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91.
Sarapulova G. I. Safronova L. P. Andreev M. V. Medvedeva A. S. 《Russian Journal of Organic Chemistry》2004,40(3):329-333
Analysis of the IR spectral parameters and the results of AM1 quantum-chemical calculations indicated distortion of the planar structure of the amide fragment and destabilization of the nitrogen configuration in new N-functionalized 3-trimethylsilylpropynamides Me3SiCCC(O)NHR. This effect is most pronounced in N-hydroxy-3-trimethylsilylpropynamide upon formation of intramolecular hydrogen bond C=O···H-O. 相似文献
92.
A method allowing subwavelength resolution within the framework of optical interferometric microscopy is proposed. It is shown that overcoming the diffraction limit is not a necessary requirement. Generally speaking, subrayleigh resolution and overcoming the diffraction limit are basically different concepts. The method developed uses the all-parameter modulation of the light source and separation of the phase shifts generated due to different reasons. In this method, a topological phase technique is used to separate the phases and therefore determine the corresponding characteristics of an object. The approach developed provides for a way to create a new type of optical devices. Within the framework of a uniform measuring procedure these devices make possible determining both geometrical and material parameters of the object under study. 相似文献
93.
Budantseva N. A. Andreev G. B. Krot N. N. Antipin M. Yu. 《Russian Journal of Coordination Chemistry》2003,29(3):222-226
X-ray diffraction and spectroscopic data for a new Np(V) compound, namely, [NpO2{OC(NH2)2}5](NO3) (I) are presented. Crystals are monoclinic, space group P21, a = 11.142(2) Å, b = 7.6379(9) Å, c = 11.143(2) Å, = 108.9(1)°, Z = 2, V = 897.1(2) Å3. The neptunium atom has a typical pentagonal-bipyramidal environment with five oxygen atoms of the carbamide molecules in the equatorial plane. The nitrate ion is in the outer sphere. Carbamide is a strong molecular ligand with respect to Np(V) and hence, cation–cation bonds of the NpO2
+ ions are not realized in structure I. The wave length of the f–f transition in the electronic absorption spectra of crystalline complex I and Np(V) in a saturated carbamide solution is virtually the same and is equal to 991 nm. 相似文献
94.
V. D. Andreev 《Journal of Structural Chemistry》2001,42(3):404-411
Using the model potential approach we have obtained a generalized potential of interatomic interactions for two condensed states providing an abrupt change in thermodynamic functions at a point of a solid to liquid transition. A kinematic model is considered for the transition of the diamond lattice with pure covalent bonds to the melted state. The model is based on the concept of crash destruction of the lattice during the conformational transformation of the initial symmetry of the chosen atomic group. The kinetic energy of the thermal motions of atoms does not exceed the potential energy of lattice atomization. The kinematic patterns of the positions of 150 atoms at T T
m and T T
m are given for the two-dimensional hexagonal net. 相似文献
95.
Measurement of the energy penetration depth into solid targets irradiated by ultrashort laser pulses
Fraenkel M Zigler A Henis Z Eliezer S Andreev NE 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1899-1903
The energy penetration depth of a short (100 fs) Ti-sapphire laser pulse (0.8 &mgr;m) of intensity 3x10(16) W/cm(2), in solid density materials has been measured. High-Z (BaF2) and low-Z (MgF2) solid layers targets were used. The penetration depth was determined from the measurement of the x-ray emission spectra, as a function of the target thickness. The investigation of these spectra showed that in the low-Z case, solid density material to a depth of 50 nm was heated to a peak electron temperature of approximately 150 eV. For the high-Z material, the penetration depth corresponding to this temperature exceeded 100 nm. This is evidence of a larger heat penetration depth in a high-Z material in comparison to a low-Z material. A model based on electron heat conduction is used to estimate the energy penetration depth. It is suggested that the larger heat penetration in high-Z material is due to heating of the material, caused by the radiation flux, generated by the electron heat conduction. 相似文献
96.
A. V. Andreev V. E. Asadchikov A. V. Buzmakov A. A. Konovko S. V. Kuzin A. A. Pertsov Yu. V. Ponomarev R. A. Senin I. S. Smirnov S. V. Shestov V. N. Shkurko 《JETP Letters》2007,85(1):98-100
The experimental results on the two-dimensional 20× magnification of an x-ray image obtained in an asymmetric-reflection x-ray microscope with the use of a laboratory source of x rays are discussed. The field of view is determined by the linear sizes of the detector and is equal to 0.5 × 0.5 mm in our experiment for an exposure time of 600 s. 相似文献
97.
A. A. Andreev V. M. Komarov A. V. Charukhchev K. Yu. Platonov 《Optics and Spectroscopy》2007,102(6):944-948
The results of experimental measurement and analytical estimation of the coefficient of backward reflection from targets made of various materials upon their irradiation by a picosecond laser pulse having the intensity of (0.8–4) × 1018 W/cm2 are presented. It is shown that the induced surface instability leads to the formation of a profile backscattering the incident radiation. The coefficient of backward reflection achieves a few percent and has an intensity optimum depending on the target material. 相似文献
98.
Preliminary experimental investigation of photoacoustic pressure signals induced by nanosecond laser pulses in aluminum targets
contacting a water layer was performed. It was shown that for some laser intensities the signal has a two-peak structure.
The first peak is due to the thermoelastic effect, while the other results from the explosive evaporation. At low intensities,
only the first peak is observed. At sufficiently high intensities, the signal recovers the one-peak shape and becomes narrower
as compared with the two-peak shape because of the rapid increase in evaporation pressure and earlier beginning of the explosive
evaporation. 相似文献
99.
Bulk evaporation process in absorbing condensed matter irradiated with laser pulses was studied using the one-dimensional
thermal model with additional interfaces between different phases. Within this approach, it was shown that the repeated explosive
boiling mode can be achieved using nanosecond laser pulses, if the nucleation time is shorter than 0.1 ns. This mode can be
observed if the surface pressure is lower than the critical pressure P
c of the liquid-vapor phase transition. The dependences of these processes on the laser pulse intensity and duration, as well
as on evaporation kinetics were studied. Explosive boiling and spallation of a transparent liquid film on a pulse-heated absorbing
target, as well as the photoacoustic signal in the target before the explosion, were considered. 相似文献
100.
An algorithm has been developed for calculating radii, direction vectors, and coordination numbers (c.n.) for an arbitrary number of coordination spheres (CS) of the diamond lattice. It is established that the space of CS of the diamond lattice has imaginary CS in addition to real ones. The imaginary CS are defined by a direction vector, one of the components of which is an imaginary value. The coordination numbers of such CS are zero. For a great number of tabulated CS, we have studied the hierarchies of structural groups (motifs), forming in the space of coordination spheres and determining the X-ray spectra of lattice CS, the crystallomorphological growth forms of diamond crystals, and the forms of diamond fragmentation induced by thermal destruction and melting. 相似文献