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101.
Hydrogen bond pairs involving the chromophore indole have been extensively studied in the gas phase. Here, we report high resolution electronic spectroscopy experiments on the indole-NH(3) hydrogen bond pair in the absence and presence of an electric field. The S(1)-S(0) origin band of this complex recorded in zero field at high resolution reveals two overlapping spectra; a consequence of NH(3) hindered internal rotation. The barrier to internal rotation is predicted by theory to be less than 20 cm(-1) in the ground state, therefore requiring a non-rigid rotor Hamiltonian to interpret the spectra. Conducting the experiment in the presence of an applied electric field further perturbs the already congested spectrum of the complex, but makes possible the measurement of the permanent electric dipole moments in its S(0) and S(1) states. These values reveal significant changes in electron distribution that arise from hydrogen bonding effects. 相似文献
102.
The incorporation of nitrogen atoms into the aryl rings of conventional diphenylamine antioxidants enables the preparation of readily accessible, air-stable analogues, several of which have temperature-independent radical-trapping activities up to 200-fold greater than those of typical commercial diphenylamines. Amazingly, the nitrogen atoms raise the oxidation potentials of the amines without greatly changing their radical-trapping (H-atom transfer) reactivity. 相似文献
103.
Manson JL Baldwin AG Scott BL Bendix J Del Sesto RE Goddard PA Kohama Y Tran HE Ghannadzadeh S Singleton J Lancaster T Möller JS Blundell SJ Pratt FL Zapf VS Kang J Lee C Whangbo MH Baines C 《Inorganic chemistry》2012,51(14):7520-7528
[Ni(HF(2))(3-Clpy)(4)]BF(4) (py = pyridine) is a simple one-dimensional (1D) coordination polymer composed of compressed NiN(4)F(2) octahedra that form chains with bridging HF(2)(-) ligands. In spite of significant distortion of the HF(2)(-) bridge, a quasi-1D antiferromagnetic (AFM) behavior was observed with J(FHF) = 4.86 K. 相似文献
104.
105.
Scheicher R. H. Cammarere D. Briere T. M. Sahoo N. Das T. P. Pratt F. L. Nagamine K. 《Hyperfine Interactions》2001,136(3-8):755-758
The microscopic details of the electron transfer in cytochrome c (cyt c) are being investigated by the Muon Spin Relaxation
(μSR) technique. We are using the Hartree–Fock Cluster Procedure to determine the most likely trapping sites for μ+ and muonium (Mu) in the protein chain, and have performed extensive calculations in single amino acid molecules of the protein
chain of cyt c. The double-bonded oxygen atom of the carboxyl group was identified as the trapping site for both μ+ and Mu. Utilizing the wave functions we obtained from the Hartree–Fock calculations, we have determined the hyperfine field
that the μ+ in Mu experiences while the latter is trapped at the oxygen.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
106.
We consider near-zero minima in the photon–atom elastic scattering cross section, possible signatures of the presence of a particular element in a target, using the S-matrix approach. However, the usual formulation of this approach performs an averaging over magnetic substates at the level of the scattering amplitude that is approximate (except for the case of fully filled subshells). We consider whether the predicted near-zero minima persist in a more proper treatment. We find that near-zero minima seen below thresholds in scattering from ground-state atoms generally persist, but near-zero minima seen above thresholds in scattering from excited states may be spurious. 相似文献
107.
H. S. Miley R. J. Arthur E. A. Lepel S. L. Pratt C. W. Thomas 《Journal of Radioanalytical and Nuclear Chemistry》2001,248(3):651-656
An International Monitoring System (IMS) is being created to monitor the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Radionuclide aerosols will be monitored to provide positive proof of an atmospheric explosion. In addition, a group of laboratories will perform quality assurance and confirmatory analyses of samples of interest. The field and laboratory systems will perform gamma-ray spectrometric analysis of air filters. While laboratories may undertake additional analysis such as chemical separation and beta counting, the scope of the work reported here is to make evaluations with respect only to gamma-ray spectrometry. Activation products have not been completely considered and are shaded with uncertainty, from the probability of escape from an underground test and the dependence on the sub-surface elemental composition. 相似文献
108.
A procedure has been developed to extract qualitative and quantitative information on the muonium fractions, in particular the Mu* fraction, in polycrystalline and amorphous materials from their longitudinal field repolarization curves. Preliminary results for amorphous silicon suggests that both the Mu* and Mu* fractions here are generally lower than in crystalline silicon at temperatures below 200K, but the Mu* fraction may survive to room temperature in this disordered host. 相似文献
109.
110.
Scott Pratt 《Acta Physica Hungarica A》2006,25(2-4):329-335
The ability to measure characteristics of source shapes using nonidentical particle correlations is discussed. Both strong-interaction induced and Coulomb induced correlations are shown to provide sensitivity to source shapes. By decomposing correlation functions with spherical or Cartesian harmonics, details of the shapes can be especially well isolated. 相似文献