摘要:

AbstractBy a condensation reaction oftBu2Si(OH)2(L) with titanium and germanium tetrahalides several eight‐membered titanium and germanium cyclosiloxane compounds were prepared in polar solvents. These were crystallized and identified by the usual physical techniques (1H,13C and29Si NMR spectroscopy, x‐ray diffraction and mass spectrometry). Raman and IR spectra were also recorded, which confirmed the structure obtained by x‐ray diffraction. The rings are well characterized by breathing modes which appear around 620–660 cm−1and Si‐O‐M stretching‐bending modes which appear around 950–1000 cm−1. The vibrational modes characterizing thetert‐butyl group are weakly coupled with those of the heterocycles. The corresponding observed bands are close to t

ISSN:0377-0486    

DOI:10.1002/jrs.1250261202

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Raman spectra of liquid 3‐methylstyrene 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 0.8 + 0.2 kJ mol−1was obtained for the liquid phase. On the other hand,ab initiocalculations at the 3‐21G**and MP2/3‐21G* levels predict acisform more stable than thetransform by less than 0.15 kJ mol−1, in good agreement with gas‐phase lit

ISSN:0377-0486    

DOI:10.1002/jrs.1250261203

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractA constrained non‐linear deconvolution method was used to analyse the Raman spectrum of amorphous carbon. The method was tested by applying it to a model spectrum. Before the deconvolution the observed Raman spectrum was smoothed by a least‐squares convoluting procedure. The proper width of the spread function used in the deconvolution was determined by examining the reversibility of the deconvolution process. The deconvolution result for the Raman spectrum of amorphous carbon has a form very similar to the phonon density of states of graphite. This is taken to be additional evidence for Shuker and Gamon's model for Raman spectra of amorphous materials. Potentially, the deconvolution method can also be used for other aspects of Raman spectrum analysis of amorphous materials, such as finding the relative intensity of each peak of study the structure of the mater

ISSN:0377-0486    

DOI:10.1002/jrs.1250261204

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractIt is demonstrated that in the ferroelectric phase of the PLZT‐x/95/5 ceramics the spontaneous polarization is the order parameter, the fluctuations of which are mainly responsible for the dielectric relaxations manifested in the Raman spectra by the appearance and the evolution of a central peak. ForT>315°C, in the paraelectric phase, the spontaneous polarization fluctuations are substituted by the fluctuations of the appearing local concentration polarization. Above the Curie temperature, the thermally activated relaxation process gives an activation energy of 0.7

ISSN:0377-0486    

DOI:10.1002/jrs.1250261205

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe influence of the35Cl/37Cl isotopic disorder of natural chlorine on the Raman and infrared lineshapes of the vibrational modes in PtCl chains was calculated as a function of the interionic force constants in a one‐dimensional model. It is shown that the fine structure of the Raman line is strongly dependent of the Pt3+σ‐Cl and Pt3‐σ‐Cl force constants, and so it can be used to estimate the charge disproportion σ. From the case of [Pt(en)2][Pt(en)2Cl2](ClO4)4it appears that the description of the high‐wavenumber infrared line (v2) requires one to take into account interactions with more distantations. It is also shown that the intensity of the lowwavenumber infrared‐active mode (v3) is so weak that the corresponding line may have never

ISSN:0377-0486    

DOI:10.1002/jrs.1250261206

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe refractive index n(ω,T, p) of molecular chlorine, Cl2, was measured in the ranges of temperatureTbetween 290 and 1100 K and pressurepbetween 104and 2 × 105Pa and at three wavelengths λ = 2μco/ω between 632.990 and 543.516 nm. From these measurements the frequency and temperature dependence of the mean dipole polarizability<α(ω)Tof Cl2was obtained. The polarizabilities were analysed according to theories of Bell and Buckingham, yielding 1020[∂α(ω)/∂r]o/m2= 2.02(22) + 6.27(51) × 10−32(ω/s−1)2for the frequency dependence of the polarizability derivative of chlorine between ω = 0 and 3.5 × 1015s−1. This result is in fair agreement withab initiocalculations, but disagrees with polarizability derivatives obtained from measurements of the differential Raman sc

ISSN:0377-0486    

DOI:10.1002/jrs.1250261207

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe surface‐enhanced Raman (SER) spectra of 1,8‐naphthyridine (napy) adsorbed on silver colloids were measured. An edge‐on configuration for the molecule is suggested, based on a comparison of the SER spectra of napy compared with the conventional Raman spectra of two of its complexes, Ag2,(μ‐napy)2(NO3)2and OsO4(napy), the former serving as a model for an edge‐on configurati

ISSN:0377-0486    

DOI:10.1002/jrs.1250261208

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe backscattered Raman optical activity (ROA) spectra of the β(1‐3)‐linked polysaccharide laminarin, and its dimer repeating unit D‐laminarihiose, together with those of the predominantly α(l‐4)‐linked polysaccharide pullulan, and its trimer repeating unit D‐maltotriose, between 350 and 1500 cm−1in aqueous solution are reported and discussed. Several differences are evident between the ROA spectra of laminarin and D‐laminaribiose which are ascribed to triple helix formation in the polysaccharide. In particular, the signs of four ROA signals betweenca. 1050 and 1150 cm−1are reversed and two ROA signals assigned to vibrations involving the glycosidic link observed atca. 445 and 1431 cm−1change sign and increase in intensity, respectively. In contrast, pullulan, which adopts a random coil‐type structure in aqueous solution, generates an ROA spectrum that closely resemble

ISSN:0377-0486    

DOI:10.1002/jrs.1250261209

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractSurface enhanced resonance Raman scattering (SERRS) from cobalamins is reported. To achieve efficient adsorption and strong SERRS, the molecule is adsorbed on a polysine‐treated silver colloid surface. This provides an organic barrier between the cobalamin and the metal, preventing denaturation, and gives positively charged groups for efficient adsorption. The technique can be used forin situstudies of changes in the metal coordination sphere, as is illustrated by reduction on the surface using dithionite for both cyanocobalamin and 5′‐deoxyadenosylcobalamin. The efficient energy transfer at the surface appears to prevent photodegradation, which is a problem with resonance, and the efficiency of SERRS allows measurements at low effective concentra

ISSN:0377-0486    

DOI:10.1002/jrs.1250261210

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY

摘要:

AbstractMicro‐Raman spectra of picogram to sub‐femtogram quantities of several chromophoric substances adsorbed from dilute solution on silver were measured and compared with similar measurements on some non‐chromophoric substances. The silver surface enhanced resonance Raman measurements require no redox roughening of the surface, sometimes no applied potential and only 1‐2 mW of defocused laser power. The new method by which silver surface enchancement is achieved requires contact of the surface with halide ion solution for several hours. The most astounding results thus far were achieved with 1, 1′‐diethyl‐2,2′‐cyanine iodide (2,2′‐cyanine). Raman spectra of the adsorbate from 20 ml of 1 × 10−17M solution of the dye were measured using the method. Further characteristics of the phenomenon were obtained based on extensive Raman measurements on 2,2′‐cyanine. Some further details resulting from thes

ISSN:0377-0486    

DOI:10.1002/jrs.1250261211

出版商:John Wiley&Sons, Ltd.    

年代:1995

数据来源: WILEY