Vol 103, No 12 (2016)

The hyperfine structure of the ground 2²S-states of the three-electron atoms and ions is investigated. By using our recent numerical values for the doublet electron density at the atomic nucleus, we determine the hyperfine structure of the ground (doublet) 2²S-state(s) in the ⁶Li and ⁷Li atoms. Our predicted values (228.2058 and 803.5581 MHz, respectively) agree well with the experimental values 228.20528(8) MHz (⁶Li) and 803.50404(48) MHz (⁷Li [R.G. Schlecht and D.W. McColm, Phys. Rev. 142, 11 (1966)]). The hyperfine structures of a number of lithium isotopes with short lifetimes, including ⁸Li, ⁹Li, and ¹¹Li atoms are also predicted. The same method is used to obtain the hyperfine structures of the three-electron ⁷Be⁺ and ⁹Be⁺ ions in their ground 2²S-states. Finally, we conclude that our approach can be generalized to describe the hyperfine structure in the triplet n³S-states of the four-electron atoms and ions.

Work of Lev Landau had a profound impact on the physics in 20th century. Landau had created the paradigms that had framed the conversations on the outstanding problems in physics for decades. He had laid foundations for our understanding of quantum matter like superfluidity, superconductivity and the theory of Fermi liquid. Here we present some Nobel Archive data on the winning nomination that led to the Nobel Prize in Physics in 1962.

We present fermionic model based on symmetric resonant tunneling heterostructure, which demonstrates spontaneous symmetry breaking in respect to combined operations of space inversion (P) and time reversal (T). PT-symmetry breaking manifests itself in resonance coalescence (collapse of resonances). We show that resonant energies are determined by eigenvalues of auxiliary pseudo-Hermitian PT-invariant Hamiltonian.

The dispersion relation for magnetoplasmons in a planar superlattice with periodically alternating regions of gapless and gapped modifications of graphene has been derived within the frame of the random-phase approximation. The contribution of virtual transitions between the lower electron miniband and the upper hole miniband to the polarization operator has been taken into account in addition to the contribution of virtual intra-miniband transitions.

Experimental data have been presented to confirm the thermal nature of broadband visible radiation emitted from Yb³⁺- and Er³⁺-doped nanocrystalline particles of orthophosphates and orthophosphate hydrates irradiated by 972-nm near-infrared laser radiation. The mechanism of appearance of this radiation has been discussed.

Inelastic processes and the reemission of attosecond and shorter electromagnetic pulses by atoms have been considered within the analytical solution of the Schrödinger equation in the sudden perturbation approximation. A method of calculations with the exact inclusion of spatial inhomogeneity of the field of an ultrashort pulse and the momenta of photons in the reemission processes has been developed. The results have been presented in the form of analytical formulas. The probabilities of inelastic processes and spectra of reemission of ultrashort electromagnetic pulses by single-electron atoms have been calculated.

A new phenomenon has been discovered where a bend of a plasma channel becomes of a source of one or several diffuse jets that have a length (at a given voltage) up to 4–6 cm and are directed across the plasma channel at a pulse-periodic spark discharge in air under normal conditions. The phenomenon is called apokamp discharge (apokamp). The spectrum of radiation of the apokamp includes primarily the bands of electron-vibrational transitions of the second positive system of molecular nitrogen. The conditions of the formation of apokamp have been experimentally revealed and it has been established that it consists of plasma bunches moving from the plasma channel at each pulse at a velocity of about 220 km/s.

The security of keys in quantum cryptography systems, in contrast to mathematical cryptographic algorithms, is guaranteed by fundamental quantum-mechanical laws. However, the cryptographic resistance of such systems, which are distributed physical devices, fundamentally depends on the method of their implementation and particularly on the calibration and control of critical parameters. The most important parameter is the number of photons in quasi-single-photon information states in a communication channel. The sensitivity to a bright-pulse attack has been demonstrated in an explicit form for a number of systems. A method guaranteeing the resistance to such attacks has been proposed and implemented. Furthermore, the relation of physical observables used and obtained at the control of quantum states to the length of final secret keys has been obtained for the first time.

The response time of a plasmonic terahertz detector is investigated using two independent experimental techniques relying on time-resolved and heterodyne measurements, respectively. Both methods demonstrate that the detector response time does not exceed 110 ps. The results obtained suggest that the designed terahertz detector can be used as a component of high-speed telecommunication systems of a new generation.