摘要:

AbstractThe Raman scattering from echelette silver gratings coated withp‐nitrobenzoic acid (PNBA) films was measured as a function of the angle of incidence of the exciting laser beam. It was found that on excitation of surface plasmon polaritons (SPPs) on the grating, the Raman scattering intensity of the adsorbed PNBA−species is enhanced by a factor of five compared with its intensity at off‐resonance angles of incidence. However, an enhancement of about a factor of 10 in our estimation is observed withs‐polarized radiation independent of the angle of incidence, indicating the presence of some supplementary mechanism other than the high‐field intensity of SPP in the enhancement process. No Raman bands due to PNBA were observed in the thickness range up

ISSN:0377-0486    

DOI:10.1002/jrs.1250250502

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe Raman, resonance CARS (coherent anti‐Stokes Raman scattering) and CSRS (coherent Stokes Raman scattering) spectra of α, α′, β, β′‐deuteratedtrans, trans‐1,4‐diphenylbuta‐1,3‐diene (DPB‐d4) in theSo,S1,T1, radical cation and radical anion states were studied. The radical ions were produced transiently by ns‐pulsed UV irradiation in a solution containing electron donors ar acceptors. A comparative study of the observed Raman frequencies with those of DPB‐d0permitted vibrational assignment of the transient species of DPB. Features relating to spectral and structural characteristics of the transient species of the shorter diphenylpolye

ISSN:0377-0486    

DOI:10.1002/jrs.1250250503

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractMeasurements of the low‐frequency Raman spectra (LFRS) (below 100 cm−1) of poly(methyl methacrylates) in solution are reported. The reduced intensity exhibits a power law dependence on the frequency at any concentration and at any conversion rate of the polymerization reaction. Even monomeric liquids such as toluene and methyl methacrylate show such a power law behaviour. The results are compared with recent theories on low‐frequency Raman scattering from fractal structures and suggest that a more careful interpretation of LFRS is n

ISSN:0377-0486    

DOI:10.1002/jrs.1250250504

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractA simple method is described for constructing symmetry‐allowed polar tensors forn‐photon processes of rank three and four by using polar tensors of rank one and two. The consideration is restricted here to the triclinic, monoclinic and orthorhombic crystal classes and intrinsic symmetry is not taken into account. Expansion to higher order tensors is possi

ISSN:0377-0486    

DOI:10.1002/jrs.1250250505

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe vibrational spectra of NaNH4SO4· 2H2O (SASD) and its 5% deuterated system were observed in the region of the O–X and N–X stretches (X = H or D) over the temperature range 300–25 K. A similarity was found in the Raman spectral features associated with water molecules at room temperature and belowTc, which were, however, different from those just aboveTc. A λ type of temperature dependence with a large wavenumber jump atTcwas found for the main Raman band at 3423 cm−1. This was explained qualitatively in terms of the strong correlation between the Raman mode and the order parameter. A similar result was observed for the decoupled OD modes. The analysis of their temperature dependence revealed characteristics of the phase transition mechanism in SASD. The λ type of temperature dependence was not found in decoupled modes associated with a

ISSN:0377-0486    

DOI:10.1002/jrs.1250250506

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractRaman spectra of a 3‐methyl‐4‐nitropyridineN‐oxide crystal were investigated as a function of pressure in a diamond‐anvil cell up to 93 kbar at room temperature. The crystal shows successive reversible phase transitions at 8, 20 and 60 kbar. Above 60 kbar, all of the external Raman peaks and most of the internal peaks were found to vanish, and this is interpreted as due to polymerization or a crystalline‐to‐amorphous phase transition. On decreasing the pressure, this amorphous state persists to about 20 kbar, and then the spectrum can be recovered completely on decreasing the pressure continuously to ambient, Zallen and Slade's vibrational scaling law was success

ISSN:0377-0486    

DOI:10.1002/jrs.1250250507

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractResults of a high‐temperature Raman spectroscopic investigation up to 522 K carried out at ambient pressure on an antiferroelectric PbHfO3multi‐domain single crystal are reported. The changes in the Raman spectral features show that temperature‐induced phase transitions occur at 435 ± 1 and at 484 ± 1 K. The first transition is possibly to a tetragonal structure and the second is to the cubic perovskite phase. The behavior is consistent with the earlier x‐ray study of PbHfO3. No soft mode behavior associated with the transitions was detected in the Raman spectra of PbHfO3. The changes observed in the high‐temperature Raman spectra of PbHfO3are similar to those found in the spectra of isostruct

ISSN:0377-0486    

DOI:10.1002/jrs.1250250508

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractFourier transform (FT) Raman spectroscopy has been proved to be an adequate technique for the study of the quantitative structural changes which take place in poly(ethylene terephthalate) on annealing. The two‐phase conformational model proposed previously in the infrared domain using photoacoustic FTIR has been extended to the Raman domain. Moreover, typical Raman spectral changes with the thermal process have been directly related to conformational rather than crystallinity changes. The correlation between the percentage of thetransisomer obtained by FT‐Raman and skin layer crystallinity values obtained by differential scanning calorimetry allows the crystalline and amorphoustransisomer contents to be obtained and their evolution with the annealing process to be follo

ISSN:0377-0486    

DOI:10.1002/jrs.1250250509

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractFT‐Raman spectroscopy has been proved as a useful tool to form the quantitative study of conformational changes in glass‐fibre‐reinforced annealed poly(ethylene terephthalate) (PET). Based on composite Raman bands directly related to the ethylene glycol fragment in thetransandgaucheconformations, it was observed that glass‐fibre‐reinforced PET exhibits the same two‐phase conformational model as the isolated matrix. In contrast to the matrix, annealing thermal treatment of the composite does not seem to affect the composite microstructure since the isomer contents remain constant with annealing temperature. Thus, the microstructure is mainly determined by the fabrication process and its effect is similar to that observed in an annealed matrix at the highest temperatures. Therefore, the disorderedtransisomer content can be considered negligible in the composite. In contrast to the spectroscopic results, the crystallinity values of the composite obtained by differential scanning calorimetry (DSC) only tend to coincide with those of the annealed matrix at temperatures above 150°C, and below this temperature they are always lower. A comparison between the results obtained by FT‐Raman and DSC techniques seems to indicate an improvement in the fibre–matrix interface in which an interfacial structure with a low degree of perfection changes to more

ISSN:0377-0486    

DOI:10.1002/jrs.1250250510

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY

摘要:

AbstractAb initioSCF MO calculations at the 3–21G level and the vibrational spectra [Raman and Fourier transform (FT) IR] of liquid‐phase 2‐chloro‐ and 3‐chlorostyrene are reported. For 2‐chlorostyrene, theab initiocalculations predict skew andgaucheminima, with an energy difference of 11.5 kJ mol−1, and no evidence of more than one conformer was found in the liquid‐phase Raman and FTIR spectra. The Raman spectra of liquid 3‐chlorostyrene show pairs of bands whose temperature‐dependent intensities clearly suggest the occurrence of a conformational equilibrium. From these bands, assigned to non‐planarcisandtransconformers, atrans–cisenergy difference of 2.3 ± 0.5 kJ mol−1was obt

ISSN:0377-0486    

DOI:10.1002/jrs.1250250511

出版商:John Wiley&Sons, Ltd.    

年代:1994

数据来源: WILEY