Logarithmic contributions in the particle-mass ratio to the fine shift of <Emphasis Type="Italic">S</Emphasis> energy levels of hydrogen-like atoms in the fifth order in the fine-structure constant

A high-precision investigation of a logarithmic contribution in the particle-mass ratio to the fine shift of the S energy levels of hydrogen-like atoms from the exchange of a Coulomb photon is performed. It is shown that diagrams describing the exchange of one transverse photon and two Coulomb photons do not make such contributions.     

Heavy quark 1/m Q expansion of meson weak decay form factors in the relativistic quark model

The method of systematical expansion in the inverse powers of the heavy quark masses of the weak current matrix elements between heavy meson states is developed in the framework of the relativistic quark model based on the quasipotential approach in quantum field theory. The comparison of the first and second order terms of this expansion with the structure predicted by the heavy quark effective theory imposes strong constraints on the form of the long-range confining potential of quark-antiquark interaction. It is found that the confinig $q\bar q$ potential is effectively vector, while scalar potential is anticonfining and helps to reproduce the correct nonrelativistic limit. At large distances quarks have nonperturbative anomalous chromomagnetic moments. The obtained values of the potential parameters are in accord with the ones found in our previous consideration of meson masses and decay rates. We calculate the Isgur-Wise function. The first and the second order form factors within 1/m _Q expansion.     

Experimental and theoretical study of the reaction of difluorostannylene with methyl chloride. The first direct IR spectroscopic detection of a complex between a carbene analog and an alkyl halide in low temperature inert matrix

Complex between a carbene analog (SnF₂) and organo halide (CH₃Cl) was stabilized by a low-temperature (Ar, 12 K) matrix isolation technique and characterized by IR spectroscopy for the first time. The bands at 567 and 543 cm^–1 were assigned to this complex. The potential energy surface of the system SnF₂ + CH₃CI was studied byab initio MP2/ 3-21G(d)//HF/3-21G(d) and semiempirical PM3 methods. Calculations shown that the reaction between SnF₂ and CH₃C1 results in the formation of a donor-acceptor complex. The calculated energy of the complex formation is 14.2 kcal mol^–1 (ab initio) and 15.7 kcal mol^–1 (PM3). Quantum-chemical calculations were used to interpret the IR spectrum of the complex. Insertion of SnF₂ into the C-Cl bond with formation of CH₃SnF₂Cl is an energetically favored process but it requires surpassing of a high energetic barrier and does not occur under the experimental conditions. A complex of CH₃CI with H₂O codeposited in argon matrix was detected by IR spectroscopy for the first time.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1121–1128, May, 1996.     

Experimental and quantum-chemical study of complexation of carbene analogs with dinitrogen. Direct IR-spectroscopic observation of Cl2Si·N2 complexes in low-temperature argon-nitrogen matrices

Interaction of dichlorosilylene with dinitrogen in mixed Ar—N₂ matrices at 9 - 10 K was studied by IR spectroscopy. A donor-acceptor complex Cl₂Si·N₂ was found and characterized by six bands of symmetric (at 511.2, 508.9, and 506.5 cm^–1) and antisymmetric (at 500.1, 496.9, and 495.1 cm^–1) stretching vibrations of Si—Cl bonds in the most abundant isotopomers. Two bands at 498.7 and 493.5 cm^–1 observed in mixed matrices were tentatively assigned to Cl₂Si·(N₂)₂ complex. Several stretching vibration bands of minor isotopomers of SiCl₂ were detected for the first time in argon matrices. Assignment has been done for the isotopic structure of SiCl₂ associates with dinitrogen observed in N₂ matrices. Dimerization of SiCl₂ and its complexation with one and two N₂ molecules were studied by quantum-chemical DFT calculations (PBE and B3LYP functionals). The structures, energies, and vibrational frequencies of the Cl₂Si·N₂ and Cl₂Si·(N₂)₂ complexes and the Si₂Cl₄ dimer were determined. The energies of SiCl₂ complexation with one and two N₂ molecules obtained from PBE and B3LYP calculations are 0.3 and 0.6 kcal mol^–1, respectively. More accurate G2(MP2,SVP) calculations using the B3LYP geometries have predicted a higher stability of the Cl₂Si·N₂ complex (1.2 kcal mol^–1). The calculated and experimental vibrational frequencies of reagents and complexes are in good agreement. A correlation has been established between the PBE calculated energies of complexation of EHal₂ (E = Si, Ge, Sn, Pb) with N₂ and the experimentally observed shifts of E—Hal stretching vibrations in EHal₂ upon complexation. The strength of the complexes with N₂ increases on going from dihalosilylenes to dihaloplumbylenes.     

Heavy baryons in the relativistic quark model

In the framework of the relativistic quasipotential quark model the mass spectrum of baryons with two heavy quarks is calculated. The quasipotentials for interactions of two quarks and of a quark with a scalar and axial vector diquark are evaluated. The bound state masses of baryons with are computed.     

Energy Interval 1S–2S in Muonic Hydrogen and Helium

Journal of Experimental and Theoretical Physics - The interval of a large structure of energy spectrum (1S–2S) in muonic helium and hydrogen is calculated using a quasi-potential method in...     

Baryon properties in the relativistic quark model

Properties of heavy and strange baryons are investigated in the framework of the relativistic quark-diquark picture. It is based on the relativistic quark model of hadrons, which was previously successfully applied for the calculation of meson properties. It is assumed that two quarks in a baryon form a diquark and baryon is considered as the bound quark-diquark system. The relativistic effects and diquark internal structure are consistently taken into account. Calculations are performed up to rather high orbital and radial excitations of heavy and strange baryons. On this basis the Regge trajectories are constructed. The rates of semileptonic decays of heavy baryons are calculated. The obtained results agree well with available experimental data.     

Order (Zα)6 m e 2 /m μ corrections to the fine structure of muonium

We use the quasipotential method to calculate the total correction of order (Zα)⁶ m _e ² m _μ in the energy spectrum of the n ³ S ₁ states of muonium. The numerical value of the muonium-fine) structure interval 2³ S ₁−1³ S ₁ amounts to 0.19 MHz. Zh. éksp. Teor. Fiz. 115, 1221–1235 (April 1999)