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  • 1
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Discrete resonance Raman scattering (DRRS) from the ground X1Σg+(νg = 0, Jg = 0-2) state of H2 via excited intermediate states B1Σu+(νi = 0-3, Ji = 0-3) and C1Πu(νi = 0-3, Ji = 1-3) was studied theoretically, applying the reduced density operator formalism. The Raman Spectra for the pure rotational, fundamental and higher overtones are presented. The intensities of the Raman lines for O, Q and S branches were calculated using thermal Boltzmann factors for vibrational-rotational distribution at room temperature (300 K). The calculated DRRS cross-sections are found to be many orders of magnitude larger than normal (non-resonance) Raman cross-sections for H2 or continuum resonance Raman cross-sections for molecular ions such as HD+.
    Additional Material: 10 Ill.
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  • 2
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: IR data for vapour, liquid and matrix-isolated bis(chlorocarbonyl) disulphide and Raman data for the liquid were obtained. The observed features agree with the existence of one conformer with C2 symmetry in both the liquid and vapour phases. The 13C NMR spectrum was measured and the results were compared with those for related molecules. Some stretching force constants were derived for this conformer from semi-empirical calculations.
    Additional Material: 3 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 715-719 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By means of a conventional Raman spectrometer that had been carefully designed for near-infrared Raman excitation, it was possible to record highly resolved Raman spectra of solid polycrystalline potassium and barium permanganate. The spectra of these deeply coloured materials are of high quality and comparable to those reported hitherto, obtained using Fourier transform Raman techniques and near-infrared excitation. Full site symmetry splitting and partial factor group splitting of the bands of the permanganate ion could be observed.
    Additional Material: 8 Ill.
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The asymmetric torsional potential function of n-butane has been redefined based on a combination of results obtained from experimental and theoretical calculations. From the vibrational spectra of gaseous n-butane below 500 cm-1 the asymmetric torsional fundamentals of the more stable s-trans and high-energy gauche conformations of n-butane have been assigned at 121.28 and 116.60 cm-1, respectively, each with excited states falling to lower frequencies. Additionally, from variable-temperature studies of the Raman spectra for n-butane-d0 and d10, the conformational enthalpy difference has been determined to be 381 ± 41 cm-1 (1089 ± 117 cal mol-1) and 369 ± 72 cm-1 (1055 ± 206 cal mol-1), respectively. Optimized structural parameters, obtained from ab initio methods, for the s-trans and gauche conformers have been used to allow for structural relaxation during the asymmetric internal rotation and to place constraints on the determined potential function. The resulting potential coefficients are V1 = 584 ± 7, V2 = -96 ± 7, V3 = 1165 ± 3, V4 = 45 ± 3, V5 = -3 ± 2 and V6 = -40 + 1 and the s-trans to gauche, gauche to gauche and gauche to s-trans barriers are determined to be 1274, 1370 and 891 cm-1, respectively, with an enthalpy difference between the conformers of 383 ± 17 cm-1 (1095 ± 49 cal mol-1). This potential function is consistent with a dihedral angle for the gauche conformer of 65.4°. Additionally, this potential has a ‘syn’ barrier, which is the energy difference between the s-trans minimum and the gauche to gauche transition state, of 1753 cm-1 (5.01 kcal mol-1), which is in excellent agreement with the most recent value of 1836 cm-1 (5.25 kcal mol-1) obtained from a very high-level ab initio calculation. In order to provide a more complete description of the normal vibrational modes of n-butane, normal coordinate analyses have been completed for n-butane-d0, -d5 and -d10 based on force constants from ab initio calculations. The infrared (3500-40 cm-1) and Raman (3500-10 cm-1) spectra of n-butane-d5 and -d10 have been obtained and complete vibrational assignments are provided. The structural parameters, conformational stabilities, barriers to internal rotation and vibrational frequencies which have been determined experientally are compared with those obtained by ab initio methods.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 6
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The picosecond time-resolved Raman spectra of p-erphenyl and its deuterated analogue (dl4) in the first excited singlet (S1) electronic state were observed in heptane and acetonirile solutions. The most intense band in the S1, p-erphenyl at 750 cm-1 is assigned to an in-plane ring vibration based on the shift on the deuteration. The peak position and the bandwidth of the 750 cm-1 band change as the time delay between the pump and probe pulses changes. The initial changes in the position and width appear between 0 and 5 ps, which can be attributed to the strong electric fields of the pump and probe light pulses. After the initial changes are over, the position and the width of the 750 cm-1 band change gradually to their stationary values until about 30 ps. These changes are probably due to the cooling of the solute-solvent system. Similar changes are recorded for two other Raman bands at 993 and 1018 cm-1.
    Additional Material: 9 Ill.
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  • 7
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared, Raman and UV resonance Raman spectra of adenosine and its 1,3-15N2, 2-13C, and 8-13C isotopic analogues were measured in neutral aqueous solution (Raman and UV Raman) and in the crystalline state (infrared and Raman). The observed isotopic wavenumber shifts are useful in distinguishing adenine ring vibrations from ribose vibrations. In-plane modes of the adenine ring are selectively enhanced in UV resonance Raman spectra, which facilitates the assignment of the in-plane vibrations. In addition to the in-plane modes, a ribose vibration coupled with adenine in-plane vibrations was identified in the UV resonance Raman spectra. The fundamental wavenumbers for 22 in-plane normal modes of the 9-substituted adenine ring of adenosine in the 1700-250 cm-1 region are proposed. Although the fundamental wavenumbers of adenosine correspond well with those of adenine above 1350 cm-l and below 800 cm-1 the vibrations in the 1350-800 cm-1, region are appreciably affected by the presence of the N-9 - C-1′ glycosidic bond and the couplings between ribose and adenine ring vibrational motions. The adenosine fundamental wavenumbers and their isotopic shifts reported here may be useful in analysing vibrational spectra of adenine nucleosides and nucleotides and in improving the force field of the 9-substituted adenine ring.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The Raman spectra of α-octyl-ω-methoxyoligo(oxyethylene)s, CH3(CH2)7(OCH2CH2)mOCH3 (m = 1-4), were measured in the solid state. The molecular conformation of these compounds was determined by a spectral analysis based on the key conformational bands. The conformation of the inner oxyethylene segments changes from an extended structure to a helical structure as the number of oxyethylene units increases. The difference in the conformational behaviour between the present methoxy-ended compounds and the corresponding hydroxy-ended compounds is associated with the different layer structures of the crystals.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 631-639 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A method for picosecond time-resolved pump-probe Raman spectroscopy using temporally incoherent light (‘incoherent pump-probe Raman spectroscopy, or simply IPPR spectroscopy’) is proposed. The theoretical formulation of IPPR scattering based on Gaussian random statistics is described. It is predicted that the temporal resolution in IPPR experiment is not determined by the duration of pump and probe pulses, but by the cross-correlation time between the pump and probe lights. The delay-time dependence of the IPPR intensity is expected to show the same behaviour as that in conventional time-resolved Raman spectroscopy which uses coherent ultra-short light pulses, except for a constant background always existing in IPPR scattering. This method was examined experimentally for Raman scattering from electronically excited trans-stilbene in n-hexane solution. In accordance with the prediction, picosecond decay of the Raman band at 1565 cm-1 arising from the trans-stilbene molecules in the S1, state is observed with the use of nanosecond pump and probe pulses with a cross-correlation time of ca. 100 ps. No decay is observed for the Raman bands of the solvent. Effects of saturation arising from the frequency-doubling, pumping and Raman processes on the IPPR signal are also discussed. The ratio of the delaytime dependent part to the background (contrast ratio) is predicted to decrease in the presence of saturation.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 647-653 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rovibrational Raman spectrum of dimethylacetylene (but-2-yne) was recorded photoelectrically at medium resolution. Depolarization ratios and relative normalized scattering cross-sections were determined for five fundamentals and a number of strong overtones.
    Additional Material: 10 Ill.
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