Results 1 - 10 of 2265
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[en] The phenomena of solvent exchange control the process of solvating ions, protons, and charged molecules. Building upon our extension of Marcus’ philosophy of electron transfer, here we provide a new perspective of ultrafast solvent exchange mechanism around ions measurable by two-dimensional infrared (2DIR) spectroscopy. In this theory, solvent rearrangement drives an ion-bound water to an activated state of higher coordination number, triggering ion-water separation that leads to the solvent-bound state of the water molecule. This ion-bound to solvent-bound transition rate for a BF4--water system is then computed using ab initio molecular dynamics and Marcus theory, and is found to be in excellent agreement with the 2DIR measurement.
[en] High-resolution CARS spectra of molecular iodine were recorded with excitation frequencies in resonance with the absorption continuum of the B(3PIsub(0+u)) and the repulsive 1PIsub(1u) state. Band shapes are explained by a calculation of the third-order non-linear susceptibility for CARSsub(chi)sup((3))(ωsub(AS)). There is semi-quantitative agreement between the observed and calculated spectra. (orig.)
[en] Two morphologies of nanostructured tin dioxide (SnO2) (i.e., nanobelts and nanowires) were compressed in diamond anvil cells up to 38 GPa followed by decompression. In situ Raman spectroscopy and synchrotron X-ray diffraction were employed to monitor the structural transformations. It was found that nanostructured SnO2 behaved drastically differently than bulk material in terms of transformation pressures, phase stability regions and compressibility. These findings provide new insight into the unique pressure behaviours of nanostructured materials and have profound implications for producing controlled structures with new applications achieved by combined pressure-morphology tuning.
[en] It is not possible to estimate the efficiency of the reaction which produces the excited state in luminol chemiluminescence generated by pulse radiolysis, as was claimed, by Wuerzberg et al. (Auth.)
[en] A computational approach is presented for prediction and interpretation of core-level spectra of complex molecules. Applications are presented for several isolated organic molecules, sampling a range of chemical bonding and structural motifs. Comparison with gas phase measurements indicate that spectral lineshapes are accurately reproduced both above and below the ionization potential, without resort to ad hoc broadening. Agreement with experiment is significantly improved upon inclusion of vibrations via molecular dynamics sampling. We isolate and characterize spectral features due to particular electronic transitions enabled by vibrations, noting that even zero-point motion is sufficient in some cases
[en] This Letter reports a sensitive method using HPLC-Fluorescence detection of OH. in liquid water under high-energy heavy ion irradiation. The coumarin-3-carboxylic-acid (3CCA) molecule was selected for probing OH. and providing the fluorescent 7-hydroxy-coumarin-3-carboxylic-acid (7OH-3CCA). Since the concentration limit achievable is better than 1 nM, the radiolytic yields were determined with a sensitivity of 2 * 10-9 mol/J for 4.8 GeV-12C6+ of and 20 GeV-40Ar18+ in the ns time range. They decrease with the linear energy transfer from 2.8 * 10-7 to 1.3 * 10-7 mol/J (C6+ of 11 eV/nm) and 1.5 * 10-7 to 0.9 * 10-7 mol/J (Ar18+ of 90 eV/nm) which is in agreement with the literature data. (authors)
[en] We demonstrate here that equilibria of electrolytes between a water phase and an (organic) solvent phase containing amphiphilic extractants depend not only on complexation toward nearest neighbors but also on long range supramolecular interactions (LRI). Taking into account bulk, polarization and chain reorganization terms, we show that the net free energy difference associated with one metal ion transfer from water results from a strong inhibition (≥25 kBT/ metal ion) due to colloidal long range interactions competing with differences in complexation considered in supramolecular chemistry (≅-30 kBT/ metal ion). LRI also influence selectivity. (authors)
[en] Pulse radiolysis of deuterated aqueous LiCl glasses at temperatures in the range 6 K to 70 K show that the yield G(e-sub(IR)) of infrared absorbing electrons (e-sub(IR)) increases sharply as the temperature is lowered when [LiCl] >= 10 M. Under these conditions the yield of visible absorbing electrons (e-sub(vis)) decreases, but to a lesser extent. When [LiCl] >= 8 M, G(e-sub(IR)) and G(e-sub(vis)) are both much less dependent on temperature. These data suggest that at very low temperatures e-sub(IR) are not trapped exclusively in a purely aqueous environment. (Auth.)