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81.
K.J. Hoffman 《Journal of Molecular Spectroscopy》2009,254(2):69-20334
Tuneable diode laser absorption spectroscopy has been used to measure the room temperature pressure broadening coefficients (γ) of rotational transitions in the v5 fundamental band of methyl bromide (12CH379Br and 12CH381Br) around 6.9 μm. Nitrogen, oxygen and self-broadening coefficients have been determined for 125 lines in the RQ1, PQ3, PQ5, PQ7 and PQ8 branches and 49 P and R branch transitions. Line profiles within Q branches were recorded at incremental pressures of nitrogen and oxygen up to 15 Torr and fitted to a Voigt profile to yield the broadening coefficients. The nitrogen broadened data for 14 lines, chosen from the five Q branches, were also fitted with Galatry profiles. The line profiles of the P and R branch transitions were recorded for total nitrogen and oxygen pressures of up to 300 Torr and fitted to both Voigt and Galatry profiles. Within individual Q branches, nitrogen broadening coefficients were found to decrease monotonically with increasing J from 0.14 cm−1 atm−1 at low J to 0.09 cm−1 atm−1 at high J. The corresponding values for oxygen were approximately 25% smaller. Self-broadening coefficients were found to vary between 0.48 and 0.16 cm−1 atm−1 with a similar J dependence to the foreign gas broadening for J > 20. However, between J = 2 and J ≈ 20 the broadening coefficient was found to increase with J. The magnitude of the pressure broadening coefficient for P and R branch transitions was found to closely follow the J dependence measured for the Q branch lines. 相似文献
82.
Catherine D. Clark Morton Z. Hoffman D. Paul Rillema Quinto G. Mulazzani 《Journal of photochemistry and photobiology. A, Chemistry》1997,110(3):285-290
The photophysics of three complexes of the form Ru(bpy)3−(pypm)2+ (where bpy2,2′-bipyridine, pypm 2-(2′-pyridyl)pyrimidine and P=1, 2 or 3) was examined in H2O, propylene carbonate, CH3CN and 4:1 (v/v) C2H5OH---CH3OH; comparison was made with the well-known photophysical behavior of Ru(bpy)32+. The lifetimes of the luminescent metal-to-ligand charge transfer (MLCT) excited states were determined as a function of temperature (between −103 and 90 °C, depending on the solvent), from which were extracted the rate constants for radiative and non-radiative decay and ΔE, the energy gap between the MLCT and metal-centered (MC) excited states. The results indicate that *Ru(bpy)2(pypm)2+ decays via a higher lying MLCT state, whereas *Ru(pypm)32+ and *Ru(pypm)2(bpy)2+ decay predominantly via the MC state. 相似文献
83.
A.J. Hoffman 《Linear algebra and its applications》1977,16(2):153-165
Let G be a graph, A(G) its adjacency matrix. We prove that, if the least eigenvalue of A(G) exceeds -1 ? √2 and every vertex of G has large valence, then the least eigenvalue is at least -2 and G is a generalized line graph. 相似文献
84.
85.
Sternfeld T Hoffman RE Saunders M Cross RJ Syamala MS Rabinovitz M 《Journal of the American Chemical Society》2002,124(30):8786-8787
A 3He NMR resonance of C606- containing He is assigned to He2@C606-, thus showing that C60 can also accommodate two helium atoms. The ratio of the di-helium compound relative to the mono- is 1:200, 10 times lower than the equivalent counterpart of C70. The 3He NMR chemical shift of He2@C606- is 0.093 ppm downfield from the already known resonance of He@C606-. In the reduced endohedral mono- and di-helium C70, the 3He NMR chemical shift of He2@C706- is 0.154 ppm upfield from the peak of He@C706-. 相似文献
86.
Allan S. Hoffman 《Macromolecular Symposia》1995,98(1):645-664
One can define “intelligent” polymers as those polymers which respond with large property changes to small physical or chemical stimuli. These polymers may be in various forms, such as in solution, on surfaces, or as solids. One may also combine “intelligent” aqueous polymer systems with biomolecules, to yield a large family of polymers which respond “intelligently” to physical, chemical or biological stimuli. This article overviews such interesting and versatile polymer systems. 相似文献
87.
D.C. Hoffman 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(1):7-11
The major contributions of G. T. Seaborg to nuclear science, including co-discovery of many isotopes with practical applications in medicine and industry, co-discovery of plutonium and nine more transuranium elements, the actinide hypothesis, and searches for superheavy elements are briefly summarized. His enduring interest in science education, the history of science, and public affairs are also noted. 相似文献
88.
89.
J. Hoffman 《国际流体数值方法杂志》2009,59(11):1241-1258
General Galerkin (G2) is a new computational method for turbulent flow, where a stabilized Galerkin finite element method is used to compute approximate weak solutions to the Navier–Stokes equations directly, without any filtering of the equations as in a standard approach to turbulence simulation, such as large eddy simulation, and thus no Reynolds stresses are introduced, which need modelling. In this paper, G2 is used to compute the drag coefficient cD for the flow past a circular cylinder at Reynolds number Re=3900, for which the flow is turbulent. It is found that it is possible to approximate cD to an accuracy of a few percent, corresponding to the accuracy in experimental results for this problem, using less than 105 mesh points, which makes the simulations possible using a standard PC. The mesh is adaptively refined until a stopping criterion is reached with respect to the error in a chosen output of interest, which in this paper is cD. Both the stopping criterion and the mesh‐refinement strategy are based on a posteriori error estimates, in the form of a space–time integral of residuals times derivatives of the solution of a dual problem, linearized at the approximate solution, and with data coupling to the output of interest. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
90.