The fixed scatterer approximation and nucleon deuteron scattering

A method of solving the Schroedinger Equation for the scattering from two fixed local potentials is presented. The solutions are used within the framework of the fixed scatterer approximation to perform model calculations of N-D scattering using both effective range theory potentials and a “semi-realistic” potential with a strong repulsive core. For smooth potentials approximate solutions to the fixed scatterer problem are proposed and found to be quite accurate.Other procedures for calculating elastic scattering were compared with the exact fixed scatterer approximation. The results show that the neglect of longitudinal momentum transfer in the Glauber multiple diffraction theory is a severe effect except in the forward direction. For small angle scattering the Glauber prediction for the double scattering amplitude is quite accurate, and does not depend strongly upon either the extent of potential overlap, or the ratio $\text{V}\text{E}$. Comparisons with the Agassi and Gal results for nonoverlapping potentials indicate that the effects of potential overlap are important, at least for the lowest partial waves. Conclusions about the overall importance of off-energy shell effects in nucleon-deuteron scattering, and about the interference of these effects with the determination of the correlation structure of nuclei are not free from ambiguities.     

Group theory approach to scattering

We show that both bound and scattering states of a certain class of potentials are related to the unitary representations of certain groups. In this class, several potentials of practical interest, such as the Morse and Pöschl-Teller potentials, are included. The fact that not only bound states but also scattering states are connected with group representations suggests that an algebraic treatment of scattering problems similar to that of bound state problems may be possible.     

Ultracold collision properties of metastable alkaline-earth atoms

Ultracold collisions of spin-polarized 24Mg, 40Ca, and 88Sr in the metastable 3P2 excited state are investigated based on molecular potentials obtained from ab initio calculations. We calculate the long-range interaction potentials and estimate the scattering length and the collisional loss rate as a function of magnetic field. The scattering lengths show resonance behavior due to the appearance of a molecular bound state in a purely long-range interaction potential and are positive for magnetic fields below 50 mT. A loss-rate model shows that losses should be smallest near zero magnetic field and for fields slightly larger than the resonance field, where the scattering length is also positive.     

Generalized fresnel model for very heavy ion scattering: (II). Relation to the optical model

The generalized Fresnel model presented in part I as a simplified method for analyzing angular distributions of very heavy ion scattering is used here with an alternative parameterization of the partial-wave S-matrix. Its form is suggested by analytic expressions for the reflection function and nuclear phase shifts derived by Kauffmann from conventional optical potentials. This enables us to formulate explicitly the relationships between the l-space and r-space properties of the elastic heavy ion interaction, in particular the continuous ambiguities and other features found empirically from optical model calculations.     

投影电子束光刻中电子穿透掩膜的Monte Carlo模拟

利用基于Mott散射截面和介电函数模型的Monte Carlo方法模拟了电子穿透掩膜的能量损失分布，其计算结果与实验结果符合很好. 由此进一步计算了角度限制投影电子束光刻(SCALPEL)掩膜的穿透率和衬度，结果表明：散射体的厚度对衬度的影响较大，衬度随散射体厚度的增加而增强，而支撑体对衬度的影响较小；增大限制孔的孔径角时，透射率相应增大，但衬度会降低；衬度随入射电子的能量增加而减小. 关键词： Monte Carlo模拟 电子束光刻 掩膜     

Probing collective modes of correlated states of few electrons in semiconductor quantum dots

Low-lying collective excitations above highly correlated ground states of few interacting electrons confined in GaAs semiconductor quantum dots are probed by resonant inelastic light scattering. We highlight that separate studies of the changes in the spin and charge degrees of freedom offer unique access to the fundamental interactions. The case of quantum dots with four electrons is found to be determined by a competition between triplet and singlet ground states that is uncovered in the rich light scattering spectra of spin excitations. These light scattering results are described within a configuration-interaction framework that captures the role of electron correlation with quantitative accuracy. Recent light scattering results that reveal the impact of anisotropic confining potentials in laterally coupled quantum dots are also reviewed. In these studies, inelastic light scattering methods emerge as powerful probes of collective phenomena and spin configurations in quantum dots with few electrons.     

Theory of indirect resonant inelastic X-ray scattering

We express the cross section for indirect resonant inelastic X-ray scattering in terms of an intrinsic dynamic correlation function of the system that is studied with this technique. The cross section is a linear combination of the charge response function and the dynamic longitudinal spin density correlation function. This result is asymptotically exact for both strong and weak local core-hole potentials. We show that one can change the relative charge and spin contribution to the inelastic spectral weight by varying the incident photon energy.     

Nonlinear coherent transport of waves in disordered media

We present a diagrammatic theory for coherent backscattering from disordered dilute media in the nonlinear regime. We show that the coherent backscattering enhancement factor is strongly affected by the nonlinearity, and we corroborate these results by numerical simulations. Our theory can be applied to several physical scenarios such as scattering of light in a nonlinear Kerr medium or propagation of matter waves in disordered potentials.     

A Re-Examination of the Arguments for Baryon Parity Doublets

The arguments for baryon parity doubling are re-examined by use of a spin formalism developed by the author together with B. E. LAURENT . It is shown that the transformation between good parity amplitudes and helicity flip and non-flip amplitudes in πN scattering is ambiguous. It is further shown that the unitary condition for boson-fermion scattering gives no information of the parity of intermediate states contributing to a good parity amplitude. These ambiguities follow from the fact that for boson-fermion scattering the CPT transformation of an amplitude does not commute with the projection on a definite parity. It is finally shown how a Regge pole model with linear trajectories without parity doubling can be constructed without any specific dynamical assumptions or artifices. The constraints on the residues needed in this case do not violate any general principles.     

Polariton-mediated Raman scattering in microcavities: A Green’s function approach

We present calculations of the intensity of polariton-mediated inelastic light scattering in semiconductor microcavities within a Green’s function framework. In addition to reproducing the strong coupling of light and matter, this method also enables the inclusion of damping mechanisms in a consistent way. Our results show excellent agreement with recent Raman scattering experiments.     

Auto-correlation Properties of Scattering Light in Ultrasound-modulated Random Media

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Auto-correlation Properties of Scattering Light in Ultrasound-modulated Random Media

In this paper, the auto-correlation properties of scattering light in random media modulated by ultrasound were studied. The expression of temporal auto-correlation function of scattering light amplitude in the ultrasound-modulated media was presented. The results show that the auto-correlation function is modulated as the ultrasound is introduced into the media and the modulation amplitude decays with correlation time. The influences of ultrasound amplitude, Brownian diffusion coefficient, scattering and absorption coefficients on auto-correlation function were discussed. The auto-correlation imaging of an object hidden in random media was also studied by the use of Monte Carlo simulations.     

Effects of saturation on optical bistability with coupled surface plasmons

We present exact numerical results for a symmetric layered medium (prism/Ag film/nonlinear dielectric/Ag film/prism) where the middle dielectric slab is assumed to have a saturation-type nonlinearity. We show bistable behaviour in the power dependence of the reflectivity ofp-polarized light under the condition when coupled surface modes are excited in the structure. Moreover, we study the effect of saturation on the bistable behaviour to show that multivalued character is inhibited by saturation effects. The field distributions corresponding to the minimum reflectivity states of the nonlinear structure are also presented.     

Adiabatic approximation on the impact-parameter model

In this paper we study the impact-parameter model for the scattering of a light particle by two heavy ones in the case when the coupling constants of the potentials acting on the light particle due to the presence of the two heavy ones are the same. We study the asymptotic behavior of the transition probability when the relative velocity of the heavy particles goes to zero. We show that the probability of a transition can be arbitrarily close to the one of no transition.     

Zero-range interaction in arbitrary dimensions and in the presence of external forces

We analyze zero-range interactions in arbitrary dimensions and in the presence of external forces in terms of non-local separable potentials. We show that in one-, two- and three-dimensional cases this approach is equivalent to the standard method with a renormalization operator. Our analysis indicates that the method of a projection operator is also useful for studying processes occurring under the influence of additional forces. As an example we present exact solutions for a particle interacting with a static electric field.     

Exponentially small scattering amplitude in high energy potential scattering

The high energy scattering amplitude of spherical symmetric potentials, which are expandable in ascending even powers of r and are nonsingular in coordinate space, is calculated. The Gaussian potential, which serves as a prototype of these potentials, is dealt with extensively. The first Born approximation is completely inadequate to estimate the amplitude off the forward direction. We show that the amplitude decreases faster than any power law as function of the momentum transfer q, and thus in that respect is similar in behavior to that of elastic scattering of elementary particles. Essentially, the whole range of the scattering angle is covered. Some speculations concerning shrinkage and antishrinkage effects are briefly mentioned.     

Parity violating effects in the coherent scattering of neutrons by 209Bi

We study the rotation of the spin in the coherent scattering of polarized thermal neutrons by ²⁰⁹Bi. Contributions due to direct weak scattering by the nucleus, parity admixtures into the nuclear wave functions and scattering by the electrons are calculated. We use a parity violating potential derived in the framework of the Salam-Weinberg model and several other semi-empirical potentials. The results show that the direct scattering on nuclei is the dominant contribution and some potentials predict results up to an order of magnitude larger than expected on dimensional grounds. The sign of the effect depends on the isospin properties of the potential and can distinguish between potentials with large isotensor or large isovector contributions.