用光谱分辨的双光束耦合方法测量χ（2）:χ（2）级联非线性相移

针对重要的χ^(2):χ^(2)级联非线性相移,在理论上论证了可以用光谱分辨的双光束耦合方法来测量χ^(2)：χ^(2)级联非线性相移,在实验上研究了飞秒时域级联非线性相移随波矢失配置的变化规律。这一新疑的测量方法灵敏度高,实际使用简单,应用低能量的飞秒激光振荡器,就能方便地测量微弱χ（2）晶体的级联非线性相移。     

Differential cross section and polarization for 2.63 MeV neutrons scattered from 12C

The differential cross section and polarization of 2.63 MeV neutrons scattered from ¹²C have been measured at eight angles between 17° and 118° in the laboratory system. By simultaneously fitting the cross section and polarization data, a set of scattering phase shifts was obtained. The values of the resulting d-wave phase shifts were larger than those of other existing sets of phase shifts in the energy region. A subsequent R-function analysis, reflecting these larger d-wave phase shifts, gave excellent fits to other experimental data below 3 MeV neutron energy region. The influence of narrow states at 7.50 and 7.55 MeV excitation energy in ¹³C is discussed.     

Calculations on the three-nucleon system using a separable expansion of local potentials

A separable expansion for local potentials called the unitary pole expansion (UPE) has been applied to the singlet-S soft-core Reid potential. The separable potentials obtained are used in conjunction with a separable tensor potential to calculate the triton binding energy, the nd doublet scattering length and the nd phase shifts in the state above and below break up. The convergence of the UPE is good especially for repulsive terms. The one term approximation (UPA) gives a triton energy differing by 0.04 MeV and a doublet scattering length differing by 0.14 fm from the values found for the local potential. The calculated phase shifts are in good agreement with the phase-shift analysis of Van Oers and Seagrave.     

Pion-nucleon phase shifts below 270 MeV

Pion-nucleon phase shifts below 270 MeV are derived from fixed t-dispersion relations using as input the π⁺p total cross sections measured by Bugg et al. below 290 MeV and CERN phase shifts above that energy. No particular high-energy model is needed.

It is pointed out that the predicted d-wave phase shifts — in contradiction to those belonging to earlier phase-shift solutions — are in good agreement with partial-wave dispersion relations and recent information on the helicity amplitudes describing the process . Furthermore our prediction for the P₁₃ wave has very recently got strong support from the work by Bugg et al. on pion-nucleon charge-exchange scattering.     

Elastic scattering using an artificial confining potential

The discrete energies of a scattering Hamiltonian calculated under the influence of an artificial confining potential of almost arbitrary functional form can be used to determine its phase shifts. The method exploits the result that two short-range Hamiltonians having the same energy will have the same phase shifts upon removal of the confining potential. An initial verification is performed on a simple model problem. Then the stochastic variational method is used to determine the energies of the confined e(-)-He(2)S(e) system and thus determine the low energy phase shifts.     

Deep l-independent potentials from supersymmetric inversion

Central potentials, independent of both the energy and the angular momentum l, are constructed from elastic phase shifts. The ambiguities of a fixed- l inversion are exploited to fit the phase shifts of other partial waves. The fitted quantities are the energy and normalization constant of forbidden bound states, and the small-distance behavior of the potential. The method is based on supersymmetric transformations of the radial Schrodinger equation. It is applied to the alpha+alpha collision in nuclear physics, and to the e(-)+Ne collision in atomic physics.     

Investigation on the phase shifts of extinction and phase gratings in polymethyl methacrylate

The phase shifts of the extinction and refractive index gratings to the illumination pattern are revealed in doped polymethyl methacrylate （PMMA）. The dynamic process of these shifts is studied via two-wave coupling at 351 nm. It is shown that these shifts are from the strain and the shrinkage inside the sample and accompanied with the photo-repolymerization process during the building process of the holographic grating. Such shifts will cause obvious energy exchange between the two recording beams and enough attention should be paid to the nonlocal property of the holographic gratings of the material in the application.     

Discrete representation of the spectral shift function and the multichannel <Emphasis Type="Italic">S</Emphasis>-matrix

A new method for solving the multichannel quantum scattering problem in a wide energy range based on the single diagonalization of the Hamiltonian matrix of the system in a finite-dimensional basis is briefly described. It has been shown that the interaction-matrix-induced shifts of the eigenvalues of the free Hamiltonian matrix in the continuous spectrum are directly related to the partial phase shifts. The two-channel scattering problem with shifted channel thresholds is considered for illustration.     

THE TWO-BOSON SCATTERING PHASE SHIFTS IN THE GENERAL φ6 THEORY WITH THE GAUSSIAN WAVE-FUNCTIONAL APPROACH

The two-particle scattering phase shifts with a λφ⁴ +ξφ⁶ interaction are com-puted in (1 + 1) and (2 + 1) dimensions using the Gaussian wave-functional approach.Through numerical analysis, we give the phase-shift curves with respect to the scat-tering energy for most cases of this theory. In (1 + 1) and (2 + 1 ) dimensions, for the symmetry vacuum the phase shifts are positive or negative depending on the signs of the renormalized parameter, while for the asymmetric vacuum the phase shifts are negative.     

NN potential with a six-quark core from the constituent quark model

A mesonic nucleon-nucleon potential from an effective quark interchange mechanism for non-overlapping nucleons is obtained from the constituent quark model. This is supplemented at short range by a phenomenological, non-mesonic potential describing the transition to a six-quark core with a discrete energy spectrum. NN phase shifts and low energy parameters are calculated and compared with data and phase shift analyses. Core parameters are extracted from the fits.     

The nuclear force and a magnetic monopole model of hadrons

The two-pion exchange potential of the nuclear force is constructed from the phase shifts of the low energy πN and ππ scattering. The large difference between the potentials thus constructed from the phenomenological potentials of Hamada-Johnston and of Bryan is pointed out. It is found that this difference has the form of the attractive Van der Waals potential plus an inner repulsive core. The existence of the Van der Waals force is discussed in connection with the magnetic monopole model of hadrons.     

The viscosity cross-section for elastic electron-xenon collisions including electron spin polarization

The results of the evaluation of the viscosity cross-section for elastic electron-xenon collisions, taking into account the spin-orbit interaction of the continuum electron, in the energy interval from 0.1 eV to 50 eV are presented and discussed. The calculations are performed on the basis of three theoretically derived sets of phase shift data obtained by different authors and on the deduced relativistic expression for the viscosity cross-section in terms of phase shifts discerning the spin-up and spin-down states of the scattered electrons. Comparison with viscosity cross-sections, as evaluated from non-relativistic phase shifts extracted from experiments, strongly favours the relativistic results. The assumption of isotropic scattering is critically examined and the error induced by its use is shown to persist to the same extent as in non-relativistic calculations, at least in the energy region considered. Received: 22 April 1998 / Received in final form: 16 December 1998     

COULOMB CORRECTION OF THE p-4He LOW ENERGY SCATTERING PHASE SHIFTS

A simple approach of Coulomb correction to the p-⁴He low energy scattering phase shifts is proposed,in which the channel radius of each partial wave is taken as an adjustable parameter.By using the Coulomb correction the n-⁴He scattering observables predicted from p-⁴He scattering phase shifts are in excllent agreement with experiment.Our calculations show that the neutron polarization depends sensitively on the channel radius of p waves and the obtained channel radius are adeguate to the different sets of phase shifts.     

π-Λ耦合常数和π-Λ低能P3/2波散射

本文将改进的Chew-Low展开应用到π-A的P_3/2分波散射,以从共振参量(能级和宽度)来确定π∧∑的耦合常数和P_3/2相移随能量的变化。当共振宽度采用目前比较公认的值50MeV时,给出的π-A耦合常数为g²=34或f²=0.12.文中亦给出了其他可能的宽度值所相应的结果。所得到的P_3/2相移曲线虽无实验可以比较,但估计在质心系总能量W≈1450MeV以下,应该是可靠的。     

Die Winkelabhängigkeit der Resonanzstreuung niederenergetischer Elektronen an He,Ne, Ar und N2

The energy dependence of the elastic resonance scattering of low energy electrons from He, Ne, Ar, and N₂ has been measured in the angular range from 8° to 110°. From the measurements are derived the total angular momenta and hence the configurations of the quasistationary negative ion states. The line shapes depend very strongly on the phase shifts for the potential scattering and on the interference of different partial waves. In the cases of He and Ne phase shifts are determined. The resonance structure in the elastic scattering from N₂ in the energy range from 1.75 eV to about 3,5 eV seems to be due to the formation of the N ₂ ^? -ion in its electronic ground state with a²Π configuration. The separations of its first few vibrational states are 237±10 meV, the natural half-width of these states being approximately 150 meV.     

Parametrization of phase shifts in the muffin-tin approximation

In the present paper, a new parametrization variant is proposed that enables one, for a minimal number of experimentally determined parameters (one for the s, p, and d phase shifts in the case of nontransition elements), to describe with good accuracy the behavior of the phase shifts in a wide range of variation of the energy. The dependence of the introduced parameters on the chemical state of the considered center is investigated.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 74–79, April, 1980.     

A fast and accurate semiclassical calculation of the total elastic cross section in the glory energy range

A method for the semiclassical calculation of the total cross section in atomic and molecular elastic collisions, for the glory energy range, is reported. The parameters needed for the calculation of the glory undulatory component of the cross section are obtained from a few JWKB phase shifts for impact parameters near the glory impact parameter. The smooth component of the cross section is obtained from JB phase shifts for the long range attraction. The procedure, suitable for every potential model, is accurate and much faster than a full JWKB calculation. A discussion of some typical results is reported and an analysis of the information obtainable from experimental absolute cross sections is also given.     

Phase control of Goos-Hänchen shifts in a four-level quantum dot nanostructure

In this letter, phase control of the Goos-Hänchen shifts of the reflected and transmitted probe light beams through a cavity containing four-level InGaN/GaN quantum dot nanostructure is theoretically discussed. In order to achieve the wave functions and their corresponding energy levels of the mentioned quantum dot nanostructure, Schrödinger and Poisson equations must be solved in a self consistent manner for carriers (here electron) in quantum dot. It is found that the coupling field, the pumping field as well as the cycling field can enhance the GH shifts of the reflected and transmitted probe beams. The effect of relative phase and the detuning of the probe light on the GH shifts of the reflected and transmitted probe beams are also investigated. We find that the GH shifts can be switched between the large positive and negative values by adjusting the controllable parameters.     

ZnS结构相变、电子结构和光学性质的研究

运用第一性原理平面波赝势和广义梯度近似方法, 对闪锌矿结构(ZB)和氯化钠结构(RS) ZnS的状态方程及其在高压下的相变进行计算研究, 分析相变点附近的电子态密度、能带结构和光学性质的变化机理. 结果表明: 通过状态方程得到ZB相到RS相的相变压强值为18.1 GPa, 而利用焓相等原理得到的相变压强值为18.0 GPa; 在结构相变过程中, sp³轨道杂化现象并未消失, RS相ZnS的金属性明显增强; 与ZB相ZnS相比, RS相ZnS的介电常数主峰明显增强, 并向低能方向出现了明显偏移, 使得介电峰向低能方向拓展, 在低能区电子跃迁大大增强. 关键词： 硫化锌 相变 电子结构 光学性质     

Variational calculation of the excited states in the sinh-Gordon field theory

The Gaussian wave-functional variational approximation is used to calculate the energy of one-particle state as well as the energy and wave function of two-particle state in the sinh-Gordon model in (1+1) dimensions. We find that there are no bound states in this model. The phase shifts of the scattering states are investigated in detail.