摘要:

AbstractThe resonance Raman excitation profiles of tryptophan in the region 240‐200 nm were calculated, taking into account the molecular properties of its chromophore, indole. The relevant quantities such as state displacements and vibronic coupling terms were evaluated by means of quantum mechanical semi‐empirical methods. The results allow the identification of the strongest modes and of the main mechanism governing the Raman scattering. It is found that the spectrum is dominated by the terms in resonance with theBbandBastates of indole, with possible interference between these contributions. The vibronic effects, negligible in resonance, become important in preresonance regi

ISSN:0377-0486    

DOI:10.1002/jrs.1250220702

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractIt is demonstrated that the use of pulsed lasers in near‐infrared Fourier transform Raman spectroscopy can give a significant increase in signal‐to‐noise ratios over continuous‐wave measurements made using the same average laser power. It is also shown that when a thermal (or other relatively long‐lived) background is present, the use of pulsed excitation can greatly reduce its effect and, under certain circumstances, can allow it to be subtracted c

ISSN:0377-0486    

DOI:10.1002/jrs.1250220703

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractPolarized IR spectra in the 20–400 cm−1region and Raman spectra in the 0–200 cm−1region were measured at room and liquid nitrogen temperature for crystals of two phases ofm‐nitrophenol (mNPh). The Raman spectra of the orthorhombic mNPh crystal were measured as a function of temperature from room temperature up to 360 K for spectroscopic evidence of a phase transition. The symmetries of lattice and low‐frequency internal vibrations are discussed. The influence of decreasing temperature on the bands produced by the hydrogen bridge vibration is presented. The role of the hydrogen bond in the mechanism of the phase transition and the metastability of the monoclinic phase i

ISSN:0377-0486    

DOI:10.1002/jrs.1250220704

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe use of a liquid nitrogen‐cooled unintensified charge‐coupled device (CCD) multi‐channel array detector combined with a continuous‐wave Nd: YAG laser operating at 1064 nm and a triple grating spectrograph to obtain Raman data in the low‐frequency range down to 25 cm−1is reported. The capabilities of near‐infrared multichannel Raman microanalysis, which permits the acquisition, with a conventional optical microscope attachment, of Raman spectra with a spatial resolution of better than a few micrometres, is als

ISSN:0377-0486    

DOI:10.1002/jrs.1250220705

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractSingle crystals of the fluoride compound KY3F10(Oh5) were studied by Raman scattering from 40 to 950 K. Group theory analysis predicts 3A1g+ 4Eg+ 6F2gRaman‐active modes, but the experimental spectra show twoF2gmodes missing. Over the whole temperature range the frequency shifts are negligible whereas the line widths show a strong increase with temperature. Both reversible and irreversible line width behaviour are exhibited for different temperature runs, indicating a complex microscopic phenomenon underlying the creation of defects responsible for these line widths and their interaction with the different phonon modes. An approximate activation energy for defect creation of ΔE≈︁ 0.3 eV can be obtained from the temperature behaviour of the line widths. This activation energy may be connected with the high‐temperature ionic conduction mentioned previously for this

ISSN:0377-0486    

DOI:10.1002/jrs.1250220706

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe polarized Raman spectra and infrared absorption spectra of NiI2· 6H2O were measured in the 50–4000 cm−1region at low temperatures. Deuterated samples were also studied and gave results which were useful for interpretation purposes. Satisfactory assignments of water internal and external modes and lattice vibrations were made. The vibrational analysis, on the basis of which the assignments were made, was related to theD34factor group; however, the symmetry of the Raman‐active bands, as deduced from polarized spectra, suggests that for water librations theC2hfactor group provides a better basis for interpre

ISSN:0377-0486    

DOI:10.1002/jrs.1250220707

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractA high‐resolution (0.003 cm−1) coherent anti‐Stokes/Stokes Raman spectrometer has been used for recording the resolved rotational structure of theQ‐branch of nitrogen in argon‐nitrogen mixtures. Spectra were obtained at pressures of 50‐760 Torr and temperatures of 295 and 140 K with the object of determining argon collisional‐broadening coefficients of nitrogen rotational lines. Semi‐classical calculations of these coefficients, employing a number of model potentials, were carried out. the experimental and theoretical data are compare

ISSN:0377-0486    

DOI:10.1002/jrs.1250220708

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Raman and IR spectra of lactic acid and sodium lactate in aqueous solution and methyl lactate as a pure liquid were recorded from 3600 to 100 cm−1. Vibrational assignments are proposed for the three compounds. The effects of hydrogen bonding on the ΔOH vibrations of the hydroxyl alcohol group were studied and the results suggest both inter‐ and intra‐molecular hydrogen‐bonded ass

ISSN:0377-0486    

DOI:10.1002/jrs.1250220709

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman phonon spectroscopy in the 10–150 cm−1shift range was used to study the phase transition in ano‐aminobenzoic acid crystal (II). At 77 K, twelve distinct phonon modes are observed whereas at 300 K the spectrum shows ten phonon bands. The temperature dependence of the phonon frequencies and band widths suggests that the crystal goes through a phase transition atca.200 K. The temperature dependence of the internal modes predicts that the phase transition is associated with some structural change in the phenyl

ISSN:0377-0486    

DOI:10.1002/jrs.1250220710

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY

摘要:

AbstractRaman and infrared spectra of NH4H2(IO3)3and KH2(IO3)3were recorded and analysed. The observed splittings of the stretching modes of IO3−are due to the distortion of the IO6octahedra. In NH4H2(IO3)3, the ammonium ion can rotate freely and the NH4+group forms only weak hydrogen bonds with the oxygen atom. Owing to Fermi resonance, three stretching bands are observed for the OH vibration in both compounds. The hydrogen bonds are slightly shorter in KH2(IO3)3than in NH4H2(IO3)

ISSN:0377-0486    

DOI:10.1002/jrs.1250220711

出版商:John Wiley&Sons, Ltd.    

年代:1991

数据来源: WILEY