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Abstract— Illumination of chlorophyll at low temperature, in solvents containing organic Lewis bases and oxygen, leads to oxidation of the C-2 vinyl group. This oxidation proceeds through a series of thermal and photochemical changes, including initial formation of a new compound (I) absorbing at 620 nm. This undergoes further rapid photochemical (or thermal) conversion back to a chlorin-like substance (II), and much slower phototransformation to a third intermediate (III) absorbing near 500 nm. The reaction requires complexed metal (Mg or Zn), but not an intact cyclopentanone ring. The ‘620’ photoproduct is assigned to a cyclic peroxide involving C-1 of chlorophyll and the vinyl group. 相似文献
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Different thermal treatments were used in order to follow the structural relaxation of m-toluidine by thermally stimulated depolarization currents (TSDC) in the sub-T g temperature region. In some of these thermal treatments, the ageing time, t a, and the probing (or polarization) time, t P, are varied independently in order to allow a clear understanding of the exploration of the energy landscape which occurs as a consequence of the structural relaxation. The TSDC results show that ageing induces a shift to higher temperatures of the TSDC peaks, in a way similar to that observed in the calorimetric heat capacity overshoot. More importantly, TSDC results show that ageing induces a decrease of the activation energies with regard to the window defined by the probing time and a sharpening of the energy distribution of the modes of motion that are present in the glass, in the studied sub-T g temperature region. 相似文献
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CHRISTOPHE LEROT MARC LENGELÉ JACQUES WALRAND JEAN-PIERRE BOUANICH GHISLAIN BLANQUET 《Molecular physics》2013,111(22):3521-3527
Using a tunable diode laser spectrometer, we have measured O2 broadening coefficients of 12C32S2 for 31 lines in the v 3 fundamental band near 6.5 μm and 12 lines in the v 3—v 1 band near 11.4 μm. The collisional halfwidths are obtained by fitting the spectral lines with a Voigt and a Rautian profile. The broadening coefficients of 12C32S2-O2 are also calculated from semiclassical theory involving, in addition to electrostatic interactions, successively the atom-atom Lennard-Jones model and a simple formulation for the anisotropic dispersion forces, leading to more satisfactory results. 相似文献
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DIFFRACTION BY A FINITE STRIP 总被引:1,自引:0,他引:1
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