共查询到20条相似文献,搜索用时 31 毫秒
1.
X.H. Zhou M. Oshima Y. Toh Y.H. Zhang Y. Zheng M. Koizumi A. Osa T. Hayakawa Y. Hatsukawa T. Shizuma M. Sugawara 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):285-289
Based on the systematic investigation of the data available for nuclei with A≥ 40, a Z
1/3-dependence for the nuclear charge radii is shown to be superior to the generally accepted A
1/3 law. A delicate scattering of data around R
c/Z
1/3 is inferred as owing to the isospin effect and a linear dependence of R
c/Z
1/3 on N/Z (or (N - Z)/2) is found. This inference is well supported by the microscopic Relativistic Continuum Hartree-Bogoliubov (RCHB) calculation
conducted for the proton magic Ca, Ni, Zr, Sn and Pb isotopes including the exotic nuclei close to the neutron drip line.
With the linear isospin dependence provided by the data and RCHB theory, a new isospin-dependent Z
1/3 formula for the nuclear charge radii is proposed.
Received: 23 September 2001 / Accepted: 21 January 2002 相似文献
2.
3.
A new type of atomic orbital is proposed for use in molecular problems of quantum mechanics. This orbital is formally similar to Slater's orbitals but is characterized by an effective nuclear charge Z eff which is an explicit function of the angles ? and φ. The fundamental state of the molecule H2 + is studied using such an orbital. 相似文献
4.
We consider a large neutral molecule with total nuclear charge Z in non-relativistic quantum mechanics with a self-generated classical electromagnetic field. To ensure stability, we assume that Z α 2 ≤ κ 0 for a sufficiently small κ 0, where α denotes the fine structure constant. We show that, in the simultaneous limit Z → ∞, α → 0 such that κ = Z α 2 is fixed, the ground state energy of the system is given by a two term expansion c 1 Z 7/3 + c 2(κ) Z 2 + o(Z 2). The leading term is given by the non-magnetic Thomas-Fermi theory. Our result shows that the magnetic field affects only the second (so-called Scott) term in the expansion. 相似文献
5.
We use the finite size scaling method to study the critical points, points of non-analyticity, of the ground state energy as a function of the coupling parameters in the Hamiltonian. In this approach, the finite size corresponds to the number of elements in a complete basis set used to expand the exact eigenfunction of a given molecular Hamiltonian. To illustrate this approach, we give detailed calculations for systems of one electron and two nuclear centres, Z + e ?Z+. Within the Born-Oppenheimer approximation, there is no critical point, but without the approximation the system exhibits a critical point at Z = Zc = 1.228279 when the nuclear charge, Z, varies. We show also that the dissociation occurs in a first-order phase transition and calculate the various related critical exponents. The possibility of generalizing this approach to larger molecular systems using Gaussian basis sets is discussed. 相似文献
6.
E. S. Gusarevich 《Journal of Experimental and Theoretical Physics》2017,124(2):196-201
The energy losses of fast structural ions in collisions with atoms have been considered in the eikonal approximation. The structural ions are ions consisting of a nucleus and a certain number of electrons bound to it. The effect of nuclear charge Z of the ion on its effective deceleration κ(p) (energy losses associated with excitation of only intrinsic ion shells) has been analyzed. It is shown that the allowance for the interaction of an atom with the ion nucleus for Z a Z/v > 1, where Z a is the charge of the atomic nucleus and v is the velocity of collisions in atomic units, considerably affects the value of κ(p), which generally necessitates taking into account nonperturbatively the effect of both charges Z a and Z on κ(p). 相似文献
7.
Yu. V. Zorenko I. V. Konstankevich V. I. Gorbenko P. I. Yurchishin 《Journal of Applied Spectroscopy》2002,69(5):769-776
The possibility of obtaining scintillators with a high effective atomic number of the element Z
ef based on Lu3Al5O12:Ce3+ singlecrystal films (SCF) on doping with La3+ and Sc3+ ions on Y3Al5O12 substrates has been investigated. It is established that the SCF of (LuLaY)3Al5O12:Ce3+ (Z
ef = 58.9 and = 6.67 g/cm2) does not rank below those of Y3Al5O12:Ce3+ (Z
ef = 29 and = 4.52 g/cm2) in the conversion efficiency of radiation at the band with max = 515 nm. This allows their use as screens of xray images with a space resolution of 0.75–1.00 m. It is suggested that in the SCF of Lu3Al5O12 the isoelectronic impurities of lanthanum and scandium form radiative recombination centers of the type LaLu, ScLu, and ScAl as well as the centers Lu as a consequence of the effect of replacement of some Lu3+ ions by the La3+ ions to octanodes of the garnet lattice. The low efficiency of Ce3+ radiation in the SCF of (LuSc)3(AlSc)5O12:Ce is explained by substantial losses due to excitation of the recombination luminescence in the UV region of the centers formed by the isoelectronic impurities of scandium and to the possible existence of the channel of energy excitation dissipation related to the transitions between extrema of the allowed energy bands and activator levels. 相似文献
8.
O. V. Ivanov D. A. Shport E. G. Maksimov 《Journal of Experimental and Theoretical Physics》1998,87(1):186-199
First-principles calculations are performed relating to the stability of a series of perovskite crystals with respect to transition
to the ferroelectric and the antiferroelectric state. The calculations employ the generalized Gordon-Kim method, in which
the total charge density of an ionic crystal is represented as a superposition of the densities of the individual ions. In
the spirit of the nonequilibrium thermodynamics of Leontovich the charge density of an individual ion is calculated in the
presence of external auxiliary fields which deform this density. Multipole deformations up to quadrupole are taken into account.
The actual magnitude of the deformation is found by minimizing the total energy of the crystal in the Thomas-Fermi-Dirac approximation.
The calculated values of the ion shifts in the ferroelectric phase for BaTiO3, and also the electron contribution to the dielectric constant ε
∞ and the dynamic Born effective charges Z
eff are found to be in good agreement with the experimental data. The proposed method allows one to obtain an analytical expression
for ε
∞, Z
eff, and the dynamic vibration matrix. It is shown that these expressions formally coincide with the expressions arising in the
phenomenological models of the polarized and deformed ion. Analysis of the expressions obtained confirms the validity of the
classical theory of ferroelectrics of displacement type for perovskite crystals.
Zh. éksp. Teor. Fiz. 114, 333–358 (July 1998) 相似文献
9.
An adjustment to 782 ground-state nuclear charge radii for nuclei with N, Z
3 \ge8 leads to R0 = 1.2257 A1/3\ensuremath R_0 = 1.2257 A^{1/3} fm and s \sigma = 0.124 fm for the charge radius. Assuming such a Coulomb energy
Ec = \frac35 e2Z2/1.2257 A\frac13\ensuremath E_c = \frac{3}{5} e^2Z^2/1.2257 A^{\frac{1}{3}} , the coefficients of different possible mass formulae derived from the liquid drop model and including the shell and pairing
energies have been determined from 2027 masses verifying N, Z
3 \ge8 and a mass uncertainty £ \le150 keV. These formulae take into account or do not the diffuseness correction ( Z2/A\ensuremath Z^2/A term), the charge exchange correction term ( Z4/3/A1/3\ensuremath Z^{4/3}/A^{1/3} term), the curvature energy, the Wigner terms and different powers of I = (N - Z)/A . The Coulomb diffuseness correction or the charge exchange correction term play the main role to improve the accuracy of
the mass formulae. The different fits lead to a surface energy coefficient of around 17-18MeV. A possible more precise formula
for the Coulomb radius is R0 = 1.2332A1/3 + 2.8961/A2/3 - 0.18688A1/3I\ensuremath R_0 = 1.2332A^{1/3} + 2.8961/A^{2/3} - 0.18688A^{1/3}I fm with s \sigma = 0.052 fm. 相似文献
10.
M. K. Srivastava 《Pramana》2004,63(5):1053-1062
An approximate simple scaling law is obtained for asymmetric (e, 3e) process on helium-like ions for double ionization by fast electrons. It is based on the equation (Z
′3π) exp[-Z(r1 + r2)],Z′ = Z – (5/16) for ground state wave function of helium-like ions and Z′2 scaling of energies. The scaling law is found to work very well if the lower energy electron is ejected along the momentum
transfer direction and the other one is ejected in the opposite direction. It also works quite well if this electron is ejected
within about 90° of the momentum transfer direction with the other electron going in the opposite direction. The scaling law
becomes increasingly accurate as the target nuclear charge and the energy increase. 相似文献
11.
N. V. Novikov Ya. A. Teplova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(2):206-210
Theoretical estimation of the equilibrium charge distribution of carbon and oxygen ions passed through a matter is obtained. The coefficient considering the effect of density on the charge distribution of these ions is calculated for an amorphous medium consisting of atoms with the nuclear charge Z t (Z t ≤ 54). An oscillating dependence of the average ion charge on the nuclear charge of the target atom is obtained which cannot be described by empirical relations. 相似文献
12.
Novel methods for determining the 1s Lamb shift of hydrogenic ions are outlined. In one method the energy of a 2–1 transition
in the hydrogenic ion of nuclear charge Z is compared to a 4–2 transition in the hydrogenic ion of charge 2Z. A second method exploits close coincidences between Lyman series transitions in ions of similar Z.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
N. V. Novikov Ya. A. Teplova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(2):264-267
The dependence of the cross section of electron loss on the nuclear charge Z of a bombarding ion and on the nuclear charge Z t of a target atom for fast collisions is studied theoretically using the plane-wave Born approximation and the sum rule. The results of calculations show that the cross section of electron loss for fast collisions increases monotonically as Z and Z t increase, which can be used to interpolate cross sections for the processes for which there are no experimental data. 相似文献
14.
A series of polymer nanocomposite films based on intercalation of (PAN)8LiCF3SO3 into the nanometric clay channels of an organomodified clay has been prepared using the standard solution-casting technique.
The role of organoclay concentration on polymer–ion interaction, ion–ion interaction, and ion–clay interaction in clay-based
nanocomposite films has been analyzed using Fourier transform infrared (FTIR) analysis. Substantial ion dissociation is observed
even at a very low clay loading (1–2 wt.%) in the nanocomposites. FTIR results suggest the presence of both uncoordinated
CF3SO3
− (free-anions) and ion pairs in the nanocomposite evidenced by changes in CF3SO3
− symmetry from C3ν to Cs and marked asymmetry in the profile of degenerate δd(CF3
−) mode. The experimental results suggest a direct correlation of clay-assisted ion dissociation process with variation in
conductivity (σ
dc) and glass transition temperature (T
g) as a function of clay concentration. A model has been proposed to explain the observed correlation on the basis of polymer–ion–clay
interaction. The proposed scheme of ion transport mechanism appears to be consistent with the experimental observation. 相似文献
15.
I. S. Dmitriev Ya. A. Teplova Yu. A. Fainberg 《Journal of Experimental and Theoretical Physics》1999,89(5):830-836
The electron loss and electron capture cross sections σ
i,i+m and σ
i,i−m for boron ions and atoms traveling at the velocities V=1.19 and 1.83 a.u. in H2, He, N2, Ne, Ar, and Xe are measured. The known experimental data on these cross sections at velocities near the cross-section maximum
are analyzed. It is found that the electron loss cross sections can be described by a formula which was previously derived
in the free-collision approximation and takes into account features of both the ions and the ambient atoms. As the nuclear
charge Z
t of the ambient atoms increases, the cross sections vary nonmonotonically, increasing on average as Zt
t
1/2
. A formula based on the model of independent electrons is proposed for electron capture by ions with small values of the
charge i. It describes the dependence of the electron capture cross section σ
i,i−1 on the mean binding energy of an electron in an ion with the charge i−1. The total electron capture cross section σ
i,i−1 is proportional to the number of vacancies in the unfilled electron shell nearest the nucleus. The cross sections 0σ
i,i−1 exhibit substantially nonmonotonic variation with Z
t, increasing on average as Z
t
1/3
.
Zh. éksp. Teor. Fiz. 116, 1539–1550 (November 1999) 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.
Using the semiclassical Green’s function in the Coulomb field, we analyze the probabilities of single and multiple e
+
e
− pair production at a fixed impact parameter b between colliding ultrarelativistic heavy nuclei. We perform calculations in the Born approximation with respect to the parameter
Z
Bα and exactly in Z
Aα, where Z
A and Z
B are the charge numbers of the corresponding nuclei. We also obtain the approximate formulas for the probabilities valid for
Z
Aα, Z
Bα ≲ 1.
The text was submitted by the authors in English. 相似文献
18.
V. N. Lokhman D. D. Ogurok E. A. Ryabov 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(1):59-67
We report about effective ionization of iodine atoms and CF3I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation
of the CF3I molecules is the I+ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on
the intensity
of the ion signal and the shape of its time-of-flight peak. Based on the
analysis of the results obtained, we have suggested the mechanism of this
effect. The conclusion drawn is that the ionization of the iodine atoms by
the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in
turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and
the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground
state I(2P3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization
from the metastable state I*(2P1/2). The ionization of the CF3I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation
of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms. 相似文献
19.
We used CR39 plastic nuclear track detectors (C12H18O7) in combination with automatic track measurement to determine total charge changing and partial cross sections for the production of fragments of chargeZ=6 andZ=7 in collisions of16O beam nuclei at energies of 60 GeV/nucleon and 200 GeV/nucleon in targets H, C, CR39, CH2, Al, Cu, Ag and Pb. Total charge changing cross sections due to the process of electromagnetic dissociation are calculated based on a theoretical model and found to be consistent with total and partial electromagnetic dissociation cross sections derived from this experiment. The energy dependence of pure nuclear fragmentation is investigated. 相似文献
20.
G. H. Hovhannisyan A. S. Danagulyan A. R. Balabekyan J. Adam V. G. Kalinnikov V. S. Pronskikh A. A. Solnyshkin V. M. Tsoupko-Sitnikov N. M. Vladimirova 《Physics of Atomic Nuclei》2012,75(2):125-135
The formation cross sections for about 110 products of interaction between a 12C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes 112,118,120,124Sn were calculated. Massyield and charge distributions were obtained for 112,118,124Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Z
p
, are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products
originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions
are compared for proton-, deuteron- and ion-nucleus reactions. 相似文献