摘要:

AbstractX‐ray diffraction analysis was applied to a BaLaGa3O7single crystal obtained by the Czochralski technique. It crystallizes in the tetragonal system with the space groupP421m(D 2d3) and two formula units in the unit cell of dimensionsa= 8.145 (2),c= 5.382 (2) Å at 300 K. Polarized IR transmission and Raman scattering spectra of oriented single crystals were measured and are discussed in terms of factor group analysis and x‐ray structure. A vibrational assignment is pr

ISSN:0377-0486    

DOI:10.1002/jrs.1250260402

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractLes spectres infrarouge et Raman de l'acide adipique et de ses sels de potassium en solution aqueuse ont été analysés. Une attribution des fréquences fondamentales est proposée. L'analyse de l'état de polarisation des raies Raman montre que les deux sels appartiennent au groupe de symétrieCstandis que l'acide répond au groupe de symétrieC1. A l'état cristallin, le sel acide est de type A selon la classification de Speakmann. Une comparaison des conformations avec celles déterminées en série alcanedioique a

ISSN:0377-0486    

DOI:10.1002/jrs.1250260403

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractPolarized Raman spectra of liquids within a solid—liquid interface were analysed. The liquid, deposited on the solid surface, is illuminated by an evanescent electromagnetic wave; the penetration depth isl≤ 100 nm. Interface liquid spectra are compared with the polarized spectra of the isotropic liquid. It is found that the changes observed in the spectra cannot be explained merely by structural changes in the molecules; the influence of changes in the main characteristics of the exciting electric field, arising from defects of the solid surface, must also be considered. With rutile surfaces, the experimental spectra are linear combinations of the isotropic liquid spectra; the electric field, partially depolarized by the surface defects, is still a long‐range field: no structural changes for the molecules are found within the illuminated part of the interface. With thin silver film‐coated surfaces, however, the spectra cannot be reduced to linear combinations of the liquid spectra. Structural changes for the molecules are also involved. The electric field is enhanced by the excitation of the surface plasmon of silver but, because of the surface defects, the field, partially depolarized, spreads over a range much shorter thanl, and is strongly dependent on the defect geometry. The short‐range enhancement can mask a possible further orientation of the molecules, preventing any determination of the range of the solid—liquid interaction. Time dependence of the spectra related to an increase in the silver surface roughness leads to surface‐enhanced Raman scat

ISSN:0377-0486    

DOI:10.1002/jrs.1250260404

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman spectrum of piperazine hexahydrate was observed over the whole wavenumber region at various temperatures (300—29 K). The splitting between the N—H stretch and the polaron was found to be 21 cm−1at 44 K. The bands due to the axial configuration of piperazine were above 200 K in both the H and D systems. The enthalpy difference in the equatorial—axial equilibrium was calculated to be 8.1 and 7.6 kJ mol−1in the H and D systems, respectively. The phase transition was found atca.170 K, and is ascribed to the order—disorder type associated with the axial configuration. The polaron was discussed group theoretically and reinvestigated on the basis of the coupling of the N—X stretch with optical lattice modes. It is noted that the polaron is little affected by the phase transition at 170 K or disorder in hydro

ISSN:0377-0486    

DOI:10.1002/jrs.1250260405

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractRaman OH stretching spectra were measured for a range of alcoholic LiCl solutions in the glassy state. The sharp OH stretching Raman peak due to alcohol molecules weakly hydrogen bonded to chloride ions shifts to lower wavenumbers with an increase in the molecular weight of an alcohol. A simple model calculation suggests that the shift can be mainly ascribed to the change in the mass of an alkyl group of the alcohol rather than a change in the strength of the hydrogen bond.

ISSN:0377-0486    

DOI:10.1002/jrs.1250260406

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractRaman spectra of oblique phonons in tetragonal BaTiO3and Ce : BaTiO3single crystals were obtained for different values of the angle θ which the phonon wavenumber q̄ makes with thec‐axis. On the basis of Merten's equation, the directional dispersion curves were fitted and plotted. The results show that theA1(TO) phonons of BaTiO3at 275 and 514 cm−1come from first‐order scattering, which is evidence for the order—disorder model of the ferroelectric phase transition. The Raman spectra of Ce : BaTiO3are reported for the first time and the results indicate that Ce atoms have little effect on the structure

ISSN:0377-0486    

DOI:10.1002/jrs.1250260407

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSodium metavanadates in α (α‐NaVO3), β (β‐NaVO3) and hydrated (NaVO3· 2H2O) forms were studied down to 10 K. All the phases were found to be stable at low temperatures. The hydrated to β transformation above room temperature was found to occur at 305 K. This transition is first order and most likely a one‐step process, rather than a two‐step process as had been suggest

ISSN:0377-0486    

DOI:10.1002/jrs.1250260408

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman and IR spectra of poly(L‐lactic acid) in the amorphous and semicrystalline states were recorded from 3600 to 100 cm−1. Complete vibrational assignments are proposed. In the Raman spectra, the splittings of thevC=O stretching and the δCCO bend are characteristic of the crystalline phase and the presence of the two lines at 923 and 520 cm−1indicates a 103helical confor

ISSN:0377-0486    

DOI:10.1002/jrs.1250260409

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe combination of Raman spectrometry and radiotracer techniques allowed accurate measurements of ion‐exchange kinetics. The exchange of chloride for benzoate or benzenesulphonate ions was studied. These ions were selected as models to simulate the fouling of membranes, a major inconvenience frequently encountered in membrane processes, especially in bio‐industries. The experimental data were compared with the theoretical treatment proposed for two possible hypotheses, namely particle or film diffus

ISSN:0377-0486    

DOI:10.1002/jrs.1250260410

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractTryptophan‐2,4,5,6,7‐d5(dTrp), in which all the carbon atoms of the indole ring are deuterated, is sometimes used for isotopic labelling of Trp residues in proteins and peptides. The vibrational wavenumbers of the deuterated indole ring were examined in the Raman spectra of eight crystals of dTrp derivatives and compared with the crystal structure and the indole N1‐H stretching wavenumber, a direct indicator of hydrogen bonding strength. The comparison has shown that the Wd4 mode around 1445 cm−1and the Wd5 mode around 1410 cm−1of dTrp increase in wavenumber with increase in the strength of hydrogen bonding at the indole N1H site. Another in‐plane vibration of the deuterated indole ring, Wd3, around 1520 cm−1has been found to change in wavenumber as a function of the absolute value of the torsional angle |χ2, 1| about the Cα—Cβ—C3—C2linkage. These marker bands of hydrogen bonding and conformation are expected to be useful in the structural analysis of proteins and peptides that

ISSN:0377-0486    

DOI:10.1002/jrs.1250260411

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY