Non-partial-wave Coulomb-Born theory for the excitation of many-electron atomic ions II: Numerical description and application

A non-partial-wave Coulomb-Born theory is recently formulated to treat the excitation of many-electron atomic ions for impact by an arbitrary charged particle [Y.B. Duan et al., Phys. Rev. A 56, 2431 (1997)]. The multiple expansion of the transition matrix element is decomposed into the target form factor and the projectile form factor. These are the matrix elements of the tensor operators between quantum states so that any complicated wave function for the target ion can be employed. In this formal theory, an infinitesimally small positive quantity is introduced artificially to guarantee the convergence of integrals. As a supplementary part of the theory, we discuss how to choose the value of . It is found that the should be taken as functions of the momentum transfer and multipolarity . Illustrations are carried out by calculating the cross-sections for some typical transitions n _a l _a -n _b l _b of hydrogen-like ions for impact by electron, positron, and proton, respectively. The resulting cross-sections are in good agreement with ones produced by using a method available for ion targets with Slater-type orbitals [N.C. Deb, N.C. Sil, Phys. Rev. A 28, 2806 (1993)]. Comparisons demonstrate that the Coulomb-Born theory with non-partial wave analysis provides a powerful method to treat the excitation of many-electron atomic ions impact by an arbitrary charged particle. Received 6 April 1999     

Introduction of quantum finite-size effects in the Mie's theory for a multilayered metal sphere in the dipolar approximation: Application to free and matrix-embedded noble metal clusters

A mixed classical/quantum model for calculating the optical response of free and matrix-embedded multilayered metal spheres in the dipolar approximation is presented. The conduction electrons are quantum-mechanically treated in the framework of the time-dependent local-density-approximation formalism (TDLDA), whereas the surrounding matrix, the ionic metal backgrounds and the non-metallic materials are classically described through homogeneous charge distributions or/and dielectric media. Except for the TDLDA calculations, the present formalism is completely analytical and can be applied to coated spheres with any number of metal or dielectric layers. Contrary to the previous TDLDA-based models involving an inner or/and an outer dielectric medium (one or two interfaces), all the dielectric effects (screening and absorption) are self-consistently calculated. In particular, the interband transitions and the mutual interplay between the conduction and core electrons are self-consistently treated. The deficiencies of the previous models are analyzed, and the results are compared with the classical Mie's theory, over the entire spectral range. The building-up of the classical absorption spectrum, consisting of the surface plasmon resonance and the interband transitions, is clearly observed as the cluster size increases. Received 15 March 1999 and Received in final form 11 October 1999