Proton-polarizability contribution to the hyperfine splitting in hydrogen

The contribution of the proton polarizability to the hyperfine splitting in hydrogen is evaluated on the basis of modern experimental and theoretical results on the proton polarized structure functions. The value of this correction is 1.4 ppm.     

Hyperfine structure of the <Emphasis Type="Italic">S</Emphasis>- and <Emphasis Type="Italic">P</Emphasis>-wave states of muonic deuterium

Corrections of order α⁵ and α⁶ to the hyperfine structure of the S- and P-wave states of muonic deuteriumwere calculated on the basis of the quasipotential approach in quantum electrodynamics. Relativistic corrections, vacuum-polarization and deuteron-structure effects, and recoil corrections were taken into account in this calculation. The resulting hyperfine-splitting values can be used in a comparison with experimental data obtained by the CREMA Collaboration.     

The conductivity of heterostructures based on linear-chain carbon

Results are presented from investigations into the conductivity of heterostructures based on two-dimensionally ordered (TDO) linear-chain carbon (LCC) in the form of Al-LCC-Al and pSi-LCC-Al. The Al-LCC-Al structure is shown to possess a nonlinear ohmic contact with a barrier height of around 0.7 eV. It is shown that an over-barrier (Schottky) mechanism of electron injection to LCC in the forward direction and a tunneling effect (Fowler-Nordheim tunnel injection mechanism) in the backward direction occur in the pSi-LCC-Al heterostructure.     

How to measure chi(3) of a nanoparticle

Most of the known methods to measure the nonlinear optical properties of materials deal with the bulk properties, but there are many demanding applications that require those measurements to be done on a single particle or a single molecule. We report a novel application of nonlinear optics to measure the third-order nonlinear optical susceptibility of nanoparticles in solutions. By measuring the power of the third harmonic generated in a diluted solution of nanoparticles, both the size and chi(3) can be extracted from a simple set of measurements.     

Complexes of carbene analogs with Lewis bases: matrix IR spectroscopy and quantum-chemical studies

The results of studies on complexes of carbene analogs ER₂ (E = Si, Ge, Sn, Pb) with Lewis bases by matrix IR spectroscopy and quantum chemistry methods are considered. Trends in changes in the spectral characteristics, structures, and stability of the complexes are outlined.     

Studies of vacuum pyrolysis of 3-sila- and 3-germa-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) and low-temperature matrix stabilization of monomeric silicon dioxide from the gas phase

Vacuum pyrolysis of 3-sila-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) leads to the formation of monomeric silicon dioxide and 1,3-butadienes, whereas under the same conditions 3-germa-3,3′-spirobi(6-oxabicyclo[3.1.0]hexanes) afford germanium monoxide, the corresponding divinyl ethers, and 1,3-butadienes. A multistage mechanism of pyrolytic decomposition of the above spirobicyclohexanes was proposed on the basis of experimental data and calculations. The different behavior of the silicon and germanium compounds having similar structures can be explained by an increase in the bivalent state stability and by a decrease in the energy of the metal-oxygen double bond on the transition from silicon to germanium.     

First gas-phase detection of dimethylstannylene and time-resolved study of some of its reactions

Using a laser flash photolysis/laser probe technique, we report the observation of strong absorption signals in the wavelength region 450-520 nm (highest intensity at 514.5 nm) from four potential precursors of dimethylstannylene, SnMe(2), subjected to 193 nm UV pulses. From GC analyses of the gaseous products, combined with quantum chemical excited state CIS and TD calculations, we can attribute these absorptions largely to SnMe(2), with SnMe(4) as the cleanest source of the species. Kinetic studies have been carried out by time-resolved monitoring of SnMe(2). Rate constants have been measured for its reactions with 1,3-C(4)H(6), MeC[triple bond]CMe, MeOH, 1-C(4)H(9)Br, HCl, and SO(2). No evidence could be found for reaction of SnMe(2) with C(2)H(4), C(3)H(8), Me(3)SiH, GeH(4), Me(2)GeH(2), or N(2)O. Limits of less than 10(-13) cm(3) molecule(-1) s(-1) were set for the rate constants for these latter reactions. These measurements showed that SnMe(2) does not insert readily into C-H, Si-H, Ge-H, C-C, Si-C, or Ge-C bonds. It is also unreactive with alkenes although not with dienes or alkynes. It is selectively reactive with lone pair donor molecules. The possible mechanisms of these reactions are discussed. These results represent the first visible absorption spectrum and rate constants for any organo-stannylene in the gas phase.     

Theory of the hyperfine structure of the <Emphasis Type="Italic">S</Emphasis> states of muonic tritium

The hyperfine structure of the energy spectrum of the S levels of muonic tritium has been calculated using the quasi-potential method in quantum electrodynamics (QED). The α⁵- and α⁶-order effects on the polarization of vacuum, the structure and recoil of the nucleus, and relativistic corrections have been taken into account. The obtained numerical values of hyperfine splittings of 239.819 meV (1S state) and 29.965 meV (2S state) can be treated as reliable estimates for comparing with future experimental data of the CREMA collaboration, and hyperfine structure interval Δ₁₂ = 8ΔE ^hfs (2S)–ΔE ^hfs (1S) =–0.100 meV can be used for verifying the QED predictions. The resultant precision values of hyperfine splitting are also important for calculating the rates of formation of (μ dt) mesomolecules in muonic catalysis reactions.