Two Electron States in a Thin Spherical Nanolayer: Reduction to the Model of Two Electrons on a Sphere

Two electron states in a thin spherical nanolayer are discussed. Adiabatic approach is used to divide the system to fast (radial) and slow (angular) subsystems. This leads the Coulomb interaction to be dependent on angular variables, more precisely, on the relative angle between electrons. Approximated Coulomb interaction potential is discussed. Analytical solutions for angular part of Schrödinger equation as well as for energy spectrum for the case of harmonic approximation are obtained. Also the first order of correction energy is discussed by using perturbation theory. For the ground state an analytical expression for the first order correction energy dependent on effective radius of the nanolayer is obtained. Obtained results are compared with exact Coulomb interaction model presented by Loos and Gill.     

THE EFFECT OF-NUCLEAR DISTORTION IN DEEP INELASTIC SCATTERING

We have investigated the process of deep inelastic scattering by means of a phenomenological model which assumes that the colliding nuclei undergo quadrupole length distortion after sticking each other.The energy dissipations and the angular distributions and so on are in agreement with experimental data.The results may describe qualitatively the main characteristics of the quasi-fission.The total kinetic energy of the exit channel is the Coulomb repulsion energy of the fragments and the interaction time of the process is scaled by 10-22—10-21sec.In addition,the effect of 1 window of complete fusion is also given.     

Target fragmentation in hadron-nucleus collisions at high energy

We discuss target fragmentations in hadron-nucleus collisions at high energy (5–400 GeV). A model is developed which is based on the two-step (fast and slow) processes. A high-energy hadron drills a linear hole inside the nucleus, kicking out several nucleons (fast process). Along the linear hole, the target breaks up into a few pieces. One of the fragments forms an observed nucleus, absorbing some of the recoil nucleons (slow process). During the breakup, the Coulomb interaction between the fragment and the rest is taken into account. This leads to the consideration of a three-body breakup process which influences significantly the low-energy part of the energy distribution in the h+A → B+X reaction. The model is applied to the angular and the energy distributions in this collision. It achieves a nice agreement with experiment.     

Angular distributions of the fragments from coulomb explosions of diatomic molecules in intense laser fields

The angular distributions of the fragments from a Coulomb explosion of a diatomic heteronuclear molecule during multielectron dissociative ionization in a superintense field are considered in terms of classical mechanics. The patterns of angular distributions of the Coulomb explosion fragments are shown to differ in different ranges of laser pulse parameters. In particular, there are two distinct modes of fragment separation: separation in a Coulomb field and separation in the field of an effective “fragment + field” potential. The effective potential includes both the force of Coulomb repulsion between the fragments and the period-averaged force exerted on the system by the field; it can be determined by using the Kramers-Henneberger method. The limits of applicability of the Kramers-Henneberger method to the problem in question are discussed. These limits specify the range of field parameters in which the fragments fly apart in a direction perpendicular to the field for the initially arbitrary orientation of the molecular axis relative to the field.     

Nucleus-Nucleus Scattering Based on a Modified Glauber Theory

A modified microscopic Glauber theory has been extended to investigation of the reaction and elastic differential cross sections of various projectile-target collisions at low and intermediate energies. Through a systematic study, we find that the inclusion of the finite range interaction and Coulomb modifications plays very important role in the Glauber theory to reproduce the experimental data at these energy ranges. Usually the effect of the Coulomb modification is to decrease the reaction cross sections, on the contrary that of the finite range interaction modification increases them. The angular distributions calculated by the Glauber theory including these two corrections are in good agreement with the experimental data.     

Microscopic study of the 12C + 16O system

An angular momentum projected microscopic calculation is performed for the ¹²C + ¹⁶O system with an effective nuclear force and the exact Coulomb interaction. The ¹²C wave function is projected on a 0⁺ state. Parametrizations of the Coulomb interaction between the nuclei are fitted. The L-projected energy curves present a quite complicated structure especially for the negative parity states. The role played by critical angular momenta is put into evidence. A generator coordinate calculation gives several bands of bound, quasibound and virtual states. Excellent agreement in energy and angular momentum is obtained with the 13.7 MeV (J = 9), 19.7 MeV (J = 14), 22.7 MeV (J = 15) and other resonances.     

Angular distributions of fast electrons, ions, and Bremsstrahlung x/gamma-rays in intense laser interaction with solid targets

We study the angular distributions of fast electrons, ions, and bremsstrahlung x/ gamma-rays generated during the interaction of an ultrashort intense laser pulse with solid targets. A relation is found on the angular directions for fast electrons and ions as a function of the particle's kinetic energy, experienced Coulomb potential changes, and the incident angle of the laser pulse. It is valid independent of the acceleration mechanisms and the polarization of the laser pulse, as confirmed by particle-in-cell simulations. The angular distribution of bremsstrahlung x/gamma-rays is presented to show explicitly its correlation with the corresponding angular distributions of electrons.     

Dynamic and geometric alignment of molecules induced by intense laser fields

We present a method to discuss simultaneously the relative importance of molecular dynamic and geometric alignment induced by intense laser fields in theoretical view. This method divides the process of molecular alignment into three steps, which are tightly correlated with that of molecular multielectron dissociative ionization and Coulomb explosion. A fourth-order Runge-Kutta algorithm and a developed counting approach are used to calculate the angular distribution of molecules in the first and second steps of molecular alignment. The last step is described by a field-ionization, Coulomb explosion model. The angular distribution of molecules at the critical distance originated from geometric alignment is obtained by calculating the volume of shells associated with a series of particular angle. The final angular distributions of molecules are obtained by properly weighting the results of three steps. The numerical results of distinguishing between dynamic and geometric alignment for certain conditions are presented and discussed. Our computational results show that the alignment mechanism, which dominates the observed anisotropy of angular distributions of ionic fragments for a given condition, is determined by the dependences of the extent of dynamic and geometric alignment on laser parameters and molecular parameters.     

Coulomb exploded directional double ionization of N_2O molecules in multicycle femtosecond laser pulses

We experimentally investigate Coulomb exploded directional double ionization of N_2O molecules in elliptically polarized femtosecond laser pulses.The denitrogenation and deoxygenation channels are accessed via various pathways.It leads to distinct asymmetries in directional breaking of the doubly ionized N_2O molecules versus the instantaneous laser field vector, which is revealed by tracing the sum-momentum spectra of the ionic fragments as a recoil of the ejected electrons.Our results demonstrate that the accessibility of the Coulomb exploded double ionization channels of N_2O molecules are ruled by the detailed potential energy curves, and the directional emission of the fragments are governed by the joint effects of the electron localization-assisted enhanced ionization of the stretched molecules and the profiles of the molecular orbitals.     

Investigation of Intermediate Mass Fragments Emitted in the Reaction of 294MeV 20Ne+159Tb

Intermediate mass fragments(2Z≤11) emitted from 294 MeV ²⁰Ne+¹⁵⁹Tb reaction have been measured by △E-E telescope counters at the angle of 10°—150°region.The energy spectra of the fragments at back angle(>90°) have bell shape,and their peaks locate near the Coulomb barrier of exit channel.The analysis of the energy spectra has been done in terms of moving source and indicate that all the fragments are emitted from a common source,the compound nuclei formed in incomplete fusion process.The charge and angular distributions of the fragments originated from the asymmetric binary decay of the formed compound nuclei have been calculated based on statistical GEMINI code,and the results are in well agreement with the experimental data.     

奇Z超重核的禁戒α衰变(英文)

采用密度依赖的结团模型研究了奇Z 超重核的禁戒α衰变, 粒子与子核之间的微观核势通过双折叠模型对M3Y 核子-核子相互作用势以及 粒子与子核的密度积分给出。 粒子与子核之间的库仑相互作用也通过 粒子与子核的电荷密度积分给出。计算发现,由于非零角动量带来的禁戒效应和小的α粒子预形成几率,奇Z 超重核的α衰变寿命会明显变长。We investigate the α-transition of odd-Z superheavy nuclei by the density-dependent cluster model (DDCM). The microscopic nuclear potential between the -particle and the daughter nucleus is evaluated numerically from the double-folding model with the standard M3Y nucleon-nucleon interaction. The Coulomb potential is also obtained from the double-folding integral of the proton-proton Coulomb interaction with the charge density distributions of α-particle and daughter nucleus. From our calculations, enhanced stability againstα-decays is found for the odd-Z superheavy nuclei due to the hindrance effect of non-zero angular momentum and the small preformation factor of the -particle.     

Finite Range Effects on Fusion and/or Breakup of ^6He^＋238U and ^11Li＋^208pb Systems

We have studied the effects of the finite range of the interaction between the fragments of the projectile on the fusion and/or breakup of ⁶He+²³⁸U and ¹¹Li+²⁰⁸Pb systems at near barrier energies within the framework of dynamic polarization potential approach. It has been found that at near barrier energies the maximum flux is lost to the breakup channel and at energies well above the Coulomb barrier the fusion coupled with the breakup channel opens up, initially with sharp rise and later becoming saturated at energy nearly twice of theCoulomb barrier. Further, it is found that the breakup cross section increases with the increasing range of the interaction between the fragments of the projectile while the fusion coupled with the breakup channel cross section decreases with the increasing range.     

库仑作用对同位旋分馏过程的影响

利用同位旋相关的量子分子动力学模型研究了中能重离子碰撞中库仑作用对同位旋分馏过程的影响.研究结果表明,在所研究的能区,无论是丰(缺)中子碰撞系统或者轻(重)反应系统,库仑作用都使同位旋分馏过程减弱,而这种影响主要来自于库仑作用对质子的排斥作用,使更多的质子发射,从而降低了气相中子–质子比所导致     

Coulomb asymmetry in above-threshold ionization

A new method for including effects of the Coulomb potential in strong-field laser atom interaction is presented. The model is tested by comparing its results with experimental data of energy resolved angular distributions of photoelectrons. For elliptical polarization these exhibit a strong asymmetry. Our theory shows that this strong asymmetry for the low-energy electrons is induced by a small Coulomb force acting on the tunneling electron just after the exit of the tunnel. This is in contrast to the situation for high electron energies where the asymmetry arises via rescattering by the parent ion.     

Momentum transfer in light-ion-induced fission reactions

Angular correlations and angular distributions of the fission fragments produced in the bombardment of a ²³²Th target with protons, deuterons and α-particles in the energy range between 35 and 1000 MeV/nucleon have been measured. From these measurements, the distributions of linear momentum imparted to fissioning nuclei have been deduced in the various energy regimes; dominating reaction mechanisms are classified according to the fraction of the available incident momentum transferred to the target. The experimental results are compared to the predictions of intra-nuclear cascade calculations. An optimum excitation energy supported by the fissioning nuclei could be the dominant limitation to momentum transfer at high incident energies. The angular distributions of the fission fragments were used to extract fission cross sections and upper limits of the angular momentum imparted to the fissioning nuclei.     

BABAR measurement of baryon time-like form factors via initial state radiation

BABAR has measured with unprecedented accuracy the e+e-→p(p-)and e+e-Λ(Λ-)cross sections by means of the initial state radiation technique,which has the advantages of good efficiency,good energy resolution and full angular acceptance,even exactly at threshold.A peculiar feature of these cross sections is their non-vanishing values at threshold.In the case of charged baryons,this phenomenon is expected according to the Coulomb interaction between the outgoing baryon and antibaryon.Once this Coulomb enhancement factor is taken into account,the striking result is achieved that the proton form factor at threshold is |GP(4M2p)|=1,that is what is expected for pointlike fermion pairs,in spite of the proton structure.However a Coulomb enhancement factor is not expected for neutral fermions,likely in contradiction with the BABAR data.Qualitatively this behaviour is consistent with Coulomb interactions at the valence quark level.     

A Discrete Density Matrix Theory for Atoms¶in Strong Magnetic Fields

This paper concerns the asymptotic ground state properties of heavy atoms in strong, homogeneous magnetic fields. In the limit when the nuclear charge Z tends to ∞ with the magnetic field B satisfying B>> Z ^4/3 all the electrons are confined to the lowest Landau band. We consider here an energy functional, whose variable is a sequence of one-dimensional density matrices corresponding to different angular momentum functions in the lowest Landau band. We study this functional in detail and derive various interesting properties, which are compared with the density matrix (DM) theory introduced by Lieb, Solovej and Yngvason. In contrast to the DM theory the variable perpendicular to the field is replaced by the discrete angular momentum quantum numbers. Hence we call the new functional a discrete density matrix (DDM) functional. We relate this DDM theory to the lowest Landau band quantum mechanics and show that it reproduces correctly the ground state energy apart from errors due to the indirect part of the Coulomb interaction energy. Received: 20 October 2000 / Accepted: 3 November 2000     

Heavy ion reactions around the Coulomb barrier

The angular distributions of fission fragments for the 32S+184W reaction near Coulomb barrier energies are measured. The ex perimental fission excitation function is obtained. The measured fission cross sections are decomposed into fusion-fission, quasi-fission and fast fission contributions by the dinuclear system (DNS) model. The hindrance to completing fusion both at small and large collision energies is explained. The fusion excitation functions of 32S+90,96Zr in an energy range from above to below the ...