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1989 (196)
101Author    W. Mühle, J. Krzystek, H.J U C Von Schütz, WolfRequires cookie*
 Title     
 Abstract    rip le t E x c ito n a n d T r a p S t a te s in th e C h a r g e -T r a n s f e r C r y s ta l A n th r a c e n e /T e tr a c h lo r o p h th a lic A n h y d rid e (A /T C P A) Mobile triplet excitons in A/TCPA have been detected from 1.2 to 300 K via ESR and zero-field ODMR. Their features such as linewidth and zero-field-splitting (zfs) parameters arc discussed in terms of the temperature-dependent crystal structure. Between 1.2 and 4.2 K the excitons are caged by barriers. When raising the temperature a thermally activated hopping takes place between two triplet bands separated by 40 cm"1, having different zfs parameters | Z)A | = 2126.5, |£A| = 241.0, | DB | = 2112.5, i E^ | = 238.0 MHz and different zfs tensor orientations. Above 100 K an increase of the librations of the anthracene molecules broadens the homogeneous excitonic lines. The homogeneous linewidth is measured by the free induction decay. The CT character of the triplet state is estimated as 4 t ^ 4%. 
  Reference    Z. Naturforsch. 44a, 610 (1989); received April 19 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0610 
 Volume    44 
102Author    W. Bauhofer, Hj Mattausch, A. SimonRequires cookie*
 Title    D0 ) -H 2  
 Abstract    ie Ä n d e ru n g d e s e le k tris c h e n W id e r s ta n d s bei d e r re v e rs ib le n R e a k tio n G d B r H x G d B r H 2 (0 .6 7 g j c g 1. 28, 1989 + H, The Change of Electrical Resistivity during the Reversible Reaction GdBrH x < > GdBrH2 (0.67^x^1.0) " The electrical resistivity of GdBrHx (0.67 ^ x ^ 1.0) and GdBrH-, has been measured as a function of temperature and environment (H2, vacuum). A two-electrode dc method and a contactless microwave technique were used. Both methods indicate a metal-to-semiconductor transition for the reaction GdBrH <==► GdBrH,. — h2 Key words: GdBrH. Electrical resistivity, Contactless method. Metal-to-semiconductor transition. 1. Einleitung Die Hydrierung von GdBrH^ bzw. die Dehydrie­ rung von GdBrH2 [1] sollte mit einer Änderung der elektrischen Leitfähigkeit verbunden sein [2]. Dies folgt einerseits aus der Vorstellung über die chemische Bindung, nach der Gd3 + Br"H~e" ein delokalisiertes Elektron pro Formeleinheit in einem Gd-Gd-binden-den Band enthält, während Gd3 + Br"(H")2 eine nor­ male ionisch-kovalente Valenzverbindung ist. Zum anderen tritt bei der Reaktion von GdBrHA . (graphit­ artig) zu GdBrH2 (durchsichtig) eine Änderung auf, die einem Metall-Halbleiter-Übergang entspricht. Zur Klärung dieser Frage haben wir die elektrische Leit­ fähigkeit sowohl der beiden Endprodukte, als auch während des Ablaufs der chemischen Reaktionen ge­ messen. Die Messungen wurden grundsätzlich da­ durch erschwert, daß die Proben nur in feinkristalliner Form vorlagen. Unter diesen Voraussetzungen sind nur qualitative Aussagen über die Größenordnung der elektrischen Leitfähigkeit möglich. Zur gegenseiti­ gen Überprüfung und Ergänzung haben wir zwei ver­ schiedene Meßmethoden verwendet. 2. Experimentelle Angaben 2.1. Präparation Die Hydridbromide werden nach [3] aus GdBr3 und GdH2 präpariert. 
  Reference    Z. Naturforsch. 44a, 625—628 (1989); received March 
  Published    1989 
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 Identifier    ZNA-1989-44a-0625 
 Volume    44 
103Author    J. Peinke, J. Parisi, U. Rau, W. Clauß, M. WeiseRequires cookie*
 Title     
 Abstract    h a r a c te r is tic R e la x a tio n T im e s o f L o w -te m p e ra tu re S e m ic o n d u c to r B re a k d o w n K in e tic s The nonlinear transport behavior during low-temperature avalanche breakdown of extrinsic germanium is associated with the self-generated formation of spatio-temporal current structures. Very close to the critical phase transition between different conducting states, the underlying physical relaxation processes develop on relatively slow macroscopic time scales in the ms range. We have evaluated the slowing down of the characteristic time constants from independent measurements of the system response behavior to external pulsed excitations. 
  Reference    Z. Naturforsch. 44a, 629 (1989); received April 28 1989 
  Published    1989 
  Keywords    Semiconductor breakdown, Nonequilibrium phase transition, Structure formation, Nonlinear carrier transport, Relaxation processes 
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 Identifier    ZNA-1989-44a-0629 
 Volume    44 
104Author    S. Dobos, G. Winnewisser, F. Kling, J. MinkRequires cookie*
 Title      
 Abstract    The absorption spectra of carrier free 14C160 2 in the spectral range of 2290-2150 cm"1 by a medium resolution FTIR spectrometer, and the spectral region of 2258 -2229 cm~1 with a high resolution tunable diode laser spectrometer have been recorded. Spectroscopic constants were calculated from the 00° 1 00°0 and Ol'l -Ol'O transitions. Im p ro v e d S p e c tro s c o p ic C o n s ta n ts f o r 14C 160 2 O b ta in e d fro m th e v3 B a n d 
  Reference    Z. Naturforsch. 44a, 633—639 (1989); received May 10 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0633 
 Volume    44 
105Author    S. Dobos, F. Kling, G. Winnewisser, G. KereszturyRequires cookie*
 Title      
 Abstract    The infrared absorption lines of a mixture of 14C2H2 and 12C14CH2 around 725 cm-1 have been recorded with a high resolution (0.04 cm-1) FTIR spectrometer. Rotational structures of P, R and Q branches of the V 5 bands were analyzed and molecular constants v0, B', B", D' and D" calculated. I n f r a r e d S p e c tr a o f 14C 2H 2 a n d 12C 14C H 2: T h e v | B a n d 
  Reference    Z. Naturforsch. 44a, 640—644 (1989); received May 11 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0640 
 Volume    44 
106Author    M. S. El, S. Naschie, Z. Al, NaturforschRequires cookie*
 Title      
 Abstract    The paper discusses the interrelationship between statical chaos and dynamical initial value problems. It is pointed out that approximate homoclinic and heteroclinic solitons can be perturbed to produce spacial asymptotic chaos in some buckled structural elastic systems which constitute strictly speaking boundary value problems. O n th e C o n n e c tio n b e tw e e n S t a t i c a l a n d D y n a m ic a l C h a o s 
  Reference    Z. Naturforsch. 44a, 645—650 (1989); received March 18 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0645 
 Volume    44 
107Author    P. Wolf, W. StahlRequires cookie*
 Title     
 Abstract    h e D e te rm in a tio n o f S p in -R o ta tio n a n d S p in -S p in I n te r a c tio n C o n s ta n ts fro m th e M ic ro w a v e S p e c tr u m o f M e th a n e High sensitivity and resolution of our microwave Fourier transform (MWFT) spectrometer and careful analysis of the measured transients enabled us to determine very accurate spin-rotation and spin-spin interaction constants of methane. In addition we were able to increase the accuracy of the existing centrifugal distortion constants. 
  Reference    Z. Naturforsch. 44a, 651—654 (1989); received April 21 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0651 
 Volume    44 
108Author    Olaf Böttcher, Nils Heineking, DieterHermann SutterRequires cookie*
 Title    4N  
 Abstract    Q u a d r u p o le C o u p lin g in th e R o ta tio n a l S p e c tr a o f C y c lo p ro p y la m in e a n d C y c lo p ro p y l C y a n id e his 65 th Birthday The 14N hyperfine structure in the rotational spectra of cyclopropylamine and cyclopropyl cyanide has been reinvestigated by microwave Fourier transform spectroscopy. The observed quadrupole coupling constants in units of MHz are: .Yfla = 2.3338(18), Xbb = 1.7874(20), Xcc = -4.1209(20) for cyclopropylamine and Xaa= -3.4536(35), Xhh= 1.7468(51), Xcc= 1.7068(51) for cyclopropyl cyanide. 
  Reference    Z. Naturforsch. 44a, 655—658 (1989); received April 24 1989 
  Published    1989 
  Keywords    Cyclopropylamine, Cyclopropyl cyanide, 14N quadrupole coupling 
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 Identifier    ZNA-1989-44a-0655 
 Volume    44 
109Author    Armin Kehrer, Shi-Qi Dou, Alarich WeissRequires cookie*
 Title      
 Abstract    ,8 iB r _ i27j_N q R a n d C r y s ta l s t r u c t u r e o f G ly c y l-l-a la n in e H y d ro b ro m id e M o n o h y d r a te a n d H y d r o io d id e M o n o h y d r a te The crystal structures of glycyl-l-alanine hydrobromide monohydrate, 1, and glycyl-l-alanine hydroiodide monohydrate, 2, were determined and the temperature dependence of the 127I NQR frequencies was investigated in the temperature range 77 ^ T/K ^ 370. The 127I NQR frequencies are strongly influenced by hydrogen bonds and this is proved by the frequency shift of the H D exchange. By deuteration the nuclear quadrupole coupling constant e2 qQh~ 1(127I) of 2 is shifted downwards 2.72 MHz at room temperature. The title compounds are isotype, and at room temperature they crystallize monoclinic with the space group C2 P2l5 with two molecules in the unit cell. The lattice constants for 1 are a = 1068.7 pm, b = 6\4A pm, c = 762.0 pm, and ß= 108.55° and for 2 are a = 1093.3 pm, 6 = 637.1 pm, c = 770.9 pm, and ß= 107.29°. 
  Reference    Z. Naturforsch. 44a, 659—668 (1989); received April 5 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0659 
 Volume    44 
110Author    N. Heineking, M.C L GerryRequires cookie*
 Title      
 Abstract    Dedicated to Professor Helmut Dreizler on the Occasion of his 60 th Birthday The 14N nuclear quadrupole hyperfine structure in the rotational spectra of three isotopic species of methyl azide, CH314N3, CH315N14N2, and CH314N215N, has been resolved using microwave Fourier transform spectroscopy. The quadrupole coupling constants of 14N at all three positions have been evaluated and are compared with those from an ab initio calculation in the literature. Since the spectra of the substituted species have been obtained for the first time, they have provided new structural information: the rotational constants are consistent with a structure in which the NNN chain is slightly bent. I4N N u c le a r Q u a d r u p o le H y p e r fin e S tr u c tu r e 
  Reference    Z. Naturforsch. 44a, 669 (1989); received May 15 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0669 
 Volume    44 
111Author    V. Villa-B, F. Fischer3, J. ThiembRequires cookie*
 Title     
 Abstract    e r ro e le k tris c h e F lü s s ig k r is ta ll-M is c h u n g e n m it K o h le n h y d ra t-D e riv a te n a ls D o tie r s to f f e Ferroelectric Liquid Crystal Mixtures with Carbohydrate Derivatives as Dopants For the first time carbohydrate derivatives were studied as dopants for calamitic smectic phases. Fast switching ferroelectric cells could be realized, and electroclinic effects were observed. By inversion of configuration at a chiral center of these compounds switching times, solubility, and helical twisting power vary by orders of magnitude. The studied derivatives showed modest solubil­ ity properties. 
  Reference    Z. Naturforsch. 44a, 675—679 (1989); eingegangen am 8. April 1989 
  Published    1989 
  Keywords    Ferroelectric liquid crystal mixtures, Carbohydrate derivatives, Diastereomeres, Switching time 
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 Identifier    ZNA-1989-44a-0675 
 Volume    44 
112Author    Michael Krüger, Helmut DreizlerRequires cookie*
 Title     
 Abstract    h e G ro u n d S t a te M ic ro w a v e S p e c tru m a n d D ip o le M o m e n t o f 2 -I s o c y a n o -P r o p a n e The ground state rotational spectrum of 2-isocyano-propane is assigned. The rotational constants and the quartic centrifugal distortion constants arc determined by Microwave Fourier Transform (MWFT) Spectroscopy. The analysis of the Stark effect leads to a total dipole moment of 4.055(1) D. 
  Reference    Z. Naturforsch. 44a, 680 (1989); received May 18 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0680 
 Volume    44 
113Author    A. MetropoulosRequires cookie*
 Title      
 Abstract    The strong diabaticity of the 2Z* excited states of He2 has been computationally verified in the region of the well known avoided crossing between the 1 2I * and the 22£g + adiabatic states. A large transition rate between these two states has been found, wnich is of the order of 1015 sec-1. 
  Reference    Z. Naturforsch. 44a, 683—686 (1989); received April 14 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0683 
 Volume    44 
114Author    W. H. Stolze, D. H. SutterRequires cookie*
 Title      
 Abstract    The rotational Zeeman effect of 1,2,4-trifluorobenzene has been studied for 8 low-J rotational transitions in magnetic fields between 1.9 and 2.4 Tesla. The observed susceptibility anisotropics and molecular ^/-values are: (2/aa-^ b()-x cc) = 37.85(69) • 10~6 erg G~2 mole" \ (2xbb--/.cc-x aa) = 56.85(54)-IO'"6 erg G "2 mole"1, gaa= -0.0393(3), ^"=-0.0277(3), and gcc = 0.0042(2). The Zeeman parameters have been used to derive the molecular electric quadrupole moments and vibronic ground state expectation values for the electronic second moments. The observed out-of-plane quadrupole moment is discussed with reference to an additivity scheme proposed earlier. The observed out-of-plane component of the molecular magnetic susceptibility tensor is in excellent agreement with the value predicted earlier from the CNDO/2-7i-electron density alternation at the ring atoms. 
  Reference    Z. Naturforsch. 44a, 687 (1989); received May 11 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0687 
 Volume    44 
115Author    A. Kilian, S. HessRequires cookie*
 Title     
 Abstract    e r iv a tio n a n d A p p lic a tio n o f a n A lg o rith m fo r th e N u m e ric a l C a lc u la tio n o f th e L o c a l O r ie n ta tio n o f N e m a tic L iq u id C r y s ta ls Starting from a relaxation equation for the alignment tensor, an algorithm is derived which allows the numerical calculation of the dynamic and static behavior of the director field n with the correct nematic symmetry property, where n and — n are equivalent. As a first application, a two-dimensio­ nal problem is treated where the typical nematic defects with half-integer winding numbers only occur when the algorithm with the correct nematic symmetry property is used. Furthermore, the method is applied to the static and dynamic behavior of a Frederiks cell with strong and weak anchoring. 
  Reference    Z. Naturforsch. 44a, 693—703 (1989); received June 16 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0693 
 Volume    44 
116Author    Requires cookie*
 Title     
 Abstract    G e n e ra l T h e o re m f o r C o m p le x C h e m ic a l S y s te m s 
  Reference    Z. Naturforsch. 44a, 704 (1989) 
  Published    1989 
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 Identifier    ZNA-1989-44a-0704 
 Volume    44 
117Author    Doğan Demirhan, Fevzi BüyükkiliçRequires cookie*
 Title    O n a V a  
 Abstract    ria b le o f th e Q u a s i-p a r tic le T r a n s f o r m a tio n o f th e H a m ilto n ia n o f a n O d d -N u c le u s The canonical transformation of the general BCS Hamiltonian has been performed. The energy spectrum of 73Ta181 is determined and the calculated energy values arc plotted as a function of the auxiliary variable z of the transformation for three different values of the deformation parameter. 
  Reference    Z. Naturforsch. 44a, 707—710 (1989); received June 13 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0707 
 Volume    44 
118Author    B. Vassilikou-Dova, S. Jansen, F. Wallrafen, G. LehmannRequires cookie*
 Title     
 Abstract    Dedicated to Prof. Dr. K. Recker on the occasion of his 65th birthday KTi0P04 single crystals doped with V20 4 were grown from fluxes between 1323 and 1123 K with dimensions up to (10x5x5) mm3. Two crystallographically inequivalent centers of V02+ in the occupation ratio of 10:1 were detected by EPR at room temperature. Their z axes of largest hyperfine splitting are oriented close to the directions of the very short Ti O bonds of the two Ti in the structure. An energy difference for incorporation of V02+ into these two sites of —9.4+ 1.7 kJ/mol per pm difference in bond lengths was obtained from the occupation ratio, the large limits of error being mainly due to uncertainties in the bond lengths. Additional hyperfine splitting caused by 31P nuclei as next-nearest neighbors was also resolved in most orientations. E P R o f V 0 2+ in K T i 0 P 0 4 S in g le C r y s ta ls 
  Reference    Z. Naturforsch. 44a, 711—714 (1989); received June 17 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0711 
 Volume    44 
119Author    Hans SallhoferRequires cookie*
 Title      
 Abstract    After a discussion of the one-component Schrödinger (1926) and the four-component Dirac (1928) representation of hydrogen it is shown that the six-component electrodynamic picture turns out to be considerably simpler and clearer. The computational effort is reduced to a fraction. Again we start with covariant source-free electro­ dynamics [1] (1) with its complex components rot E + -H = 0 c rot H £ = 0 dive £ =0 d \\fiH = 0 rot £ + -/ / = 0 c rot H + — £ = 0 c (1) 
  Reference    Z. Naturforsch. 44a, 715—717 (1989); received 7 July 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0715 
 Volume    44 
120Author    P. Mittler, G. Winnewisser, K.M T YamadaRequires cookie*
 Title      
 Abstract    The rotational spectrum of 34S-substituted disulfane, HS34SH, has been measured between 60 and 420 GHz, yielding for the first time the rotational constants A = 146694.949 MHz, B = 6779.018 MHz and C = 6776.339 MHz, together with a complete set of J4 and J6 distortion constants. S u b m illim e te r W a v e S p e c tr u m o f H S 34S H 
  Reference    Z. Naturforsch. 44a, 718—722 (1989); received June 27 1989 
  Published    1989 
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 Identifier    ZNA-1989-44a-0718 
 Volume    44 
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