摘要:

AbstractThe infrared and Raman spectra of liquid 2, 4‐dimethoxypyrimidine and solid 6‐chloro‐2,4‐dimethoxypyrimidine and the near ultraviolet spectra of their vapours are reported. An assignment of fundamentals is proposed. Spectra in polar solvents in the UV region are also reported and the effect of solvents is di

ISSN:0377-0486    

DOI:10.1002/jrs.1250160102

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe intensities of the Raman lines corresponding to the intramolecular stretching modes of (HCl)2have been calculated from an SCF wavefunction. It is found that the derivatives of the mean polarizability and of the polarizability anisotropy of the proton donor unit are enhanced, while the corresponding properties of the proton acceptor unit remain unaffected. The theoretical intensity ratio is calculated to be 1.69 in qualitative agreement with experiment.

ISSN:0377-0486    

DOI:10.1002/jrs.1250160103

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractLes spectres Raman et infrarouge de l'acide diéthylmalonique et de ses sels alcalins en solution aqueuse (H2O et D2O) ontété étudiés dans le domaine 3500‐200 cmminus;1. L'analyse du facteur de dépolarisation des raies Raman nous permet de conclure que l'acide diéthylmalonique et le sel neutre, comme I'acide diméthylmalonique et son sel neutre, appartiennent au groupe de symétrieC2tandis que le sel acide répond au groupeCs; I'existence d'une liaison hydrogéne intramoléculaire dans le sel acide est discutée. Une attribution des vibrations fondamentale

ISSN:0377-0486    

DOI:10.1002/jrs.1250160104

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe totally symmetric ν1vibrational modes of the anionsN3−and NO3−have been studied in aqueous solution with very high precision. The effect of different alkali metal cations (Li+, Na+, K+, Rb+and Cs+) has been systematically recorded as a function of the solution concentration. The experimental results show that the anion ν1mode frequencies are dependent on both the cation present and on the solution concentration. Extrapolation of the experimental data yielded precise values of the anion ν1frequencies in the limit of infinite dilution. These frequencies are 1342.7 ± 0.1 cm−1for N3−and 1047.4 ± 0.1 cm−1for NO3−. When Li+or Na+was present in solution with the azide anion, the ν1frequency was shifted to a higher value than the infinite dilution frequency, with both cations having approximately the same effect, whereas when K+, Rb+or Cs+was present the ν1frequency was decreased, the largest decrease being caused by Cs+, followed by Rb+, with the smallest decrease being caused by K+. In the case of the nitrate anion, the cations Na+, K+, Li+and Rb+were all responsible for an increase in the NO3−ν1frequency with respect to the infinite dilution value, with the magnitude of the perturbation decreasing from Na+to Rb+. WhenCs+was present the NO3−ν1frequency was observed to decrease by a very small amount. It is suggested that for the vibrationally excited azide anion, the cation perturbation occurs through a form of polarizability interaction. However, the cation‐nitrate anion interaction is thought to occur through the effect that the hydrated cation has on the vibrationally excited nitrate a

ISSN:0377-0486    

DOI:10.1002/jrs.1250160105

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe resonance Raman spectra of13C‐ and2H‐substituted carotenoids were observed from photosynthetic bacteria cultured in13C‐and2H‐substituted media, respectively. The observed Raman bands of13C‐ and2H‐substituted carotenoids could be reasonably assigned on the basis of the normal coordinate analysis of a model molecule. This gave substantial support to the previous assignments of the Raman and infrared bands of

ISSN:0377-0486    

DOI:10.1002/jrs.1250160106

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractRaman spectra of the arabinonucleosides ARA‐A and ARA‐C and their protonated species have been recorded and compared with those of adenosine and cytidine and protonated adenosine and cytidine. The vibrational modes of the molecules have been studied and the characteristic frequencies have been assigned. Thecis‐transgeometry of the sugar hydroxyl groups is clearly indicated from the Raman spectra of the solids and aqueous solutions. The lattice modes of these species are observed in the low‐frequency region of the spectra below 200 cm−1and they, too, reflect the different puckering of thecis‐transsugar hydroxy grops in t

ISSN:0377-0486    

DOI:10.1002/jrs.1250160107

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractGraphite intercalation compounds are of considerable scientific interest for both applied and fundametal reasons (structural ordering). Micro Raman spectroscopy has been used to investigate graphites intercalated with sulphur trioxide. In these compounds, theE2g2vibrational layer mode of the graphite lattice shows the known linear frequency dependence with the inverse of the step as observed for many acceptor‐type intercalates. The frequency behaviour of this mode is also indicative of a difference between intercalated graphites prepared with either liquid or gaseous SO3. A study of the Raman spectra as a function of time allowed information on the intercalation kinetics and the ageing of these materials to be obtaine

ISSN:0377-0486    

DOI:10.1002/jrs.1250160108

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractCalorimetric (DTA), infrared, Raman and inelastic neutron scattering (INS) measurements have been performed for the trimethyloxosulphonium iodide compounds (CH3)3SOI and (CD3)SOI over the range 10–450 K. Two solid‐solid phase transitions were found at about 200 and 250 K and the vibrational study showed that only the low‐temperature crystalline form (III) is completely ordered. From a temperature dependence study of the optical and INS spectra it is concluded that methyl group reorintations are mainly involved in the phase (III)⟷phase (II) transition, while the whole molecule reorientations about the three‐fold axis, partly involved in the phase (II)⟷phase (I) transformation, must be much slower than and decoupled from methyl motions. Finally, the potential barrier height against methyl rotations has been estimated to 13.3 kJ mol−1from the observed torsional frequencies and compares favourably with the activation energies derived from previous NMR experiments (10.9 kJ mol−1) and from quasi‐elastic neutron scattering result

ISSN:0377-0486    

DOI:10.1002/jrs.1250160109

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) by pyridine on gold electrode surfaces to arise from the adsorption of pyridine in or on surface carbon present after the oxidation‐reduction cycle (ORC). Similar Raman ring‐breathing mode spectra for both gold and silver electrodes and sols indicate a common intensely scattering phase which is independent of the metal substrate. The common phase proposed is [carbon‐pyridine]. Auger electron spectroscopy indicates that the SERS spectrum arises from a surface microzone having aCto Au ratio ofca7. Cathodic elimination of microzone carbon results in the elimination of pyridine SERS. Carbon‐enriched (sputtered) gold surfaces exhibit the same ring‐breathing mode pattern as for the conventional SERS surface. Laser carbonization effects are suggested by differences in the SERS intensities observed for the presence and absence of laser flux during the ORC. Laser decarbonization appears to be the origin of the characteristic decay of SERS from gold electrodes. It is proposed that the decay is instantaneous for 514.5 nm Ar+excitation and slower for 647.1 nm Kr+. Differences in pyridine SERS intensities from silver and gold electrodes are attributed to differences detected by Auger spectroscopy in the extent of laser microzone carbonization. On the basis of these findings Au/pyridine SERS has been classifie

ISSN:0377-0486    

DOI:10.1002/jrs.1250160110

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY

摘要:

AbstractSurface‐enhanced Raman scattering (SERS) by pyridine on anodized copper electrode surfaces has been shown to arise from laser damage zones. On the basis of pH dependence studies, the intensely scattering species appears to be a copper complex. Evidence for semi‐macroscopie laser damage zones (ca0.1 mm in diameter,ca500 nm orca1400 atom layers in depth) emerges from laser perforation of thin film electrodes, visual examination, scanning electron micrescopy (SEM), Raman line intensification for laser illumination during the oxidation‐reduction cycle (ORC), uniform laser‐flux perturbations of the cyclic voltammograms and laser interruption intensity studies. These results argue for a much reduced metal surface enhancement factor for this system and against the use of copper SERS effects in studies of electrosorption on undamaged surfaces. SERS from this system at excitation wavelengths greater than 620 nm is expected to involve conventional (non‐surface)resonance enhancement arising from copper(II)‐pyridine complexes (λmax⩾ 590 nm) formed by copper corrosion within the laser damage zone. On the basis of these findings theCu/pyridine system has been classified as

ISSN:0377-0486    

DOI:10.1002/jrs.1250160111

出版商:John Wiley&Sons, Ltd.    

年代:1985

数据来源: WILEY