}) -plane have been calculated for the lowest single quasi-particle configurations in 149Nd using the Strutinski method and the axially deformed Woods-Saxon potential. The predicted occurrence of the octupole-deformed
K = 5/2 configuration is in agreement with experiment. Unexpectedly low |D0|\ensuremath \vert D_0\vert values obtained for the Kp = 5/2±\ensuremath K^{\pi} = 5/2^{\pm} parity doublet bands may result from cancellation between the proton and neutron shell correction contributions to |D0|\ensuremath \vert D_0\vert . 相似文献
4.
THE MEASUREMENT OF COMPLETE FUSION CROSS-SECTIONS FOR THE REACTIONS 12C+27Al, 12C+209Bi AND 14N+Pb
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Mica track detectors were used for the measurement of evaporation residues and fission fragments of compound nuclei formed in 12C+27Al, 12C+209Bi and 14N+Pb reactions. The complete fusion cross-sections and excitation functions were then obtained. By using the sharp cut-off model approximation, the values of the critical angular momenta were extracted from the complete fusion cross-sections. The results obtained were compared with the calculations based on current theories for critical angular momentum; they were found to agree within experimental uncertainties. 相似文献
5.
A. I. Svirikhin A. V. Yeremin I. N. Izosimov A. V. Isaev A. N. Kuznetsov O. N. Malyshev A. G. Popeko Yu. A. Popov E. A. Sokol M. L. Chelnokov V. I. Chepigin B. Andel M. Z. Asfari B. Gall N. Yoshihiro Z. Kalaninova S. Mullins J. Piot E. Stefanova D. Tonev 《Physics of Particles and Nuclei Letters》2016,13(4):480-482
Spontaneous fission properties of the short-lived neutron-deficient 256Rf nucleus produced in the complete fusion reaction with a beam of multiply charged heavy 50Ti ions from the U-400 cyclotron (FLNR, JINR) are experimentally investigated. Its half-life and decay branching ratio are measured. The average number of neutrons per spontaneous fission of 256Rf (\(\bar v = \;4.47 \pm \;0.09\)) is determined for the first time. 相似文献
6.
Mass distribution and evaporation residue measurements have been carried out in the reaction 19F + 197Au using the recoil catcher technique followed by off-line γ-ray spectrometry. The random neck rupture model (RNRM) has been
used to compute the variance of the mass distribution ( σ2A) and the average kinetic energy ( ˉ) of the fission fragments for the present system. The results of model calculations have
been found to be in good agreement with the experimental observations. Measured evaporation residue cross-sections have been
compared with the statistical model calculations. 相似文献
7.
Yu. E. Penionzhkevich 《Physics of Atomic Nuclei》2009,72(10):1617-1628
Excitation functions are measured for complete-fusion and transfer reactions induced by the interaction of 6He and 6Li with 206Pb, 209Bi, and Pt. Data obtained for fusion reactions induced by 6He ions deviate from the predictions of the statistical model of compound-nucleus decay at projectile energies in the vicinity
of the Coulomb barrier height. A strong enhancement of cross sections for fusion reactions induced by the interaction of 6He with target nuclei is observed. The cross sections for reactions of cluster transfer, neutron transfer from 6He, and deuteron transfer from 6Li at deep-subbarrier energies are also found to be enhanced. These results are discussed from the point of view of the effect
of the cluster structure of nuclei on the interaction probability at energies in the vicinity of the Coulomb barrier height. 相似文献
8.
B. V. Zhuravlev A. A. Lychagin N. N. Titarenko V. G. Demenkov V. I. Trykova 《Physics of Atomic Nuclei》2010,73(7):1111-1115
The spectra of neutrons from the (p, n) reactions on the 208Pb and 209Bi nuclei were measured in the proton-energy range 8–11 MeV. These measurements were performed by using a time-of-flight spectrometer
of fast neutrons on the basis of the pulsed tandem accelerator EGP-15 of the Institute of Physics and Power Engineering (Obninsk,
Russian Federation). A high resolution and stability of the time-of-flight spectrometermade it possible to identify reliably
low-lying discrete levels alongwith the continuum section of the neutron spectra. The measured data were analyzed on the basis
of the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations were performed
by using the precise formalism of Hauser-Feshbach statistical theory together with the generalizedmodel of a superfluid nucleus
and the back-shifted Fermi gas model for the nuclear-level density. The nuclear-level densities in 208Bi and 209Po were determined along with their energy dependences and model parameters. Our results are discussed together with available
experimental data and recommendations of model systematics. 相似文献
9.
A. Sibirtsev J. Haidenbauer H. -W. Hammer U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2007,32(2):229-241
We utilize existing inclusive data on K+-meson momentum spectra of the reaction pp→K
+
X at T
p = 2.3-2.85GeV to deduce total cross-sections for pp→K
+
Σ
+
n. The method used to extract those cross-sections is explained and discussed in detail. Our result for T
p = 2.85GeV is consistent with the data point from a direct measurement at the same beam energy. The cross-section obtained
for T
p = 2.3GeV is with 13.7±2.3μb considerably smaller than the value found in a recent experiment by the COSY-11 Collaboration
at a somewhat lower beam energy, indicating that the pp→K
+
Σ
+
n reaction cross-section could exhibit a rather unusual energy dependence. 相似文献
10.
I. Nishinaka H. Nakahara Y. Nagame 《The European Physical Journal A - Hadrons and Nuclei》2007,33(2):231-236
The most probable charges of secondary fragments, produced after neutron evaporation from primary fragments, have been evaluated
using fractional cumulative and mass yields in the 12MeV proton-induced fission of 232Th . The nuclear-charge polarization of primary fragments at scission has been obtained by correcting the most probable charge
of secondary fragments for neutron evaporation. The fragment mass dependence of the nuclear-charge polarization at scission
shows good agreement with that for thermal neutron-induced fission of 235U , indicating that the nuclear-charge polarization is nearly insensitive to mass and excitation energy of the fissioning
nucleus for asymmetric fission in the actinide region. 相似文献
11.
Yu. M. Smirnov 《Journal of Applied Spectroscopy》2009,76(5):611-616
Electron-impact excitation of odd 3
F
o levels of the nickel atom has been studied experimentally. A total of 45 NiI line emission cross-sections at 50-eV exciting-electron
energy were measured. Eight optical excitation functions in the 0–200 eV electron-energy range were recorded. 相似文献
12.
A. Ya. Rusanov M. G. Itkis N. A. Kondratiev I. V. Pokrovsky V. S. Salamatin G. G. Chubarian 《Physics of Atomic Nuclei》2007,70(10):1669-1678
Correlations between folding angular distributions of fission fragments and the gamma-ray multiplicity are studied for 18O + 208Pb interactions at energies of the beam of 18O ions in the range E lab = 78–198.5 MeV. The probabilities are determined for complete-and incomplete-fusion processes inevitably followed by the fission of nuclei formed in these processes. It is found that the probability of incomplete fusion followed by fission increases with increasing energy of bombarding ions. It is shown that, for the incomplete-fusion process, folding angular distributions of fission fragments have a two-component structure. The width of folding angular distributions (FWHM) for complete fusion grows linearly with increasing energy of 18O ions. The multiplicity of gamma rays from fission fragments as a function of the linear-momentum transfer behaves differently for different energies of projectile ions. This circumstance is explained here by the distinction between the average angular momenta of participant nuclei in the fusion and fission channels, which is due to the difference in the probabilities of fission in the cases where different numbers of nucleons are captured by the target nucleus. 相似文献
13.
N. K. Skobelev Yu. E. Penionzhkevich A. A. Kulko N. A. Demekhina V. Kroha A. Kugler S. M. Lukyanov J. Mrazek Yu. G. Sobolev V. A. Maslov Yu. A. Muzychka E. I. Voskoboynik A. S. Fomichev 《Physics of Particles and Nuclei Letters》2013,10(3):248-255
New data on the cross sections of reactions occurring during the interaction of 6He nuclei with 197Au at energies of 6He from 40 to 120 MeV are presented. The experiments were performed in the ACCULINNA secondary beam separator of the Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research. To identify the reaction products, the activation method for measuring the gamma activity of the target assembly of thin foils was used. The excitation functions for fusion reactions involving the evaporation of up to ten neutrons from the compound nucleus as well as reactions with the emission of charged particles and nucleon transfer in the investigated energy region are obtained. Data analysis was carried out using two codes: ALICE-MP and NRV. The cross sections for the (6He, xn) reactions occurring through the compound nucleus are mostly in agreement with the results of model calculations based on the statistical approach. It is shown that, up to the energies of 114 MeV, the cross-section drop in the complete fusion reactions is negligible. The experimental excitation functions of reactions leading to the formation of isotopes of mercury and gold (transfer reaction) indicate that the main contribution to their formation is made by direct processes and that evaporation reactions (6He, pxn) and (6He, αxn) play a minor role, as is evidenced by a comparison of the measured cross sections with the calculation results. 相似文献
14.
F.?P.?He?berger S.?Antalic D.?Ackermann S.?Heinz S.?Hofmann J.?Khuyagbaatar B.?Kindler I.?Kojouharov B.?Lommel R.?Mann 《The European Physical Journal A - Hadrons and Nuclei》2010,43(2):175-180
The isotope 261Bh was produced in the reaction 209Bi(54Cr, 2n)261Bh and its \( \alpha\) decay has been remeasured. It was found that it populates by an unhindered transition of \( \approx\) 10 MeV an excited level at E * > 350 keV in the daughter nucleus 257Db . The latter decays by internal transitions either into the isomeric state or the ground state. A somewhat improved half-life value of T 1/2 = 11.8+3.9 -2.4 ms was obtained for 261Bh . The data support the previous assignment of the \( \alpha\) activities 257Db (1) and 257Db (2) to the isomer and to the ground state, respectively. No evidence for an isomeric state in 261Bh decaying by \( \alpha\) emission was found. Based on the experimental results and theoretical calculations a partial decay scheme of 261Bh including spin and parity assignments of the ground-state and excited levels in the daughter nucleus 257Db populated by the \( \alpha\) decay and succeeding internal transitions have been suggested. 261Bh represents so far the heaviest nucleus for which such an attempt has been made. No spontaneous fission (SF) events that could be attributed to 261Bh were observed, resulting in an SF branching b SF < 0.05 . The measured production cross-section is (64±15) pb at E * = 22 MeV. 相似文献
15.
Partial-fusion cross-sections for the systems 6Li + 208Pb, 9Be + 209Bi have been determined. The effect of breakup on fusion for weakly bound projectiles 6Li and 9Be incident on 208Pb or 209Bi targets has been discussed comparing experimental fusion cross-section excitation functions to those evaluated with a semi-classical
approach. It is shown that complete fusion of a weakly bound projectile with heavy target is reduced, whereas the breakup
process has very little influence on the total-fusion cross-section for some of the studied systems at energies above the
Coulomb barrier. 相似文献
16.
H. Naik R.J. Singh R.H. Iyer 《The European Physical Journal A - Hadrons and Nuclei》2003,16(4):495-507
Charge distribution studies for heavy-mass fission products were carried out in the fast-neutron-induced fission of 232Th, 238U, 240Pu and 244Cm using radiochemical and gamma-ray spectrometric techniques. The width parameter( σZ/σA), the most probable charge/mass ( Z
P/A
P), the charge polarization (ΔZ) and the slope of charge polarization [ δ(ΔZ)/δA
′] as a function of the fragment mass (A
′) were deduced. The average charge dispersion parameter ( 〈σZ〉) and proton odd-even effect ( δp) were also obtained for these fissioning systems. The 〈σZ〉 and δp values in the fissioning systems 241Pu * and 245Cm * were determined for the first time. The δ(ΔZ)/δA
′ value is also determined for the first time in the fissioning systems 239U * , 241Pu * and 245Cm * . These data along with the literature data for even-Z fissioning systems such as 230Th * , 232Th * , 233U * , 234U * , 236U * , 238U * , 239Pu * , 240Pu*, 242Pu * , 246Cm * , 250Cf * and 252Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from the saddle to the scission point. The
role of the excitation energy in low-energy fission is also discussed.
Received: 26 July 2002 / Accepted: 3 December 2002 / Published online: 3 April 2003
RID="a"
ID="a"Present address: Emeritus Scientist (CSIR) Bhabha Atomic Research Centre, Nuclear Recycle Group, WIP Building, Trombay, Mumbai-400085, India;
e-mail: rhiyer@magnum. barc.ernet.in
Communicated by D. Schwalm 相似文献
17.
The nuclear spectroscopic quadrupole moments for the πh9/25/2-, 1/2-[541] and the πh11/29/2-, 9/2-[514] isomeric states in 169Ta have been measured employing the time differential perturbed angular-distribution technique following the nuclear reaction
159Tb(16O, 6nγ)169Ta at beam energy 104 MeV. The ratio of the intrinsic quadrupole moments
has been derived as 1.87(13) from the measured quadrupole precession frequencies of the corresponding states. The model-independent
analysis of the equilibrium deformation indicates strong prolate- and oblate-driving nature of the 1/2-[541] and 9/2-[514] orbitals in 169,171Ta isotopes, respectively. 相似文献
18.
We carry out a systematic study on the fusion-fission and evaporation residue excitation functions for the reactions of 6,7Li, 9Be, 10,11B + 209Bi and 6,9Li, 9Be + 208Pb, in which the projectiles are loosely bound and have low threshold energies against breakup. The fusion cross sections are calculated by the coupled-channel model. The compound nuclei decay are analyzed with the standard statistical model. The fission and evaporation residue excitation functions are well reproduced by our calculations, proving the validity of the standard statistical model in describing the compound nuclei decay in these characteristic reactions. For the compound nuclei with A=215-220 and Z=86-88, the liquid drop fission barriers need to be scaled by 0.80-1.02 to reproduce the experimental data. And a decreasing trend of the scaling factor with increasing fissionability parameter Z2/(50A) is found. 相似文献
19.
Santosh Kumar Rai 《Pramana》2007,69(5):815-818
Loop-driven decay modes of the Higgs are sensitive to new physics contributions because of new particles in the loops. To
highlight this we look at the dilepton-dijet signal in the dominant Higgs production channel at a linear e
+
e
− collider. We show that by taking a simple ratio between cross-sections of two different final states such contributions can
be very easily identified.
相似文献
20.
We present a fully microscopic study of the 16O + 208Pb fusion using the density-constrained time-dependent Hartree-Fock theory. The calculated fusion cross-sections are in good
agreement with the experimental data for the entire energy range indicating that the incorporation of dynamical effects is
crucial in describing heavy-ion fusion. 相似文献