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51.
We report on measurements of the spin lifetime of nuclear spins strongly coupled to a micromechanical cantilever as used in magnetic resonance force microscopy. We find that the rotating-frame correlation time of the statistical nuclear polarization is set by the magnetomechanical noise originating from the thermal motion of the cantilever. Evidence is based on the effect of three parameters: (1) the magnetic field gradient (the coupling strength), (2) the Rabi frequency of the spins (the transition energy), and (3) the temperature of the low-frequency mechanical modes. Experimental results are compared to relaxation rates calculated from the spectral density of the magnetomechanical noise. 相似文献
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P. G. Baranov I. V. Il’in A. A. Soltamova A. Ya. Vul’ S. V. Kidalov F. M. Shakhov G. V. Mamin S. B. Orlinskii M. Kh. Salakhov 《JETP Letters》2009,89(8):409-413
Individual nitrogen centers N0 and nitrogen pairs N 2 + have been detected and identified in natural diamond nanocrystals by means of the high-frequency electron spin resonance method. The N0 nitrogen centers have been observed in synthetic diamond nanocrystallites with a size of less than 10 nm produced by high-temperature high-pressure sintering of detonation nanodiamonds. Thus, the possibility of the stable state of impurity nitrogen atoms in diamond nanoparticles has been demonstrated. 相似文献
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We cool the fundamental mechanical mode of an ultrasoft silicon cantilever from a base temperature of 2.2 K down to 2.9+/-0.3 mK using active optomechanical feedback. The lowest observed mode temperature is consistent with limits determined by the properties of the cantilever and by the measurement noise. For high feedback gain, the driven cantilever motion is found to suppress or "squash" the optical interferometer intensity noise below the shot noise level. 相似文献
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A. S. Morkovnik L. N. Divaeva A. I. Uraev K. A. Lyssenko R. K. Mamin I. G. Borodkina G. S. Borodkin A. S. Burlov A. D. Garnovskii 《Russian Chemical Bulletin》2008,57(7):1496-1507
Quantum chemical calculations, 1H and 13C NMR, and X-ray studies showed that, in contrast to 4-arylazo-2-pyrazolin-5-ones, 4-(1-alkylbenzimidazol-2-ylazo)-2-pyrazoline-5-ones
mainly exist in the condensed phase as unusual ketoazine tautomers of high polarity, while the ketohydrazone tautomer stabilized
by intramolecular hydrogen bond apparently predominates in the gas phase. According to calculations, various types of tautomerism
are possible for 4-(benzimidazol-2-ylazo)-2-pyrazolin-5-ones, including mono- and bimolecular 1,3-, 1,5-, and 1,7-prototropic
migrations proceeding by the single- and double-proton transfer mechanism with low activation energies (ΔE
≠ ≈ 2–14 kcal mol−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1467–1478, July, 2008. 相似文献
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JETP Letters - We consider particle collisions in the background of nonextremal spherically symmetric static black holes. It is shown that debris of collision can have indefinitely large energy at... 相似文献
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D. P. Pavlov I. I. Piyanzina V. M. Mukhortov A. M. Balbashov D. A. Tayurskii I. A. Garifullin R. F. Mamin 《JETP Letters》2017,106(7):460-464
The temperature dependence of the electrical resistance has been studied for heterostructures formed by antiferromagnetic LaMnO3 single crystals of different orientations with epitaxial films of ferroelectric Ba0.8Sr0.2TiO3 deposited onto them. The measured electrical resistance is compared to that exhibited by LaMnO3 single crystals without the films. It is found that, in the samples with the film, for which the axis of polarization in the ferroelectric is directed along the perpendicular to the surface of the single crystal, the electrical resistance decreases significantly with temperature, exhibiting metallic behavior below 160 K. The numerical simulations of the structural and electronic characteristics of the BaTiO3/LaMnO3 ferroelectric?antiferromagnet heterostructure has been performed. The transition to the state with two-dimensional electron gas at the interface is demonstrated. 相似文献
59.
Using the 6-31+G** and aug-cc-pvDz basis sets, the ab initio (MP2, CASSCF, MRMP2) and DFT (B3LYP) calculation of the reactivity of the strained C=C bond in 1,1-dichloroethylene and 1-chloroethylene towards ozone was carried out. The concerted and unconcerted mechanisms were investigated. The strain (?) was introduced into the problem by varying the C=C bond length and specifying it as the unoptimized coordinate. The data were analyzed using the previously developed approach that allows one to derive, from calculated data, an analytical relationship between the activation energy E a and the force acting on the reaction site and to relate the strain-induced change in E a to the length and rigidity of the initial and transition states. 相似文献
60.
A. F. Puchkov N. A. Tret’yakova E. A. Mamin M. P. Spiridonova 《Polymer Science Series D》2018,11(2):117-121
The conformations of the ε-caprolactam molecule were calculated using a software package, and three of its conformers were established. It is shown that the conformational change of molecules creates the prerequisites for organizing the nearest contact and strong hydrogen bonds of ε-caprolactam with molecules of other substances. The molecule of ε-caprolactam can be “adapted to a neighbor” to a greater degree, since it can take a different, more advantageous conformation to provide the necessary contact. With the use of ε-caprolactam, molecular complexes have been obtained that have found application in the production of adhesives for rubber–cord systems. 相似文献