Three‐Body Approximation for the Investigation of Efimov States in Molecular Systems

Using the three‐body approximation with the well‐known interatomic potential, the Efimov states in molecular systems are calculated. A mechanism of appearance and dissappearance of the Efimov states in the helium trimer in the three‐body approximation is considered when the interatomic‐interaction force is varied. Geometrical structure of these unusual quantum states are presented.     

Numerical simulation of the evolution of ion clouds in a mass spectrometer by the particle-in-cell method

At present, mass spectrometry is the main analytical technique used in the studies on determining the composition of biomolecules. In such studies, the accuracy of determining the mass values is affected by hidden parameters (Coulomb interaction of analyzed ions with each other and with the walls of the mass-spectrometer trap).The problem consists in the development of a parallel computer code that allows simulation of the millions of charged ions and can reproduce the times of a real experiment in order to study the influence of Coulomb forces on the mass spectrum.The mathematical formulation of the original physical problem is presented. It is proposed to use the particle-in-cell method for simulation of the motion of ion clouds in the trap. The equations of motion are integrated with the use of a scheme with frequency correction. This approach ensures exact reproduction of the cyclotron motion and the ion cyclotron resonance. The Poisson equation is solved at each time step with the use of a method based on the fast Fourier transform. The code is written in Fortran 90 and is parallelized with the use of OpenMP directives.Comparison is performed with a real experiment with protein cytochrome c. The effect of coalescence of spectral peaks is demonstrated at high charge densities in the case of three masses.     

Resonances in Scattering. I. Basic Equations and Main Approximations

We describe the main features of resonances in scattering, determining the resonances in view of the theory of collisions in a two-body system, as well as the resonances emerging as a result of collisions in a few-body system. We analyze regularities in the emergence of such resonances and their characteristics. We discuss the results of calculations of the resonant processes occurring during collisions of electrons with diatomic molecules, in view of the quantum theory of scattering in a few-body system based on the Faddeev–Yakubovsky equations.     

Collisions of electrons with molecules in excited vibrational-rotational states

Results are presented of calculations of cross sections for scattering of electrons by diatomic molecules in specific excited vibrational-rotational states. The calculations were made using an approximation based on a quantum theory of scattering in a system of several bodies which can be applied to calculations of direct reactions and reactions involving the formation of an intermediate transition complex. Results of calculations of cross sections for collisions of electrons with hydrogen, nitrogen, lithium, sodium, and hydrogen halide molecules are compared with existing experimental data and the results of calculations made by other authors.     

Electron-molecule and atom-molecule scattering within the few-body approximation

A quantum theory of few-body scattering based on the Faddeev-Yakubovsky equations is applied to the calculation of cross sections of electron and atom scattering by diatomic molecules in specified excited rovibrational states. The results of the calculations are compared with the available experimental data and other calculations.     

Electrical transport and magnetic ordering in R 2Ti3Ge4 (R=Dy, Ho and Er) compounds

New R ₂Ti₃Ge₄ (R=Dy, Ho and Er) intermetallic compounds have been synthesized and characterized by X-ray diffraction and low temperature ac magnetic susceptibility, electrical resistivity and thermoelectric power measurements were carried out. The compounds crystallize in the parent, Sm₅Ge₄-type orthorhombic structure (space group Pnma) and lanthanide contraction is observed as one moves along the rare-earth series. The changeover from paramagnetic to antiferromagnetic phase happens at low temperatures and the ordering temperature scales with the de Gennes factor. The electrical resistivity is metallic with a negative curvature above 100 K. Thermopower displays a weak maximum at temperatures less than 50 K signifying the possible phonon and magnon drag effects.     

Elastic properties of the Ta–V system: bcc Ta0.33V0.67 and C15 TaV2

Resonant ultrasound spectroscopy was used to measure the elastic constants of bcc Ta_0.33V_0.67 over the temperature range 3.5–300?K; the results were compared to earlier measurements on C15 TaV₂. The temperature dependence of the polycrystalline shear modulus is completely different in the two phases; that of the bcc phase decreases with temperature whereas that of the C15 phases increases in an anomalous fashion. This difference is consistent with a model involving doubly-degenerate levels at the X point of the Brillouin zone in the C15 phase with the Fermi level lying near the doubly degenerate level. This model accounted for the unusual behaviour of the C15 phase. Debye temperatures were determined from the ultrasonic measurements: 295?K for the C15 phase and 315?K for the bcc phase.