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1.
J.-M. CAILLOL 《Molecular physics》2013,111(11):1617-1634
We present an exact field theoretical representation of the statistical mechanics of simple classical liquids with short-range pairwise additive interactions. The action of the field theory is obtained by performing a Hubbard-Stratonovich transformation of the configurational Boltzmann factor. The mean field and Gaussian approximations of the theory are derived and applications to the liquid-vapour transition considered. 相似文献
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Tractable approximations for probabilistic models: the adaptive Thouless-Anderson-Palmer mean field approach 总被引:1,自引:0,他引:1
We develop an advanced mean field method for approximating averages in probabilistic data models that is based on the Thouless-Anderson-Palmer (TAP) approach of disorder physics. In contrast to conventional TAP, where the knowledge of the distribution of couplings between the random variables is required, our method adapts to the concrete couplings. We demonstrate the validity of our approach, which is so far restricted to models with nonglassy behavior, by replica calculations for a wide class of models as well as by simulations for a real data set. 相似文献
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The scattering of atoms and molecules by the force of stimulated light pressure appearing in a standing wave is considered. It is shown that short (10-8s) light pulses of tunable lasers can deviate resonance atoms through an angle of about 5°. A high selectivity of scattering is retained in a standing wave even in conditions of great saturation. Therefore the considered effect can be used for the separation of isotopes. 相似文献
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Ionizing collisions of long lived excited particles with atoms and molecules are studied by a cross beam technique. For the first time reactions of atoms in high Rydberg states are included in the investigation. In this paper we report relative cross sections for the production of the ions RH+, RH 2 + , and H 2 + by collisions of excited rare gas atoms R* with H2. With HD as the target molecule the isotope effect for the production of RD+ and RH+ has been determined. In the case of argon and krypton, ions are produced only by the high Rydberg states, whereas in the case of helium and neon only the metastable states contribute to a measurable extent. The data indicate, that the reaction mechanism is different in principle for metastable and highly excited atoms. Simple models are proposed to explain the experimental results. 相似文献
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Penning electron distributions arising from the ionization of Na and K by He (1s 2s 1,3 S)-metastables in thermal collisions, as well as the absolute cross section for Penning ionization of Na by He (23 S) and relative cross sections for ionization of Na and K by He(21 S) and He(23 S) are measured. It is shown that under fairly general conditions the well depth ε* of the interaction potential between the metastable and the target particle can be obtained directly from the measured electron distributions. ε*-values are reported for the moleules He(1s 2s 1,3 S)-Na(2 S), K(2 S) (2,2Ω), and for He(1s 2s 1,3 S)-Hg(1 S)(1,3Ω). These latter values are obtained from previously published measurements and are to be considered preliminary. Further, additional evidence is given, that Penning ionization with metastables is an electron exchange process. 相似文献
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From a He-beam excited by electron impact we eliminated the He(21 S) component to better than 0.5% by irradiating light from a He discharge. The quenching process ishv(21 P→21 S)+He(21 S)→He(21 P)→He(11 S +hv) (21 P 1)1 S. By measuring the ions produced in collisions of the He-metastables with various target gases in a mass spectrometer, singlet to triplet Penning-cross section ratios were obtained. These ratios are without exception close to one, which is taken as evidence for the previously proposed electron exchange mechanism of the Penning ionization. In the case that more ions are produced in the collision of He (21 S) and He(23 S) with a target gas, separate relative production cross sections are obtained for the two metastables. For the rare gases the measurements are performed at two temperatures of the He-beam, 320 and 90 °K. It is found that the cross section ratio of associative — to Penning ionization increases considerably as the temperature is decreased for both, He(21 S) and He(23 S), the effect being much more pronounced for He(21 S). The results of this work are found to confirm conclusions drawn from measured energy distributions of the electrons ejected in the Penning process. 相似文献
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Intense-laser ionization rates for rare gas atoms and diatomic molecules have been precisely compared by making simultaneous measurements of ionization yield vs laser intensity for mixed atomic and molecular targets. At a given laser intensity, the N (2) and F (2) ionization yields are slightly greater than that of Ar. Conversely, comparison of O (2) and S (2) with Xe indicates significant ionization suppression in these molecules. Recent molecular ionization models that successfully describe ionization suppression in O (2) and its absence in N (2) fail to explain our observations in F (2) and S (2). 相似文献
8.
A. B. Manenkov 《Optical and Quantum Electronics》1991,23(1):81-90
The problem of surface mode reflection from an abrupt-ended optical fibre is considered. The analysis is made by the variational technique. By investigating the problem the accuracy of several approaches used for field representations is examined, including scalar, quasi-vector approximation techniques and numerical methods (the finite difference method and the method of the integral equation). 相似文献
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A method is suggested for simultaneous cooling and trapping of atoms and molecules in a low-pressure gas under forces caused by recoil during spontaneous or induced transitions of the particles in the resonance field of a three-dimensional standing light wave. It is shown that at light field intensities ~0.01–0.1 W/cm2 it is possible to cool atoms and molecules to the resonance field photon momentum and to hold the particles in the light field volume during a long period of time. The proposed approach opens the way for high-resolution Doppler-free spectroscopy of a small number of atoms and molecules. 相似文献
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Green's functions for atoms and molecules with a degenerate ground state are evaluated by means of tensorial analysis. The final results obtained are of simple character allowing the usual diagrammatic approach via Wick's theorem for non-degenerate ground states. As an example the ionization of a σ orbital of O2 is considered and an equivalent approach to the frozen orbital approximation is discussed. 相似文献
13.
The adiabatic separation of electronic and positronic degrees of freedom is proposed. The positronic charge in expressions for the potential energy is partitioned between the electronic and positronic Hamiltonians. This partitioning assures an acceptable electron density distribution around the positron. Our adiabatic method gives good values of binding energies and annihilation rates for model systems, in which the positron is weakly bound. On the other hand, it does not work well if the wave function contains a significant contribution of the positronium cluster. 相似文献
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An analytical review of the theory of elementary atomic and molecular processes in the field of intense laser monochromatic radiation is presented. The discussion focuses on near-threshold processes involving Rydberg intermediate complexes, which play an important role in Earth’s upper atmosphere. The possibilities of the stationary method of radiative scattering matrix, based on the formalism of the renormalized Lippmann-Schwinger equations, are demonstrated. The approach is used to describe in a unified way a variety of near-threshold processes, the probability amplitudes of which are elements of the radiative scattering matrix for all possible reaction channels. They also include processes of restructuring of the particles (predissociation, associative ionization, exchange reactions, etc.), which in principle cannot be described using traditional nonstationary theories. 相似文献
18.
The proposed paradigm of plasmonic atoms and plasmonic molecules allows one to describe and predict the strongly localized
plasmonic oscillations in the clusters of nanoparticles and some other nanostructures in uniform way. Strongly localized plasmonic
molecules near the contacting surfaces might become the fundamental elements (by analogy with Lego bricks) for the construction
of fully integrated opto-electronic nanodevices of any complexity and scale of integration.
PACS 78.67.-n; 73.20.Mf; 32.50.+d 相似文献
19.
《Physics letters. A》1986,114(4):191-194
This note clarifies the role of the Fried-Martin factor in the calculation of dipole matrix elements for transitions between muonic and hardronic states. Formulae are given which are appropriate for exotic atoms or molecules and which take account of screening. 相似文献
20.
Reflection of neutral atoms and molecules by a pulsed standing wave with a duration on the order of nanoseconds is studied. It is shown that, with a suitable choice of the laser parameter values, each period of the standing-wave pattern functions as an independent mirror, thus providing a novel way to manipulate large samples of neutral gas-phase particles even with a single laser pulse. At moderate field intensities, the pulsed standing-wave mirror would be directly applicable, e.g., for the manipulation of buffer-gas cooled molecules. 相似文献