Formalism for Multiphoton Plasmon Excitation in Jellium Clusters

We present a new formalism for the description of multiphoton plasmon excitation processes in jellium clusters. By using our method, we demonstrate that, in addition to dipole plasmon excitations, the multipole plasmons (quadrupole, octupole, etc) can be excited in a cluster by multiphoton absorption processes, which results in a significant difference between plasmon resonance profiles in the cross sections for multiphoton as compared to single-photon absorption. We calculate the cross sections for multiphoton absorption and analyse the balance between the surface and volume plasmon contributions to multipole plasmons.Comment: 29 pages, 1 figur

Atomic absorption spectra in the vacuum ultraviolet

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Wigner scattering theory for systems held together by Coulombic forces

The relevance of Wigner Scattering theory and in particular of its K-matrix formulation is stressed for all systems held together by Coulombic forces including not only atoms and molecules but also clusters. Originally developed and formulated for nuclear scattering, Wigner’s theory is extremely general, with application in many branches of physics. Atomic Physics often makes use of an apparently separate formalism (MQDT) which is in fact a specialisation of Wigner’s theory. The advantage of the K-matrix is that analytic expressions can be given for interactions between resonances in terms of a meromorphic pole structure in the special case of asymptotically Coulombic potentials. By using the K-matrix, a number of novel effects (q-reversals, vanishing radiative and particle widths, vanishing fluctuations, etc.) are understood as general phenomena

Confining and compressing the atom

Abstract A review of effects due to the confinement and compression of atoms is presented. It is argued that they provide new insights into the properties of atoms and, in particular, into their interactions with the microscopic environment. Studies of confined atoms allow one to understand better the changes of behaviour which occur under pressure. Some applications to practical situations are also suggested. Graphical abstract </jats:sec

A new angle on resonances in confined atoms and ions

Abstract A new type of resonance in a confined atomic system is suggested. It would migrate strongly in energy as a function of the degree of confinement, moving up or down in the Rydberg manifold according to the properties of the confining shell.</jats:p

The Atom at the Heart of Physics

A number of reasons are advanced for which atoms stand at the heart of research in the physical sciences. There are issues in physics which are both fundamental and only partly resolved or, at least, imperfectly understood. Rather than chase them towards higher and higher energies, which mainly results in greater complexity, it makes sense to restrict oneself to the simplest systems known, held together by the best understood force in nature, viz. those governed by the inverse square law. Our line of argument complements the adage of Richard Feynman, who asked: should Armageddon occur, is there a simple, most important idea to preserve as a testament to human knowledge? The answer he suggested is: the atomic hypothesis.</jats:p