Monodromy-Quasifree Singular Points of the Sturm–Liouville Equation of Standard Form on the Complex Plane

Differential Equations - For the Sturm–Liouville equation of standard form on the complex plane, we study the existence of potentials with monodromy-quasifree singular points, i.e., singular...     

The photodissociation of molecules near the ionisation threshold

The photodissociation (PD) of the moleculeXY near the ionisation threshold is considered within the framework of the multichannel quantum defect theory. The general analytical dependence, determining the relation between the PD amplitude, the adiabatic amplitudes of dipole transitions and elements of the collisions matrix describing the associative ionisation (X+Y→e ^?+XY ⁺) and resonance scattering of atoms (X+Y→X′+Y′), has been obtained. The collisions matrix is determined by the system of algebraic equations and is expressed via the parameters which can be reconstructed from the molecule terms adiabatic picture. The obtained expressions can be used in case of a random number of Rydberg and dissociative channels. The role of the resonance mechanism of the molecules intermediate predissociative and autoionisational states population has been investigated. The peculiarities of the PD spectra structure for different physical situations have been studied. It has been shown that the Rydberg continuum states population increases the process general efficiency (the PD cross-section averaged over resonances increases). The NO molecule near-threshold PD, proceeding through thenpπ Rydberg states is calculated.     

Evolution of the structural and superconducting properties of FeSe crystals upon long-term storage

A comprehensive analysis of the evolution of the structural and superconducting properties of FeSe crystals stored in air for several years has been performed. It is established that the structure and phase composition of the samples remained invariable, while the superconducting parameters significantly degraded. These changes may be due to the stress relaxation or redistribution of defects in the samples.     

Potential energy surface of the Rydberg states of the NO molecule in an intense IR radiation field

A method taking into account valence (non-Rydberg) and dissociative configurations has been developed for calculation of potential energy surfaces of the NO molecule in an intense IR radiation field. The resonance rovibronic structure of the Rydberg molecule–laser field quantum system has been analyzed within the steady-state formalism of the radiation collision matrix using multi-channel quantum defect theory. Special conditions for field control of predissociation involving intermediate Rydberg and valence states have been formulated.     

The optical module of Baikal-GVD

In April 2015, the first cluster of Baikal-GVD was deployed in Lake Baikal and put into operation. It comprises eight strings. Each string consists of 24 optical modules. An optical module is a detection element of Baikal-GVD; it includes a Hamamatsu R7081-100 photomultiplier tube with a high quantum sensitivity. We describe the design of the optical module, the front-end electronics, and the laboratory characterization and calibration.     

Chemical physics of the upper atmosphere

Modern concepts of the structure of the ionosphere and dynamics of its perturbations related to geomagnetic and solar activity perturbations are considered. It is shown that communication and navigation satellite systems depend substantially on the state of the ionosphere. The role played by Rydberg atoms and molecules of neutral ionospheric plasma components excited in collisions with electrons in the formation of microwave radiation of the upper atmosphere is discussed. A new physical mechanism of the delay of satellite signals cased by a cascade of reemissions from Rydberg states over the decimeter range is suggested.     

Thermovoltaic effect in samarium sulfide-based heterostructures

The thermovoltaic effect in samarium sulfide-based bulk heterostructures with compositions Sm_{1 − x} Eu _x S and Sm_{1 − x} Gd _x S is considered in the temperature interval 300–460 K. It is shown that this effect can be observed when an external temperature gradient is absent, i.e., when the sample temperatures near the contacts from which a generated voltage is tapped off are the same. The temperature is measured with thermocouples and also by a contactless method using a thermal imager.     

Growth and properties of layered oxycarbonate Bi2Sr4Cu2CO3O8 single crystals

Layered oxycarbonate Bi₂Sr₄Cu₂CO₃O₈ single crystals have been obtained for the first time by free growth in closed vapor-phase cavities. The morphology, structure, composition, and superconducting properties of these crystals have been investigated.     

Collision of Rydberg atom A** with atom B in the ground electronic state. Optical potential

A method for calculating the complex optical potential of slowly colliding Rydberg atom A^** and neutral atom B in the ground electronic state is suggested. The method is based on the asymptotic approach and the theory of multichannel quantum defects, which uses the formalism of renormalized Lippmann-Schwinger equations. The potential is introduced as the 〈q|V _opt|q〉 matrix element of the optical interaction operator, for which the integral equation is derived, and is calculated in the basis set of free particle wave functions |q〉. Fairly simple equations for the shift and broadening of the ionic term are obtained, and the principal characteristics of these equations are analyzed. By way of illustration, the optical potential of the Na^**(nl)+B systems, where B is a rare gas atom, is calculated.