Atomic and Molecular Clusters
Using molecular dynamics simulation technique, we have studied the melting behaviours of free, icosahedral PtN clusters in the size range of N=12-14. Voter and Chen version of an embedded-atom model, derived by fitting to experimental data…
A simple model is developed that quantitatively describes intense interactions of a VUV laser pulse with a xenon cluster. We find good agreement with a recent experiment [H. Wabnitz et al., Nature Vol. 420, 482 (2002)]. In particular, the…
In this paper we examine the behavior of small cluster of atoms in a short (10-50 fs) very intense hard x-ray (10 keV) pulse. We use numerical modeling based on the non-relativistic classical equation of motion. Quantum processes are taken…
We present a method (the Aufbau/Abbau method) for optimizing the structure of a whole series of clusters without making any assumptions on the structure. Subsequently, the method is combined with the embedded-atom method in determining the…
We investigate the equilibrium geometries and the systematics of bonding in various isomers of a 24-atom boron cluster using Born-Oppenheimer molecular dynamics within the framework of density functional theory. The isomers studied are the…
A two-step optimization is proposed to represent an arbitrary quantum state to a desired accuracy with the least number of gaussians in phase space. The Husimi distribution of the quantum state provides the information to determine the…
A flexible scheme for decomposing the vibrational density of states in terms of pair vibrational density of states is presented. This scheme provides the linkage between the site vibrational density of states and pair vibrational density of…
Energetic, highly-charged oxygen ions, $O^{q+}$ ($q\leq 6$), are copiously produced upon laser field-induced disassembly of highly-charged water clusters, $(H_2O)_n$ and $(D_2O)_n$, $n\sim$ 60, that are formed by seeding high-pressure…
The disassembly of molecular clusters $(N_2)_n$ ($n$=50-3000) in strong optical fields is investigated using two-dimensional time-of-flight spectrometry. Very highly charged ions are formed with a two-component energy distribution. A…
Using neon and its dimer as a specific example, it is shown that excited Auger decay channels that are electronically stable in the isolated monomer can relax in a cluster by electron emission. The decay mechanism, leading to the formation…
The pair correlations in mesoscopic systems such as $nm$-size superconducting clusters and nuclei are studied at finite temperature for the canonical ensemble of fermions in model spaces with a fixed particle number: i) a degenerate…
Low-energy orbital magnetic dipole excitations, known as scissors mode (SM), are studied in alkali metal clusters. Subsequent dynamic and static effects are explored. The treatment is based on a self-consistent microscopic approach using…
Energy spectra and angular distributions have been measured of electrons that are emitted upon disassembly of $Xe_{150000}$ following irradiation by intense (10$^{15}-10^{16}$ W cm$^{-2}$) laser pulses whose durations are varied over the…
Based on ab initi and density-functional theory calculations, an empirical potential is proposed to model the interaction between a fullerene molecule and many sodium atoms. This model predicts homogeneous coverage of C_60 below 8 Na atoms,…
We revisit a model in which the ionization energy of a metal particle is associated with the work done by the image charge force in moving the electron from infinity to a small cut-off distance just outside the surface. We show that this…
A detailed theoretical investigation of rare gas atom clusters under intense short laser pulses reveals that the mechanism of energy absorption is akin to {\it enhanced ionization} first discovered for diatomic molecules. The phenomenon is…
The effect of intense X-ray laser interaction on argon clusters is studied theoretically with a mixed quantum/classical approach. In comparison to a single atom we find that ionization of the cluster is suppressed, which is in striking…
Calculating the energy absorption of atomic clusters as a function of the laser pulse length $T$ we find a maximum for a critical $T^*$. We show that $T^*$ can be linked to an optimal cluster radius $R^*$. The existence of this radius can…
Differential Faddeev equations in total angular momentum representation are used for the first time to investigate ultra-low energy elastic scattering of a helium atom on a helium dimer. Six potential models of interatomic interaction are…
Pulsed (30 - 100 microseconds) nozzle beams have been used to generate helium droplets (<N> = 10^4-10^5). The dependence of the beam intensity and the mean droplet size on the source stagnation pressure and temperature are studied via mass…