Van der Waals induced polarization of atoms and molecules adsorbed in spherical cavities in a metal: anisotropy and nonlocality effects (original) (raw)

Spectroscopic Probe of the van der Waals Interaction between Polar Molecules and a Curved Surface

Physical Review A, 2016

We study the shift of rotational levels of a diatomic polar molecule due to its van der Waals (vdW) interaction with a gently curved dielectric surface at temperature T , and submicron separations. The molecule is assumed to be in its electronic and vibrational ground state, and the rotational degrees are described by a rigid rotor model. We show that under these conditions retardation effects and surface dispersion can be neglected. The level shifts are found to be independent of T , and given by the quantum state averaged classical electrostatic interaction of the dipole with its image on the surface. We use a derivative expansion for the static Green's function to express the shifts in terms of surface curvature. We argue that the curvature induced line splitting is experimentally observable, and not obscured by natural line widths and thermal broadening.

Van der Waals coefficients of atoms and molecules from a simple approximation for the polarizability

Physical Review B, 2009

A simple and computationally efficient scheme to calculate approximate imaginary-frequency dependent polarizability, hence asymptotic van der Waals coefficient, within density functional theory is proposed. The dynamical dipolar polarizabilities of atoms and molecules are calculated starting from the Thomas-Fermi-von Weizsäcker (TFvW) approximation for the independent-electron kinetic energy functional. The van der Waals coefficients for a number of closed-shell ions and a few molecules are hence calculated and compared with available values obtained by fully first-principles calculations. The success in these test cases shows the potential of the proposed TFvW approximate response function in capturing the essence of long range correlations and may give useful information for constructing a functional which naturally includes van der Waals interactions.

Van der Waals interaction mediated by an optically uniaxial layer

Physical Review E, 2001

We study the van der Waals interaction between macroscopic bodies separated by a thin anisotropic film with uniaxial permittivity tensor. We describe the effect of anisotropy of the media on the magnitude and sign of the interaction. The resulting differences in the van der Waals interaction are especially important for the stability of strongly confined liquid crystals, nano-structures characterized by highly uniaxial macroscopic molecular arrangement, such as in self-assemblies of long organic molecules forming films, membranes, colloids, etc. We introduce an improved expression for the Hamaker constant which takes into account the uniaxial symmetry of a medium. In special cases neglecting the optical anisotropy even leads to incorrect sign of the interaction.

van der Waals coefficients for alkali-metal atoms in material media

Physical Review A, 2014

The damping coefficients for the alkali atoms are determined very accurately by taking into account the optical properties of the atoms and three distinct types of trapping materials such as Au (metal), Si (semi-conductor) and vitreous SiO2 (dielectric). Dynamic dipole polarizabilities are calculated precisely for the alkali atoms that reproduce the damping coefficients in the perfect conducting medium within 0.2% accuracy. Upon the consideration of the available optical data of the above wall materials, the damping coefficients are found to be substantially different than those of the ideal conductor. We also evaluated dispersion coefficients for the alkali dimers and compared them with the previously reported values. These coefficients are fitted into a ready-to-use functional form to aid the experimentalists the interaction potentials only with the knowledge of distances.

Van der Waals coefficients for molecules adsorbed on metal surfaces

Chemical Physics, 1988

The infinite barrier model is used to determine the non-local dispersion coefficients C,, of various molecules adsorbed on noble metal surfaces. The dynamical polarizabilities of the admolecules are obtained from ab initio calculations or refractive index data as an expansion in terms of Cauchy moments. The metal is schematized within the framework of the hydrodynamical model. The behaviour with the adsorption distance of the C,, coefficients (n = 3, 4) is given for HZ, Nz, 02, COZ, HF, HCI, NO, NH,, Hz0 and NzO, and for the Al, Ag and Cu surfaces. A comparison with previous models is also done for some rare gases and simple atoms (Li, Be, N, 0).

Exploring the van der Waals atom-surface attraction in the nanometric range

Europhysics Letters (EPL), 2007

Optical tests of quantum theory 34.50.Dy Interactions of atoms and molecules with surfaces; photon and electron emission; neutralization of ions 32.70.Jz Line shapes, widths, and shifts The van der Waals atom-surface attraction, scaling as C 3 z-3 for z the atom-surface distance, is expected to be valid in the distance range 1-1000 nm, covering 8-10 orders of magnitudes in the interaction energy. A Cs vapour nanocell allows us to analyze the spectroscopic modifications induced by the atom-surface attraction on the 6P 3/2 →6D 5/2 transition. The measured C 3 value is found to be independent of the thickness in the explored range 40-130 nm, and is in agreement with an elementary theoretical prediction. We also discuss the specific interest of exploring short distances and large interaction energy.

Anisotropic atom-surface interactions in the Casimir-Polder regime

Physical Review A, 2014

The distance-dependence of the anisotropic atom-wall interaction is studied. The central result is the 1/z 6 quadrupolar anisotropy decay in the retarded Casimir-Polder regime. Analysis of the transition region between non-retarded van der Waals regime (in 1/z 3 ) and Casimir-Polder regime shows that the anisotropy cross-over occurs at very short distances from the surface, on the order of 0.03λ, where λ is the atom characteristic wavelength. Possible experimental verifications of this distance dependence are discussed. PACS numbers: 34.35.+a, 03.75.Be, 12.20.Fv The force between neutral polarisable systems is a ubiquitous phenomenon in nature, with many applications in physics, chemistry, biology. . . A paramount example is the long-range interaction potential between neutral microscopic quantum systems, like atomic systems, and a solid surface. For plane surfaces this interaction is usually governed by a power-law attractive potential . For atom-surfaces distances z smaller than the wavelengths of the optical transitions involved in the atomic polarisability, the interaction is of the dipoleinduced dipole type, and governed by the well-known non-retarded van der Waals potential in −C 3 /z 3 , which reflects the correlations of dipole fluctuations [1]. At larger distances, retardation effects get important, and asymptotically lead to a −C 4 /z 4 potential, as demonstrated in the pioneering work of Casimir and Polder [2].