Suppression of inelastic bound state resonance effects by the dimensionality of atom-surface scattering event

We develop a multidimensional coupled channel method suitable for studying the interplay of bound state resonance and phonon assisted scattering of inert gas atoms from solid surfaces in one, two and three dimensions. This enables us to get insight into the features that depend on the dimensionality of inelastic resonant processes typically encountered in low energy He atom scattering from surfaces, in general, and to elaborate on the observability of recently conjectured near threshold resonances in scattering from Einstein phonons, in particular.Comment: 2 figure

How simple can a model of an empty viral capsid be? Charge distributions in viral capsids

We investigate and quantify salient features of the charge distributions on viral capsids. Our analysis combines the experimentally determined capsid geometry with simple models for ionization of amino acids, thus yielding the detailed description of spatial distribution for positive and negative charge across the capsid wall. The obtained data is processed in order to extract the mean radii of distributions, surface charge densities and dipole moment densities. The results are evaluated and examined in light of previously proposed models of capsid charge distributions, which are shown to have to some extent limited value when applied to real viruses.Comment: 10 pages, 10 figures; accepted for publication in Journal of Biological Physic

Phonons and specific heat of linear dense phases of atoms physisorbed in the grooves of carbon nanotube bundles

The vibrational properties (phonons) of a one-dimensional periodic phase of atoms physisorbed in the external groove of the carbon nanotube bundle are studied. Analytical expressions for the phonon dispersion relations are derived. The derived expressions are applied to Xe, Kr and Ar adsorbates. The specific heat pertaining to dense phases of these adsorbates is calculated.Comment: 4 PS figure

Vibrations of a chain of Xe atoms in a groove of carbon nanotube bundle

We present a lattice dynamics study of the vibrations of a linear chain of Xe adsorbates in groove positions of a bundle of carbon nanotubes. The characteristic phonon frequencies are calculated and the adsorbate polarization vectors discussed. Comparison of the present results with the ones previously published shows that the adsorbate vibrations cannot be treated as completely decoupled from the vibrations of carbon nanotubes and that a significant hybridization between the adsorbate and the tube modes occurs for phonons of large wavelengths.Comment: 3 PS figure

Comment on "Quantum Scattering of Heavy Particles from a 10 K Cu(111) Surface"

In the original paper Althoff et al. (see ibid., vol.79, p.4429 (1997)) reported a study of scattering of thermal Ne, Ar, and Kr atoms from a Cu(111) surface in which they assessed the corresponding Debye-Waller factor (DWF) as a function of the particle mass m in a wide range of substrate temperature T. The experiments were interpreted by the semiclassical DWF theory in which the projectile moves on the classical recoilless trajectory and the surface vibrations are quantized. Siber and Gumhalter claim that the experiments described by Althoff et al. were carried out in the quantum scattering regime in which the semiclassical scalings of Althoff et al. do not hold and the semiclassical DWE significantly deviates from the exact quantum one both in the low and high T limits. Hence, it is claimed, the quantum scattering data of Althoff et al. cannot be reliably interpreted by the semiclassical theory.Comment: 1 page (2 figures) - comment in Phys. Rev. Let

Shapes and energies of icosahedral fullerenes: Onset of ridge sharpening transition

Shapes and energies of icosahedral fullerenes are studied on an atomically detailed level. The numerical results based on the effective binary carbon-carbon potential are related to the theory of elasticity of crystalline membranes with disclinations. Depending on fullerene size, three regimes are clearly identified, each of them characterized by different geometrical properties of the fullerene shape. For extremely large fullerenes (more than about 500000 atoms), transition of fullerene shapes to their asymptotic limit is detected, in agreement with previous predictions based on generic elastic description of icosahedral shells. Quantum effects related to delocalized electrons on the fullerene surface are discussed and a simple model introduced to study such effects suggests that the transition survives even in more general circumstances.Comment: Revised to discuss the effects of electronic delocalization on the ridge-sharpening transition. Submitte

Quantum virial expansion approach to thermodynamics of 4^4He adsorbates in carbon nanotube materials: Interacting Bose gas in one dimension

I demonstrate that $^4$He adsorbates in carbon nanotube materials can be treated as one-dimensional interacting gas of spinless bosons for temperatures below 8 K and for coverages such that all the adsorbates are in the groove positions of the carbon nanotube bundles. The effects of adsorbate-adsorbate interactions are studied within the scheme of virial expansion approach. The theoretical predictions for the specific heat of the interacting adsorbed gas are given.Comment: 5 PS figure

Incoherent white light solitons in logarithmically saturable noninstantaneous nonlinear media

We analytically demonstrate the existence of white light solitons in logarithmically saturable noninstantaneous nonlinear media. This incoherent soliton has elliptic Gaussian intensity profile, and elliptic Gaussian spatial correlation statistics. The existence curve of the soliton connects the strength of the nonlinearity, the spatial correlation distance as a function of frequency, and the characteristic width of the soliton. For this soliton to exist, the spatial correlation distance must be smaller for larger temporal frequency constituents of the beam

Dispersion Interactions between Optically Anisotropic Cylinders at all Separations: Retardation Effects for Insulating and Semiconducting Single Wall Carbon Nanotubes

We derive the complete form of the van der Waals dispersion interaction between two infinitely long anisotropic semiconducting/insulating thin cylinders at all separations. The derivation is based on the general theory of dispersion interactions between anisotropic media as formulated in [J. N. Munday, D. Iannuzzi, Yu. S. Barash and F. Capasso, {\sl Phys. Rev. A} {\bf 71}, 042102 (2005)]. This formulation is then used to calculate the dispersion interactions between a pair of single walled carbon nanotubes at all separations and all angles. Non-retarded and retarded forms of the interactions are developed separately. The possibility of repulsive dispersion interactions and non-monotonic dispersion interactions is discussed within the framework of the new formulation

Quantum states and specific heat of low-density He gas adsorbed within the carbon nanotube interstitial channels: Band structure effects and potential dependence

We calculate the energy-band structure of a He atom trapped within the interstitial channel between close-packed nanotubes within a bundle and its influence on the specific heat of the adsorbed gas. A robust prediction of our calculations is that the contribution of the low-density adsorbed gas to the specific heat of the nanotube material shows pronounced nonmonotonic variations with temperature. These variations are shown to be closely related to the band gaps in the adsorbate density of states