 2  Author
 BertholdGeorg Englert  Requires cookie*   Title
 Remarks on Some Basic Issues in Quantum Mechanics    Abstract
 Twoway interferometers with whichway detectors are not only of importance in physical research, they are also a useful teaching device. A number of basic issues can be illustrated and discussed, even at the level of undergraduate teaching. Among these issues are: the physical meaning of a state vector; entangled systems; EinsteinPodolskyRosen correlations; statistical operators and the asif realities associated with them; quantum erasure; Schrödinger's cat; and, finally, waveparticle duality.   
Reference
 Z. Naturforsch. 54a, 11—32 (1999); received October 26 1998   
Published
 1999   
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3  Author
 Hwang Lee, MarianO. Scully  Requires cookie*   Title
 Manifestation of Quantum Interference in Lasing Without Inversion    Abstract
 In terms of quantum interference we demonstrate the physical mechanisms which lead to light amplification without population inversion. The similarities and differences between the two model schemes, namely, A and Vtype, are emphasized. A coherent radiation field, on one hand, which drives one of the lasing levels, yields the quantum mechanical two paths via AutlerTownes splittings. On the other hand, the spontaneous emission in this driving transition plays a key role in the asymmetries between the absorption and the stimulated emission in the lasing transition.   
Reference
 Z. Naturforsch. 54a, 33—38 (1999); received May 5 1998   
Published
 1999   
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 default:Reihe_A/54/ZNA199954a0033.pdf    Identifier
 ZNA199954a0033    Volume
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4  Author
 JánosA. Bergou, Pál Bogár  Requires cookie*   Title
 Phase Structures in the Micromaser Photon Statistics    Abstract
 In the photon number distribution p(9,k) of the micromaser, distinct structures are formed by the ridges connecting the peaks in the 9 k space. We refer to these structures as phases. By a simple condition we can distinguish between "semiclassical" and "quantum" regimes of operation near and far above threshold, respectively. In the semiclassical regime, the equations of state of the phases 9 = 9{k) are monotonous and coincide with the steady state solutions of the semiclassical theory. They reflect typical features of the micromaser dynamics. The transition jumps, e. g., between the phases decrease with increasing pumping parameter 9, signifying the onset of the JaynesCummings collapse. On increasing 9 further, the phases first disintegrate and then restructure into new kinds of phases in the quantum regime. The equations of state are no longer monotonous. Large single peaks, the quantum island states (QIS), develop in the neighborhoods of minima. The system undergoes oscillations between two kinds of quantum island states, QIS and QIS + , as a function of 9. The disintegration and transformation of phases recur periodically as 9 is varied, and the phases in the semiclassical region are followed by consecutive phase structures in the quantum regime. The subsequent collapses and revivals of phases are directly connected to the JaynesCummings collapse and revival. The observation of these phase structures and the accompanying QIS is experimentally feasible. PACS 42.50.Dv, 42.52+x   
Reference
 Z. Naturforsch. 54a, 39—9 (1999); received September 24 1998   
Published
 1999   
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6  Author
 Michael Fleischhauer, Oliver Veits  Requires cookie*   Title
 Longtime Dynamics of Spontaneous Parametric Downconversion and Quantum Limitations of Conversion Efficiency    Abstract
 We analyze the longtime quantum dynamics of degenerate parametric downconversion from an initial subharmonic vacuum (spontaenous downconversion). Standard linearization of the Heisenberg equations of motion fails in this case, since it is based on an expansion around an unstable classical solution and neglects pump depletion. Introducing a meanfield approximation we find a periodic exchange of energy between the pump and subharmonic mode goverened by an anharmonic pendulum equation. From this equation the optimum interaction time or crystal length for maximum conversion can be determined. A numerical integration of the 2mode Schrödinger equation using a dynamically optimized basis of displaced and squeezed number states verifies the characteristic times predicted by the meanfield approximation. In contrast to semiclassical and meanfield predictions it is found that quantum fluctuations of the pump mode lead to a substantial limitation of the efficiency of parametric downconversion.   
Reference
 Z. Naturforsch. 54a, 57—6265 (1999); received June 25 1998   
Published
 1999   
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7  Author
 S. Typel, H. H. Wolter  Requires cookie*   Title
 Dynamical Description of Coulomb Dissociation    Abstract
 We present a simple and efficient method for a fully dynamical treatment of Coulomb excitation in the semiclassical approximation by solving the timedependent Schrödinger equation. It allows to investigate the importance of higher order effects in the breakup process. The method is applied to the Coulomb breakup of 7 Li scattered on ly7 Au at 42 MeV projectile energy.   
Reference
 Z. Naturforsch. 54a, 63—76 (1999); received November 21 1998   
Published
 1999   
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 ZNA199954a0063    Volume
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8  Author
 H. Huber, M. K. Weigel, F. Weber  Requires cookie*   Title
    Abstract
 It is shown that the modern equations of state for neutron star matter based on microscopic calculations of symmetric and asymmetric nuclear matter are compatible with the lower bound on the maximum neutronstar mass for a certain range of hyperon coupling constants, which are constrained by the binding energies of hyperons in symmetric nuclear matter. The hyperons are included by means of the relativistic Hartreeor HartreeFock approximation. The obtained couplings are also in satisfactory agreement with hypernuclei data in the relativistic Hartree scheme. Within the relativistic HartreeFock approximation, hypernuclei have not been investigated so far.   
Reference
 Z. Naturforsch. 54a, 77—82 (1999); received Oktober 19 1998   
Published
 1999   
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9  Author
 K. Strobel, F. Weber, M. K. Weigel  Requires cookie*   Title
 Symmetrie and Asymmetrie Nuclear Matter in the ThomasFermi Model at Finite Temperatures    Abstract
 The properties of warm symmetric and asymmetric nuclear matter are investigated in the frame of the ThomasFermi approximation using a recent modern parameterization of the effective nucleonnucleon interaction of Myers and Switecki. Special attention is paid to the liquidgas phase transition, which is of special interest in modern nuclear physics. We have determined the critical temperature, critical density and the socalled flash temperature. Furthermore, the equation of state for cold neutron star matter is calculated.   
Reference
 Z. Naturforsch. 54a, 83—9075 (1999); received July 29 1998   
Published
 1999   
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11  Author
 G. Spinolo, P. Ghigna, G. Chiodelli, M. Ferretti, G. Flor  Requires cookie*   Title
 Resistivity and Carrier Mobility of the SmBa 2 Cu 3 0 6+x Superconductor with Different Oxygen Doping Levels    Abstract
 DC conductivity measurements between 15 and 300 K are reported for SmBa 2 Cu30 6+J samples with different oxygen doping amounts (x) produced by annealing under appropriate high temperature and oxygen pressure conditions and quenching. Samples with jc>0.5 are superconductors: 7* c ~60 K at Jt=0.7, 7* c >80 K at ;c=0.9. The transition from superconduction to nonsuperconduction corresponds to the tetragonal to orthorhombic structural transition and to the transition from semiconducting to metallic temperature dependence of the resistivity. Oxygen doping causes a sudden increase of hole mobility near x=0.5. Below this threshold, the behavior of the carrier mobility is in agreement with an Anderson localization.   
Reference
 Z. Naturforsch. 54a, 95—100 (1999); received December 21 1998   
Published
 1999   
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13  Author
 Joäo Manuel, Marques Cordeiro, Luiz Carlos, Gomide Freitas  Requires cookie*   Title
 Study of Water and Dimethylformamide Interaction by Computer Simulation    Abstract
 Monte Carlo simulations of waterdimethylformamide (DMF) mixtures were performed in the isothermal and isobaric ensemble at 298.15 K and 1 atm. The intermolecular interaction energy was calculated using the classical 612 LennardJones pairwise potential plus a Coulomb term. The TIP4P model was used for simulating water molecules, and a sixsite model previously optimised by us was used to represent DMF. The potential energy for the waterDMF interaction was obtained via standard geometric combining rules using the original potential parameters for the pure liquids. The radial distribution functions calculated for waterDMF mixtures show well characterised hydrogen bonds between the oxygen site of DMF and hydrogen of water. A structureless correlation curve was observed for the interaction between the hydrogen site of the carbonyl group and the oxygen site of water. Hydration effects on the stabilisation of the DMF molecule in aqueous solution have been investigated using statistical perturbation theory. The results show that energetic changes involved in the hydration process are not strong enough to stabilise another configuration of DMF than the planar one.   
Reference
 Z. Naturforsch. 54a, 110—116 (1999)   
Published
 1999   
Keywords
 Monte Carlo Simulation, Solvent Effects, Statistical Perturbation Theory, Hydration of Peptides   
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 ZNA199954a0110    Volume
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14  Author
 M. Rauh, H.U Finzel, P. Wißmann  Requires cookie*   Title
 The Oxidation Kinetics of Thin Copper Films Studied by Resistivity Measurements    Abstract
 Resistivity measurements on thin metal films allow to study the kinetics of oxidation. The method is applied to 50 60 nm thick copper films deposited on glass substrates under UHV conditions. After annealing at 150 °C, the films are exposed to pure oxygen at various temperatures in the range 85 135 °C, and the electrical resistivity is recorded in situ. At these temperatures, the oxygen begins to penetrate into the interior of the films, which results in a relatively steep increase in the film resistivity. A linear time law is valid to good approximation, which can be attributed to the influence of the dissociation of an adsorbed molecular species of oxygen on the reaction velocity. A potential diffusion of oxygen in the grain boundaries is also discussed.   
Reference
 Z. Naturforsch. 54a, 117—123 (1999); received July 29 1998   
Published
 1999   
Keywords
 Oxidation, Kinetics, Resistivity, Thin Metal Films   
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 ZNA199954a0117    Volume
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15  Author
 Thomas Wieder  Requires cookie*   Title
 A Generalized Debye Scattering Formula and the Hankel Transform    Abstract
 The diffracted intensity of an xray or neutron diffraction experiment is expressed as an integral over an atomic position distribution function. A generalized Debye scattering formula results. Since this distribution function is expanded into a series of spherical harmonics, an inverse Hankel transform of the intensity allows the calculation of the expansion coefficients which describe the atomic arrangement completely. The connections between the generalized Debye scattering formula and the original Debye formula as well as the Laue scattering formula are derived.   
Reference
 Z. Naturforsch. 54a, 124—130 (1999); received December 15 1998   
Published
 1999   
Keywords
 Xray Scattering, Debye Formula, Hankel Transform   
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 ZNA199954a0124    Volume
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16  Author
 V. Ahrens, G. Winnewisser  Requires cookie*   Title
 Pure Rotational Spectra of CS    Abstract
 The pure rotational spectra of CS and its isotopomers 12 C 33 S, 12 C 34 S, 13 C 32 S, 13 C 33 S, 13 C 34 S including the very rare isotopomer 12 C 36 S were observed. The rotational spectra include ground and vibrationally excited transitions up to v = 16. The new measurements have been performed with the Cologne terahertz spectrometer covering the frequency region from 259 to 1075 GHz. These newly observed rotational transitions together with earlier data were fitted to a Dunhamtype Hamiltonian. The obtained isotopically invariant parameters include vibrational and rotational expansion coefficients.   
Reference
 Z. Naturforsch. 54a, 131—136 (1999); received November 21 1998   
Published
 1999   
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 ZNA199954a0131    Volume
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17  Author
 H. Klein, E. Klisch, G. Winnewisser  Requires cookie*   Title
 Rotational Spectra of Phosphorus Monosulfide up to 1 THz    Abstract
 The submillimeterwave rotational spectrum of the PS radical in the electronic and vibrational ground state (A' 2 77I/ 2 , X 2 IJ 3 / 2) was recorded with the Cologne terahertz spectrometer in the frequency region between 540 GHz and 1.07 THz, covering rotational quantum numbers from J = 30.5 to 60.5. The PS radical has been produced by discharging PSC1 3 buffered with Ar. For all transitions the yldoubling was resolved for both the 2 77I/2 and 2 77 3 / 2 states. For some transitions with AF = 0 the hyperfine structure (hfs) caused by the Patom could partially be resolved even for rather high J values. Analysis of the complete rotational data set of PS allows the derivation of a full set of molecular parameters, including the rotational constants B, D, H, the finestructure constants A, 7, D 1 , the parameters for the yldoubling p, D p , q, and the magnetic hyperfine constants a, b, c, d, Ci. All parameters have been determined, whereby a, c, and the nuclear spin rotationconstant Ci were obtained for the first time.   
Reference
 Z. Naturforsch. 54a, 137—145 (1999); received November 21 1998   
Published
 1999   
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18  Author
 J. Ackermann, T. Kirner  Requires cookie*   Title
 Parasites and Pattern Formation    Abstract
 Biological information is coded in replicating molecules. To maintain a given amount of information a cooperative interaction between these molecules is essential. The main problem for the stability of a system of prebiotic replicators are emerging parasites. Stabilization against such parasites is possible if space is introduced in the model. Complex patterns like spiral waves and selfreplicating spot patterns have been shown to stabilize such systems. Stability of replicating systems, however, occurs only in parameter regions were such complex patterns occur. We show that parasites are able to push such systems into a parameter region were life is possible. To demonstrate this influence of parasites on such systems, we introduce a parasitic species in the GrayScott model. The growing concentration of parasites will kill the system, and the cooperative GrayScott system will be diluted out in a well mixed flow reactor. While considering space, in the model stabilizing pattern formation in a narrow parameter region is possible. We demonstrate that the concentration of the parasitic species is able to push the system into a region were stabilizing patterns emerge.   
Reference
 Z. Naturforsch. 54a, 146—152 (1999); received December 15 1998   
Published
 1999   
Keywords
 Pattern Formation, ReactionDiffusion, Molecular Evolution, Parasites, Coevolution, Cooperation   
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 ZNA199954a0146    Volume
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19  Author
 N. Sinyavsky, M. Maćkowiak, N. Velikite  Requires cookie*   Title
 Influence of the rf Field Inhomogeneity on Nutation NQR Spectra of Spin 3/2 Nuclei in Powders    Abstract
 The influence of the rf field inhomogeneity on the NQR nutation spectra of spin / = 3/2 nuclei in powder samples is investigated. To eliminate the rf field inhomogeneity effects, a method of reconstruction of the NQR nutation spectra, based on finding the deconvolution of the Fourier nutation spectrum with a function of the rf field distribution, is used. The method is successfully demonstrated for simulated and experimental NQR nutation spectra of 35 C1 in TiCl 4 . The lineshape analysis of reconstructed nutation spectra allowing the determination of the EFG asymmetry parameter is given. The real advantage of the proposed method is that the highresolution nutation spectrum may be obtained for a sample filling up the entire coil.   
Reference
 Z. Naturforsch. 54a, 153—158 (1999); received November 24 1998   
Published
 1999   
Keywords
 Nuclear Quadrupole Resonance, 2D Nutation Spectroscopy, Electric Field Gradient Tensor   
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 ZNA199954a0153    Volume
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20  Author
 F. Ucun, A. Sağlam, F. Köksal, S. Bahçeli  Requires cookie*   Title
 An EPR Study of Mo 5+ Introduced into NaY Zeolites by SolidState Reactions    Abstract
 By means of an EPR investigation of Mo 5+ ions introduced into NaY zeolites by solidstate reactions, the location and coordination of Mo 5+ in zeolites were investigated. Two different locations, free and distorted tetrahedral, were found. The molecular orbital coefficient, ß 2 , and the effective charge, Q, for the MO 5+ ions in a distorted tetrahedral structure were calculated and interpreted.   
Reference
 Z. Naturforsch. 54a, 159—161 (1999); received December 2 1998   
Published
 1999   
Keywords
 EPR, Zeolite, Mo 5+, NaY   
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