The jellium model of simple metal clusters has enjoyed remarkable empirical success, leading to many theoretical questions. In this review, we first survey the hierarchy of theoretical approximations leading to the model. We then describe the jellium model in detail, including various extensions. One important and useful approximation is the local-density approximation to exchange and correlation effects, which greatly simplifies self-consistent calculations of the electronic structure. Another valuable tool is the semiclassical approximation to the single-particle density matrix, which gives a theoretical framework to connect the properties of large clusters with the bulk and macroscopic surface properties. The physical properties discussed in this review are the ground-state binding energies, the ionization potentials, and the dipole polarizabilities. We also treat the collective electronic excitations from the point of view of the cluster response, including some useful sum rules.

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The physics of simple metal clusters: self-consistent jellium model and semiclassical approaches

http://myweb.rz.uni-augsburg.de/~eckern/WEH-287/ABSTRACTS/ruitenbeek.pdf

Quantum properties of atomic-sized conductors

Atomic force microscopy-based infrared spectroscopy (AFM-IR) is a rapidly emerging technique that provides chemical analysis and compositional mapping with spatial resolution far below conventional optical diffraction limits. AFM-IR works by using the tip of an AFM probe to locally detect thermal expansion in a sample resulting from absorption of infrared radiation. AFM-IR thus can provide the spatial resolution of AFM in combination with the chemical analysis and compositional imaging capabilities of infrared spectroscopy. This article briefly reviews the development and underlying technology of AFM-IR, including recent advances, and then surveys a wide range of applications and investigations using AFM-IR. AFM-IR applications that will be discussed include those in polymers, life sciences, photonics, solar cells, semiconductors, pharmaceuticals, and cultural heritage. In the Supporting Information, the authors provide a theoretical section that reviews the physics underlying the AFM-IR measurement and d...

AFM-IR: Technology and Applications in Nanoscale Infrared Spectroscopy and Chemical Imaging

A density-functional formalism comparable to the theory of Hohenberg, Kohn and Sham is developed for electronic systems subject to time-dependent external fields. The formalism leads to a set of time-dependent Kohn-Sham equations which, in addition to the external potential, contain a time-dependent Hartree term and a local time-dependent exchange-correlation potential. Rigorous properties and explicit approximations of the latter are discussed in detail. Generalizations of the basic formalism to incorporate the nuclear motion and to deal with magnetic effects are described. Within the regime of linear-response theory, the time-dependent Kohn-Sham equations lead to a formally exact representation of the frequency-dependent linear density response. Applications within the linear-response regime include the computation of photoabsorbtion cross sections, the determination of van der Waals forces and the calculation of excitation energies. The latter is based on the fact that the frequency-dependent linear density response has poles at the true excitation energies of the interacting many-body system. The time-dependent Kohn-Sham formalism then leads to a simple additive correction of the Kohn-Sham single-particle excitation energies. Beyond the linear-response regime, the time-dependent Kohn-Sham scheme is applied to atoms in strong femto-second laser pulses to describe multi-photon ionization and harmonic generation in a non-perturbative way.

Density functional theory of time-dependent phenomena

The field of cluster research can trace its origins back to the mid-nineteenth century when early studies of colloids, aerosols, and nucleation phenomena were reported. The field underwent a resurgence of interest several decades ago when well-defined clusters were observed in supersonic expansions that could be investigated using mass spectrometers. The advent of the laser provided a new dimension, enabling detailed spectroscopic observations through the probing of systems of varying size and degree of solvation. Modern interest derives from recognition that interrogating clusters provides a way of studying the energetics and dynamics of intermediate states of matter as cluster systems evolve from the gas toward the condensed state. Herein, we endeavor to highlight some of the significant advances which have been made during the past several decades that have led to a nearly explosive growth of interest in the field of cluster science. Finally, we conclude that the field will continue to expand through i...

Clusters: Structure, Energetics, and Dynamics of Intermediate States of Matter

Chemical mapping of the distribution of viruses into infected bacteria with a photothermal method.

Unimolecular dissociation channels of mass-selected doubly charged sodium clusters ${\mathrm{Na}}_{\mathit{n}}^{++}$ have been determined for cluster sizes near and above the critical size, ${\mathit{n}}_{\mathit{c}}$=27, from which doubly charged clusters are detectable in mass spectra. On a time scale of 50 \ensuremath{\mu}s with respect to ionization, doubly charged clusters of size n=${\mathit{n}}_{\mathit{c}}$ are found to fission asymmetrically. For cluster sizes above ${\mathit{n}}_{\mathit{c}}$, however, evaporation of a neutral monomer is the dominant channel for delayed dissociation. An estimation of the height of the Coulombic barrier is given for ${\mathrm{Na}}_{\mathit{n}}^{++}$ near the critical size, using the framework of statistical theory.

Asymmetric fission of Nan++ around the critical size of stability.

Morphology control of the supported islands grown from soft-landed clusters

Energetics and dynamics of Coulombic fission of small doubly charged potassium clusters subsequent to the ionization of singly charged ones are investigated experimentally and theoretically. Fission is shown to occur predominantly via ${\mathrm{K}}_{\mathit{n}}^{++}$\ensuremath{\rightarrow}${\mathrm{K}}_{\mathit{n}\mathrm{\ensuremath{-}}3}^{+}$+${\mathrm{K}}_{3}^{+}$ for 5\ensuremath{\le}n\ensuremath{\le}12. The close correspondence between the measured and the calculated kinetic energy release accompanying the fission process allows a deeper understanding of the dynamics and energy redistribution mechanisms in fission of metallic clusters.

M. de Frutos

Papers

Chemical mapping of the distribution of viruses into infected bacteria with a photothermal method.

Asymmetric fission of Nan++ around the critical size of stability.

Morphology control of the supported islands grown from soft-landed clusters

Dynamics and energy release in fission of small doubly charged clusters.

Optical excitation in small ionized sodium clusters: closed-shell and open-shell systems