Two-time synchronism and induced synchronization in a Kerr coupler

A pair of interacting Kerr oscillators treated as a master coupler sending chaotic or hyperchaotic signals to its slave copy is considered. We synchronize a with A and b with B through two communication channels and . The effect of synchronization is non-simultaneous, the pairs and have different times of synchronization. It is possible to synchronize an individual pair, for example, when its communication channel is turned off, provided that the second channel for the pair is turned on. The resulted synchronization is termed induced. The efficiencies of the presented synchronization precesses are studied.Received: 20 February 2003, Published online: 29 April 2003PACS: 05.45.Xt Synchronizations; coupled oscillators - 05.45.Pq Numerical simulations of chaotic systems - 42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics     

Two-step laser optogalvanic spectroscopy of the odd-parity Rydberg states of atomic mercury

We present new experimental data on the highly excited levels in mercury using the two-step laser excitation and optogalvanic detection technique in conjunction with a RF discharge cell. The 6s7s ³S₁ intermediate level has been accessed from the 6s6p ³P₂ metastable level that is collisionally populated in the mercury discharge in the presence of a buffer gas at a pressure of about 1 Torr. Two beams fromtwo different dye lasers pumped with a common excimer laser were passed through the discharge cell containing mercury vapors. The first laser was tuned to 6s7s ³S₁ level whereas the second laser was scanned covering the wavelength region between 544-458 nm. We have observed the 6snp ³P₀ ( ), 6snp ( ), 6snp ( ) and 6snp ) Rydberg series. The 6snp Rydberg series to such high n-value has been reported for the first time. The first ionization potential of mercury is determined from the 6snp Rydberg series as 84184.15 0.05 cm^-1. Some collisionally induced parity forbidden transitions have also been located that are identified as 6sns ( ) series.Received: 5 November 2003, Published online: 20 January 2004PACS: 31.50.-x Potential energy surfaces - 32.30.Jc Visible and ultraviolet spectra - 32.80.Rm Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)     

Optical manipulation of long-range interactions at the 3s + 3p asymptote of $\mathsf{Na_2}$

We investigate the influence of a laser field, which is near-resonant to the atomic sodium 3²P_1/2 3²D_3/2 transition, on the last bound levels of the A state in Na₂. In a molecular beam experiment level shifts up to 100 MHz and light induced line broadenings were observed using an optical double resonance excitation scheme. Moreover, the coupling laser can reduce the number of bound levels of the A state by one or more units, which effectively means that in the picture of a collision of a 3²S_1/2 and a 3²P_1/2-atom the scattering phase is altered by more than . The observed effects are interpreted as light induced couplings of the A state, which correlates to the 3s _1/2 + 3p _1/2 asymptote, to the and states at the 3s _1/2 + 3d _3/2 asymptote. We performed multi-channel calculations, applying the mapped Fourier grid method, which reproduce our experimentally observed level shifts well.Received: 7 October 2003, Published online: 21 November 2003PACS:   34.50.Rk Laser-modified scattering and reactions - 33.80.-b Photon interactions with molecules - 42.62.Fi Laser spectroscopy     

Modular construction of special mixed quantum states

For a homogeneous quantum network of N subsystems with n levels each we consider separable generalized Werner states. A generalized Werner state is defined as a mixture of the totally mixed state and an arbitrary pure state : with a mixture coefficient . For this density operator to be separable, will have an upper bound . Below this bound one should alternatively be able to reproduce by a mixture of entirely separable input-states. For this purpose we introduce a set of modules, each contributing elementary coherence properties with respect to a generalized coherence vector. Based on these there exists a general step-by-step mixing process for any . For being a cat-state it is possible to define an optimal process, which produces states right up to the separability boundary ( ).Received: 3 December 2002, Published online: 29 July 2003PACS: 03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bells inequalities, GHZ states, etc.) - 03.67.-a Quantum information - 03.65.-w Quantum mechanics     

Metastable level lifetimes from electron-shelving measurements with ion clouds and single ions

The lifetime of the -level in singly-ionized calcium has been measured by the electron-shelving technique on different samples of rf trapped ions. The metastable state has been directly populated by exciting the dipole-forbidden transition. In ion clouds, the natural lifetime of this metastable level has been measured to be ( ) ms. For the single-ion case, we determined a lifetime of ( ) ms. The -error bars at the 2%-level have different origins for the two kinds of experiments: data fitting methods for lifetime measurements in an ion cloud and control of experimental parameters for a single ion. De-shelving effects are extensively discussed. The influence of differing approaches for the processing of the single-ion quantum jump data on the lifetime values is shown. Comparison with recent measurements shows excellent agreement when evaluated from a given method.Received: 14 November 2003, Published online: 24 February 2004PACS: 32.70.Cs Oscillator strengths, lifetimes, transition moments - 32.80.Pj Optical cooling of atoms, trapping     

The high-energy critical minimum in elastic electron scattering by argon

The position of high-energy critical minimum in elastic electron-argon scattering was investigated both experimentally and theoretically. Differential cross-sections (DCSs) were measured as a function of both incident electron energy (40-150 eV) and scattering angle ( ), in small steps around the critical minimum. The position of the high-energy critical minimum in elastic electron-argon scattering was experimentally found to be at eV and . To cover the energy and angular ranges of the present experiment, relevant relativistic ab initio calculations were carried out, based on the Dirac-Hartree-Fock method with the exchange calculated exactly. Target polarization is described by an ab initio potential taken from relativistic polarized orbital calculations. The calculated position of the high-energy critical minimum is eV, . It was shown that even slight difference of fixed scattering angle close to the critical point could affect significantly the energy dependent DCS. Discussion of behavior of DCS in the vicinity of the critical minimum was performed including convolution analysis in both energy and angle.Received: 31 October 2003, Published online: 20 April 2004PACS: 31.15.Ar Ab initio calculations - 34.80.Bm Elastic scattering of electrons by atoms and molecules     

High resolution multiphoton ionization and dissociation of acetone via $\mathsf{3s\leftarrow n}$ Rydberg transitions

Measurements of multiphoton ionization and dissociation of acetone are reported in the wavelength range 582.60-585.80 nm at photon energy resolution of 0.3 cm^-1. To our knowledge there are not available results of (3 + 2) REMPI on acetone at 0.01 nm in this region. The experiments were performed using an Nd: YAG-OPO (optical parametric oscillator) laser system coupled to time-of-flight mass spectrometer. The ion yield and the single ion channel are presented. The high-resolution three-photon resonance multiphoton spectrum of the acetone Rydberg transition is also reported. The experimental results show three dissociation channels of the acetone ion, leading to the products: (CH₃CO ⁺ ), (CH₃ ⁺ ) and (COH ⁺ ); the channel CH₃COCH ₃CO ⁺ + CH₃ being the most favored. The acetone and acetyl ions are observed in all wavelength range investigated. In addition, we have measured the origin of the and transitions, and vibrational bands of the 3s state.Received: 21 March 2004, Published online: 11 May 2004PACS: 33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states) - 33.15.Ta Mass spectra - 33.80.Gj Diffuse spectra; predissociation, photodissociation     

Efficient long-term laser excitation of a collimated beam of potassium atoms on the D2 line

With the aim to provide a reliable scheme for efficient laser excitation of the potassium D2 line over long periods of time, we have developed a robust stabilization of a single mode laser of frequency f ₀ = (f ₁₂ + f ₂₃)/2 onto a crossover peak in the saturation spectrum of the ³⁹K(D2) line (4s ²S P . The two hyperfine transitions (frequency f ₁₂) and (frequency f ₂₃) are simultaneously excited by the first order sidebands of the laser beam (f ₀), generated by its electro-optical modulation at the frequency f _EOM = (f ₁₂-f ₂₃)/2. In this way stable excitation of the two transitions on their proper frequencies is achieved and hyperfine pumping compensated.Received: 10 March 2004, Published online: 29 June 2004PACS: 39.30. + w Spectroscopic techniques - 32.80.Bx Level crossing and optical pumping - 42.60.Fc Modulation, tuning, and mode locking     

Experimental assessment of temperature in plasma wall interaction

The purpose of this paper is to study the temperature evolution during the interaction of a plasma with an insulating wall in polyethylene ((CH₂) _n ) and polyoxymethylene ((CH₂O) _n ). The plasma is initiated by means of a capacitor bank discharge in a copper fuse wire. Due to the energy release the ablation of the insulating wall produces some insulating vapours in addition to the copper vapours corresponding to the wire vaporization. Using neutral copper line intensity ratio assuming a Bo ltzmann distribution we obtain a temperature evolution from 11 000 K to 24 000 K in the first few hundreds microseconds of the discharge. For later times the copper lines are strongly self-absorbed and make impossible the diagnostic in a spectroscopic way. Hence the temperature is deduced from the comparison between the experimental and calculated electrical conductivity. So for the decrease of the current the temperature evolves from 21 000 K down to 6 000 K and depends on the p lasma density. The results and the reliability of the two methods are discussed.Received: 25 July 2003, Published online: 14 October 2003PACS: 52.25.Kn Thermodynamics of plasmas - 52.70.Kz Optical (ultraviolet, visible, infrared) measurements - 52.80.Wq Discharge in liquids and solids     

Triple differential cross-sections of Ne (2s<Superscript>2</Superscript>) in coplanar to perpendicular plane geometry

The distorted wave Born approximation (DWBA) with the spin averaged static exchange potential has been used to calculate the triple differential cross-sections (TDCSs) for Ne (2s ²) ionization by electron impact in coplanar to perpendicular plane symmetric geometry at 110.5 eV incident electron energy. The present theoretical results at gun angles (coplanar symmetric geometry) and (perpendicular plane geometry) are in satisfactory agreement with the available experimental data. A deep interference minimum appears in the TDCS in the coplanar symmetric geometry and a strong peak at scattering angle caused by the single collision mechanism has been observed in the perpendicular plane geometry. The TDCSs at the gun angles , and are predicted.Received: 16 July 2002, Published online: 22 July 2003PACS: 34.80.Gs Molecular excitation and ionization by electron impact - 34.80.Dp Atomic excitation and ionization by electron impact     

Updated estimate of the muon magnetic momentusing revised results from <Emphasis Type="Italic">e</Emphasis><Superscript> + </Superscript><Emphasis Type="Italic">e</Emphasis><Superscript>-</Superscript>annihilation

A new evaluation of the hadronic vacuum polarization contribution to the muon magnetic moment is presented. We take into account the reanalysis of the low-energy e ⁺ e ^-annihilation cross section into hadrons by the CMD-2 Collaboration. The agreement between e ⁺ e ^-and spectral functions in the channel is found to be much improved. Nevertheless, significant discrepancies remain in the center-of-mass energy range between 0.85 and , so that we refrain from averaging the two data sets. The values found for the lowest-order hadronic vacuum polarization contributions are where the errors have been separated according to their sources: experimental, missing radiative corrections in e ⁺ e ^-data, and isospin breaking. The corresponding Standard Model predictions for the muon magnetic anomaly read where the errors account for the hadronic, light-by-light (LBL) scattering and electroweak contributions. The deviations from the measurement at BNL are found to be (1.9 ) and (0.7 ) for the e ⁺ e ^-- and -based estimates, respectively, where the second error is from the LBL contribution and the third one from the BNL measurement.Received: 7 September 2003, Published online: 30 October 2003     

Hyperfine structure and isotope shift study in singly ionized lead

Hyperfine structure and isotope shifts in five optical transitions: 424.5 nm ( – ), 537.2 nm ( – ), 554.5 nm ( – ), 560.9 nm ( – ) and 666.0 nm ( – ) of Pb  II have been measured. As a light source the discharge tube was used. The hyperfine structure measurements were performed using metallic isotope ²⁰⁷Pb. For isotope shifts measurements natural lead was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The hyperfine structure observations yielded the splitting constants A for seven levels of Pb II. The isotope shift studies enabled to separate the mass and the field shifts and to determine values of changes of the mean square nuclear charge radii.     

Accurate asymptotic ground state potential curves of Cs$\mathsf{_2}$ from two-colour photoassociation

Over 100 high lying level energies of the lowest electronic states and in Cs₂ are determined in a -like scheme two-colour photoassociation spectroscopy. The results are analyzed with a coupled channel model using an asymptotic approach, based on nodal lines. From this analysis we determine the long range dispersion coefficient C₆ to 6846.2 15.6 a.u. We also obtain the first experimental determination of the amplitude of the asymptotic exchange term.Received: 4 November 2003, Published online: 20 January 2004PACS: 34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions - 32.80.Pj Optical cooling of atoms; trapping - 03.65.Ge Solutions of wave equations: bound states     

Investigation of highly excited states of calcium by three-photon ionization

The three-photon ionization in Ca from S₀ ground state is studied. The two-photon process is a near -- resonance process with one of the following bound states: 4s4d ¹D₂, 4p P₂, 4s6s ¹S₀, 4 D₂ and 4 S₀ while the third photon reach either directly the continuum or one of the autoionizing states. The succession of bound states as well as the transitions above the ionization limit are discussed. The dynamics of the multiphoton excitation processes is also discussed and radiative decay of 4 S₀ Ca state with two-photon excitation as well as (the measured) decay times of the Ca autoionizing states using the proper line profiles for different quantum numbers has been determined.Received: 29 September 2003, Published online: 18 May 2004PACS: 32.70.-n Intensities and shapes of atomic spectral lines - 32.70.Cs Oscillator strengths, lifetimes, transition moments - 32.80.Fb Photoionization of atoms and ions - 32.80.Rm Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)     

Hyperfine quenching of the 4s4p <Superscript>3</Superscript>P<Subscript>0</Subscript> level in Zn-like ions

In this paper, we used the multiconfiguration Dirac-Fock method to compute with high precision the influence of the hyperfine interaction on the [Ar] P₀ level lifetime in Zn-like ions for stable and some quasi-stable isotopes of nonzero nuclear spin between Z=30 and Z=92. The influence of this interaction on the [Ar] P P₀ separation energy is also calculated for the same ions.     

EIT-assisted atomic squeezing

The interaction of classical and quantized electromagnetic fields with an ensemble of atoms in an optical cavity is considered. Four fields drive a double- level scheme in the atoms, consisting of a pair of systems sharing the same set of lower levels. Two of the fields produce maximum coherence, , between the ground state sublevels 1 and 2. This pumping scheme involves equal intensity fields that are resonant with both the one- and two-photon transitions of the system. There is no steady-state absorption of these fields, implying that the fields induce a type Electromagnetically-Induced Transparency (EIT) in the medium. An additional pair of fields interacting with the second system, combined with the EIT fields, leads to squeezing of the atom spin associated with the ground state sublevels. Our method involves a new mechanism for creating steady-state spin squeezing using an optical cavity. As the cooperativity parameter C is increased, the optimal squeezing varies as C ^-1/3. For experimentally accessible values of C, squeezing as large as 90% can be achieved.Received: 28 May 2003, Published online: 12 August 2003PACS: 42.50.Lc Quantum fluctuations, quantum noise, and quantum jumps - 42.50.Dv Nonclassical states of the electromagnetic field, including entangled photon states; quantum state engineering and measurements - 42.65.Pc Optical bistability, multistability, and switching, including local field effects     

Spectroscopic studies of NaCs for the ground state asymptote of Na + Cs pairs

The ground state X of NaCs was studied by laser induced fluorescence Fourier-transform spectroscopy. An accurate potential energy curve was derived from more than 5000 transitions. This potential reproduces the experimental observations within their uncertainties of cm^-1 and covers about 99.97% of the potential well depth. Few vibrational levels of the shallow state a below the atomic ground state asymptote were observed. The identification is mainly done by the observed and quantitatively interpreted molecular hyperfine structure applying atomic parameters of the ground states of Na and Cs. An estimated potential curve for a is reported which can be used together with that of X for coupled channel calculations of cold collisions between Na and Cs. An example is given. Electronic supplementary material to this article is available at and is accessible for authorized users. Received: 10 September 2004, Published online: 23 November 2004 PACS: 31.50.Bc Potential energy surfaces for ground electronic states - 33.20.Kf Visible spectra - 33.20.Vq Vibration-rotation analysis - 33.50.Dq Fluorescence and phosphorescence spectra Supplementary tables (Tabs. I-III) are only available in electronic form at http: //www.eurphysj.org     

Molecular beam electric resonance without A- and B-fields

We report on a novel phenomenon observed during the passage of a pulsed NO beam seeded in He through a combined homogeneous, static electric and RF field, denoted as C-field in a standard molecular beam electric resonance (MBER) experiment. Although we refrain from the state selective A- and B-fields, which are considered crucial for a MBER experiment, the transmitted intensity exhibits as a function of the RF frequency conspicuous dips at resonance frequencies that depend strictly linearly on the static field strength E ₀. Their spectral width is by a factor of 4 smaller than the time of flight broadening. Both, the resonance frequencies and their linear field dependence can be precisely predicted applying a simple expression for the Stark effect to a transition of a single rotational state (J = 3/2) of the electronic ground state . However, this formula is valid only in the high field limit (E ₀ > 1000 kV/m) while the employed field (E ₀ = 1.47 kV/m) was in the extreme low field domain where the large type doubling and hyperfine coupling lead to a purely quadratic Stark effect. We assume that the phenomenon is due to a yet unknown collective rather than to an isolated particle process.Received: 9 May 2003, Published online: 12 August 2003PACS: 33.20.Bx Radio-frequency and microwave spectra - 32.60. + i Zeeman and Stark effects Author for correspondence: A. González Ureña     

A precise measurement of the tau lifetime

The tau lepton lifetime has been measured with the events collected by the DELPHI detector at LEP in the years 1991-1995. Three different methods have been exploited, using both one-prong and three-prong decay channels. Two measurements have been made using events in which both taus decay to a single charged particle. Combining these measurements gave . A third measurement using taus which decayed to three charged particles yielded These were combined with previous DELPHI results to measure the tau lifetime, using the full LEP1 data sample, to be .Received: 12 November 2003, Revised: 1 June 2004, Published online: 20 July 2004     

Isospin breaking in $K \rightarrow \pi\pi$ decays

We perform a complete analysis of isospin breaking in amplitudes in chiral perturbation theory, including both strong isospin violation ( ) and electromagnetic corrections to next-to-leading order in the low-energy expansion. The unknown chiral couplings are estimated at leading order in the 1/N_c expansion. We study the impact of isospin breaking on CP conserving amplitudes and rescattering phases. In particular, we extract the effective couplings g₈ and g₂₇ from a fit to branching ratios, finding small deviations from the isospin-limit case. The ratio measuring the enhancement is found to decrease from in the isospin limit to in the presence of isospin breaking. We also analyze the effect of isospin violation on the CP violation parameter , finding a destructive interference between three different sources of isospin violation. Within the uncertainties of large-N_c estimates for the low-energy constants, the isospin violating correction for is below 15%.Received: 21 November 2003, Published online: 4 February 2004Work supported in part by IHP-RTN, Contract No. HPRN-CT2002-00311 (EURIDICE) and by Acciones Integradas, Project No. 19/2003 (Austria), HU2002-0044 (MCYT, Spain)