Vol 51, No 1 (2016)

The results ofmeasurements on the search for the cluster decay of ²⁵²Cfnucleus with the emission ofthe bound state of eight neutrons are presented. The value of an upper limit ofthe partial probabilities for this process is obtained, which contradicts to the results ofthe recently published work, in which the possible existence of octaneutron was declared. Based on the results of our measurements, the estimations for the upper limits ofpartial probabilities for the emission of ²⁰C, ²⁴O, ²⁸Ne, 32Mg, ³⁶Si, ⁴⁰S, ⁴⁰P, and ⁴⁰Si clusters are given. The estimation for the upper limit of the partial probability of ²⁵⁰Cf decay with the emission of the bound state of six neutrons is also obtained.

The spectra of two photon generation in the process of spontaneous parametric down conversion are studied in a waveguide containing the nonlinear segments with the spatial chirp. Three photon parametric interaction is investigated for the waveguide containing only a spatial fundamental mode. The peculiarities of spectra broadening of photon pair in the chirped waveguide are studied.

The possibilities of LiNbO₃-Ho³⁺ crystals for optical cooling based on the anti-Stokes luminescence in the wavelength range 2000-2200 nm are investigated. The efficiency and cooling temperature under the continuous wave (CW) excitation at the wavelengths 2035-2071 nm by ~100 W power are estimated. It is shown that under the CW excitation at 2035 nm wavelength the maximum cooling temperature is equal to 2.5 K, and at 2071 nm wavelength is equal to 10.9 K.

Several modem methods of nanowires fabrication and their characterization are presented and discussed. Electronic and thermal transport measurement techniques ofnanowire arrays as well as of an individual nanowire in the wide temperature range are presented.

Intra-subband transitions caused by light absorption in a parabolic quantum well is considered taking into account the scattering by ionized impurity centers. To calculate the scattering matrix element, the Born approximation is used and the interaction with the impurity is described by the Coulomb potential. An analytical expression for the absorption coefficient of processes with the initial absorption of photon and further scattering by an ionized impurity center is obtained. For absorption coefficient the frequency characteristics and dependence on the width of quantum well are examined.

The Laue-Bragg diffraction from monolithic crystal systems was realized. It was shown that a multiple increase in the number ofreflections leads to a supercollimation ofthe beam. A precision method for measuring the reflection coefficients is proposed, in which this beam is used as the primary one.

The X-ray interferometric Fresnel holography was proposed and theoretically investigated. It was shown that under definite conditions the recorded interference pattern formed at the output surface ofthe analyzer crystal (the third block of interferometer) is the X-ray interferometric hologram (generally the Fresnel one) of the object under investigation. Further reconstruction of an image is performed with the help of visible light or a numerical method. As an example the recording of a Fresnel hologram of the simplest case of one-dimensional object, a narrow slit, and the reconstruction of an image by means of visible light were considered. This method may be used in X-ray microscopy and realized using synchrotron sources ofX-ray radiation, as well as X-ray free electron lasers.

Within the frameworks of generalized model of polypeptide chain (GMPC) the concentrational behavior of helix-coil transition temperature of biopolymer in two-component solvent was observed on the simplest models. It is shown that if the solvent and the ligand interact with the biopolymer at different binding sites, and even if both components influence the helical state in the same way, the model allows one to obtain the non-monotone character of the melting temperature behavior of biopolymer depending on the ligand concentration. It is shown that changes in the regime of helical state stability is not always related with the competition of stabilizing and destabilizing interactions of blend components but can be the result of the cumulative effect of both components.