Vol 53, No 2 (2018)

The scheme of multi-momentum atom interferometer based on the resonant Kapitza–Dirac diffraction is considered. The conclusion is made that the arms of counter propagating waves forming the standing wave, which scatters the atoms, should have the equal length.

A new method is proposed to determine the subpicosecond laser pulse chirp in the middle IR range at the central wavelength of 10 μm, based on the generation of the second-harmonic pulses both by the bandwidth-limited and frequency-modulated subpicosecond pulses and the subsequent noncollinear generation of the fourth-harmonic radiation by the corresponding second-harmonic pulses. The time dependences are given of the instantaneous frequency of the frequency-modulated second-harmonic pulse at the central wavelength of 5 μm, generated in the field of the frequency-modulated subpicosecond IR pulse, propagating in the negative uniaxial AgGaS₂ crystal along the direction of 61°36′ relative to the optical axis. These results can be used in designing a nonlinear optical phase correlator to determine the phase and time profile of the subpicosecond laser pulse in the middle IR range.

The possibility of using a vibrating wire as a target in the method of scanning transverse profiles of the thin beams in particle accelerators has been studied. In the case where the transverse dimensions of the beam are comparable to the amplitude of the wire oscillations, the vibrating wire can be used for a fast measurement of the transverse beam profile without moving the sensor. The scanning procedure is replaced by the use of the movement of the wire during its mechanical oscillations. The method is tested on a focused beam of a semiconductor laser with a spot size at the focus of ∼0.1 mm. The reconstruction of the transverse profile is performed on the basis of the measurements of the photons reflected from the vibrating wire by using fast photodiodes.

Simple expressions were obtained for the thermal expansion coefficients of the rare-earth garnets, which allow to estimate their values in a wide temperature range in cases, when either the lattice unit cell parameters or the density of the material are known at 300 K. The expression giving the relationship between the thermal expansion and thermal conductivity coefficients for the rare-earth garnets has also been obtained. It is shown that the calculated values obtained with the use of these expressions are in a good agreement with the available experimental data for the garnets of different composition.

The X-ray asymmetric Bragg diffraction in a perfect semi-infinite crystal with plane entrance surface is considered taking into account the two-dimensional curvature of the wave front of an incident wave. An expression for reflection coefficient using the Green function is obtained in the approximation of locally plane wave and the rocking curves are investigated as functions of angular departure from the selected exact Bragg direction in the diffraction plane and in the direction perpendicular to the diffraction plane. The shape, position and dimensions of total reflection region of rocking curves are studied depending on the degree of asymmetry of diffraction geometry. The requirements to the spatial and temporal coherence for obtaining the rocking curves are estimated.

Factors that influence both the thermodynamics of hybridization and the stability of the DNA–DNA duplexes are analyzed. The noncompetitive DNA hybridization cases in the presence of mono- and bivalent positively charged ligands have been investigated and the comparison is made with the case of uncharged ligands. It has been shown that the charged ligands enhance the sensitivity of the DNA chips as compared with the uncharged ones.

In page 7, the text: This is a property of invariance of the representation of the four-dimensional momentum P through the velocity of the reference system β′ = V/c.

Should be read as follows: This is a property of invariance of the representation of the four-dimensional momentum P in terms of the velocity of the particle β′ = v/c.