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161.
The energy and approximate structure of certain S(0)/S(1) conical intersections (CI) are shown computationally to be deducible from those of two bound states: the first triplet (T(1)), which is iso-energetic with the CI, and the second excited singlet state (S(2)). This is demonstrated for acepentalene (I) and its perfluoro derivative (II) using the twin state concept for three states systems and based on the fact that the triplet T(1) is almost degenerate with the CI. The stable S(2) (C(3v) configuration) state exhibits unusual exaltation of Jahn-Teller active degenerate mode-ν(JT) = 2058 cm(-1) (~500 cm(-1) higher than analogous e-mode of the symmetric (C(3v)) T(1) and the dianion I(-2) or any C-C vibration of the Jahn-Teller distorted (C(s)) ground state minimum). The acepentalene molecule, whose rigid structure and possibility to attain the relatively high symmetry C(3v) configuration, is a particularly suitable candidate for this purpose. 相似文献
162.
Density-dependent liquid nitromethane decomposition: molecular dynamics simulations based on ReaxFF 总被引:3,自引:0,他引:3
Rom N Zybin SV van Duin AC Goddard WA Zeiri Y Katz G Kosloff R 《The journal of physical chemistry. A》2011,115(36):10181-10202
The decomposition mechanism of hot liquid nitromethane at various compressions was studied using reactive force field (ReaxFF) molecular dynamics simulations. A competition between two different initial thermal decomposition schemes is observed, depending on compression. At low densities, unimolecular C-N bond cleavage is the dominant route, producing CH(3) and NO(2) fragments. As density and pressure rise approaching the Chapman-Jouget detonation conditions (~30% compression, >2500 K) the dominant mechanism switches to the formation of the CH(3)NO fragment via H-transfer and/or N-O bond rupture. The change in the decomposition mechanism of hot liquid NM leads to a different kinetic and energetic behavior, as well as products distribution. The calculated density dependence of the enthalpy change correlates with the change in initial decomposition reaction mechanism. It can be used as a convenient and useful global parameter for the detection of reaction dynamics. Atomic averaged local diffusion coefficients are shown to be sensitive to the reactions dynamics, and can be used to distinguish between time periods where chemical reactions occur and diffusion-dominated, nonreactive time periods. 相似文献
163.
Korbakov N Timmerman P Lidich N Urbach B Sa'ar A Yitzchaik S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(6):2580-2587
An inclusion complex between water-soluble p-sulfocalix[n]arene (Cn, n=4, 6, 8) and the chromophore trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium-p-toluenesulfonate (D) formed the basis for a highly sensitive sensor for the selective detection of neurotransmitter acetylcholine (ACh). Formation of the [Cn.D] complex (Ka=approximately 10(5) M(-1)) was accompanied by a drastic increase (up to 20-60-fold) in the chromophore relative quantum yield and by a large hypsochromic shift of the emission band maximum. The observed optical effects are fully reversible: ACh displaces the chromophore molecules from the calixarene cavity as shown by the reappearance of the free chromophore emission band. Formation and dissociation of the complex were studied by fluorescence, 1H NMR, and UV-vis absorption spectroscopies. The [Cn.D] complex is capable of sensing ACh selectively in solution at sub-micromolar concentrations. Immobilization of monocarboxyl p-sulfocalix[4]arene (C4m) on an oxide-containing silicon surface is in keeping with its properties, such as chromophore binding and the ability of the immobilized inclusion complex to detect ACh. The unique [Cn.D] complex optical switching paves the way for application in ACh imaging and optoelectronic sensing. 相似文献
164.
We study the discreteness of the spectrum of Schrödinger operators which are defined on a class of radial N-dimensional rooted trees of a finite or infinite volume, and are subject to a certain mixed boundary condition. We present a method to estimate their eigenvalues using operators on a one-dimensional tree. These operators are called width-weighted operators, since their coefficients depend on the section width or area of the N-dimensional tree. We show that the spectrum of the width-weighted operator tends to the spectrum of a one-dimensional limit operator as the sections width tends to zero. Moreover, the projections to the one-dimensional tree of eigenfunctions of the N-dimensional Laplace operator converge to the corresponding eigenfunctions of the one-dimensional limit operator. 相似文献
165.
The photochemistry of the pyrrole-ammonia cluster is analyzed theoretically. Whereas in neat pyrrole the dominant photochemical reaction is H-atom cleavage, recent experiments show that in pyrrole-ammonia clusters the major reaction is H-transfer to form the NH(4) radical (solvated by ammonia molecules in the case of large clusters) and the pyrrolyl radical. A mechanism involving the hydrogen-bonded Rydberg state is offered to account for these results and verified computationally. Two minima are located on the lowest excited singlet PES. Both of them are Rydberg states, one leads to the formation of NH(4) and pyrrolyl radicals, the other is connected to the πσ* state through a relatively high barrier, leading to a 3-body dissociation reaction to form a pyrrolyl radical, ammonia and an H-atom. The former is the energetically and statistically preferred one. 相似文献
166.
Elish Eyal Brandis Michal Haquin Gustavo Hershko Itzhak Yungrais Zohar Aviv Ofer Moyal Amiram Assulin Maor Nawi Yehuda Solomon Oren Zakon Yevgeni Rubinshtein Arnon Astrachan Boaz 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(1):51-60
Journal of Radioanalytical and Nuclear Chemistry - An orphan radium-beryllium (Ra–Be) neutron source (Nuclear Chicago Corporation) detected inside a scrap metal shipping container, was seized... 相似文献