| | 2 | Author
| Berthold-Georg Englert | Requires cookie* | | | Title
| Remarks on Some Basic Issues in Quantum Mechanics  | | | | Abstract
| Two-way interferometers with which-way 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; Einstein-Podolsky-Rosen correlations; statistical operators and the as-if realities associated with them; quantum erasure; Schrödinger's cat; and, finally, wave-particle duality. | | | |
Reference
| Z. Naturforsch. 54a, 11—32 (1999); received October 26 1998 | | | |
Published
| 1999 | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0011.pdf | | | | Identifier
| ZNA-1999-54a-0011 | | | | Volume
| 54 | |
| 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 am-plification without population inversion. The similarities and differences between the two model schemes, namely, A and V-type, are emphasized. A coherent radiation field, on one hand, which drives one of the lasing levels, yields the quantum mechanical two paths via Autler-Townes 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/ZNA-1999-54a-0033.pdf | | | | Identifier
| ZNA-1999-54a-0033 | | | | Volume
| 54 | |
| 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 Jaynes-Cummings 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 Jaynes-Cummings 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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| default:Reihe_A/54/ZNA-1999-54a-0039.pdf | | | | Identifier
| ZNA-1999-54a-0039 | | | | Volume
| 54 | |
| 6 | Author
| Michael Fleischhauer, Oliver Veits | Requires cookie* | | | Title
| Long-time Dynamics of Spontaneous Parametric Down-conversion and Quantum Limitations of Conversion Efficiency | | | | Abstract
| We analyze the long-time quantum dynamics of degenerate parametric down-conversion from an initial sub-harmonic vacuum (spontaenous down-conversion). Standard linearization of the Heisen-berg 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 mean-field 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 2-mode Schrödinger equation using a dynamically optimized basis of displaced and squeezed number states verifies the characteristic times predicted by the mean-field approximation. In contrast to semiclassical and mean-field predictions it is found that quantum fluctuations of the pump mode lead to a substantial limitation of the efficiency of parametric down-conversion. | | | |
Reference
| Z. Naturforsch. 54a, 57—6265 (1999); received June 25 1998 | | | |
Published
| 1999 | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0057.pdf | | | | Identifier
| ZNA-1999-54a-0057 | | | | Volume
| 54 | |
| 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 time-dependent 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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| default:Reihe_A/54/ZNA-1999-54a-0063.pdf | | | | Identifier
| ZNA-1999-54a-0063 | | | | Volume
| 54 | |
| 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 neutron-star 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 Hartree-or Hartree-Fock approximation. The obtained couplings are also in satisfactory agreement with hypernuclei data in the relativistic Hartree scheme. Within the relativistic Hartree-Fock 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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| default:Reihe_A/54/ZNA-1999-54a-0077.pdf | | | | Identifier
| ZNA-1999-54a-0077 | | | | Volume
| 54 | |
| 9 | Author
| K. Strobel, F. Weber, M. K. Weigel | Requires cookie* | | | Title
| Symmetrie and Asymmetrie Nuclear Matter in the Thomas-Fermi Model at Finite Temperatures | | | | Abstract
| The properties of warm symmetric and asymmetric nuclear matter are investigated in the frame of the Thomas-Fermi approximation using a recent modern parameterization of the effective nucleon-nu-cleon interaction of Myers and Switecki. Special attention is paid to the liquid-gas phase transition, which is of special interest in modern nuclear physics. We have determined the critical temperature, crit-ical density and the so-called 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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| default:Reihe_A/54/ZNA-1999-54a-0083.pdf | | | | Identifier
| ZNA-1999-54a-0083 | | | | Volume
| 54 | |
| 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 non-superconduction corresponds to the tetragonal to orthorhombic structural tran-sition 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 be-havior 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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| default:Reihe_A/54/ZNA-1999-54a-0095.pdf | | | | Identifier
| ZNA-1999-54a-0095 | | | | Volume
| 54 | |
| 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 water-dimethylformamide (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 6-12 Lennard-Jones pairwise potential plus a Coulomb term. The TIP4P model was used for simulating water molecules, and a six-site model previously optimised by us was used to represent DMF. The potential energy for the water-DMF interaction was obtained via standard geometric combining rules using the original potential parameters for the pure liquids. The radial distribution functions calculated for water-DMF 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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| default:Reihe_A/54/ZNA-1999-54a-0110.pdf | | | | Identifier
| ZNA-1999-54a-0110 | | | | Volume
| 54 | |
| 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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| default:Reihe_A/54/ZNA-1999-54a-0117.pdf | | | | Identifier
| ZNA-1999-54a-0117 | | | | Volume
| 54 | |
| 15 | Author
| Thomas Wieder | Requires cookie* | | | Title
| A Generalized Debye Scattering Formula and the Hankel Transform | | | | Abstract
| The diffracted intensity of an x-ray 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
| X-ray Scattering, Debye Formula, Hankel Transform | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0124.pdf | | | | Identifier
| ZNA-1999-54a-0124 | | | | Volume
| 54 | |
| 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 Dunham-type 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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| default:Reihe_A/54/ZNA-1999-54a-0131.pdf | | | | Identifier
| ZNA-1999-54a-0131 | | | | Volume
| 54 | |
| 17 | Author
| H. Klein, E. Klisch, G. Winnewisser | Requires cookie* | | | Title
| Rotational Spectra of Phosphorus Monosulfide up to 1 THz | | | | Abstract
| The submillimeter-wave 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 fre-quency 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 yl-doubling 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 P-atom 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 fine-structure constants A, 7, D 1 , the parameters for the yl-doubling 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 rotation-constant Ci were obtained for the first time. | | | |
Reference
| Z. Naturforsch. 54a, 137—145 (1999); received November 21 1998 | | | |
Published
| 1999 | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0137.pdf | | | | Identifier
| ZNA-1999-54a-0137 | | | | Volume
| 54 | |
| 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 in-formation 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 self-replicating 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 Gray-Scott model. The growing concentration of parasites will kill the system, and the cooperative Gray-Scott 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, Reaction-Diffusion, Molecular Evolution, Parasites, Coevolution, Cooperation | | | |
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| default:Reihe_A/54/ZNA-1999-54a-0146.pdf | | | | Identifier
| ZNA-1999-54a-0146 | | | | Volume
| 54 | |
| 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 high-resolution 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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| default:Reihe_A/54/ZNA-1999-54a-0153.pdf | | | | Identifier
| ZNA-1999-54a-0153 | | | | Volume
| 54 | |
| 20 | Author
| F. Ucun, A. Sağlam, F. Köksal, S. Bahçeli | Requires cookie* | | | Title
| An EPR Study of Mo 5+ Introduced into NaY Zeolites by Solid-State Reactions | | | | Abstract
| By means of an EPR investigation of Mo 5+ ions introduced into NaY zeolites by solid-state 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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| | | | | TEI-XML for
| default:Reihe_A/54/ZNA-1999-54a-0159.pdf | | | | Identifier
| ZNA-1999-54a-0159 | | | | Volume
| 54 | |
|
