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91.
Vassil B. Delchev Hans Mikosch Georgi St. Nikolov 《Monatshefte für Chemie / Chemical Monthly》2001,72(2):339-348
The mechanism of the keto-enol interconversion of pentane-2,4-dione (trivial name: acetylacetone, acac) was examined at the restricted Hartree-Fock (HF) level and the DFT correlation functional BLYP method using the 6-311G** basis, both included in the program GAUSSIAN 98. Two initial enol forms are considered: the omega and sickle forms, related
by a rotation of 180° around the OC*CC bond. The study is restricted to the through-space transfer of the hydroxyl proton
to C(2). The two geometry-optimized enol forms are planar; the geometry optimization of the diketone forms leads to the same
non-planar structure, regardless of the starting enol geometry. The transition state of the through-space omega-enol→diketone
conversion has also a non-planar structure, indicating that the hydroxyl proton moves outside of the CCC plane. The BLYP-calculated
energy barrier of the forward (omega-enol→diketone) conversion is 245 kJ·mol−1, that of the reverse (diketone→omega-enol) conversion 222 kJ·mol−1; thus, an almost symmetric barrier, which is not thermally accessible, is defined. The energy barrier for the sickle-enol→diketone
conversion is considerably lower (187 kJ·mol−1), to access the sickle form from the more stable omega form, a rotation is needed (energy barrier: 88 kJ·mol−1). The HF-calculated barriers are 1.3–1.4 times higher than those obtained with the BLYP method. 相似文献
92.
Ch. Georgi 《Crystal Research and Technology》1987,22(6):777-781
Epitaxial AIN grown by MOCVD on (011 2)Al2O3 substrates usually is (12 10)-oriented. Here for the first time (12 16)AIN was found in MOCVD layers. This AIN orientation is known from other growth techniques, its origin is generally not understood. An explanation is given based on twinning in the early growth stages which is also applicable to the growth of (12 16)ZnO on (011 2)Al2O3. 相似文献
93.
EMR studies of bis(benzene-dithiocarboxylato)copper(II) in the form of the pure solid sample, in solution as well as magnetically diluted in the host lattices of the corresponding complexes of NiII, ZnII, PdII, and PtII are reported. Two different samples (violet and blue) have been obtained in the NiII complex host lattice with EMR spectra indicating a superposition of several individual CuII signals. The EMR spectrum of the violet sample is explained by a superposition of the individual signals of (thio-, perthio-carboxylate)CuII and bis(perthiocarboxylate)CuII while that for the blue Cu/Ni(dtb)2 complex, as well as for Cu/Pd (dtb)2 is explained by different positions of the CuII species in the host lattices. The EMR spectrum typical for the magnetically diluted sample caused by self redox reaction has been recorded in the pure solid sample of copper(II) dithiocarboxylate complex. 相似文献
94.
Currently two scenarios exist which explain SU(2) × U(1) breaking: the Higgs mechanism, and standard hypercolor schemes. In this paper, a third scenario called “oblique hypercolor” is proposed. A hyperquark condensate is formed which, although kinematically allowed to point in an SU(2) × U(1) preserving direction, is forced by Yukawa interactions of the hyperquarks to misalign by a small angle, breaking SU(2) × U(1). The low energy spectrum involves normal fermions with correct masses, a partially composite Higgs boson, and physical charged scalars. 相似文献
95.
Mircho Georgiev Nikolay Goutev Zhorro S. Nickolov Georgi Georgiev 《Central European Journal of Physics》2005,3(1):104-114
Excess thermodynamic functions of D2O water have been calculated from the vibrationally decoupled O−D stretching spectra of very dilute solutions of HOD in H2O. Comparison of the results with reference calorimetric data for water showed a good correspondence for excess heat capacity
above the melting point of ice. The excess enthalpy at the melting point also coincides well with latent heat of melting. 相似文献
96.
Gelmini and Roncadelli have proposed a model of neutrino masses in which B?L symmetry is spontaneously broken by a small vacuum expectation value of a Higgs triplet. We give an exegesis of this model. We show that the massive neutrinos in this model cannot be cosmologically relevant today and that conflicting analyses of double beta decay experiments can be reconciled. 相似文献
97.
98.
Claudio?FernándezEmail author Georgi. D.?RaikovEmail author 《Annales Henri Poincare》2004,5(2):381-403
We consider the three-dimensional Schrödinger operators
and
where
, A is a magnetic potential generating a constant magnetic
field of strength
, and
where
decays fast enough at infinity. Then, A. Pushnitskis representation of the spectral shift function (SSF)
for the pair of operators
is well defined for energies
We study the behaviour of the associated representative of the equivalence class
determined by the SSF, in a neighbourhood of the Landau levels
Reducing our analysis to the study of the eigenvalue asymptotics for a family of
compact operators of Toeplitz type, we establish a relation between the type of the
singularities of the SSF at the Landau levels and the decay rate of V at infinity.
Communicated by Bernard HelfferSubmitted 23/09/03, accepted 15/01/04 相似文献
99.
Vladimir A. Bushenkov J. P. Prates Ramalho Georgi V. Smirnov 《Journal of computational chemistry》2001,22(10):1058-1066
For the monolayer adsorption on a homogeneous surface, including arbitrary range lateral interactions, the isotherm can be written as a power series of the Langmuir isotherm. If this isotherm is used as the kernel in the adsorption integral equation, this integral equation can be solved in an analytical form. Because the global isotherm is usually known as a set of experimental values, the use of a numerical method is inevitable. A new numerical method for solving the adsorption integral equation with a kernel of general form is developed. It is based on recent results concerning the structure of the local isotherm and on the ideas of complex approximation with constraints, and allows reduction of the problem under consideration to a linear‐quadratic programming problem. Results of numerical experiments are presented. The method can be useful for the evaluation of the adsorption energy distribution from experimental data. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1058–1066, 2001 相似文献
100.
Zhaokai Meng Georgi I. Petrov Vladislav V. Yakovlev 《Applied physics. B, Lasers and optics》2013,112(1):99-103
Stimulated Raman scattering (SRS) microscopy is a powerful tool for chemically sensitive non-invasive optical imaging. However, ultrafast laser sources, which are currently employed, are still expensive and require substantial maintenance to provide temporal overlap and spectral tuning. SRS imaging, which utilizes continuous-wave laser sources, has a major advantage, as it eliminates the cell damage due to exposure to the high-intensity light radiation, while substantially reducing the cost and complexity of the setup. As a proof-of-principle, we demonstrate microscopic imaging of dimethyl sulfoxide using two independent, commonly used lasers, a diode-pumped, intracavity doubled 532-nm laser and a He–Ne laser operating at 632.8-nm. 相似文献