Atom Symmetry Break and Metastable Level Coupling in Rare Gas Atom-Surface van der Waals Interaction (original) (raw)
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van der Waals-induced level coupling in metastable atom on surface collisions
2001
The symmetry of atomic wave functions is broken by the quadrupolar component of the van der Waals interaction between the atom and a planar surface. This results into a coupling able to mix levels of same parity such as 3P0 and 3P2 metastable levels of heavy rare gas atoms. The 3P0-3P2 transition in Ar and Kr has been evidenced in a time-of-flight experiment using as a surface the edge of a copper slit. .
Van der Waals contribution to the inelastic atom-surface scattering
Journal of Electron Spectroscopy and Related Phenomena, 2003
A calculation of the inelastic scattering rate of Xe atoms on Cu(111) is presented. We focus in the regimes of low and intermediate velocities, where the energy loss is mainly associated to the excitation electron-hole pairs in the substrate. We consider trajectories parallel to the surface and restrict ourselves to the Van der Waals contribution. The decay rate is calculated within a self-energy formulation. The effect of the response function of the substrate is studied by comparing the results obtained with two different approaches: the Specular Reflection Model and the Random Phase Approximation. In the latter, the surface is described by a finite slab and the wave functions are obtained from a one-dimensional model potential that describes the main features of the surface electronic structure while correctly retains the imagelike asymptotic behaviour. We have also studied the influence of the surface state on the calculation, finding that it represents around 50% of the total probability of electron-hole pairs excitation.
The European Physical Journal D, 2001
A theory of van der Waals (vdW) interaction between an atom (in ground or excited state) and a birefringent dielectric surface with an arbitrary orientation of the principal optic axis (C-axis) is presented. Our theoretical approach is based on quantum-mechanical linear response theory, using generalized susceptibilities for both atom and electromagnetic field. Resonant atom-surface coupling is predicted for excited-state atoms interacting with a dispersive dielectric surface, when an atom de-excitation channel gets into resonance with a surface polariton mode. In the non-retarded regime, this resonant coupling can lead to enhanced attractive or repulsive vdW surface forces, as well as to a dissipative coupling increasing the excited-state relaxation. We show that the strongly non-scalar character of the interaction with the birefringent surface produces a C-axis-dependent symmetry-breaking of the atomic wavefunction. Changes of the C-axis orientation may also lead to a frequency shift of the surface polariton mode, allowing for tuning on or off the resonant coupling, resulting in a special type of engineering of surface forces. This is analysed here in the case of cesium 6D 3/2 level interacting with a sapphire interface, where it is shown that an adequate choice of the sapphire C-axis orientation allows one to transform vdW surface attraction into repulsion, and to interpret recent experimental observations based on selective reflection methods [H. Failache et al., Phys. Rev. Lett. 83, 5467 (1999)].
EPL (Europhysics Letters), 2012
van der Waals-Zeeman transitions between magnetic states of metastable rare gas atoms Ar*, Kr* and Xe* ( 3 P 2 ) induced by a solid surface in the presence of a magnetic field, are investigated theoretically and experimentally. By use of a Zeeman slower, metastable argon atoms with various velocities ranging from 170 to 560 m/s allow us to investigate the small impact-parameter range (3-7 nm) within which these transitions occur, as well as the effect of atom polarisation on the sharing out of the M states.
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.
Measuring the van der Waals forces between a Rydberg atom and a metallic surface
Physical review. A, 1988
We have observed the deflection of Rydberg atoms towards a metallic surface by the van der %'aals force. Cs and Na atoms in states of principal quantum number n were sent between two parallel gold-coated mirrors, spaced by a gap m (2.1 pm & au & 8.5 pm). %e measured the value n at which the transmission cuts off' and from the variation of n versus u, we obtained a measure of the atom-surface interaction. For 12' n g30 this interaction is 3-4 orders of magnitude larger than for ground-state atoms"and it obeys the scaling laws of the Lennard-Jones model. The van der Waals interaction between a metallic surface and an atom is an Important process in atomic physics. If the metal behaves as a perfect conductor at characteristic atomic frequencies, the interaction can be viewed, after Lennard-Jones, ' as resulting from the coupling of the atomic dipole with its electrostatic images in the surface. This coupling gives rise to energy-level shifts proportional to z 3 (where z is the atom-surface dis-tance}, and the derivative of these shifts with respect to the distance corresponds to the dipole-image van der Waals force Fvw-z that puBs the atom towards the metal. This assumes that z is small compared with any characteristic atomic-transition wavelength so that retardation is negligible.
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].