Samarqand, Uzbekistan

Samarkand State University
Samarqand, Uzbekistan
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Redkin P.V.,Samarkand State University | Danailov M.B.,Elettra - Sincrotrone Trieste | Ganeev R.A.,Institute of Electronics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We investigate the high-order harmonic generation in ordinary buckyball C60, endohedral In@C60 fullerene, and endohedral Sb@C 60 fullerene by means of time-dependent density functional theory. In all cases the resonant enhancement of several high-order harmonics in the plateau region up to two orders of magnitude was predicted. Theoretical investigation of absorption spectra of C60 showed absorption peaks in the regions of the resonant HHG enhancement. In both endohedral fullerenes, peaks of plasmon absorption and resonance enhancement were shifted toward the corresponding atomic resonant transitions, which may be used to control the spectral distribution of groups of resonant harmonics and obtain bright attosecond pulse trains. © 2011 American Physical Society.

Redkin P.V.,Samarkand State University | Kodirov M.K.,Samarkand State University | Ganeev R.A.,Institute of Electronics
Journal of the Optical Society of America B: Optical Physics | Year: 2011

Our study is devoted to finding an explanation of the observed phenomena of resonance enhancement of the single high-order harmonic in indium plasma [Opt. Lett. 31, 1699 (2006)]. Computations were performed on the basis of time-dependent density functional theory (TDDFT). The results of TDDFT calculations of the high-order harmonic generation (HHG) for indium ion were found in good qualitative coincidence with experimental data. This allowed us to introduce a theory of resonant recombination for the HHG and prove it by HHG simulations with specially chirped pulses. It can also be used to predict the most promising targets for resonant HHG and to increase its efficiency by control of the pump radiation's parameters. © 2010 Optical Society of America.

Redkin P.V.,Samarkand State University | Ganeev R.A.,Academy of Sciences of Uzbekistan
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We performed a series of simulations of resonant high-order harmonic generation (HHG) by means of a multiconfigurational time-dependent Hartree-Fock (MCTDHF) approach for three-dimensional fullerenelike systems. The results proved the theory of resonant recombination proposed in this article and showed the ways of resonant HHG optimization. The results of MCTDHF calculation of the HHG for C60 were in good qualitative agreement with reported experimental data. © 2010 The American Physical Society.

The behavior of the adiabatic compressibility βS with variation in temperature t and concentration x in the aqueous solution of a nonelectrolyte is experimentally studied from the fine structure spectra of light scattering. A sign inversion of the derivative of the adiabatic compressibility with respect to the concentration βS(x) is observed in the isotherms of the dependences dβS(x)/dx. The inversion point (concentration x0 at which dβS(x)/dx=0) is shifted to the region of lower concentrations as the temperature increases. In the temperature-concentration phase diagram, the dependence x0(t) determines the line of transition from the solution structure characterized by the continuous network of the hydrogen bonds to the structure with the fragmentary network. © 2010 Allerton Press, Inc.

Kurtaliev E.N.,Samarkand State University
Journal of Fluorescence | Year: 2011

The spectral-luminescent characteristics of newly synthesized styrylcyanine dyes on the base of dyes Sbo ((E)- 2-(4-(dimethylamino)styryl)-3-methylbenzo[d] oxazol-3-ium iodide) and Sil ((E)-2-(4-(dimethylamino)styryl)-1,3,3- trimethyl-3H-indolium perchlorate) in aqueous solutions without and in the presence of bovine serum albumin (BSA) were studied. It was established that the absorption spectra of dyes Tol-6, Dbo-10 and Dil-10 with increasing amount of BSA appear new bands with λ max=505 nm, λ max= 512 nm and λ max=566 nm, respectively, whose intensity increases in proportion to the amount of albumin. The intensity of the glow of the main band of fluorescence in the presence of BSA sharply increases. The binding constant (K) and the number of binding sites (N) of studied dyes with BSA were determined. The dependence of binding constants with BSA on the dipole moment of dye molecules was determined, which indicates that besides electrostatic forces of attraction between molecules styrylcyanine dyes with BSA, hydrophobic interactions are essential. © Springer Science+Business Media, LLC 2009.

Muminov M.E.,Samarkand State University | Aliev N.M.,Samarkand State University
Theoretical and Mathematical Physics | Year: 2012

We consider a system of three arbitrary quantum particles on a one-dimensional lattice interacting pairwise via attractive contact potentials. We prove that the discrete spectrum of the corresponding Schrödinger operator is finite for all values of the total quasimomentum in the case where the masses of two particles are finite. We show that the discrete spectrum of the Schrödinger operator is infinite in the case where the masses of two particles in a three-particle system are infinite. © 2012 Pleiades Publishing, Ltd.

Kurtaliev E.N.,Samarkand State University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2011

The influence of concentration, solvent nature on the intermolecular interaction and its spectroscopic manifestations in solutions of styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino)styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and its homodimers, i.e. dyes with two interconnected chromophores, was studied. It was found out that, depending on the concentration, the structure of dye molecules, the nature of the solvent various forms of associated molecules are forms; each of these forms is manifested in the spectra of absorption and fluorescence in its own way. It is shown that the intensity of the main absorption band of the studied dyes in aqueous solutions and in a mixture of water + ethanol decreases in the process of light irradiation and a new band is observed in the region of shorter wavelengths; the intensity of the new band increases with increase of radiation exposure of solutions. © 2011 Elsevier B.V. All Rights Reserved.

Shakarov K.O.,Samarkand State University
Russian Physics Journal | Year: 2016

The Ruderman–Kittel–Kasuya–Yosida exchange interaction (RKKY) is semi-empirically studied for the first time in compounds of binary REM – Al systems (REM – rare-earth metals: Gd, Dy, Ho, Er) using experimental values of paramagnetic Curie point (θр) of these compounds. Prediction of the RKKY theory was confirmed, i.e. there is a direct proportional dependence of θр value on de Gennes factor for equiatomic compounds of heavy REM with aluminum, just as in the case of pure REM. Values of the indirect exchange interaction parameter were semi-empirically estimated for the studied compounds. In general, it was established that RKKY-type exchange interaction is typical for REM compounds with aluminum, just as for pure REM. © 2016, Springer Science+Business Media New York.

Kurtaliev E.N.,Samarkand State University
Journal of Luminescence | Year: 2012

The spectral-fluorescent characteristics of styrylcyanine dye Sbt ((E)-2-(4-(dimethylamino) styryl)-3-methylbenzo[d]thiazol-3-ium iodide) and homodimers, dyes conjugated with two chromophores in aqueous solutions without and in the presence of bovine serum albumin (BSA), are studied. It is established that in the presence of BSA for dyes Dbt-5 and Dbt-10, an increase of the absorptivity, a slight broadening and the emergence of new band on the short wavelength range with λ max=410 nm is observed; also hypsochromic shift of the absorption and fluorescence at 30 nm and 7 nm, respectively for the dye D-183 is observed. The intensity of the fluorescence emission fundamental band in all the studied dyes in the presence of BSA increases by 3.5 to 55 times. The binding constant (K) and number of binding sites (N) of studied dyes with BSA are determined. The dependence of the binding constants with BSA from the dipole moment of dye molecules is identified, which shows that in addition to the electrostatic attraction forces between molecules of styrylcyanine dyes with BSA, hydrophobic interactions are essential. It is shown that the aggregation of dye affects the processes of interaction of the dyes with the BSA. © 2012 Elsevier B.V. All rights reserved.

Lakaev S.N.,Samarkand State University | Holmatov S.Y.,Samarkand State University
Journal of Physics A: Mathematical and Theoretical | Year: 2011

The Hamiltonian of a system of two quantum-mechanical particles moving on the d-dimensional lattice ℤd and interacting via zero-range attractive pair potentials is considered. For the two-particle energy operator Hμ(K), K ∈ double-struck T signd = (-π, π]d - the two-particle quasi-momentum - the existence of a unique positive eigenvalue z(μ, K) above the upper edge of the essential spectrum of Hμ(K) is proven and asymptotics for z(μ, K) are found when μ approaches to some μ0(K) and K → 0. © 2011 IOP Publishing Ltd.

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