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1982[X]
41Author    Günter Gauglitz, Alwin Lorch, Dieter OelkrugRequires cookie*
 Title    Fluorescence Quantum Yields of Laser Dyes Determined by On-Line Computer Evaluation  
 Abstract    The determination of relative fluorescence quantum yields has been improved to better than 3% precision by use of a multichannel analyzer and an on-line desk-top computer. The new combined device for data acquisition and handling as well as a new correction procedure are de-scribed. Drifts of excitation source and dark current can be omitted. The yields for laser dyes, emitting at short wavelengths, are presented in dependence on excitation wavelength. These results simplify the optimal choice of the pump conditions of laser dyes, which usually are not photostable. 
  Reference    Z. Naturforsch. 37a, 219—223 (1982); received February 15 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0219 
 Volume    37 
42Author    M. Christahl, J. ThönnissenRequires cookie*
 Title    Exzeßenthalpien und Solvatationsverhalten der Systeme LiBr/Methanol, ZnBr2/Methanol und LiBr/ZnBr2/Methanol  
 Abstract    The excess enthalpy reaction of solvatation of the systems Li Br I Methanol, Zn Br 2/Methanol, and Li Br/Zn Br 2/Methanol For the binary systems LiBr/methanol and ZnBr2/methanol as well as for the ternary system LiBr/ZnBr2/methanol the integral enthalpies of mixing are experimentally determined. The mixing of LiBr and methanol is more exothermic than in the case of ZnBr2. The excess enthalpy is largest for the ternary system. From the mathematical approximation of experimental data the differential enthalpies of solution and of dilution are obtained. In the discussion it is con-cluded that in diluted solutions the salts are surrounded by a strongly coordinated inner solvation sphere (coordination number N — 4) and a less coordinated outer solvation sphere (N = 6) resulting in a total solvation number of N = 10. 
  Reference    Z. Naturforsch. 37a, 224—231 (1982); eingegangen am 8. Januar 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0224 
 Volume    37 
43Author    Iv, Horacio Grinberg, Julio Marañon, OscarM. SorarrainRequires cookie*
 Title    Molecular Orbital Theory of the Electronic Structure of Organic Compounds A CNDO/S-CI SCF MO Study on the Lower Electronic States of Large Molecules. Singlet-triplet Transitions of Dioxodiazacycloalkanes  
 Abstract    The semiempirical molecular orbital CNDO/S-CI spectral parameterization has been used to elucidate the lower triplet electronic states of a series of dioxodiazacycloalkanes. The l 3 B2(no-T*) and l 3 A2 (no-T*) triplet spectroscopic states involve intramolecular charge transfer from the oxygen to the carbon atom of the carbonyl group, which is supported by electron density cal-culations of these excited states. The solvation energy was incorporated in the calculations. 
  Reference    Z. Naturforsch. 37a, 232—237 (1982); received October 22 1981 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0232.pdf 
 Identifier    ZNA-1982-37a-0232 
 Volume    37 
44Author    K. H. Stephan-Rossbach, F. J. ComesRequires cookie*
 Title    Superfluorescence from Chemically Pumped Iodine Molecules  
 Abstract    Stimulated emission from chemically formed excited iodine molecules has been observed. The emission originates from the vibrational state v' — 55 of /2(B 3 /7). The excited molecules are pro-duced by a three body recombination reaction. In 1938 Porret and Goodeve [1] suggested that dissociation of methyl iodide by ultraviolet light results in formation of iodine atoms mostly in an excited state. The resulting population inversion of atomic iodine states was subsequently success-fully utilized by Kasper and Pimentel [2] to produce stimulated 1315 nm infrared emission. Later studies [3, 4] showed that particularly high inversion occurs in the dissociation of perfluorinated alkyl iodides. Another important factor contributes to the high laser amplification in these systems: the excited iodine atoms in the 2 PI/2 state exhibit a very low deactivation rate in collisions with the parent molecules. Measurements of the effective lifetime of excited iodine atoms in the presence of per-fluorinated alkyl iodides [5, 6] showed this to be almost equal to the natural lifetime under the ex-perimental conditions. In 1979 Stephan and Comes [7] discussed a chemiluminescence occurring during the photolysis of W-C3F7I; the effect was attributed to the recom-bination of two iodine atoms, one of them in the excited 2 PI/2 state: 
  Reference    Z. Naturforsch. 37a, 238—240 (1982); received February 15 1982 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0238.pdf 
 Identifier    ZNA-1982-37a-0238 
 Volume    37 
45Author    MichaelC. BöhmRequires cookie*
 Title    The Validity of the Hartree-Fock (HF) Picture in Diamagnetic Binuclear Transition Metal Compounds: trans[(y) 5 -C5H5)Fe(CO)2]2  
 Abstract    The Thouless instability conditions in the binuclear iron complex 1 have been investigated by means of a semiempirical INDO approach. The behaviour of the restricted Hartree-Fock (HF) wave function with respect to singlet, non-singlet and complex variations of the orbitals is studied. The existence of a spin decoupled solution near the diamagnetic closed shell groundstate is de-monstrated. The nature of the correlation processes (angular vs left-right) for the various orbital fluctuations is discussed. 
  Reference    Z. Naturforsch. 37a, 241—247 (1982); received February 4 1982 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0241.pdf 
 Identifier    ZNA-1982-37a-0241 
 Volume    37 
46Author    Ivan GutmanRequires cookie*
 Title    Topological Resonance Energy of Linear Polyaeenes  
 Abstract    A method for computation of the topological resonance energy (TRE) of linear polyaeenes is described. When the length of the polyacene chain increases, TRE tends to 0.02 ß units per 71-electron, contrary to a previous prediction [1]. The ionization potential and the energy of the p-band of linear polyaeenes are found to be excellently correlated with TRE. In a recent paper [1] the topological resonance energy of very large (infinitely large) benzenoid hydrocarbons has been estimated using a semi-empirical two-parameter topological formula TRE = fa J/2 n6 (log K)& + b, (1) with riß and K being the number of six-membered rings and the number of Kekule structures, respec-tively, of the corresponding hydrocarbon. In addi-tion, a = 0.3541 and b = 0.0679. The validity of the above equation in the case of small and medium size benzenoid systems (i.e. Wß^lO) has been verified on a large number of examples [2]. On the basis of (1) one concluded [1] that the resonance energy per 71-electron of linear polyaeenes tends to zero w r hen the number of six-membered rings tends to infinity. In the present paper the exact topological resonance energy of linear poly-aeenes will be determined and it will be shown that, contrary to the previous estimate, lim n-> 00 TRE 0.019 (2) This result indicates that one must be rather cau-tious with the application of (1) to very large benzenoid systems. In the present communication we shall fully fol-low the notation and terminology of our previous papers [1, 3], where also further references about TRE can be found. Hence, the topological reso-nance energy will be presented in the form TRE = E 
  Reference    Z. Naturforsch. 37a, 248—250 (1982); received January 28 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0248 
 Volume    37 
47Author    B. N. Cytin, P. Klaeboe, J. C. Whitmer, S. J. CyvinRequires cookie*
 Title    Condensed Aromatics. Part XV. Chrysene  
 Abstract    The in-plane and out-of-plane molecular vibrations of chrysene are analysed. Complete sets of independent symmetry coordinates are constructed. The in-plane vibrational frequencies are calculated both by the simple five-parameter approximation and the method of Califano with collaborators. They show a satisfactory agreement with observed values. Calculated frequencies for the out-of-plane vibrations were obtained from a five-parameter approximation. Mean ampli-tudes of vibration are discussed, and selected values reported. Spectra of chrysene were recorded in Raman and infrared. An almost complete assignment of observed fundamentals was achieved with the aid of the calculated frequencies. 
  Reference    Z. Naturforsch. 37a, 251—258 (1982); received December 18 1981 
  Published    1982 
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 Identifier    ZNA-1982-37a-0251 
 Volume    37 
48Author    I. Gryczyński, A. Kawski, Ch Jung, I. JanićRequires cookie*
 Title    Experimentelle und Quantenchemische Untersuchungen der Dipolmomente von Donator-substituierten 4-Isocyanat-trans- Stilbenen im nichtrelaxierten angeregten Singulettzustand * Experimental and Quantum Chemical Investigations of Dipole Moments of Donor Substituted 4-Isocyanate-trans-stilbene in Relaxationless Excited Singlet State  
  Reference    Z. Naturforsch. 37a, 259—261 (1982); eingegangen am 18. Januar 1982 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0259.pdf 
 Identifier    ZNA-1982-37a-0259 
 Volume    37 
49Author    Jerzv Grzywacz, Stanislawa TasznerRequires cookie*
 Title    Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution  
 Abstract    Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pK*'s values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely. 
  Reference    Z. Naturforsch. 37a, 262—265 (1982); received December 11 1981 
  Published    1982 
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 Identifier    ZNA-1982-37a-0262 
 Volume    37 
50Author    PaulG. Gerber Zfe, F. Hoffmann, -La Roche, Co,. BasleRequires cookie*
 Title    Dielectric Relaxation of Long Molecules in Nematic Host Matrices  
 Abstract    The relaxation times r of the slowest processes in the parallel dielectric permittivity of various nematic guest-host systems have been measured as a function of temperature. A correlation between r and its temperature dependence is found, indicating increasing temperature dependence for increasing T, independent of structural details of the guest molecules or properties of the host matrices which, however, had similar clearing temperatures. Alternations in r for a homol-ogous series of guest molecules are observed. Increasing host permittivity leads to increased values of r while the viscous properties of the host show little influence on r. 
  Reference    Z. Naturforsch. 37a, 266—270 (1982); received January 8 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0266 
 Volume    37 
51Author    R. Kadibelban, R. Ahrens-Botzong, P. HessRequires cookie*
 Title    Low Temperature Vibrational Relaxation of Gaseous CF3CI, CF3Br, CHF2C1, and CH3Cl  
 Abstract    Ultrasonic absorption measurements are reported for gaseous CF3CI, CFsBr, CHF2CI, and CH3CI between room temperature and the lower temperatures 163 K, 193 K, 198 K, and 213 K, respectively. Starting from a statistical point of view, the relaxation behavior is divided into three classes, which are associated with the positive, zero, and negative slope in a log(&) versus 1/T plot. On this basis the vibrational relaxation behavior of CF4, CF3CI, CF3Br, CHF3, CHF2C1, CH3CI, NF3, PF3, and BF3 is discussed especially in the critical temperature to boiling point region. This temperature region is used as a reference for comparing different molecules. 
  Reference    Z. Naturforsch. 37a, 271—276 (1982); received December 11 1981 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0271.pdf 
 Identifier    ZNA-1982-37a-0271 
 Volume    37 
52Author    Joachim Sauer, Günter EngelhardtRequires cookie*
 Title    Relative Stability of 7 AI—O—Al^ Linkages in Zeolites. A Nonempirical Molecular Orbital Study  
 Abstract    Nonempirical quantum chemical ST0-3G calculations were performed for cluster models of two oxygen-bridged T04 tetrahedra (T = Si, Al). The models are based on [(H0)3T0T(0H)3]"-structures and, in case of Al-containing models (n = 1,2), their electric neutrality is ensured by adding positive point charges. The calculations suggest the occurrence of X4.I — O —Al^ pairings provided certain electric fields act at the corresponding sites. 
  Reference    Z. Naturforsch. 37a, 277—279 (1982); received December 29 1981 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0277.pdf 
 Identifier    ZNA-1982-37a-0277 
 Volume    37 
53Author    A. Requardt, F. Hill, G. LehmannRequires cookie*
 Title    A Firmly Localized Hole Center in the Mineral Brazilianite NaAl3(P04)2(0H)4  
 Abstract    A hole center on an oxygen adjacent to one aluminum and one phosphorous was detected and analyzed in natural and X-ray irradiated brazilianite. The slightly anisotropic 27 A1 shfs splitting is larger than in many other hole centers in which the Al is a lower valency impurity ion with only a coordinative bond to an oxygen lone pair. The hole is trapped at an oxygen with particularly long bond distances to one P and two Al. Thus one structural Al must be substituted by a presumably divalent cation of yet unknown nature. No optical absorption is associated with this center, therefore the large distortion of the coordination polyhedra must be responsible for absence of a light-induced hole transfer between different oxygen ions. Com-parison with other systems suggests that the energy differences for other configurations of the hole center are also too high to allow thermal hopping of the hole at or below room temperature. Possible mechanisms for formation and destruction of this center are deduced from experimental results. 
  Reference    Z. Naturforsch. 37a, 280—286 (1982); received February 5 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0280 
 Volume    37 
54Author    G. H. SchleserRequires cookie*
 Title    The Response of C02 Evolution from Soils to Global Temperature Changes  
 Abstract    Own experiments and literature data point at a strong correlation between mineralization processes in soils i.e. the corresponding CO2 release and temperature variations. This seems to be important with regard to the global CO2 problem, since it implies that due to the global temper-ature increase over 80 years (1860—1940) large additional amounts of CO2 were released to the atmosphere. These additional quantities seem to have been at least as important as the anthro-pogenic release of CO2 from the burning of fossil fuels. 
  Reference    Z. Naturforsch. 37a, 287—291 (1982); received November 30 1981 
  Published    1982 
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 Identifier    ZNA-1982-37a-0287 
 Volume    37 
55Author    MyriamS. De Giambiagi, Mario Giambiagi, DarciM S EsquivelRequires cookie*
 Title    Allowance for a Different Pairing of 5-Fluorouracil  
 Abstract    A different pairing of 5-fluorouracil with adenine and guanine is proposed; this pairing may contribute to ex-plain its mutagenic effect. IEHT charges and bond indices support the assumption. The effect of 5-fluorouracil (5FU) incorporation into RNA has since long been pondered on [1]. There exists plentiful theoretical and experimental literature about its structure [2], The problem of its mutagenic effect has been approached by con-sidering base pairs involving 5 FU as supermolecules in a CNDO/2 treatment [3]. Since 5FU is always supposed to pair like U, the mutagenic effect has been ascribed to the greater probability of finding 5FU under enol form compared to U, due to its lower [3]. G-5FÜ Pig. 1. Proposed pairing for 5FU with A and G. 
  Reference    Z. Naturforsch. 37a, 292—293 (1982); received January 7 1982 
  Published    1982 
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 Identifier    ZNA-1982-37a-0292_n 
 Volume    37 
56Author    Heinrich Hora, IanB. HoyleRequires cookie*
 Title    Turbulence Limits in Rotating Plasmas for Isotope Separation  
 Abstract    With the aim of using rotating plasmas (driven byjxBorExB forces) for isotope separation, several experimental configurations have been studied and theory has been developed with respect to numerical models, the Alfven ionization limit, D'Angelo's shear instability, while turbulence was suggested qualitatively only. A more detailed study of the limit of laminar flow is presented taking into account the magnetic anisotropy of viscosity and interaction with neutrals. In all cases of experiments, the Reynold's numbers are below critical values of 10 4 by at least a factor 100. The pessimistic conclusions of Boeschoten for his experiment can there-fore not be shared with respect to the turbulence problems. The published cases of isotope separation by rotating plasmas are then discussed extensively. 
  Reference    Z. Naturforsch. 37a, 294—304 (1982); received October 1 1981 
  Published    1982 
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 Identifier    ZNA-1982-37a-0294 
 Volume    37 
57Author    GerhardC. Hegerfeldt, Reinhard ReiboldRequires cookie*
 Title    A New Formula for the Spectral Line Broadening in Plasmas with Application to the Asymmetry of Ly-a  
 Abstract    Some time ago, von Waidenfels [4] derived a systematic series expansion of the exact line shape function in case of a single perturber species. In view of the involved mathematics it re-mained unclear to what physical approximation the first order term of the series corresponds. Here we generalize the approach to two perturber species, one of which is treated quasi-statically (ions), and give a direct physical derivation of the first order term. This term incorporates non-commutativity of ion and electron potentials. In the numerical evaluation for Ly-a it turns out that the noncommutativity effects are washed out to a large extent by the averaging process. 
  Reference    Z. Naturforsch. 37a, 305—315 (1982); received August 31 1981 
  Published    1982 
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 Identifier    ZNA-1982-37a-0305 
 Volume    37 
58Author    Augustine0. Allen, WernerF. SchmidtRequires cookie*
 Title    Determination of the Energy Level V0 of Electrons in Liquid Argon over a Range of Densities  
 Abstract    The energy level Fo of electrons injected into liquid argon was determined over the range of temperatures and densities in which the electron mobility passes through a maximum. A mini-mum in Fo was found, not at the density of the mobility maximum as expected, but at a some-what higher density. 
  Reference    Z. Naturforsch. 37a, 316—318 (1982); received March 13 1982 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0316.pdf 
 Identifier    ZNA-1982-37a-0316 
 Volume    37 
59Author    D. Ploumbidis, G. HüberRequires cookie*
 Title    Electrical Conductivity and NMR-Investigations in the A15-and a-Phase of V-Co Compounds in the High Temperature Range  
 Abstract    The electrical resistivity of the A15-and cx-phase of V-Co compounds has been measured in the temperature range 300 to 1300 K. Its temperature coefficient is found to be positive for the A15-phase, but negative for the cr-phase. For the same compounds we carried out 55 V-and ^Co-Knight shift measurements in the high temperature range (300—HOOK). The 51 V-NMR-line corresponding to the central transition (m = = — J) shows over the entire temperature range the characteristic splitting due to the second-order quadrupole interaction, whereas the 59 Co-NMR-line does not show any splitting. Using these NMR measurements we determined for the A15-phase the isotropic and anisotropic parts of the 51 V-Knight shift, the quadrupole cou-pling constant e^qQIh and the "line width" ZlB. The experimental results are discussed in the frame of models concerning hyperfine field and electric conductivity of transition metals and their alloys. 
  Reference    Z. Naturforsch. 37a, 319—324 (1982); received February 17 1982 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0319.pdf 
 Identifier    ZNA-1982-37a-0319 
 Volume    37 
60Author    E. CzuchajRequires cookie*
 Title    Adiabatic Potentials and Oscillator Strengths of Thallium-Noble Gas Atom Pairs  
 Abstract    Baylis' semiempirical method has been applied for calculating interatomic potentials and oscillator strengths as a function of internuclear separation of the thallium-noble gas systems. The new potentials for the four lowest molecular states of each diatomic have been compared with the corresponding ones deduced by Cheron et al. from the measurement of continuum emis-sion intensities on the extreme wings of the TI resonance lines due to noble gas perturbers. The calculated potentials differ considerably from the latter ones. The molecular oscillator strengths have been calculated for both the allowed and the forbidden TI transitions. The asymptotic values of the first ones are compared with the corresponding atomic oscillator strengths of other calculations and measurements. The agreement is generally quite good. 
  Reference    Z. Naturforsch. 37a, 325—333 (1982); received November 7 1981 
  Published    1982 
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 TEI-XML for    default:Reihe_A/37/ZNA-1982-37a-0325.pdf 
 Identifier    ZNA-1982-37a-0325 
 Volume    37 
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