Spike-burst and other oscillations in a system composed of two coupled, drastically different elements

The dynamics of a system composed of two nonlinearly coupled, drastically different nonlinear and eventually oscillatory elements is studied. The rich variety of attractors of the system is studied with the help of phase space analysis and Poincare maps. Received 19 March 1999 and Received in final form 1 November 1999     

A stability criterion for financial markets

Using the theory of random cluster models, we give a stability criterion for financial markets with random communications between agents. Received 25 September 1999 and Received in final form 2 October 1999     

Frequency measurement, isotope shift and hyperfine structure of the transition in atomic silver

The frequency of the centroid of the transition in Ag I has been determined by laser spectroscopy of a collimated metastable thermal atomic beam. We find MHz. The isotope shift MHz. For the magnetic hyperfine structure constant of the state, assuming IJ coupling, we find, MHz and MHz. Received 16 July 1999 and Received in final form 7 October 1999     

Affine turbulence

We present a generalization of the multiplicative model for velocity increments involving an affine process. The consequences on the shape of the probability distribution functions for the velocity increments are explored, and shown to be better compatible with the existence of a scale variation of the skewness. Received 29 March 1999 and Received in final form 14 September 1999     

ac Stark effect for a two-level atom in a squeezed vacuum via a two-photon process

The nondegenerate two-photon interaction of a two-level atom with a broadband multimode squeezed vacuum is investigated. We find that in the two-photon process the squeezed vacuum has a driving effect on the atom which can lead to an ac Stark effect when the average photon number of the squeezed vacuum is larger than a critical value. Received: 2 February 1999 / Received in final form: 20 April 1999     

Structural transformation from the AlCuFe icosahedral phase to the 1/1 cubic (AlSi)CuFe approximant phase; three dimensional models of translation defects

Unusual results are obtained by High Resolution Electron Microscopy (HREM) studies of the 1/1 cubic approximant phase of the (AlSi)CuFe icosahedral phase. We study, in a 3D model of AlCuFe icosahedral phase, the possibilities of transformation of this structure into a periodic cubic structure. We propose a model of transformation coherent with the experimental results. Received 31 May 1999 and Received in final form 23 December 1999     

Semiclassical steady-state analysis of a degenerate two-photon laser

The steady-state analysis of a single-mode two-photon laser are treated semiclassically by using the Maxwell-Bloch equations. The theory is applied to a ring-laser model. We find similarities and significant differences between the one- and two-photon polarizations of the medium, population inversion and mode-pulling formula. The population inversion and the longitudinal variation of the steady-state modulus of the field are studied numerically. Received: 1 March 1999 / Received in final form: 8 April 1999     

Experimental investigations of oscillator strengths for ultraviolet transitions in LaII

f-values for ultraviolet transitions from nine excited levels in LaII have been deduced by a combination of lifetime and branching ratio measurements using time-resolved laser spectroscopy and the emission spectrum from a hollow cathode lamp. Part of the present results is compared with previous results. Received 10 February 1999 and Received in final form 22 April 1999     

On the measurement of photon flux in parametric down-conversion

We report the measurement of the photons flux produced in parametric down-conversion, performed in photon counting regime with actively quenched silicon avalanche photodiodes as single photon detectors. Measurements are done with the detector in a well defined geometrical and spectral situation. By comparison of the experimental data with the theory, a value for the second order susceptibilities of the non linear crystal can be inferred. Received 2 July 1999 and Received in final form 2 August 1999     

Qualitative analysis of molecular rotation starting from inter-nuclear potential

We study how qualitative features of the molecular rotational dynamics can be derived directly from the internuclear (vibrational) potential. This approach is presented on the example of a tetrahedral molecule A₄ using several increasingly elaborated models of the potential. Received: 16 February 1999 / Received in final form: 4 May 1999     

The -relaxation dynamics of a simple liquid

We present a detailed analysis of the -relaxation dynamics of a simple glass former, a binary Lennard-Jones system with a stochastic dynamics. By testing the various predictions of mode-coupling theory, including the recently proposed corrections to the asymptotic scaling laws, we come to the conclusion that in this time regime the dynamics is described very well by this theory. Received 5 February 1999 and Received in final form 7 June 1999     

Use of a fast beam target for the determination and reduction of the cascade contribution to electron excitation cross-section measurements

This paper describes a method for reducing the influence of cascades on the measurement of electron excitation cross sections using the optical method and a fast beam atomic target. By using a fast beam of target atoms one can reduce the influence of cascades on a measurement, and estimate the cascade contribution to the excitation signal. Received 19 April 1999 and Received in final form 10 August 1999     

Precision laser ablation of dielectrics in the 10-fs regime

Received: 4 January 1999 / Accepted: 5 January 1999     

Experimental observation of noise-induced sensitivity to small signals in a system with on-off intermittency

An experimental (electronic circuit) realization and analytic studies of overdamped Kramers oscillator with an exponential nonlinearity under combined effect of a large multiplicative noise and a small periodic signal were performed. Under certain conditions, when the system exhibits on-off intermittency, it becomes sensitive to very small periodic signals, amplifying them greatly. Received 21 May 1999 and Received in final form 28 December 1999     

High repetition rate planar laser induced fluorescence of OH in a turbulent non-premixed flame

Received: 1 February 1999 / Revised version: 17 February 1999     

Two body loss rate in a magneto-optical trap of metastable He

We have measured the two body loss rate in a magneto-optical trap containing triplet metastable He atoms. We find a rate constant cm³/s at a -8 MHz detuning, with an uncertainty of a factor 2. This measurement is in disagreement with a recent experiment which measures the absolute, ion-producing collision rate, but agrees with several other published measurements. Received 20 April 1999 and Received in final form 12 July 1999     

Foam target experiments with the PF-1000 plasma focus facility

This paper describes experiments on foam liners performed with the PF-1000 plasma focus facility. A streak camera has been used to observe interaction of a hydrogen plasma current sheath with a cylindrical foam target. It is shown that a thin foam liner can be uniformly imploded by a plasma focus current sheath. Received: 11 February 1999 / Received in final form: 30 March 1999     

Orientation phenomena for direct s-p electron-ion collisional excitations in weakly coupled plasmas using the screened hyperbolic-orbit trajectory method

Orientation phenomena for direct electron-ion collisional excitations in weakly coupled plasmas () are investigated using the semiclassical curved trajectory method including the close-encounter effects. The results show that the orientation parameters including the close-encounter effects obtained by the hyperbolic-orbit trajectory method have maxima and minima for small impact parameter regions. Received 18 August 1999 and Received in final form 6 December 1999     

Hierarchies of stability regions for η-pairing superconducting ground states of generalized Hubbard models

For a class of generalized one dimensional Hubbard models, we study the stability region for the superconducting -pairing ground state. We exploit the Optimum Ground State (OGS) approach and the Lanczos diagonalization procedure to derive a sequence of improved bounds. We show that some pieces of the stability boundary are asymptotic, namely independent on the OGS cluster size. The phenomenon is explained by studying the properties of certain exact eigenstates of the OGS Hamiltonians. Received 27 July 1999 and Received in final form 29 September 1999     

Cubic phases of amphiphilic molecular aggregates

Stability and geometry of the lyotropic periodic cubic mesophases are considered in the framework of a general symmetry based phenomenological approach. A limited number of cubic structural types is shown to be formed by amphiphilic molecular aggregates due to the specific nature of self-organizing units. The related thermodynamic models predict topology of phase diagrams and specific features of transitions between isotropic, lamellar, cubic bicontinuous and cubic micellar phases. Received 25 February 1999 and Received in final form 29 June 1999