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Dynamics of atoms trapped in an optical dipole trap formed by a train of femtosecond laser pulses is studied in detail on example of Rb atoms. In computer simulation, it is proved that such a trap effectively confines the atoms at the pumping laser beam power in between 1 mW and 3 kW (pulse duration 100 fs). It is also shown that the resonant dipole-dipole interaction (RDDI) through which closely spaced in the micropotential wells atoms interact between each other becomes essential and can be significantly increased by shining the atoms with resonant probe laser beam. Varying both the parameters of the trap and intensity of the probe laser field, role of the RDDI in the atomic dynamics in the trap is clarified in detail.

Theoretical study and computer modeling results of the spectra of coherent dark resonances resulted from excitation of Zeeman sublevels of the F g =2→F e =1 transition of the D 1 line in 87 Rb atoms by a frequency-modulated laser field are presented and discussed in detail. The influence of the nonlinear Zeeman effect on the structure of the coherent dark resonances is observed. It is shown that calculated for different values of the magnetic field spectra are in a good agreement with the experimental data.

The results of frequency-modulation (FM) spectroscopy of coherent dark resonances from the Zeeman sublevelsof the transition F =2 $ F =1 of D 1 line in absorption of 87 Rb atoms are presented and discussed in detail.By contrast with the conventional spectroscopy of coherent dark resonances employing two laser beams, relativefrequency of which can be varied, these data has been obtained with the help of a single frequency-modulatedlaser ¯eld. Variation of the modulation frequency plays then similar role with variation the relative frequencyin conventional spectroscopy. Experimental data are ¯t to the theoretical calculations, which are based onthe theory of FM spectroscopy of coherent dark resonances recently developed by us. Feasibility of using suchexperimental technique for accurate measurements of magnetic ¯elds is also discussed.Keywords: Coherent population trapping, absorption, dark resonance, magnetometry, metrology 1. INTRODUCTION The coherent population trapping (CPT) is one of the most intriguing quantum interference phenomena thatcan be most vividly seen in a three-level system in ¤-con¯guration. In this system, if two monochromaticpumping ¯elds are tuned into the resonance with the respective transitions, all the population is captured in thecoherent superposition of two low-lying levels, which gives the name of the phenomenon|coherent populationtrapping [1]. This means that the media of such three-level atoms under CPT will not emit °uorescence and donot absorb photons. In absorption spectra it is revealed as a narrow sharp dip in the absorption pro¯le whilescanning frequency of one of the pumping laser ¯elds. These resonances are called the coherent dark resonances.Due to the rather small spectral width of the dark resonances they found applications in precision spectroscopicapplications, such as metrology

A one-dimensional planar model is considered of the atmosphere with multi-layer clouds illuminated by a mono-directional parallel flux of solar radiation. A new approach is proposed to radiation transfer modeling and daylight bakground formation for the atmosphere with such clouds that is represented as a heterogeneous multi-layer system each layer of which is described by different optical characteristics. The influence functions of each layer are determined by solutions of the radiation transfer boundary problem with an external mono-directional wide flux while the contribution of multiple scattering and absorption in the layer is taking into account.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Multiple scattering and absorption of inclined narrow beam can be obtained in theory of radiation transfer as a generalized solution in the five-dimensional phase domain of spatial and angular variables concerning boundary layer problem for kinetic equation with a mono-directional pointed source on the boundary of the plane layer. This solution is interpreted in wide classes of mathematical physics problems as an influence function and can be found by the spatial-frequency characteristics method with these characteristics being considered as Fourier-transforms of the influence function on horizontal coordinates.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Boundary-value problem of radiation transfer in optically thick layers is considered while describing ocean, cloudiness, aerosol particle outbreaks, dust traces and other specific effects resulted from large fires (forest, peat-lands, in steppe regions, anthropogenic). Space and angular distributions of radiation in view of polarization and depolarization inside the relevant layer of these media as well as reflected and passed through the layer radiation are formed as a result of multiple scattering and absorption.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A more detailed modeling of interactions between the solar radiation and smoke medium and also of mechanisms of radiative transfer between air and smoke media is required. One-dimensional models of solar-radiation transfer in the atmosphere-smoke system (SAS), i.e. atmosphere with admixtures that arose under the effect of large scale fires (forest, peat, industrial) and lead to forming extending smoke screen, are being developed by us on the basis of two approaches. In one model, calculations are performed by the iteration method of characteristics ofr a two-medium SAS: underlying layer - smoke screen, upper layer- atmosphere. The second model uses the optical transfer operator (OTO) to express the SAS radiation through the influence functions (IFs) of the atmosphere and smoke.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A theoretical model of the coherent population trapping (CPT) in multilevel samarium atom and its comparison with experimental spectroscopic data are presented. Theoretical model describes a degenerated (Lambda) -system in Sm atom formed of the transitions 4f66s2(7F0) mutually implies 4f6(7F)6s6p(3Po)9Fo1 mutually implies 4f66s2(7F1) and includes also a fourth level 4f66s2(7F2), which complements the model making it an open system. An open character of the system reduces the contrast of the resonance curves in the CPT- spectra, but does not change the width of the CPT resonance. Numerical modeling of the CPT resonances in Sm atom was carried out for the case of applied longitudinal and transverse magnetic fields in 7- and 12-level models, as well.