Faculty of Physics
M.V.Lomonosov Moscow State University
Theoretical and mathematical physics

## Molecular nanocluster fluorescence in microwave infrared-radiation fields

### V.V. Komarov$^1$, A.M. Popova$^1$, I.O. Stureiko$^1$, L. Schmidt$^2$, H. Jungclas$^2$

Moscow University Physics Bulletin 2013. 68. N 5. P. 339

The paper considers a donor-acceptor nanocluster fluorescing in a microwave infrared radiation field. It is assumed that the nanocluster consists of two dipole-dipole interacting organic molecules. It is shown that the fluorescence process of the nanocluster occurs if the donor molecule contains a substructure of identical diatomic pairwise interacting bonds of dipoles (an IR antenna). This antenna is capable of accumulating vibrational energy as a sum of collective vibrational quanta (excimols). The acceptor molecule has no permanent dipole moment and cannot be excited by microwave IR radiation. This molecule is polarized in the dipole moment field of the donor IR antenna and can receive energy accumulated in the IR antenna of the donor molecule. If the acceptor molecule has an electronically excited state in the long-wavelength visible region of its absorption spectrum, then after receiving energy equal to the energy of this state from the donor antenna, the electronic excitation of the acceptor molecule and its fluorescence is possible. As an example, the fluorescence of a nanocluster is considered whose donor molecule has a С$_n$H$_{2n}$ IR antenna. The acceptor molecule is aromatic and the external infrared frequency, 1.1·10$^{14}$ s$^{−1}$, is equal to the frequency of the excimol in the donor infrared antenna.

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## Modeling of spectral dependences for 2D photonic crystal waveguide systems

### A.N. Bogolubov, G.V. Belokopytov, Z.O. Dombrovskaya

Moscow University Physics Bulletin 2013. 68. N 5. P. 344

A numerical algorithm is designed and implemented based on the joint application of the finite-difference time-domain (FDTD) method with absorbing boundary conditions (a combination of the perfectly matched layer (PML) and Mur first-order conditions) and the total-field/scattered-field technique (TF/SF). A complete formulation of the algorithm is given. The results of computing the spectral characteristics of the 2D photonic crystal with defects in the form of waveguides are presented. They demonstrate that it is possible to conduct calculations in a wide range of frequencies.

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## Maslov’s asymptotic methods in problems of the theory of optical lattices

### D.E. Bulychev

Moscow University Physics Bulletin 2013. 68. N 5. P. 351

Application of Maslov’s asymptotic methods to equations that arise in the theory of optical lattices was considered. The occurrence of a small parameter in the Schrödinger equations with potentials of three-dimensional and controlled optical lattice was investigated and the conditions of application of Maslov’s asymptotic methods for solving these equations was determined. Consideration of different conditions imposed on the parameters in these potentials led to the use of two different methods for solving the arising equations: Maslov’s method of a complex germ and Maslov’s operator-valued method of a complex germ. Expressions that can be used to calculate the desired characteristics of the atomic systems under consideration in optical lattices were derived.

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Physics of nuclei and elementary particles

## The calibration of an LHCb electromagnetic calorimeter by recovering the invariant mass of neutral pions

### I.M. Belyaev$^1$, D.Yu. Golubkov$^1$, V.Yu. Egorychev$^1$, D.V. Savrina$^{1,2}$

Moscow University Physics Bulletin 2013. 68. N 5. P. 360

The precise calibration of an electromagnetic calorimeter is extremely important for flavor tagging and for the study of B-mesons decays and therefore is of great importance for implementing the physics program of the LHCb experiment. The purpose of the calibration process is to achieve a 2% accuracy when measuring the energies of electrons and photons. At the last step of a multi-stage procedure, the method of restoring the invariant mass of a neutral pion in its decay into two photons is used.

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## The search for $D^0\to\mu^+\mu^-$ decay

### D.Yu. Golubkov, V.Yu. Egorychev, Yu.M. Zaitsev

Moscow University Physics Bulletin 2013. 68. N 5. P. 367

Studies of rare decays of charmed mesons are used to test the Standard Model and search for new physics. In the present paper we review the progress in the experimental methods of searching for the $D^0\to\mu^+\mu^-$ rare decay in recent studies of proton-nuclear and hadron-hadron interactions.

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## $D^*$ meson production cross sections in $e^-p$ and $e^+p$ scattering processes at the HERA collider

### R.K. Dement’ev

Moscow University Physics Bulletin 2013. 68. N 5. P. 373

The cause of the $D^*$ meson production cross sections in $e^-p$ and $e^+p$ deep inelastic scattering processes in the ZEUS experiment at the HERA collider that are anomalously different is determined.

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## Transient reflectivity of pulse signals from layered structures with losses

### A.V. Kozar, A.V. Trofimov

Moscow University Physics Bulletin 2013. 68. N 5. P. 377

Experimental, analytical, and numerical investigation of the transient reflectivity of the electromagnetic pulse from an antireflective structure with losses is conducted. Analytical investigations have shown that the envelope of the amplitude modulated reflected signal changes significantly even under small losses. The experimental, analytical, and numerical results are analyzed and compared.

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Optics and spectroscopy. Laser physics

## Optoacoustic study of laser-induced near-critical states of thin aluminum films

### A.A. Karabutov$^{1,2}$, A.G. Kaptilniy$^3$, A.Yu. Ivochkin$^4$, D.M. Ksenofontov$^5$, A.D. Trofimov$^5$

Moscow University Physics Bulletin 2013. 68. N 5. P. 383

The results of the optoacoustic study of aluminum states within a temperature range of 3–14 kK and a pressure range of 0.1–4 kbar were considered. These high-energy states were achieved by heating a submicron metal film confined by a transparent dielectric via nanosecond laser pulses with a fluence of up to 11 J/cm$^2$. The dynamics of the temperature, pressure, and reflectivity of aluminum was studied at a nanosecond time resolution.

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Condensed matter physics

## The optoelectronic properties of nitrogen- and carbon-doped nanocrystalline titania

### V.B. Zaitsev$^1$, E.A. Konstantinova$^{1,2}$, D.M. Deygen$^1$, M.N. Rumyantseva$^3$, E.V. Podol’ko$^3$, M.V. Pustovalov$^3$, P.K. Kashkarov$^{1,2}$

Moscow University Physics Bulletin 2013. 68. N 5. P. 387

Carbon- and nitrogen-doped nanocrystalline titania specimens were studied by optical spectroscopy and electron paramagnetic resonance. The doping of this material was established to result in the appearance of additional absorption in the visible spectral region. The doping with admixture nitrogen was revealed to lead to the formation of nitrogen-containing paramagnetic sites, namely, N· and NO· radicals. The effect of the recharging of the detected sites under light was revealed. The obtained results could be useful for the development of photocatalytic filters on the basis of doped nanocrystalline titania.

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## The effect of an external electric field on the optical properties of a quantum-dot molecule with a resonant state of the $D_2^{(-)}-$center

### V.Ch. Zhukovsky$^1$, V.D. Krevchik$^2$, A.B. Grunin$^2$, M.B. Semenov$^2$, R.V. Zaitsev$^2$

Moscow University Physics Bulletin 2013. 68. N 5. P. 397

The effect of an external electric field on the probability of the electron radiative transition from a resonant u-state to the localized $g-$state of the $D_2^{(-)}-$center in the presence of dissipative tunneling has been investigated in the model of zero-radius potential. It is shown that the probability of radiative transition increases by about two orders of magnitude in the case of the external electric field intensity for which the initially asymmetric double-well oscillator potential simulating a quantum-dot molecule becomes symmetrical.

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Biophysics and medical physics

## Self-organization as the driving force for the evolution of the biosphere

### A.E. Sidorova, Yu.V. Mukhartova

Moscow University Physics Bulletin 2013. 68. N 5. P. 405

In this paper we present a space-time model of urban ecosystems as conjugate active media. This approach is based on the representation of urban ecosystems as self-organizing systems; it aims at identifying the threshold values of control parameters and is considered promising in assessing system stability to internal and external fluctuations.

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Astronomy, astrophysics, and cosmology

## The influence of solar flares on the near-Earth space radiation environment in March and April 2013: Possibilities of operational monitoring

### I.N. Myagkova, V.O. Barinova, S.Yu. Bobrovnikov, O.G. Barinov, N.A. Vlasova, S.A. Dolenko, V.V. Kalegaev, E.A. Mouravieva, M.O. Ryazantseva, V.R. Shiroky, Ju.S. Shugai

Moscow University Physics Bulletin 2013. 68. N 5. P. 411

This paper deals with the operational analysis of the influence of solar flares, which produced solar cosmic rays, on the near-Earth radiation environment in space during the period from March 1 to April 18, 2013.

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Physics of Earth, atmosphere, and hydrosphere

## The simulation of a radar altimeter return waveform

### K.V. Pokazeev$^1$, A.S. Zapevalov$^1$, V.V. Pustovoytenko$^2$

Moscow University Physics Bulletin 2013. 68. N 5. P. 420

We analyze the capabilities and limitations of the Gram-Charlier distribution of rough sea-surface elevations in describing the return waveform during vertical sounding. We show that for typical values of skewness and kurtosis of the distribution of sea-surface elevations, the calculated return waveforms obtained with the Gram-Charlier distribution are distorted (including the occurrence of negative values). A new approach based on a combined model of the distribution of sea-surface elevations is proposed that is free of the disadvantages associated with the Gram-Charlier distribution.

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## The laboratory modeling of the catastrophic flood in Krymsk

### O.N. Mel’nikova$^1$, K.V. Pokazeev$^1$, A.E. Rozhdestvensky$^2$

Moscow University Physics Bulletin 2013. 68. N 5. P. 426

This paper suggests a physical model that explains the origin of the main front of a three-meter wave that moved along the bed of the Adagum River through the town of Krymsk on July 7, 2012 at the time of flooding during rain showers that caused catastrophic destruction and casualties. It has been proven that the cause of the wave origin was a sudden change of water flow intensity resulting from the construction of an unregulated water outlet. The construction was erected without taking changes in climate into consideration and it caused an extreme increase of the volume of rainfall run-off. First, it was experimentally proven that the sudden change of water-flow intensity was associated with the change of the runoff regime through a water outlet pipe that occurred without human involvement.

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## Interactions between jets and density currents

### B.I. Samolyubov

Moscow University Physics Bulletin 2013. 68. N 5. P. 431

We present the results of field and theoretical studies of a bottom density flow taking the pulse inflow (outflow) through the upper boundary of the current over which a stratified jet exists into account. An ambiguous parabolic relationship between jet and bottom flow discharges involved in eight systems of currents in water reservoirs and lakes with different types of water density stratification was revealed. The integral stability of stratification over the entire depth of the reservoir was shown to play a decisive role in the current interaction effects. A mathematical model of a density current interacting with a jet was modified and validated. The modifications include the resulting expressions of the turbulent flux of momentum from the jet (and the reverse), the drag coefficient at the current-bottom boundary, and the pressure gradient due to changes in the jet trajectory.

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