| | 1 | Author
| G. Brolo, DonaldE. Irish | Requires cookie* | | | Title
| Alexandre  | | | | Abstract
| Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday Raman spectra of aqueous pyrazine have been investigated in acidic media: HCl from pH = 4 up to 11 M; HC104 from 0.1 M to 12 M; H2S04 form 0.1 M to 18 M. From observation of the shifts of the bands from neutral solutions, it has been possible to identify bands uniquely characteristic of unprotonated pyrazine and its two protonated forms. The diprotonated form was only observed for high concentrations of HC104 and H2S04. From bandfitting of the spectral contours it has been possible to construct the species distribution diagram and estimate the pK values. Raman bands of the three species have been identified and assigned. The results are used to explain an unassigned band at 1235 cm-1, reported by several authors, in SERS from pyrazine on silver and gold elec trodes. R a m a n S p e c tr a l S tu d ie s o f A q u e o u s A c id ic P y r a z in e S o lu tio n s | | | |
Reference
| Z. Naturforsch. 50a, 274—282 (1995); received October 31 1994 | | | |
Published
| 1995 | | | |
Keywords
| Pyrazine, Pyrazinium, SERS, Raman spectroscopy | | | |
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| default:Reihe_A/50/ZNA-1995-50a-0274.pdf | | | | Identifier
| ZNA-1995-50a-0274 | | | | Volume
| 50 | |
| 2 | Author
| A. Chrissanthopoulos3, C. Pouchan3, G. N. Papatheodorou5 | Requires cookie* | | | Title
| Structural Investigation of Vanadium -Sodium Metaphosphate Glasses | | | | Abstract
| Paper presented a t the NATO A dvanced Study Institute, M ay 4-1 4 , 2001 (Kas, Turkey) The structure of the glass forming system (V20 5)x -(Na20 • P205)(1_^), (jc = 0-0.4), has been inves tigated using Raman spectroscopy. The stretching vibrations of various phosphate groups, connected to phosphorus or vanadium atoms, have been assigned. Variation o f the composition leads to structural changes where the sodium metaphosphate -P-O-P-chains break and then reconnect with the oxovana-dium units forming a -V-O-P-network structure. | | | |
Reference
| Z. Naturforsch. 56a, 773—7 (2001); received August 8 2001 | | | |
Published
| 2001 | | | |
Keywords
| Vanadium, Phosphates, Vanadium Glass, Raman Spectroscopy, Metaphosphates | | | |
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| default:Reihe_A/56/ZNA-2001-56a-0773.pdf | | | | Identifier
| ZNA-2001-56a-0773 | | | | Volume
| 56 | |
| 3 | Author
| D. Schiel, W. Richter, G. Döge | Requires cookie* | | | Title
| CH3F/CD3F System | | | | Abstract
| It has been proved with the aid of CH3F/CD3F mixtures that the remarkably large non-coincidence effect in the Raman scattering spectrum of the v 3 mode of liquid methyl fluoride is due to intermolecular vibrational coupling medi-ated mainly by transition dipole interaction. The amount of the effect and its temperature and mole fraction dependence are -at least qualitatively -in agreement with Logan's theoretical concept. The rather different behaviour of the isotopic species and the asymmetry and narrow width of the isotropic band, however, raise new questions which require further investigations. | | | |
Reference
| Z. Naturforsch. 45a, 1381—1382 (1990); received September 26 1990 | | | |
Published
| 1990 | | | |
Keywords
| Raman spectroscopy, Liquids, Intermolecular interactions, Isotopic dilution, Band shift | | | |
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| default:Reihe_A/45/ZNA-1990-45a-1381_n.pdf | | | | Identifier
| ZNA-1990-45a-1381_n | | | | Volume
| 45 | |
| 4 | Author
| Toshiyuki Takamuku, Kazumasa Yoshikai, Toshio Yamaguchi, Hisanobu Wakita | Requires cookie* | | | Title
| Structure of Supercooled Aqueous Zinc(II) Bromide Solutions by Raman and X-Ray Scattering Methods | | | | Abstract
| The structure of aqueous zinc(II) bromide solutions with [H 2 0]/[ZnBr 2 ] molar ratios 5 and 10 in the supercooled state and at ambient temperature has been investigated by Raman spectroscopy and X-ray scattering. Raman spectra of glassy solutions have also been measured for comparison. The Raman and X-ray data suggest that tetrabromo and hexaaqua zinc(II) complexes are favoured in the supercooled and glassy state, while dibromo-and tribromozinc(II) complexes are formed as main species in the solutions at ambient temperature. Probably the reactions 2 [ZnBr 2 (OH 2)] + 2H 2 0 [ZnBr 4 ] 2 ~ + [Zn(OH 2) 6 ] 2 + 4[ZnBr 3 (OH 2)]~ + 2H 2 0 -> 3[ZnBr 4 ] 2 ~ + [Zn(OH 2) 6 ] 2 + occur in the supercooled and glassy solutions. These equilibrium shifts are discussed. | | | |
Reference
| Z. Naturforsch. 47a, 841—848 (1992); received April 24 1992 | | | |
Published
| 1992 | | | |
Keywords
| Supercooled solution, Zinc(II) bromide, Raman spectroscopy, X-ray diffraction, Structure | | | |
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| default:Reihe_A/47/ZNA-1992-47a-0841.pdf | | | | Identifier
| ZNA-1992-47a-0841 | | | | Volume
| 47 | |
| 5 | Author
| Toshiyuki Takamuku, Mikito Ihara, Toshio Yamaguchi, Hisanobu Wakita | Requires cookie* | | | Title
| Raman Spectroscopic and X-ray Diffraction Studies on Concentrated Aqueous Zinc (II) Bromide Solution at High Temperatures | | | | Abstract
| Raman and X-ray scattering experiments have been performed on an aqueous zinc (II) bromide solution with molar ratio [H20]/[ZnBr2] = 10 at 25 to 140 °C. The intensity of the totally symmetric Zn-Br stretching vibration (v^ for the dibromozinc(II) complex increased with increasing temper-ature while that for the tetrabromo complex decreased. A broad band assigned to the symmetric Zn-O stretching vibration (vj for the aqua zinc (I I) ion decreased in intensity with increasing temperature. The X-ray diffraction data revealed that the average number of the Zn-Br interactions within the zinc (II) bromo complexes does not change with temperature, whereas the number of Br • • • Br nonbonding interactions within the complexes decreases from 1.8 at 25 °C to 1.5 at 100 °C. From both Raman and X-ray data it is concluded that with increasing temperature the dibromo species is favored, whereas the tetrabromo and aqua zinc(II) species are unstable in the solution. The analysis of the X-ray diffraction data has shown that the mean Zn-Br bond length within the zinc (II) bromo complexes shortens gradually with increasing temperature, accompanied with an increase in the interligand Br • • • Br distance. This finding suggests that the Br-Zn-Br bond angle increases with decreasing Zn-Br distance for the lower zinc(II) bromo complexes. The equilibrium shift of the zinc (II) bromo complexes with temperature is discussed on the basis of ion-ion, ion-water, and water-water interactions. | | | |
Reference
| Z. Naturforsch. 47a, 485—492 (1992); received November 27 1991 | | | |
Published
| 1992 | | | |
Keywords
| Raman spectroscopy, X-ray diffraction, Zinc(II)bromide, High temperature, Solution structure | | | |
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| default:Reihe_A/47/ZNA-1992-47a-0485.pdf | | | | Identifier
| ZNA-1992-47a-0485 | | | | Volume
| 47 | |
| 6 | Author
| Toshiyuki Takam, KeisukeN. Akam Ura, M. Ikito Ihara, Hisanobu Wakita, Toshio Yamaguchi | Requires cookie* | | | Title
| Raman Scattering and X-ray Diffraction Studies on Zinc(II) Bromide Solutions in Methanol and N,N-Dimethylformamide in the Temperature Range 77-333 K | | | | Abstract
| n Z i n c (I I) B r o m i d e S o l u t i o n s i n M e t h a n o l a n d N , N -D i m e t h y l f o r m a m i d e i n t h e T e m p e r a t u r e R a n g e 7 7 -3 3 3 K The structure o f zinc(II) brom o com plexes in m ethanol and N,N-dim ethylformam ide (D M F) (molar ratio [solvent]/[ZnBr?] = 10, temperature range 7 7 -3 3 3 K) has been investigated by Raman scattering and X-ray diffraction. In the m ethanol solution symmetric Z n -B r vibrations (vt) o f the dibrom o-and tribrom ozinc(II) com plexes were observed at 209 and 184 c m " 1, respectively. With decreasing temperature the intensity o f the vx band decreased for the dibrom o and increased for the tribromo complex. In addition, the Vj band for the tetrabromo complex appeared in the supercooled and glassy methanol solutions. In the D M F solution only one band, assigned to both the dibrom o-and tribromozinc(II) com plexes, was observed. Its intensity did not change with temper ature. The X-ray diffraction data revealed that the average number of Z n -B r interactions within the zinc (II) bromo com plexes does not change with temperature while the number of nonbonding Br • • • Br interactions within the com plexes increases from 1.5 at 298 K to 1.9 at 243 K for the methanol solution and from 1.3 at 298 K to 1.8 at 243 K for the D M F solution. These Raman and X-ray results have confirmed that in both m ethanol and D M F solutions at high temperatures the dibrom o species is predominantly formed, whereas at low temperatures the tribromo com plex is favored, the tetrabromo species being formed only in the supercooled and glassy m ethanol solutions. The temperature dependent equilibrium shifts of the zinc(II) bromo complexes in the methanol and D M F solutions are discussed together with previously reported results for the aqueous phase. | | | |
Reference
| Z. Naturforsch. 49a, 1119 (1994); received O ctober 15 1994 | | | |
Published
| 1994 | | | |
Keywords
| Raman spectroscopy, X-ray diffraction, Zinc(II) bromide, M ethanol, N, N -D im ethyl-formamide | | | |
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| default:Reihe_A/49/ZNA-1994-49a-1119.pdf | | | | Identifier
| ZNA-1994-49a-1119 | | | | Volume
| 49 | |
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