Go toArchive
Browse byFacets
Bookbag ( 0 )
Facet   section ZfN Section A:Volume 044  [X]
Facet   Publication Year 1989  [X]
Results  196 Items
Sorted by   
Publication Year
1989[X]
41Author    K.A K Ebraheem, S. T. Hamdi, A. R. Al-DerziRequires cookie*
 Title    M I N D  
 Abstract    O / 3 In v e s tig a tio n o f th e S tr u c tu r e o f th e I n tr a m o le c u la r ly H y d r o g e n B o n d e d E n o l F o rm s o f 2 -T rif lu o r o a c e ty lc y c lo a lk a n o n e s MINDO/3 SCF-MO calculations with full geometry optimization were performed to determine the structure of the intramolecularly hydrogen bonded enol forms of 2-trifluoroacetylcycloalkanones. The presence of two stable exocyclic and endocyclic enol forms with a non-planar unsymmetric hydrogen bonded chelate ring is established. It is found that the intramolecular hydrogen bond is weaker in the exocyclic enol of 2-trifluoroacetylcyclopentanone, which showed greater deviation from planarity by ~23.8°. The geometrical features predicted by the MINDO/3 method and the calculated charge distribution are discussed and found to agree with the available experimental data on these systems. The merits and limitations of the MINDO/3 method are discussed. 
  Reference    Z. Naturforsch. 44a, 239—242 (1989); received January 18 1989 
  Published    1989 
  Keywords    MINDO/3 Calculations, Fluorinated /?-Diketones, Enol forms, Intramolecular H-bond 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0239.pdf 
 Identifier    ZNA-1989-44a-0239 
 Volume    44 
42Author    F. WinterbergRequires cookie*
 Title      
 Abstract    The cause of the phenomenon of self-focusing of intense laser radiation in solids is the nonlinear inten­ sity dependent refractive index [1] n = nl + n 2E2, (1) 
  Reference    Z. Naturforsch. 44a, 243—244 (1989); received January 11 1989 revised version. 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0243.pdf 
 Identifier    ZNA-1989-44a-0243 
 Volume    44 
43Author    Einar Uggerud, PeterJ. DerrickRequires cookie*
 Title    Mechanism of Energy Transfer in Collisional Activation of Kiloelectron-Volt Macromolecular Ions  
 Abstract    An impulsive collision theory explains why helium is an effective target gas for collisionally activated decomposition of large biological ions. 
  Reference    Z. Naturforsch. 44a, 245—246 (1989); received December 9 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0245_n.pdf 
 Identifier    ZNA-1989-44a-0245_n 
 Volume    44 
44Author    Jürgen ParisiRequires cookie*
 Title    Wolfgang Buck Physikalisch-Technische Bundesanstalt, Institut Berlin  
 Abstract    On a very short time scale, breakdown of superconductivity with increasing transport current turns out to be a highly dynamical process, called "current-induced resistive state". Magnetic flux domains rapidly move perpendicular to the direction of the transport current applied, with in­ creasing velocity as the current is further increased. At sufficiently high currents, superconductivity is completely destroyed, and the sample ends up in the normal state. In this paper, the first time-resolved measurements of voltage signals induced by the motion of single flux domains are reported. A stability analysis of the superconducting state based on the "Gibbs free energy barrier model" describes the temporal voltage profile generated by a single flux domain, which is solitarily moving across the sample cross-section, as well as the superimposed signals of a series of competing domains, existing simultaneously in the sample. In the latter case, the interaction among the flux domains is taken into account by a monopole ansatz. Studying the onset of the breakdown of superconductivity in type I materials, an oscillatory behavior of the domain size was found. After a few periods, these transients change into a stationary number of flux quanta per domain. T e m p o ra l B e h a v io r o f th e B re a k d o w n o f S u p e rc o n d u c tiv ity 
  Reference    Z. Naturforsch. 44a, 247—256 (1989); received January 4 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0247.pdf 
 Identifier    ZNA-1989-44a-0247 
 Volume    44 
45Author    Slawomir Blonski, Czeslaw BojarskiRequires cookie*
 Title     
 Abstract    o n te C a r lo S im u la tio n o f E le c tro n ic E x c ita tio n M ig r a tio n a n d T ra p p in g in D is o rd e re d T w o -C o m p o n e n t S y s te m s . A C o m p a ris o n w ith A n a ly tic a l T h e o r ie s Monte Carlo simulations of quantum yield and anisotropy of fluorescence in two-component systems have been conducted with various donor and acceptor concentrations and Förster radii ratios a/RqD. The influence of excitation migration and trapping on the fluorescence of the viscous solution has been considered. The results of the simulations have shown that steady-state fluorescen­ ce of a two-component system depends on the R°x/RqD ratio as predicted in LAF theory. 
  Reference    Z. Naturforsch. 44a, 257—261 (1989); received February 3 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0257.pdf 
 Identifier    ZNA-1989-44a-0257 
 Volume    44 
46Author    H. StumpfRequires cookie*
 Title     
 Abstract    o r m a liz a tio n a n d P r o b a b ility D e n s itie s f o r W a v e fu n c tio n s o f Q u a n tu m F ie ld th e o re tic E n e rg y E q u a tio n s Quantum fields can be characterized by the set of transition amplitudes {<0|7r(j/)|a>, V|a> e where n(s/) is a representation of the field operator algebra in ir. This set has to satisfy renormalized energy equations and the elements of this set are called wavefunctions. However, these wavefunctions are not identical with wavefunctions of conventional quantum theory in Fockspace. Thus a theoret­ ical interpretation is needed. In the present paper, by means of some theorems a method of normal­ ization and construction of probability densities for these wavefunctions is given, which differs from the method of derivation of the normalization condition for Bethe-Salpeter amplitudes. The method can be applied both to nonrelativistic and relativistic fields with positive definite or indefinite state spaces, provided the renormalized energy equations possess finite solutions. PACS 11.10: Field theory; PACS 12.10 Unified field theories and models. 
  Reference    Z. Naturforsch. 44a, 262—268 (1989); received January 25 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0262.pdf 
 Identifier    ZNA-1989-44a-0262 
 Volume    44 
47Author    H. Kleindienst, M. Wolpers, D. FilbergRequires cookie*
 Title     
 Abstract    n e rg ie -u n d V a ria n z m in im ie ru n g u n te r V erw e n d u n g k o r r e lie r te r W e lle n fu n k tio n e n Minimization of the Energy and the Variance Using Correlated Wave-Junctions The influence of an additive correlation term in the wave-function on the energy and the variance is discussed for the example of He-atom. Furthermore, a correlated orbital like Ansatz is tested for this case. 
  Reference    Z. Naturforsch. 44a, 269—272 (1989); eingegangen am 22. Dezember 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0269.pdf 
 Identifier    ZNA-1989-44a-0269 
 Volume    44 
48Author    B. H. Lavenda, W. FigueiredoRequires cookie*
 Title     
 Abstract    n th e L a w o f E q u ip a r titio n f o r T r a n s la tio n a l M o tio n o f E x c ite d M o le c u le s in E q u ilib riu m w ith T h e r m a l R a d ia tio n Einstein's radiation theory consists of two parts: the derivation of Planck's radiation law from a physical mechanism of absorption and emission of radiation by excited molecules that are in thermal equilibrium with the radiation field and a demonstration of the validity of the law of equipartition of energy for the translational motion of the molecules. Several incongruities are observed: Einstein could not have legitimately substituted back into his dynamical equilibrium condition, valid at any finite temperature, a limiting condition between the coefficients of absorption and stimulated emis­ sion that he obtained in the high temperature limit. His justification of the law of equipartition involves, on the one hand, treating the motion of the excited molecule as brownian motion while, on the other hand, employing special relativity to obtain an expression for the diffusion coefficient. In the former the velocity of the molecule is a stochastic variable while in the latter it is a uniform velocity. Hence equipartition does not hold for the translational motion. 
  Reference    Z. Naturforsch. 44a, 273—277 (1989); received November 22 1988 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0273.pdf 
 Identifier    ZNA-1989-44a-0273 
 Volume    44 
49Author    A. B. Vassilikou-Dova, K. Eftaxias, G. LehmannRequires cookie*
 Title      
 Abstract    In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed. An activation energy of 215 kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents. 
  Reference    Z. Naturforsch. 44a, 278—282 (1989); received February 17 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0278.pdf 
 Identifier    ZNA-1989-44a-0278 
 Volume    44 
50Author    Raimund Quint, RuthMaria Quint, Nikola Getoff, Tsvetan Gantchev, Maria ShopovaRequires cookie*
 Title     
 Abstract    n d P h o to fr in I I in P o l a r a n d M ic ro h e te ro g e n e o u s E n v iro n m e n t Hematoporphyrin (HP) and its derivatives (HPD; e.g. photofrin II) are used as efficient sensitizers in the photodynamic treatment of tumors. The photoinduced formation of various transients result­ ing from these substrates at pH 12 and 7.4 were studied by conventional flash photolysis and by ESR techniques in the presence of various additives. EDTA is acting as an efficient reducing agent for the triplet state of the substrates. The absorption spectra of some transients (HP--, HP —OH, HPD'", HPD —OH) were obtained. Further, ESR studies (pH 4-7) showed that 3HP is mostly converted into HP' -in the presence of EDTA, but this is not the case with 3HPD. In airfree HPD solutions a longlived transient was registered, which was attributed to HPD'+ species. In aerated substrate solutions the singlet oxygen (0 2) and peroxyradicals are formed. The discussed transients very likely are involved in the photodynamic treatment of tumors in man. F la s h P h o to ly s is a n d E S R S tu d ie s on H e m a to p o r p h y rin 
  Reference    Z. Naturforsch. 44a, 283—290 (1989); received January 24 1989 
  Published    1989 
  Keywords    Hematoporphyrin (HP), Hematoporphyrin derivatives (HPD), Flash Photolysis, ESR, Free radicals 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0283.pdf 
 Identifier    ZNA-1989-44a-0283 
 Volume    44 
51Author    W. H. Stolze, D. H. Sutter, C. WentrupRequires cookie*
 Title     
 Abstract    o n firm a tio n o f th e E le c tric F ie ld G r a d ie n ts a t th e N itro g e n N u c le i in N -C y a n o m e th a n im in e , C H 2N C N , fro m L o w -/ R o ta tio n a l T ra n s itio n s The results of a high resolution microwave study of low-J rotational transitions of N-cyano-methanimine are reported. The 14N quadrupole coupling constants fitted to the observed hyper­ fine splittings are: xaa (imine) = 2.032(9) MHz, / fcfc(imine) = —4.586(7) MHz, and / aa(nitrile) = -3.254(8) MHz, / fcfc(nitrile) = 0.844(16) MHz. Knowledge of these constants together with the rotational constants and centrifugal distortion constants determined earlier provides the basis for accurate prediction of hitherto unmeasured rotational transitions for radioastronomy. 
  Reference    Z. Naturforsch. 44a, 291—294 (1989); received February 6 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0291.pdf 
 Identifier    ZNA-1989-44a-0291 
 Volume    44 
52Author    R. Zamboni, D. Schweitzer, H. J. KellerRequires cookie*
 Title    F T -I R A  
 Abstract    b s o rp tio n S p e c tr a o f P o ly c ry s ta ü in e P re s s e d S a m p le s o f th e O r g a n ic M e ta ls a n d S u p e r c o n d u c to rs a -, /? - IR absorption spectra of polycrystalline pressed samples of the organic metals a-(BEDT-TTF)2I3, /?-(BEDT-TTF)2I3 and (BEDT-TTF)2Cu(NCS)2 are presented and discussed. Normal protonated as well as deuterated materials were studied. The spectra range from 400 cm"1 to 5000 cm"1 and are similar to the IR reflectance spectra reported ealier. The data are of special interest in view of the fact that recently bulk superconductivity was observed in such polycrystalline samples of organic metals, and therefore the application of organic superconductors for the preparation of electronic devices seems possible. 
  Reference    Z. Naturforsch. 44a, 295—299 (1989); received February 18 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0295.pdf 
 Identifier    ZNA-1989-44a-0295 
 Volume    44 
53Author    Yutaka Tai, Tetsuo Asaji, Ryuichi Ikeda, Daiyu NakamuraRequires cookie*
 Title    in  
 Abstract    P y rid in iu m H e x a c h lo r o te llu r a te (I V) , H e x a c h lo r o s ta n n a te (I V) , a n d H e x a b r o m o s ta n n a te (I V) C r y s ta ls a s S tu d ie d The 'H NMR second moment M2 and the spin-lattice relaxation time T, are determined for pyridinium hexachlorotellurate(IV), hexachlorostannate(IV), and hexabromostannate(IV) at various temperatures above ca. 140 K. The phase transition temperatures already reported from halogen NQR experiments are determined as 272, 331, and 285 K, respectively, by differential thermal analysis (DTA). The DTA as well as differential scanning calorimetry measurements show that the above phase transitions are of second-order. For pyridinium hexachlorotellurate(IV) and hexa-bromostannate(I V), a sharp 'H T, dip was observed at the transition temperature. This is interpreted in terms of a phenomenon related to the critical fluctuation of an order parameter. From the measurements of 'H M2, 60° two-site jumps (60c flips) around the pseudo C6 axis of the cation are suggested to occur in the high temperature phases of the complexes. Modulation of X...'H (X = CI, Br) magnetic dipolar interactions due to the reorientational motion of the complex anions is considered as a possible relaxation mechanism in the high temperature phases. S t r u c t u r a l P h a s e T ra n s itio n s a n d Io n ic M o tio n s 
  Reference    Z. Naturforsch. 44a, 300—306 (1989); received January 21 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0300.pdf 
 Identifier    ZNA-1989-44a-0300 
 Volume    44 
54Author    Gottfried Köhler, Nikola Getoff, Maria Shopova, Tsvetan GantchevRequires cookie*
 Title     
 Abstract    n d D ih e m a to p o rp h y rin E th e r (E s te r) in H o m o g e n e o u s a n d M ic ro h e te ro g e n e o u s E n v iro n m e n ts Excitation wavelength effects on hematoporphyrin (HP) and hematoporphyrin derivative (HPD, Photofrin II) fluorescence spectra, quantum yields and decays were comparatively studied in homo­ geneous (at different pH and substrate concentrations) and microheterogeneous (Triton X 100 micelles and Bovine serum albumin) aqueous environments, in which the porphyrins are expected to be present in different monomer/aggregate equilibria. The observed wavelength dependences of the fluorescence yield and of short lived contributions to the total fluorescence do not correlate to the porphyrin aggregation state obtained from absorption spectra. In micro-heterogeneous environ­ ment the influence of local interactions between the porphyrin and hydrophobic sites of the cosolutes on HP and HPD photophysics is demonstrated. P h o to p h y s ic a l P r o p e r tie s o f H e m a to p o r p h y r in 
  Reference    Z. Naturforsch. 44a, 307—312 (1989); received February 7 1989 
  Published    1989 
  Keywords    Hematoporphyrine, Hematoporphyrine derivative Fluorescence, Fluoroscence life­ time, Environmental effects 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0307.pdf 
 Identifier    ZNA-1989-44a-0307 
 Volume    44 
55Author    Ulrich Magg, Helmut Birk, K.P R Nair, Harold JonesRequires cookie*
 Title      
 Abstract    To Professor Helmut Dreizler on the Occasion of his 60 th Birthday The infrared absorption spectrum of the gas phase IF molecule in its ground state has been observed for the first time, using a diode laser spectrometer. The wavenumbers of transitions in the v — \ «-0, and v — 2 «-1 bands have been measured with a nominal accuracy of +0.001 cm"1. These data were fitted along with the recently published microwave spectrum to produce an improved set Dunham T-parameters. Also the coefficients of the Dunham potential function for the electronic state of IF were determined by a direct fit to the experimental data. 
  Reference    Z. Naturforsch. 44a, 313—315 (1989); received February 11 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0313.pdf 
 Identifier    ZNA-1989-44a-0313 
 Volume    44 
56Author    G. Gassler, B. Reißenauer, W. HüttnerRequires cookie*
 Title     
 Abstract    u n a b le D io d e L a s e r S p e c tr a a n d A s s ig n m e n t o f th e 7 4 8 c m -1 B a n d o f P r o p a n e The rotational structure of the 748 cm"1 otype CH2-rocking fundamental of propane was analysed using tunable diode laser (TDL) techniques. On grounds of a low-resolution Fourier transform (FTIR) spectrum and of the known ground-state rotational and centrifugal-distortion constants, some 700 transitions were measured and assigned in several regions of the band. The upper-state constants determined in this way allow the prediction of rovibrational frequencies to within 0.003 cm""1, covering quantum states up to J = 50 and Ka = 20. The band appears un­ perturbed. 
  Reference    Z. Naturforsch. 44a, 316—324 (1989); received February 18 1989 
  Published    1989 
  Keywords    Propane, Diode laser spectra, Excited state, Rotational constants, Centrifugal distortion constants 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0316.pdf 
 Identifier    ZNA-1989-44a-0316 
 Volume    44 
57Author    H. TassoRequires cookie*
 Title    An Improved Estimate of the "Attractive Region" and Modelling of Fluctuation Spectra  
 Abstract    A previous estimate made by the author for the attractive region of a system of van der Pol-like oscillators is now improved. It leads to a richer class of attracting systems whose statistics generates a larger class of fluctuation spectra. 
  Reference    Z. Naturforsch. 44a, 325—326 (1989); received March 3 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0325_n.pdf 
 Identifier    ZNA-1989-44a-0325_n 
 Volume    44 
58Author    WarrenH. InskeepRequires cookie*
 Title    On Electromagnetic Spinors and Electron Theory  
 Abstract    spinor are also related by (ff-jr)f = 0, which will prove useful below. Let us define the fields Notizen The relationship between the Dirac theory and electro­ magnetic spinors is extended to the case of finite mass. Cer­ tain products of the electromagnetic fields give rise to the Dirac differential operator upon the usual subsitutions for the energy and momentum. By placing mass in the proper place for the wave mechanical approach to quantum theory, the algebra of the fields, interpreted as quantum operators, may be deduced. 
  Reference    Z. Naturforsch. 44a, 327 (1989); received February 23 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0327_n.pdf 
 Identifier    ZNA-1989-44a-0327_n 
 Volume    44 
59Author    O. E. Rössler, J. Becker, M. Hoffmann, W. NadlerRequires cookie*
 Title    Fermi Gas Like Hypothesis for Fleischmann-Pons Experiment  
 Abstract    Pauli repulsion, which is stronger than Coulomb repulsion, is absent in a gas of bosons. Coulomb repul­ sion is absent in a gas of fermions whose two Fermi seas are at a low relative temperature (like the free electron gas in a cold metal). To explain Fleischmann-Pons [1] cold fusion, it would suffice to assume that the deuterium nuclei dis­ solved in the palladium crystal, which are spin-1 bosons, nevertheless show an absence of Coulomb 
  Reference    Z. Naturforsch. 44a, 329 (1989); received April 14 1989 
  Published    1989 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0329_n.pdf 
 Identifier    ZNA-1989-44a-0329_n 
 Volume    44 
60Author    W. A. Kreiner, H. Prinz, G. MagerlRequires cookie*
 Title    D a s L a s  
 Abstract    e r -S e ite n b a n d v e r f a h r e n : I R -S p e k tr o s k o p ie m it M ik ro w e lle n g e n a u ig k e it Diese Arbeit ist Herrn Professor Helmut Dreizler am Institut für Physikalische Chemie der Univer­ sität Kiel aus Anlaß seines sechzigsten Geburtstags gewidmet. Herr Dreizler hat mir als einer der ersten die Idee vermittelt, die ursprünglich so unterschiedlichen Methoden der Mikrowellen und des Infraroten spektroskopisch als Einheit zu sehen. Dafür möchte ich ihm danken. W . A. Kreiner Infrared spectroscopy with laser sidebands at microwave modulation frequencies Infrared spectroscopy with laser sidebands at microwave modulation frequencies (12 18 GHz) is described. After the basics of this technique several examples of saturation spectroscopy on gaseous molecules are given. As a result it is shown that, in the infrared between 900 and 1100 cm" \ this broadband tunable laser source achieves resolution (3 parts in 109) as well as absolute accuracy in frequency measurement (± 3 x 10~6 cm-1) which are comparable to microwave spectroscopy. 
  Reference    Z. Naturforsch. 44a, 330—336 (1989); eingegangen am 6. Februar 1989 
  Published    1989 
  Keywords    Infrared beam modulator, laser spectroscopy, saturation dips Stark effect, double resonance 
  Similar Items    Find
 DEBUG INFO      
 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0330.pdf 
 Identifier    ZNA-1989-44a-0330 
 Volume    44 
Prev
1
2
3
4
5
...
Next