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991.
Sun QY de Smet LC van Lagen B Giesbers M Thüne PC van Engelenburg J de Wolf FA Zuilhof H Sudhölter EJ 《Journal of the American Chemical Society》2005,127(8):2514-2523
A very mild method was developed for the attachment of high-quality organic monolayers on crystalline silicon surfaces. By using visible light sources, from 447 to 658 nm, a variety of 1-alkenes and 1-alkynes were attached to hydrogen-terminated Si(100) and Si(111) surfaces at room temperature. The presence and the quality of the monolayers were evaluated by static water contact angles, X-ray photoelectron spectroscopy, and IR spectroscopy. Monolayers prepared by thermal, UV light, or visible light initiation were compared. Additionally, the ability of infrared reflection-absorption spectroscopy to study organic monolayers on silicon was explored. A reaction mechanism is discussed on the basis of investigations of the reaction behavior of 1-alkenes with silicon wafers with varying types and levels of doping. Finally, a series of mixed monolayers derived from the mixed solutions of a 1-alkene and an omega-fluoro-1-alkene were investigated to reveal that the composition of the mixed monolayers was directly proportional to the molar ratio of the two compounds in the solutions. 相似文献
992.
Coupling by the resonant dipole-dipole energy transfer between cold cesium Rydberg atoms is investigated using time-resolved narrow-band deexcitation spectroscopy. This technique combines the advantage of efficient Rydberg excitation with high-resolution spectroscopy at variable interaction times. Dipole-dipole interaction is observed spectroscopically as avoided level crossing. The coherent character of the process is linked to back and forth transfer in the np + np <--> ns + (n + 1)s reaction. Decoherence in the ensemble has two different origins: the atom motion induced by dipole-dipole interaction and the migration of the s-Rydberg excitation in the environment of p-Rydberg atoms. 相似文献
993.
We constrain energy spectra of supernova neutrinos through the avoidance of an overproduction of the 11B abundance during Galactic chemical evolution. In supernova nucleosynthesis calculations with a parametrized neutrino spectrum as a function of temperature of nu(mu,tau) and nu(mu,tau) and total neutrino energy, we find a strong neutrino temperature dependence of the 11B yield. When the yield is combined with observed abundances, the acceptable range of the nu(mu,tau) and nu(mu,tau) temperature is found to be 4.8 to 6.6 MeV. Nonzero neutrino chemical potentials would reduce this temperature range by about 10% for a degeneracy parameter eta(nu) = mu(nu)/kT(nu) smaller than 3. 相似文献
994.
995.
996.
This paper studies some cases of (0,m)-interpolation on non-uniformly distributed roots of unity that were not covered before. The interpolation problem uses as nodes the zeros of (z
k
+1)(z
3–1) with k=3n+1, 3n+2. Proof of the regularity is more intricate than when k is divisible by 3, the case included in a previous paper by the authors. The interpolation problem appears to be regular for mk+3, a result that is in tune with the case k=3n mentioned before. However, it is necessary to treat the full general 18×18 linear system. For small values of m the determinant is calculated explicitly using MAPLE V, Release 5. 相似文献
997.
Hartmann A Ducommun Y Kapon E Hohenester U Molinari E 《Physical review letters》2000,84(24):5648-5651
We investigate experimentally and theoretically few-particle effects in the optical spectra of single quantum dots (QDs). Photodepletion of the QD together with the slow hopping transport of impurity-bound electrons back to the QD are employed to efficiently control the number of electrons present in the QD. By investigating structurally identical QDs, we show that the spectral evolutions observed can be attributed to intrinsic, multi-particle-related effects, as opposed to extrinsic QD-impurity environment-related interactions. From our theoretical calculations we identify the distinct transitions related to excitons and excitons charged with up to five additional electrons, as well as neutral and charged biexcitons. 相似文献
998.
Raylene Dyson Marcel Maeder Yorck-Michael Neuhold Graeme Puxty 《Analytica chimica acta》2003,490(1-2):99-108
In kinetic or equilibrium investigations it is common to measure two-way multiwavelength data, e.g. absorption spectra as a function of time or reagent addition. Often it is advantageous to acquire experimental data at various initial conditions or even on different instruments. A collection of these measurements can be arranged in three-dimensional arrays, which can be analysed as a whole under the assumption of a superimposed function, e.g. a kinetic model, and/or common properties of the subsets, such as molar absorptivity. As we show on selected formation equilibria (Zn2+/phen) and kinetic studies (Cu2+/cyclam) from our own research, an appropriate combination of multivariate data can lead to an improved analysis of the investigated systems. 相似文献
999.
H. Rebel G. Hauser G.W. Schweimer G. Nowicki W. Wiesner D. Hartmann 《Nuclear Physics A》1974,218(1):13-42
Differential cross sections have been measured for the elastic and inelastic scattering of 104 MeV α-particles from46, 48, 49Ti. The experimental results are analyzed in terms of coupled channels on the basis of various limiting models of the collective behavior of these nuclei: symmetric rotator (46Ti), asymmetric rotator (48Ti) and anharmonic vibrator (50Ti). The analysis uses both the usual extended optical model and a semimicroscopic folding model. Prolate-oblate and γ-asymmetry effects are studied and confirm prolate deformation of 46Ti and 48Ti. Hexadecapole transitions (0+ → 41+) are found. 相似文献
1000.
R. Brandelik W. Braunschweig K. Gather V. Kadansky K. Lübelsmeyer P. Mättig H.-U. Martyn G. Peise J. Rimkus H.G. Sander D. Schmitz A.Schultz von Dratzig D. Trines W. Wallraff H. Boerner H.M. Fischer H. Hartmann G. Zobernig 《Physics letters. [Part B]》1980,94(3):437-443
We have analyzed 1113 events of the reaction e+e? → hadrons at CM energies of 12 and 30 GeV in order to make a detailed comparison with QCD. Perturbative effects can be well separated from effects depending on the quark and gluon fragmentation parameters to yield a reliable measurement of the coupling constant αS. At 30 GeV, the result is αS = 0.17 ± 0.02 (statistical) ± 0.03 (systematic). QCD model predictions, using the fragmentation parameters determined along with αS, agree with both gross properties of the final states and with detailed features of the three-jet states. 相似文献