摘要:

AbstractThe Raman spectra of liquid 3‐fluorostyrene show pairs of bands whose temperature‐dependent intensities clearly suggest the occurrence of a conformational equilibrium. From these bands, assigned tocisandtransconformers, atrans–cisenergy difference of 0.70 ± 0.20 kJ mol−1was obtained for the liquid phase, higher than the reported gas‐phase microwave andab initiovalues. The effects of dilution with several solvents of different polarity properties are reported and the improved relative stability of thecisform in high‐polarity solvents is interpreted in terms of medium effects on intramolecular through‐space dipole–dip

ISSN:0377-0486    

DOI:10.1002/jrs.1250240702

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIntensities of the OD stretching modes in the Raman spectra of LiX solutions (X = Cl, Br and I) in CH3OD were measured. It is shown that the intensities increase significantly with increasing halide concentration owing to a pre‐resonance Raman effect arising from charge‐transfer states of hydrogen bonds between halide ions and their solvated methanol molecules. The small dissociation of dissobed Lil molecules is the reason why no enhancement of the intensity is observed in the Raman OD stretching spectrum for a glassy methanolic LiI solut

ISSN:0377-0486    

DOI:10.1002/jrs.1250240703

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractGlasses in the systemxPbO·(100 –x)B2O3(0 ≤x≤ 30 mol.%) were studied by Raman spectroscopy. The conversion of boroxol rings into borate rings containing one or two BO4groups due to the transformation of threefold to fourfold coordinated boron with increasing content of lead oxide was determined from the intensities of the Raman peaks at 805 and 770 cm−1. Quantitative measurements were carried out on highly finished spherical samples to allow different reflection losses of the samples to be taken into

ISSN:0377-0486    

DOI:10.1002/jrs.1250240704

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA single‐pass total internal reflection (TIR) Raman technique for studying the stretching modes of water close to Langmuir–Blodgett (LB) films of amphiphilic molecules is described. The method is based on efficient collection of the 458 nm (argon ion laser) excited Raman scattering from water layers adjacent to a sapphire prism coated with LB films. The experimental arrangement permitted comparison between scattering from vicinal water and that from bulk water. Polarized TIR Raman spectra for D2O of reasonable signal‐to‐noise ratio were obtained at moderate laser excitation powers (50–100 mW). However, the levels of parasitic scattering from the prism compromised the collection of corresponding spectra of good quality for H2O. Comparisons were made between the OD Raman band for D2O layers adjacent to the prism coated with LB films of ω‐tricosenoic acid with that for D2O near the uncoated prism. Small but well defined increases in the intensity of the low‐frequency shoulder of the OD band near 2400 cm−1for the coated compared with the uncoated case are discussed in terms of possible structuring of the vicinal water by the hydrophobic film. Refinements to the experimental set‐up to increase further the sensitivity for probing water layers near surfaces

ISSN:0377-0486    

DOI:10.1002/jrs.1250240705

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThin‐film diamond temperature sensor arrays used in harsh aerospace environments were investigated using micro‐Raman spectroscopy. Raman spectra of three of the samples obtained under specific experimental conditions are presented. On annealing a sample, an increase in graphite content and restoration of long‐range order in its lattice are suggested. Additionally, an untreated sample on irradiation with 1064 nm radiation from a low‐power continuous‐wave Nd: YAG laser exhibits an increase in graphite content. Similar irradiation of an annealed sample shows an increase in the graphite content, a decrease in diamond‐like carbon content and the appearance of a band a

ISSN:0377-0486    

DOI:10.1002/jrs.1250240706

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThin films of polystyrene (PS), polystyrene–polyacrylonitrile (PS–AN) copolymer and poly(methyl methacrylate) (PMMA) containing embedded transition metal carbonyls were characterized by near‐IR Fourier transform (FT) Raman spectroscopy. Several of the films were also examined by FT‐Raman microspectroscopy and the distribution of the metal carbonyls throughout the films was determined by a 2D mapping procedure similar to that described earlier for 2D IR microspectroscopy. The results indicate that the 2D FT‐Raman approach is particularly useful for highly doped films when the absorbances of the ν(CO) modes in the IR spectra of the metal carbonyls are too large to measure accurately. The films are more sensitive to thermal decomposition induced by near‐IR laser irradiation than are the solid metal carbonyls and the PS films are more susceptible than are th

ISSN:0377-0486    

DOI:10.1002/jrs.1250240707

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe use of the transform method was extended so as to permit the treatment of the resonance Raman effect with the participation of two interfering electronic transitions. The relevant equations were tested in the model system [Ru(bipy)2(violurate)]PF6, the Raman excitation profiles of which show clearly the presence of two chromophoric moieties. The present results strongly suggest that the two relevant excited states participate by means of Albrecht'sAterms, whereas the vibronic coupling by theBterm is not decisive. The independence of the two chromophoric moieties is reflected in distinct displacements of the respective potential minima.

ISSN:0377-0486    

DOI:10.1002/jrs.1250240708

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractAn attempt was made to use a Fourier transform (FT) Raman spectrometer as a detector with a gel permeation chromatograph which was otherwise configured in the usual way for the measurement of molar mass distribution in polymers. A low‐volume flow cell was constructed and the detector response tested both off‐line and, in a preliminary way, in‐line with the chromatograph. The particular objective was to establish whether it would be possible to measure the microstructural variation in polybutadiene with polymer molecular weight during the chromatographic process. The detector sensitivity was assessed for a range of polybutadienes with differentcis‐1,4‐,trans‐1,4‐ and vinyl‐1,2‐ contents using tetrahydrofuran as solvent and eluent. Data obtained using visible Raman (488.0 nm) excitation and near‐infrared (1064 nm) excitation were compared. Although it has been established that the Raman spectrometer is one of the best instruments for the evaluation of the microstructure of polybutadiene when used in a conventional way, it lacks the necessary sensitivity to provide quantitative information on polydienes which elute from a chromatograph. However, there is no reason in principle why an FT‐Raman spectrometer should not be used as a concentration detector and for the simultaneous more detailed analysis of polymer composition or micro‐structure during the chromatographic process, provided that the scattering intensity of the solute is high relative to the eluent. The potential advantages and the observed problems of what appears to be a novel experiment with an FT‐Raman

ISSN:0377-0486    

DOI:10.1002/jrs.1250240709

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractA microscale capillary Raman solution flow cell has been developed utilizing conventional high‐performance liquid chromatographic capillary tubing. This cell is suitable for both liquids and gases over a wide range of pressures. The introduction of a liquid flow along the capillary allows the collection of Raman spectra of intensely coloured and highly absorbing solutions, e.g. I2CCl4, using 514.5 nm excitation. The application of this cell to the examination of supercritical fluids is demonstrated. The use of small cross‐section capillary tubing (ca10−5cm2) allows high linear flow‐rates to be maintained with comparatively small solutio

ISSN:0377-0486    

DOI:10.1002/jrs.1250240710

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThermochromism ofN‐(2‐hydroxy‐4‐methoxybenzylidene)‐4‐nitroaniline (HMBNA) was studied by Raman scattering and infrared absorption. HMBNA is yellow when freshly prepared and deepens to orange–red on heating above the melting point. On cooling at room temperature, the orange–red colour is retained for a few months. The change in colour is explained by the change in the molecular structure as indicated by the vibrational spectra. The spectra show that in the thermochromic coloured state the central group of HMBNA takes thecis

ISSN:0377-0486    

DOI:10.1002/jrs.1250240711

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY