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排序方式: 共有609条查询结果,搜索用时 31 毫秒
71.
72.
Fleming AJ Berkebile S Ules T Ramsey MG 《Physical chemistry chemical physics : PCCP》2011,13(10):4693-4708
Pre-nucleation dynamics, nucleation and templated self-assembly of a conjugated planar aromatic molecule are investigated by photoemission electron microscopy (PEEM). The high resolution of individual molecular layers in PEEM, in combination with a numerical simulation, reveals the dynamic behaviour of molecules during the pre-nucleation deposition period and their temperature dependence. The in situ deposition of p-sexiphenyl (6P) molecules on Cu(110) and Cu(110) 2 × 1-O surfaces in ultrahigh vacuum, when monitored by PEEM in real-time allows (a) layer densities, (b) meta-stable layer filling by 6P molecules, (c) dynamic surface redistributions during layer filling and (d) critical density spontaneous dewetting to be accurately measured. The comparison of 6P deposited on Cu(110) to Cu(110) 2 × 1-O enables temperature dependent 6P nucleation processes on Cu(110) to be elucidated from PEEM. The interplay between energetically stable molecular arrangements and kinetically stabilised arrangements is shown to dominate the pre- and post-nucleation processes. In combination with additional data obtained during post-nucleation deposition times, such as surface diffusion anisotropies and nucleation energies, it is concluded that the pre-requisite for 6P nucleation, in a lying down orientation, is the formation of a double tilted layer with at least one layer being meta-stable. 相似文献
73.
D. Berdichevsky R. Fleming D. W. L. Sprung F. Tondeur 《Zeitschrift für Physik A Hadrons and Nuclei》1988,329(4):393-405
Data on the isotope shift of the nuclear charge densities of the tin isotopes and of their mean square charge radii are considered from the viewpoint of the Hartree-Fock and Droplet Models. Attention is paid to the electromagnetic corrections of order 1/m2. Through a leptodermous analysis of charge and matter densities we find: (i) differences of m.s. charge radii are mainly sensitive to the external region, (ii) the electromagnetic corrections are important in that region, (iii) despite different leptodermous properties, forces Ska and GO-P lead to the same neutron skin thickness. The average rate of variation of the proton m.s. radius is interpreted as favouring either a low valueQ≈30 MeV for the droplet model asymmetry parameter, or a zero value for the saturation asymmetry parameterL. 相似文献
74.
Absolute rate constants are measured for the reactions: OH + CH2O, over the temperature range 296–576 K and for OH + 1,3,5-trioxane over the range 292–597 K. The technique employed is laser photolysis of H2O2 or HNO3 to produce OH, and laser-induced fluorescence to directly monitor the relative OH concentration. The results fit the following Arrhenius equations: k (CH2O) = (1.66 ± 0.20) × 10?11 exp[?(170 ± 80)/RT] cm3 s?1 and k(1,3,5-trioxane) = (1.36 ± 0.20) × 10?11 exp[?(460 ± 100)/RT] cm3 s?1. The transition-state theory is employed to model the OH + CH2O reaction and extrapolate into the combustion regime. The calculated result covering 300 to 2500 K can be represented by the equation: k(CH2O) = 1.2 × 10?18 T2.46 exp(970/RT) cm3 s?1. An estimate of 91 ± 2 kcal/mol is obtained for the first C? H bond in 1,3,5-trioxane by using a correlation of C? H bond strength with measured activation energies. 相似文献
75.
B. Kivel H.E. Fleming W.G. Planet 《Journal of Quantitative Spectroscopy & Radiative Transfer》1977,17(2):181-186
The effects of CO2 spectral line width and density on the atmosphere's radiant intensity at ~710 cm-1 are calculated. An increase of 30% in the currently accepted line width, justified on the basis of laboratory data, increases the prediction of radiant intensity by about 5%. The use of the increased line width leads to good agreement in a test case using satellite data. Nominal changes of a few per cent of the CO2 density result in changes in the radiant intensity of a fraction of 1%. 相似文献
76.
In order to provide a larger data base for understanding the whys and why nots of muonium formation in solids, we have been searching for Mu in predominantly crystalline environments. We have observed muonium in room temperature diamond, and report on a brief study of the temperature behaviour of its asymmetry and relaxation. These results are radically different from all previous diamond results. We have not been able to detect any Mu in SrTiO3, ZrSiO4, or TiO2, but in GeO2 there is a tiny signal in both a fused sample and a hexagonal single crystal, but none in a tetragonal crystal. Since hexagonal GeO2 is structurally similar to quartz, one would naively expect similar amounts of Mu. Such is not the case, the reasons for which are not understood at this time. In SrTiO3, the muon asymmetry is a strong function of temperature. 相似文献
77.
78.
Phenyl sulphenyl chloride is a γ-selective electrophile in its reaction with O-silylated dienolates. 相似文献
79.
80.
T. Suzuki R.J. Mikula D.M. Garner D.G. Fleming D.F. Measday 《Physics letters. [Part B]》1980,95(2):202-206
The relative capture rate has been measured for muons stopping in 22 oxides. The experimental method was to detect the decay electrons and to use the unique lifetime signature to determine which element captures the muon. 相似文献