Ch. Miniatura

Reflection of metastable neon atoms by a surface plasmon wave

Abstract Reported is an experimental realization of an atomic mirror for a metastable neon beam whose principle is based upon the dipole force extented by a surface plasmon wave. The first experimental evidence for Doppleron resonances induced by a stationary inhomogeneous wave is demonstrated.

Atomic Interferometry with Metastable Hydrogen Atoms

An atomic interferometer using the longitudinal Stern-Gerlach effect has been constructed. A thermal beam of metastable hydrogen atoms has been used to test the apparatus. Interference patterns have been obtained. The visibility of the fringes is limited by the velocity spread of the beam. The observed patterns are in good agreement with that predicted from the actual velocity distribution.

Optical potentials for Ne*(3P2,0)-Ar, N2 interactions

The differential elastic cross sections for Ne*(3P2,0)–Ar and Ne*(3P2,0)–N2 collisions have been measured in crossed beam experiments at 0.064 and 0.318 and at 0.071 and 0.295 eV, collision energies, respectively. These results have been analyzed simultaneously with integral cross sections and total ionization cross sections already available and optical spherical potentials for these two systems have been obtained. These potentials appear to be rather accurate in the distance range from 2.5 to ∼9 and from 3.0 to ∼9 A for Ne*–Ar and Ne*–N2, respectively. The well depths and equilibrium distances are 5.12 meV and 4.9 A for Ne*–Ar and 3.56 meV and 5.40 A for Ne*–N2. The short‐range repulsion in both cases exhibits a change in slope which can be correlated with the influence, for the interaction at shorter distances, of the Ne+ core of the metastable atom, which becomes less effective when the intermolecular distance increases. The optical potentials proposed here are given in analytical form suitable for th...

Geometrical Phase Factor for a Non-Hermitian Hamiltonian

In a previous paper, the measurement of an atomic Berry phase associated with two crossing levels has been suggested as a possible test for an atomic interferometry method. As one of the two levels involved is radiative, an analysis of geometrical phase factor arising in the cyclic evolution of a non-Hermitian Hamiltonian is undertaken here. It is shown that the use of the dual basis allows a simple generalization of Berrys results and that, in addition to the two possible values encountered in the Hermitian case (0, π), the geometrical phase can take on as intermediate value π/2 or even a complex value, whereas the corresponding quantum states may be permuted. The validity of the adiabatic approximation is discussed in view of the measurability of this new effect.

Polarization effects in metastable neon atom (Ne* (3P2)) on ground state neon atom collision at thermal energy

Abstract The difference Δ between the differential cross section for Ne*( 3 P 2 atoms polarized either in state | j =2, m =+2 > or | j =2, m =−2 >, colliding at thermal energy with a groundstate target (Ne,O 2 ), is measured. In the symmetric case Ne*-Ne, direct and exchange contribution are observed. General properties of Δ, derived from symmetry considerations, are established; in particular: (i) the interference character of Δ, (ii) the role played by the azimuthal dependence of the scattering amplitudes, (iii) the property Δ(0) = Δ(180°)=0. The relationship between the Fourier harmonics introduced in this discussion and the scattering amplitudes used in standard collision treatments are given.

A longitudinal stern-gerlach atomic interferometer

A new magnetic field configuration has been used in the mixing and elongating regions of the longitudinal Stern-Gerlach interferometer. This configuration has proven to considerably improve the performances of the interferometer. An analysis in terms of the vector model of a spin 1 particle is presented.

Collisions at thermal energy between metastable hydrogen atoms and hydrogen molecules: total and differential cross sections

A metastable hydrogen (deuterium) atom source in which groundstate atoms produced by a RF discharge dissociator are bombarded by electrons, provides a relatively large amount of slow metastable atoms (velocity 3–5 km/s). Total integral cross sections for H*(D*)(2s) + H2(X1Σg+,v=0) collisions have been measured in a wide range of relative velocity (2,5–30 km/s), by using the attenuation method. A significant improvement of accuracy is obtained, with respect to previous measurements, at low relative velocities. Total cross sections for H* and D*, as functions of the relative velocity, are different, especially in the low velocity range. H* + H2 total differential cross sections have also been measured, with an angular spread of 3.6°, for two different collision energy distributions, centered respectively at 100 meV and 390 meV. A first attempt of theoretical analysis of the cross sections, by means of an optical potential, is presented.

Survival of Metastable Hydrogen Atoms Passing Through Crossed Electric and Magnetic Fields

In the present experiment, the motional electric field responsible for the quenching (and polarization) of metastable hydrogen atoms passing through a magnetic field, is compensated, for a prescribed atomic velocity, by a static electric field. The resulting continuous velocity selection has been tested over a wide range of velocities ((5 ÷ 40) km/s). The relative velocity dispersion ranges from 5% at 40 km/s, to 22% at 5 km/s. As is confirmed by a calculation, the resolution is mainly determined by the quality of the matching of the two field profiles.

Longitudinal Stern-Gerlach atomic interferometry using velocity selected atomic beams

New experiments have been carried out on a velocity selected beam of H(D)*(2s12/) atoms using a longitudinal Stern-Gerlach atomic interferometer. A large number of fringes of the interference pattern has been observed. The results are in good agreement with theoretical predictions. An application to a topological phaseshift of the Aharonov-Anandan type is given.

Stern‐Gerlach Atomic Interferometry with Space‐ and Time‐dependent Magnetic Fieldsa

The basic idea of Stern-Gerlach Interferometry (SGI) is to produce entanglement of the spin variables with the external and internal motion variables. By appropriate spin projections in the preparation and analysis, one gets a signal in which phase information is related to the evolution of the different magnetic levels within the This allows a transfer of coherence from the spin variable (whose coherence is determined mainly by the direction of the magnetic field) to the external motion variables. As shown in the following section, the extracted phase information is strongly dependent 00 the way that the entanglement is being produced. No entanglement means pure spin precession and the experimental results give no information on the external motion. On the other hand, strong entanglement yields maximum information on the Fourier component distribution of thc external motion wave function. In this report, we do not focus on potential applications of atomic interf~rometry,~ but rather limit ourselves to the discussion of the coherence problems that can be studied in the experiments presently performed.