Influence of a magnetic field on deposition of diamond-like carbon films

Received: 17 February 1998/Accepted: 25 May 1998     

Gaussian-like tapered grating quarter wave-shifted DFB semiconductor lasers for high-power single-mode operation

Received: 27 July 1998/Revised version: 25 September 1998     

Electrical properties of Au–polystyrene–Au submicron structures

Received: 25 January 1998/Accepted: 28 May 1998     

Structural properties of junctions between two carbon nanotubes

Received: 9 November 1998 / Accepted: 25 November 1998     

Energies and widths of triply excited states of lithiumlike oxygen and neon

Seven low-lying triply exited states of lithium-like oxygen and neon are calculated with the multichannel saddle-point and saddle-point complex-rotation methods. The term energies are given for these excited states, along with level shifts and partial Auger widths from dominant decay channels. The mass polarization effect and relativistic corrections are included. The radiative transition rates are also calculated. These results are compared with other theoretical data in the literature. Received: 25 May 1998 / Revised: 28 July 1998 / Accepted: 25 August 1998     

Lateral variation of quantum-well confinement energy in triangular-shaped dot-like structures grown by molecular beam epitaxy on patterned GaAs (311)A substrates

Received: 13 Oktober 1997/Accepted: 25 January 1998     

Nanotomographic examinations of ion tracks in cellulose nitrate by ion energy loss spectrometry

Received: 13 October 1997/Accepted: 25 August 1998     

Specific heat jump in non-Fermi superconductors

We derive the jump in the specific heat at T=T _c for a superconductor in a non-Fermi liquid model. We took into consideration the two possible limits in this problem: the spin-charge separation model for a Fermi liquid and the usual non-Fermi liquid model which satisfies the homogeneity relation for the spectral function , ). We also derive the order parameter behavior for these two cases in the vecinity of the critical temperature. Received: 25 January 1998 / Revised: 25 March 1998 / Accepted: 25 March 1998     

Free expansion of a Bose–Einstein condensate from an Ioffe–Pritchard magnetic trap

5 rubidium-87 atoms released from an Ioffe–Pritchard magnetic trap is investigated experimentally. The expansion dynamics depend only on the trap frequencies, which are determined independently. The data are in good agreement with the expected expansion of a condensate, and are clearly distinct from the behaviour of a classical gas in the hydrodynamic regime. Received: 3 June 1998/Final version: 25 September 1998     

Silicon vacancies in 3C-SiC observed by positron lifetime and electron spin resonance

54 , 2512 (1996)]. The trapping coefficient of single-negative silicon vacancies was also derived. Received: 25 August 1997/Accepted: 27 March 1998     

Expansions for the eigenvalues of three-term recurrence relations. Two applications in molecular physics

Approximate expressions for the eigenvalue of a three-term recurrence relation with a general form describing various physical problems are proposed. Their range of availability is examined by comparison with exact values for two different problems: the bound and continuum states of monoelectronic diatomic ions and the Schr?dinger equation describing molecular alignment in intense laser fields. For each case, very good predictions have been obtained, which may be useful as initial values in iterative procedures for deriving exact solutions. Received: 30 January 1998 / Received in final form: 10 April 1998 / Accepted: 25 May 1998     

An analytical estimate of the period for the delayed logistic application and the Lotka-Volterra system

We first introduce a simple and new method for the quantitative analysis of some nonlinear oscillating systems. It is shown that if the dynamics of the system reduces to piecewise exponential growth and exponential damping phases, then the amplitude and period of the motion can be computed with accuracy in the nonlinear regime without invoking linear stability arguments or perturbative expansions. This method is then successfully applied to the delayed logistic application and to the Lotka-Volterra prey-predator model. For both of these systems, we provide an accurate analytical expression for the period of the oscillations in the nonlinear regime. Received: 27 April 1998 / Received in final form: 25 June 1998 / Accepted: 29 June 1998     

Polarization effects in ultrashort-pulse laser drilling

A strong influence of the polarization of the laser radiation on the geometry of laser-machined microdrillings has been observed for ultrashort pulses. For drillings with a certain aspect ratio, reflections at the hole walls take place, leading to a non-uniform intensity distribution deep inside the formed hole. Experimental and theoretical results on this subject are discussed. It is shown that a rotation of the polarization during the drilling process (“polarization trepanning”) significantly improves the quality of the produced holes. Received: 21 August 1998 / Accepted: 25 November 1998 / Published online: 17 March 1999     

Spatio-temporal patterns in the thermoconvection of a planar nematic layer: II. Experiments

We study experimentally the evolution of thermoconvection in a laterally extended planar nematic layer, at zero or weak stabilizing magnetic field. As the applied thermal gradient is increased, a cascade of symmetry breakings occurs, towards structures of increasing spatial complexity, and ultimately towards oscillating states. The patterns are characterized optically, and simple models for the distortion of the vertical (out of plane) component of the director field are proposed. Received: 1st December 1997 / Revised: 25 May 1998 / Accepted: 2 June 1998     

Free-electron laser for infrared SEW characterization surfaces of conducting and dielectric solids and nm films on them

2 , BaF₂, MgO, LiNbO₃ were determined. The nonlinear spectroscopy applications of SEW–FEL techniques to studies of a second-harmonic generation (SHG) on crystal surfaces in the regime of counterpropagating SEWs – the frequency dependence of efficiency and the influence of a thin film deposition on a quartz surface – are described. Received: 15 May 1998/Accepted: 25 August 1998     

Remote measurement of volcanic gases by Fourier transform infrared spectroscopy

Received: 25 March 1998     

Singularity of the specific heat of two-dimensional random Ising models

The singularity of the specific heat is studied for the dilution (J>J'>0) type and Gaussian type random Ising models using the Pfaffian method numerically. The type of singularity at the paramagnetic-ferromagnetic phase boundary is studied using the standard regression method using data up to system size. It is shown that the logarithmic type singularity is more reliable than the double-logarithmic type and cusp type singularities. The critical temperatures are estimated accurately for both the dilution type and Gaussian type random Ising models. A phase diagram relating strength of the randomness and temperature is also presented. Received: 26 February 1998 / Revised: 15 May 1998 / Accepted: 25 June 1998     

Flow equations and the Ruderman-Kittel-Kasuya-Yosida interaction

In the past different models for the magnetic salt vanadyl pyrophosphate (VO)₂P₂O₇ were discussed. Neither a spin ladder nor an alternating chain are capable to describe recently measured magnetic excitations. In this paper we propose a 2D model that fits better to experimental observations. Received: 29 May 1998 / Received in final form: 25 September 1998 / Accepted: 30 September 1998     

Melting of columnar hexagonal DNA liquid crystals

The persistence length DNA hexagonal-cholesteric phase transition upon dilution and/or increase in solvent ionic strength is investigated with polarized light microscopy. The ionic strength dependence of the transition follows Lindemann criterion , i.e., the hexagonal lattice melts when the root-mean-square fluctuations in transverse order exceed 10% of the interaxial spacing. The spacings are derived from density and the fluctuations are estimated with a theory of undulation enhanced electrostatic interactions. Additional support for this theory is given by the DNA equation of state and anisotropic neutron radiation scattering from magnetically aligned cholesteric samples just below the phase transition. Received: 17 November 1997 / Revised: 21 January 1998 / Accepted: 25 February 1998     

Spatial and angular distributions of third harmonic generation from metal surfaces

Third harmonic generation from planar and spherical metal surfaces is studied theoretically through the standard Green function method, so that the results are not affected by the uncertainty associated with previous simplified models. In general the pattern of the non-linear scattering loosely resembles the pattern of Mie scattering. The strong backward scattering is uniquely related to the non-linear process. These results differ significantly from the predictions of the surface charge model. Received: 20 May 1998 / Received in final form: 25 August 1998 / Accepted: 1st September 1998