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1996[X]
81Author    P.Craig TaylorRequires cookie*
 Title    Nuclear Quadrupole Resonance in Amorphous Semiconductors  
 Abstract    Nuclear quadrupole resonance (NQR) has provided a valuable tool for investigating the local structural order in semiconducting glasses. Measurements of NQR lineshapes and spin-lattice relaxation times help elucidate the local structural order and the unusual vibrational properties, respectively, of these glasses. In addition, NQR lineshape measurements on samples that are made under conditions that produce solids whose structures are far from equilibrium, such as fast-evap-orated films or rapidly-drawn fibers, provide detailed information on the changes in the local structural order from that which occurs in the well-annealed amorphous semiconductors. 
  Reference    Z. Naturforsch. 51a, 603—610 (1996); received November 20 1995 
  Published    1996 
  Keywords    NQR, chalcogenide glasses, amorphous semiconductors, structure, vibrational properties 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0603.pdf 
 Identifier    ZNA-1996-51a-0603 
 Volume    51 
82Author    Serge David, Michel Gourdji, Lucien Guibé, Alain PéneauRequires cookie*
 Title    Chlorine Substituted Acetic Acids and Salts. Effect of Salification on Chlorine-35 NQR  
 Abstract    The NQR of a quadrupolar probe nucleus is often used to investigate the effect of substituent in molecules. The inductive effect, based on a partial charge migration along the molecular skeleton is the only one present in saturated aliphatics, the conjugative effect appearing in conjugated molecules, especially aromatics. As the stepwise charge migration mechanism, formerly used to explain the inductive effect, is now believed obsolete, we have wanted to reexamined the case of chlorine substituted acetic acids and salts. The data in literature was extended by observing reso-nances and determining NQR frequencies in several acids and salts. The present analysis of the salification of mono-, di-and tri-chloroacetic acids, which is equivalent to a deprotonation or the substitution of the acid hydrogen by a negative unit charge, shows that a model based on the polarization of the chlorine atom(s) by the carboxyle group is consistent with experimental results: the polarization energy appears to be proportional to the NQR frequency shifts; experimental data show a correlation between the NQR frequency shifts accompanying salification and the variations of the intrinsic acidity measured in the gas phase; this, in turn shows that there is a proportionality between the polarization energy and the variations in the acid free enthalpy of dissociation. From the comparison between fluorine, chlorine, bromine and iodine, it also appears that an alternative mechanism, the polarization of the carboxyl group by the halogen, would be important only in the case of the fluoroacetic acid. 
  Reference    Z. Naturforsch. 51a, 611—619 (1996); received October 10 1995 
  Published    1996 
  Keywords    35 C1 NQR, Chloroacetic acids, Substituent effect, Inductive effect, Polarization, Intrin-sic acidity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0611.pdf 
 Identifier    ZNA-1996-51a-0611 
 Volume    51 
83Author    Tetsuaki NishidaRequires cookie*
 Title    Verification of the " Tg-A Rule" in Potassium Silicate and Sodium Tungstate Glasses  
 Abstract    A linear relationship exists in oxide glasses between glass transition temperature (T g) and quadrupole splitting (A) of Fe ,+ . DTA and Mössbauer measurements of silicate and tungstate glasses yielded large slopes of 680 and 260 °C/(mm s~ 1) from the slope of the straight lines when Fe 3+ occupied, as network former (NWF), distorted tetrahedral Si 4+ and distorted octahedral W 6+ sites, respectively. This linear relationship, named a 'T g -Z\ rule", suggests that F e is in proportion to the distortion of NWF-oxygen polyhedra and a higher activation energy is required for the fragments of glass to have a cooperative movement in the supercooled liquid state. The rule" was also valid in the case of potassium silicate glasses heat treated at the temperature close to 7g, indicating a distortion of Si0 4 and Fe0 4 tetrahedra. Substitution of Fe 3+ for individual NWF in silicate and tungstate glasses was confirmed from the Fourier transform infrared (FT-IR) spectra because only the absorption bands due to Si and W were respectively observed without the bands due to Fe. 
  Reference    Z. Naturforsch. 51a, 620—626 (1996); received November 2 1995 
  Published    1996 
  Keywords    Mössbauer effect, silicate glass, tungstate glass, glass transition temperature, quadrupole splitting 'T g -_\ rule" 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0620.pdf 
 Identifier    ZNA-1996-51a-0620 
 Volume    51 
84Author    B.Thimme Gowda, Shi-Qi Dou, Alarich WeissRequires cookie*
 Title    The Bond N-Cl. (Ill): A 35 C1 NQR and X-Ray Diffraction Study of N-Chloro-N-(2,6-Dichlorophenyl)-Acetamides  
 Abstract    The crystal structures at room temperature of the N-chloro-N-(2,6-dichlorophenyl)-chloroac-etamides 2,6-Cl 2 C 6 H 3 NClCOCCl 3 (1) and 2,6-Cl 2 C 6 H 3 NClCOCH 2 Cl (2) have been determined. (1): orthorhombic, Pbca. Z = 8, a = 2051.7(8) pm, b= 1134.8(4) pm, c = 1089.0(4) pm. (2): or-thorhombic, Pbca, Z = S, a = 2078.7 (4) pm, b= 1487.9(4) pm, c = 694.0 (2) pm. The "CI NQR spec-trum of (1) was studied in the range 77<T/K<370. At 77 K, a sextet spectrum is observed (v in MHz): vj = v(Cl (N,) = 56.327; v 2 = 40.636, v 3 = 40.317, v 4 = 40.294; v ? = 36.532, v 6 = 36.182. The lines v 2 , v 3 , and v 4 are assigned to the CC1 3 group because of their position in the frequency scale. Also, due to librational motions, this triplet part of the spectrum fades out at 320 K. There is no problem in assigning in both compounds, on the basis of the known 35 C1 NQR frequency scale, the line Vj to the CI atom attached to the nitrogen atom and the lines v 5 and v 6 to the ring chlorines (Cl <2) and Cl (6)). The crystal structures and NQR spectra of (1) and (2) are discussed together with literature data for 2,6-Cl 2 C 6 H 3 NHCOR, C 6 H 5 NC1C0R (where R = CC1 3 , CClH 2 fand other substituted acetamides. 
  Reference    Z. Naturforsch. 51a, 627—636 (1996); received August 21 1995 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0627.pdf 
 Identifier    ZNA-1996-51a-0627 
 Volume    51 
85Author    Fereidoun Khajehnouri, Shahrokh Motallebi, E.A C LückenRequires cookie*
 Title    Cu NQR Studies of Two-and Three-coordinated Complexes of Cu(I) with Siloxyl Ligands  
 Abstract    We report the 63 Cu NQR spectra of seven two-and three-coordinated complexes with the siloxyl ligand. R 3 SiO~. The frequencies are compared to those of other two-and three-coordinated species, and it is demonstrated that the partial field gradient of the R 3 SiO~ group is very similar to that of CP. 
  Reference    Z. Naturforsch. 51a, 637—640 (1996); received October 20 1995 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0637.pdf 
 Identifier    ZNA-1996-51a-0637 
 Volume    51 
86Author    E. A. Kravchenko, M. Yu, BurtzevRequires cookie*
 Title    Electronic Characteristics of Sn-Hal Bonds in Hexa-and Pentacoordinate Tin(IV) Adducts of Type R n SnHal4 _ "L x  
 Abstract    The a-and rc-electron effects of alkyl/phenyl substituents on the Sn-Hal bonds in penta-and hexacoordinate tin(IV) chloro and iodo adducts are discussed based on their 35 C1 and 127 I NQR spectra. Unexpectedly high 127 I EFG asymmetry parameters were found in most dialkyl(phenyl)-substituted adducts of thin(VI) iodides. Key words: 35 C1 and 127 I NQR; adducts of tin(IV) halides; the electronic effects of alkyl/phenyl substituents. 
  Reference    Z. Naturforsch. 51a, 641—645 (1996); received October 11 1995 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0641.pdf 
 Identifier    ZNA-1996-51a-0641 
 Volume    51 
87Author    JaeKap Jung, HaeJin Kim, KeeTae Han, SungHo ChohRequires cookie*
 Title    Electric Field Effect on NQR in Ferroelectric Materials  
 Abstract    The electric field effect on NQR in ferroelectric materials, 93 Nb in LiNb0 3 and 14 N in NaN0 2 and SC(NH 2) 2 , has been investigated at 77 K. In these crystals with single domain, only the line shift due to the external electric field was observed. In the case of NaN0 2 powder and a crystal with multi-domains, line broadening was observed in the external electric field. These phenomena can be ex-plained with the fact that the direction of spontaneous polarization in a domain is related to the di-rection of the applied electric field. The rate of the NQR line-shift due to the electric field is remark-ably smaller in mostly ionic crystals, such as LiNb0 3 and NaN0 2 , than in a molecular crystal such as SC(NH 2) 2 . This is due to the strong ionic bonding in ionic crystals. Also, the difference of the Stark shift'between NaN0 2 and SC(NH 2) 2 is discussed in terms of the local electric field and polarizability at the resonant nuclear site. 
  Reference    Z. Naturforsch. 51a, 646—650 (1996); received November 20 1995 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0646.pdf 
 Identifier    ZNA-1996-51a-0646 
 Volume    51 
88Author    T. A. Babushkina, YuV. Goltyapin, S. I. GushchinRequires cookie*
 Title    I NQR Spectra of Iodobenzoic Acid and Iodophenol Derivatives. H-Bonds and C-I Characteristic Bonds of These Substances  
 Abstract    This is a review of investigations on iodo-benzoic acid, iodohippuric acid, and iodophenol derivatives by NQR, NMR, and emission Mössbauer spectroscopy. The influence of intermolecular, intramolecular, and bifurcated O-H- • I and O-H- • O bonds on the properties of iodine-carbon bonds is demonstrated. Ionized and non-ionized forms of tyrosine differ by the probability of H-bond formation. The simultaneous use of 127 1 NQR and emission Mössbauer 12 T spectroscopy open the possibility to determine the types of tellurium-organic substances formed in the process 
  Reference    Z. Naturforsch. 51a, 651—656 (1996); received October 20 1995 
  Published    1996 
  Keywords    NQR, NMR, iodobenzoic acid, iodohippuric acid, iodophenol 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0651.pdf 
 Identifier    ZNA-1996-51a-0651 
 Volume    51 
89Author    Mutsuo Igarashi, Noriaki Okubo, Shuichi Hashimoto, Ryozo Yoshizaki, DeokJoon ChaRequires cookie*
 Title    Na Spin-Lattice Relaxation Measurements in Dehydrated Na-X Zeolite  
 Abstract    The spin-lattice relaxation time T\ of 23 Na-NMR in a dehydrated Na-X zeolite has been measured from 20 to 300 K. The recovery curve is not single-exponential at all measured temperatures and T\~ 1 increases with the square of temperature around room temperature. The results are analyzed by assuming non-equivalent sites and by applying the theory of the Raman process based on covalency. 
  Reference    Z. Naturforsch. 51a, 657—661 (1996); received October 17 1995 
  Published    1996 
  Keywords    Dehydrated Na-X zeolite, 23 Na-NMR, spin-lattice relaxation, Raman process, nonequivalent sites 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0657.pdf 
 Identifier    ZNA-1996-51a-0657 
 Volume    51 
90Author    H. Nishihara, N. Todo, T. Hagino, S. NagataRequires cookie*
 Title    Powder Spectra of 51 V NMR in CuV 2 S 4 : Possible Coexistence of Charge and Spin Density Waves  
 Abstract    NMR experiments are reported for the copper chalcogenide spinel CuV : S 4 , which has incom-mensurate lattice distortions at low temperatures in spite of the cubic symmetry at high temperature. A broad spin-echo spectrum of 51 V has been observed below 90 K at 17 MHz. but it shows a re-markable frequency dependence where it becomes sharper with decreasing frequency. Possible coexistence of charge and spin density waves is suggested at low temperatures in this material. 
  Reference    Z. Naturforsch. 51a, 662—664 (1996); received November 20 1995 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0662.pdf 
 Identifier    ZNA-1996-51a-0662 
 Volume    51 
91Author    A. I. Kharkovskii, V. L. Nizhankovskii, E. A. Kravchenko, V. G. OrlovRequires cookie*
 Title    Magnetic Properties of the Bismuth Oxide a — Bi 2 0 3  
 Abstract    A very unusual magnetic behaviour of a — Bi 2 0 3 was observed in a wide range of temperatures and magnetic fields. A longitudinal magnetoelectric effect was found at 4.2 K. The existence of an antiferroelectrically ordered subsystem of electric dipoles in a — Bi 2 0 3 is proposed. The mechanism of spin-orbit coupling is regarded as the physical origin for the occurrence of the ordered magnetic moments in a — Bi 2 0 3 . 
  Reference    Z. Naturforsch. 51a, 665—666 (1996); received February 13 1996 
  Published    1996 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0665.pdf 
 Identifier    ZNA-1996-51a-0665 
 Volume    51 
92Author    A. M. Petrosyan, V. A. ShishkinRequires cookie*
 Title    Correlation between Structural, Infrared and Nuclear Quadrupole Resonance Data of Iodates  
 Abstract    The peculiarities of the structure and the IR and NQR spectra of acid iodates and pyroiodates which contain the I 2 O s group are reported. Based in this, the results for several iodates that contain organic cations are considered. 
  Reference    Z. Naturforsch. 51a, 667—671 (1996); received January 30 1996 
  Published    1996 
  Keywords    Iodates, NQR and IR spectroscopy, Structure 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0667.pdf 
 Identifier    ZNA-1996-51a-0667 
 Volume    51 
93Author    Takahiro Ueda, Nobuo NakamuraRequires cookie*
 Title    Sb NMR and SCF-MS-Xa Studies of Quadrupole Interaction and The Electronic Structure of Mixed-Valence Compound, Cs 2 SbCl 6  
 Abstract    Cs 2 SbCl 6 is known as a typical mixed-valence compound. It crystallizes into a tetragonal space group I4 1 /amd and contains two different complex anions, Sb(III)Cl| _ and Sb(V)Clg . The dark blue color of this compound has been considered to originate from a charge transfer between the above two anions. In order to study the electronic structure of these complex anions and the existence of charge transfer between them we measured the 121 Sb NMR spectrum and carried out molecular orbital calculations on the electronic states of these anions. The 121 Sb NMR spectrum consists of two peaks at 0 and 30 kHz which can be assigned to the central transition of l21 Sb in Sb(V)Cl<~ and Sb(III)Cl| _ , respectively. The line shape analyses of the spectra led to nuclear quadrupole coupling constants of nearly zero for Sb(V)Cl7 and 4.9 ±0.5 MHz for Sb(III)Cl| at room temperature. The quadrupole coupling constant of 1 Sb(III) decreases steadily on heating. The calculations of the electronic ground state energies of both anions were calculated by the MS-Xa molecular orbital method. The calculated charge-transfer band from the A lg state of Sb(III)Clg" to the A lg state of Sb(V)Cl6 appears at 610 nm and can account for the experimental electronic spectrum, the calculated quadrupole coupling constant in Sb(III)Clg" however is far larger than the experimental one. The contribution of the charge-transferred state to the ground state is negligible and so the temperature dependence of the quadrupole coupling constant of 121 Sb(III) is attributed to an anisotropic thermal expansion of the compound. 
  Reference    Z. Naturforsch. 51a, 672—676 (1996); received October 10 1995 
  Published    1996 
  Keywords    NMR, Quadrupole interaction, Molecular orbital, Mixed valence 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0672.pdf 
 Identifier    ZNA-1996-51a-0672 
 Volume    51 
94Author    Ya-Nan Zhao, Sundara Ramaprabhu, EdwinA C LückenRequires cookie*
 Title    An NQR Study of Inclusion Compounds Formed Between Small Chlorine-containing Molecules and Ä/s(N-alkylimidazolidine-2-thione)Cu(I) Halide Complexes  
 Abstract    Twenty-five inclusion complexes formed by fe(N-alkyiimidazolidine-2-thione)cuprous halides with the small, chlorine-containing guest molecules CC1 4 , CHC1 3 , CH 2 C1 2 , CH 3 CC1 3 or C 2 H 2 C1 2 , have been prepared. Their 63 Cu and 35 C1 NQR spectra have been measured over the temperature range 77-300 K. For the corresponding bromides the 79 Br and/or 81 Br spectra have also been investigated. The studies reveal the number and symmetry of different inclusion site. The onset of rapid reorientation of the guest molecules is indicated by the fading out of their NQR signals between 77 and 300 K, whereas the resonances from the host molecules usually persist throughout this temperature range. However, as evidenced by discontinuities in the temperature-dependence of the NQR frequencies of the hosts, sixteen of the complexes show one or more phase-changes in this temperature-range. 
  Reference    Z. Naturforsch. 51a, 677—685 (1996); received December 12 1995 
  Published    1996 
  Keywords    NQR, Copper(I), Guest, Inclusion, Complex 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0677.pdf 
 Identifier    ZNA-1996-51a-0677 
 Volume    51 
95Author    Tsutomu Okuda, Shusaku Gotou, Toshirou Takahashi, Hiromitsu Terao, Koji YamadaRequires cookie*
 Title    Structure and Successive Phase Transitions of RGeBr 3 (R = Alkylammonium) Studied by Means of NQR  
 Abstract    A series of tribromogermanate(II) complexes RGeBr 3 (R = CH 3 NH 3 , (CH 3) 2 NH 2 , (CH 3) 4 N, C 2 H 5 NH 3 , (C 2 H 5) 4 N) have been synthesized and characterized by 81 Br NQR, AC conductivity, DTA, and X-rax diffraction. These measurements revealed the presence of successive phase transi-tions in these complexes. The crystal structures of Phases I and II in (NH 3) 4 NGeBr 3 were derived from the Rietveld analysis of powder X-ray diffraction. The electric conductivity was considerably high in CH 3 NH 3 GeBr 3 and (NH 3) 4 NGeBr 3 . The conduction mechanism is discussed on the basis of 81 Br NQR spin-lattice relaxation times and crystal structures. 
  Reference    Z. Naturforsch. 51a, 686—692 (1996); received October 10 1995 
  Published    1996 
  Keywords    81 Br NQR, T x, Phase Transition, Ionic Motion, Ionic Conductivity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0686.pdf 
 Identifier    ZNA-1996-51a-0686 
 Volume    51 
96Author    A. Ishikawa, A. Sasane, Y. Hirakawa, Y. MoriRequires cookie*
 Title    Motion of Water Molecules and Hydrogen Bonds in Zinc Hexachlorostannate (IV) Hexahydrate as Studied by *H NMR and 35 C1 NQR  
 Abstract    The *H NMR spin-lattice relaxation time 7\, 35 C1 NQR frequency VQ, and 35 C1 NQR spin-lattice relaxation time 7\ Q of [Zn(H 2 0) 6 ] [SnCl 6 ] (zinc hexachlorostannate(IV) hexahydrate) have been measured at temperatures between 77 and 350 K. The NQR spin echo signal with Vq— 15.689 MHz at 77 K showed a positive temperature coefficient attributable to O-H-Cl type H-bonds in the crystal. v Q at 77 K is strongly correlated with the electronegativity Xm of the metal M in the series of stannates [M(H 2 0) 6 ] [SnCl 6 ] (M = Mg, Ca, Mn, Co, Ni, Zn). A 7\ minimum observed for the Zn salt is ascribed to 180° flips of water molecules with an activation energy of 20 kJ mol -1 . The motion is influenced by repulsive forces among the water molecules within a cation rather than by attractive forces between the H-bonded H and CI atoms. 7\q proved to be mainly governed by lattice vibrations, weakly modulated by the fluctuating electric field gradient caused by the 180° flip motions. 
  Reference    Z. Naturforsch. 51a, 693—697 (1996); received October 10 1995 
  Published    1996 
  Keywords    'H NMR spin-lattice relaxation, 35 C1 NQR frequency, 35 C1 NQR spin-lattice relaxation, H-bonding, Electronegativity 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0693.pdf 
 Identifier    ZNA-1996-51a-0693 
 Volume    51 
97Author    Christovam Mendonça, SaidR. RabbaniRequires cookie*
 Title    Anharmonic Librations and the Temperature Dependence of NQR Frequencies  
 Abstract    The temperature dependence of NQR frequencies of nuclei in molecules undergoing quasi-har-monic rotational oscillations is calculated. Following the model proposed by Bayer, the instanta-neous orientation of the electric field gradient principal axes is assumed to change from its average orientation as a result of rotational oscillations, while the EFG magnitude remains constant. The eigenstates and energy eigenvalues of a rotator in a potential of the form V(0)= V 2 0 2 — K 4 0 4 are calculated by standard perturbation methods, followed by the evaluation of statistical averages of square angular amplitudes. For molecular crystals with more than one molecule in a unit cell the angular displacements are expressed in terms of normal coordinates, and the same procedure is followed. The final expression for the change in the NQR frequency consists of two terms, the first one being related to the harmonic part of the potential and the second one to the quartic term. At the absolute zero it yields a nonzero contribution to <ö 2 >, and for high temperatures it reproduces the nonlinear character of v Q (T) observed experimentally. The model has been tested with measure-ments on solid Cl 2 performed by Nakamura and Chihara, combined with libration mode frequencies measured in Raman spectroscopy by Cahill and Leroi and analysed according to our anharmonic libration picture. The fitting of our equation to experimental data supports Cahill and Leroi's hypothesis about the existence of an undetected libration mode in Cl 2 Raman spectra of frequency near 60 cm" 
  Reference    Z. Naturforsch. 51a, 698—704 (1996); received November 20 1995 
  Published    1996 
  Keywords    NQR, Bayer's Model, Anharmonic Vibrations 
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 Identifier    ZNA-1996-51a-0698 
 Volume    51 
98Author    Tetsuo Asaji, Masaki Ohkawa, Takehiko Chiba, Makoto KagaRequires cookie*
 Title    Successive Phase Transitions in Potassium Hexachloroselenate(IV) Revealed by 35 C1 NQR  
 Abstract    K 2 SeCl 6 undergoes structural phase transitions of first order at 35 K, 65 K, and 79 K. The temperature dependence of the ? C1 NQR spin-lattice relaxation time suggests that the phase transitions at 65 K and 79 K are displacive ones associated with a resonant soft mode. The presence of a precursor cluster is suggested by the temperature dependence of the signal intensity above 79 K. 
  Reference    Z. Naturforsch. 51a, 705—709 (1996); received October 20 1995 
  Published    1996 
  Keywords    Phase transition, Soft mode, NQR, Spin-lattice relaxation 
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 Identifier    ZNA-1996-51a-0705 
 Volume    51 
99Author    G. B. Furman, E. M. Kunoff, S. D. GorenRequires cookie*
 Title    Nuclear Spin-Lattice Relaxation of a Spin System with Strong Heteronuclear Magnetic Interaction  
 Abstract    Results are presented of a theroretical consideration of the nuclear quadrupole resonance and spin-lattice relaxation for a sample containing nuclei of two different types coupled by strong heteronuclear dipole-dipole interactions and influenced by an external continuous or pulsed ra-diofrequency magnetic field acting only on the nuclei of one sort with spin /> 1/2. A kinetic equation is obtained from which the time dependence of the magnetization of the sample is derived. The kinetic coefficients are calculated as a function of the concentration and distribution of the nuclei of both sorts. 
  Reference    Z. Naturforsch. 51a, 710—712 (1996); received November 20. 1995 
  Published    1996 
  Keywords    NQR spin lattice relaxation, non-exponential spin lattice relaxation, heteronuclear interaction 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0710.pdf 
 Identifier    ZNA-1996-51a-0710 
 Volume    51 
100Author    IgorA. KyuntselRequires cookie*
 Title    C1 NQR Study of Thermoactivated Motions of Nitro Groups in Picryl Chloride  
 Abstract    The temperature dependences of the 35 C1 NQR frequency (v), spin-lattice relaxation time (T^), and spin-spin relaxation time (T 2) have been studied in 2,4,6-trinitrochlorobenzene (picryl chloride) from 77 K up to the melting point (354 K). The 7\ (T) curve exhibits a pronounced composite mimimum near 300 K which gives evidence for the reorientations of the two ort ho-N0 2 groups around their two-fold symmetry axes with the activation energies of 27.4 kJ mol 1 and 31.2 kJ mol 1 . These values can be related to the ortho-N0 2 groups having the twist angles of 33° and 81°, respectively (the crystal structure of picryl chloride is known). The T 2 (T) dependence exhibits interesting features, too: a deep minimum about 140 K and a new rapid decrease above 270 K. 
  Reference    Z. Naturforsch. 51a, 713—715 (1996); received October 10 1995 
  Published    1996 
  Keywords    NQR, reorientation motion, nitro group 
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 TEI-XML for    default:Reihe_A/51/ZNA-1996-51a-0713.pdf 
 Identifier    ZNA-1996-51a-0713 
 Volume    51 
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