摘要:

AbstractFluorescein and its derivatives fluoresceinamine and diiodofluoresceiniodoacetamide have been studied by surface enhanced resonance Raman spectroscopy (SERRS). Adsorption of the dyes at the silver/electrolyte interface requires attractive interactions between polar side groups (such as NH2, OH and COOH) with the metal as a prerequisite for Raman enhancement and fluorescence quenching. It was possible to characterize two prototropic forms of fluorescein and fluoresceinamine by their SERR spectra. Only vibrations of the chromophoric part (xanthene) of the molecule contribute to the measured spectra. Substituents in the phenyl ring influence only the ability of adsorption and the structure of the adsorbed molecules.

ISSN:0377-0486    

DOI:10.1002/jrs.1250170112

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractLithium rubidium sulphate, LiRbSO4(LRS), undergoes a sequence of four phase transitions at 166, 185, 202 and 204°C. The phase between 202 and 204°C is incommensurate. Polarized phonon Raman spectra in the frequency region of 50–1200 cm−1are presented to identify the external and internal vibrational modes at room temperature. The internal mode frequencies of the sulphate ions are presented in the temperature region from −150 to 230°C covering all the phase transitions. The total integrated areas of the ν1, ν2and ν4modes show an anomalous increase across the phase transitions. The frequencies of the symmetric stretching (ν1) and symmetric bending (ν2) modes do not show any changes at the phase transitions, but the width of the ν2mode shows changes across the phase transitions. A small increase in the linewidth of the ν2mode observed in the incommensurate phase is attributed to the influence of the incommensurate modulation wave. A DSC thermogram showed endothermic peaks during heating at all the phase transitions. The IR spectrum recorded at room temperature showed the expectedAuandB

ISSN:0377-0486    

DOI:10.1002/jrs.1250170113

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractMolecular reorientation of liquid trimethylchlorosilane (TMC) has been studied by means of Raman band shape analysis for the temperatures 298, 246 and 218 K. Experimental correlation times were compared with NMR relaxation time measurements and with diffusional and hydrodynamic models. Information theory was used to predictC(1)(t) givenC(2)(t).

ISSN:0377-0486    

DOI:10.1002/jrs.1250170114

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractA general theory of Raman scattering in piezoelectric slab waveguides is presented. If the anisotropy of the uniaxial waveguide material is sufficiently large, incident slab‐guided waves can be scattered by polaritons of the upper branch of the polariton dispersion curve. The angular dependence ω2(θ) of the scattered‐wave frequency has been calculated in detail, for bothy‐ andz‐cut Ti:LiNbO3waveguides in the polariton frequency range ωp=900–5160 cm−1(pump wavelength 4880 Å). The detection of weak proton vibrations within the strong polariton Raman spectrum of proton‐exchanged Ti:LiNbO3wavegu

ISSN:0377-0486    

DOI:10.1002/jrs.1250170115

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractRaman spectroscopic (75 K) and X‐ray crystal structure (135 K) data for Na2Se·9(H, D)2O and Na2S·9(H, D)2O are compared, paying particular attention to the hydrogen bond networks in the two isostructural compounds. The crystal structures differ essentially only with respect to the hydrogen bond lengths of corresponding OH…︁Se and OH…︁S bonds, those to Se being uniformly larger by about 0.1 Å than those to S. The uncoupledνODfrequencies of isotopically dilute HOD molecules are very similar in both compounds, being larger only by about 10 cm−1on average for the selenide than for the sulphide. It can therefore be claimed that the hydrogen‐bond capabilities of the selenide and the sulphide

ISSN:0377-0486    

DOI:10.1002/jrs.1250170116

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractIn addition to CrO42−and Cr2O72−, species such as H2CrO4, HCrO4−and HCr2O72−have been considered to exist in Cr(VI) equilibria in aqueous solution. The Raman spectra of dilute solutions of Cr(VI) at different pH have confirmed the non‐existence of the last three species in a Cr(VI) concentration range between 0.1 M and the lower detection limit of concentration (ca0.003 M). The proposed equilibrium, 2CrO42−+2H+⇌Cr2O72−+H2O, seems to be the only one existing between pH 1 and 11. A quantitative Raman study of the influence of ionic strength on the corresponding apparent formation constant β′22led us to the determination of the equilibrium constant at zero ionic strength, namely log β22=14.85±0.04 at 25°C. In more acidic aqueous Cr(VI) solutions, up to 12Min HNO3, preliminary investigations corroborated the presence of the trichromate and

ISSN:0377-0486    

DOI:10.1002/jrs.1250170117

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractRaman spectroscopy was used to characterize the extremely long duration metastable state of Na2[Fe(CN)5NO]·2H2O single crystals. By excitation with light of λ>540 nm only the Raman spectrum of the ground‐state configuration is obtained. With an excitation wavelength in the range 540–450 nm, the vibrational bands of the ground‐ and metastable‐state configurations are observed together with approximately equal intensities. In the wavenumber shift range 400–2200 cm−1for each vibrational mode of the ground state a Raman band is found, but no splitting of degenerate modes appears. It is concluded that the symmetry of the molecule is not changed by pumping the metastable state. Excitation with light of λ=406.7 nm proves the existence of higher energetic states of the metastable configuration, which do not combine with the ground state. In addition to a thermal decay channel, there exists a further channel for depopulation of the metastable state using red light. Absorption spectroscopic measurements show the existence of an excited electronic state at 685 nm in the metastable configuration. This low‐lying energy level crosses with the first excited electronic level of the ground‐s

ISSN:0377-0486    

DOI:10.1002/jrs.1250170118

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe resonance excitation profile for the CC stretch mode oftrans‐polyacetylene has been measured between 1.55 and 3 eV. For the main vibrational line at 1460 cm−1a resonance enhancement of two orders of magnitude was observed for excitation with 1.7 eV. The peak position of the resonance shifted to higher values for a Raman shift larger than 1460 cm−1. The relationship between this position and the Raman shift was found to be different from that between the excitation energy and the satellite peak position. Experimental results have been compared with calculations from the particle in the box model for interrupted conjugations. Semiquantitative agreement was obtained for the various Raman shifts. The difference between the behaviour of the resonance peak and the satellite peak is shown to result from the influence of the distribution function and the lineshape function. The depolarization ratio for the CC stretch mode was observed to be 0.6, which is larger than expected for a randomly oriented anisotropic scatterer. However, it is in agreement with a situation where the scatterer is randomly oriented within

ISSN:0377-0486    

DOI:10.1002/jrs.1250170119

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractIt is shown that as a result of anharmonic coupling of the polariton waves, Stokes and anti‐Stokes waves by a pump wave, an irradiated second wave (two‐beam method) generates new waves from a slab. The frequency of the irradiated wave can be chosen from the Stokes and anti‐Stokes visible region or from the polariton in the infrared region.First numerical results are given for GaP for reflectivity in the polariton and in the Stokes visible region. The spectra show strong amplification of the irradiated

ISSN:0377-0486    

DOI:10.1002/jrs.1250170120

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Raman (10–3500 cm−1) and infrared (50–3500 cm−1) spectra have been recorded for gaseous and solid ethyldimethylphosphine, CH3CH2P(CH3)2. Additionally, the Raman spectrum of the liquid has been recorded and qualitative depolarization values have been obtained. From the fact that several distinct Raman lines disappear on going from the fluid phases to the solid state, it is concluded that the molecule exists as a mixture of thegaucheandtransconformers in the fluid phase with thegaucheconformer being more stable and the only one present in the spectrum of the solid. From a temperature study of the Raman spectrum of the liquid, the enthalpy difference between thegaucheandtransconformers was determined to be 134 ± 32 cm−1(383 ± 92 cal mol−1). Relying on group frequencies and relative intensities of the infrared and Raman bands, and in some cases infrared band contours, a complete vibrational assignment is proposed for thegaucheconformer. The assignment is supported by a normal coordinate calculation which was carried out utilizing a modified valence force field to obtain the frequencies of the normal modes and the potential energy distribution. The CH3‐P torsions have been observed at 208 and 185 cm−1in the gas phase and from these frequencies the periodic barriers to internal rotation have been calculated to be 905 ± 95 cm−1(2.56 kcal mol−1). The CH3‐C torsion was also observed in the gas phase at 217 cm−1from which a periodic barrier of 1134 cm−1(3.22 kcal mol−1) was calculated. The asymmetric torsional mode has been observed for thegaucheconformer in both the infrared and Raman spectra of the gas at 91 cm−1with evidence of ‘hot bands’ at lower frequencies. All of these results are compared with corresponding quantitie

ISSN:0377-0486    

DOI:10.1002/jrs.1250170121

出版商:John Wiley&Sons, Ltd.    

年代:1986

数据来源: WILEY