Nuclear recoil effect on the magnetic-dipole decay rates of atomic levels

The effect of finite nuclear mass on the magnetic-dipole transition probabilities between fine-structure levels of the same term is investigated. Based on a rigorous QED approach a nonrelativistic formula for the recoil correction to first order in m_e/M is derived. Numerical results for transitions of experimental interest are presented.     

Search for the KL-->pi 0 pi 0 e+e- decay in the KTeV experiment

The recent discovery of a large CP violating asymmetry in KL-->pi+pi-e+e- mode has prompted us to seach for the associated KL-->pi 0 pi 0 e+e- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7 x 10(11) K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the KL-->pi 0 pi 0 e+e- branching ratio of 6.6 x 10(-9) at the 90% C.L.     

Search for the rare decay K(L)-->pi(0)e(+)e(-)

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay K(L)-->pi(0)e(+)e(-). This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the standard model or could indicate the existence of new physics. This Letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99+/-0.35 events. We set a limit on the branching ratio of 3.5x10(-10) at the 90% confidence level. Combining with the previous result based on the data set taken in 1997 yields the final KTeV result: BR(K(L)-->pi(0)e(+)e(-))<2.8x10(-10) at 90% C.L.     

Search for the decay K(L) --> pi(0)&mgr;(+)&mgr;(-)

We report on a search for the decay K(L)-->pi(0)&mgr;(+)&mgr;(-) carried out as a part of the KTeV experiment at Fermilab. This decay is expected to have a significant CP violating contribution and a direct measurement will either support the Cabibbo-Kobayashi-Maskawa mechanism for CP violation or point to new physics. Two events were observed in the 1997 data with an expected background of 0.87+/-0.15 events, and we set an upper limit B(K(L)-->pi(0)&mgr;(+)&mgr;(-))<3. 8x10(-10) at the 90% confidence level.     

Ethenolysis of C<Superscript>5+</Superscript> Alkenes as a Method for Synthesis of Propylene

Thermodynamic calculations demonstrated that, when any C⁵⁺ alkene is subjected to ethenolysis in an excess of ethylene on a catalyst providing the occurrence of a metathesis and positional isomerization, the main reaction product is propylene. The results of the calculations were confirmed experimentally for the cases of ethenolysis of hexene-1 and heptene-1 on Re₂O₇/SO₄^2-/ZrO₂–Al₂O₃ and Re₂O₇/B₂O₃–Al₂O₃ catalysts.     

Measurements of the decay KL-->e+ e- gamma

The E799-II (KTeV) experiment at Fermilab has collected 83 262 K(L)-->e+ e- gamma(gamma) events above a background of 79 events. We measure a decay width, normalized to the K(L)-->pi0pi0pi(D)0 (pi0-->gammagamma, pi0-->gammagamma, pi(D0-->e+ e- gamma(gamma)) decay width, of Gamma(K(L)-->e+e-gamma(gamma))/Gamma(K(L)-->pi0pi0pi(D)0)=(1.3302+/-0.0046(stat)+/-0.0102(syst)) x 10(-3). We also measure parameters of two K(L)gamma*gamma form factor models. In the Bergstr?m-Massó-Singer parametrization, we find Calpha(K*)= -0.517 +/- 0.030(stat) +/- 0.022(syst). We separately fit for the first parameter of the D'Ambrosio-Isidori-Portolés model and find alpha(DIP)= -1.729 +/- 0.043(stat) +/- 0.028(syst).     

Conversion of Products Formed in Gasification of Organic Fuels in a Flow-Through Filtration Converter with Packing

Russian Journal of Applied Chemistry - Results are presented of experimental studies of the conversion of products formed in gasification of wood, peat, coal-wastes, and shale rock via the partial...     

Valley Orientation of Electrons and Excitons in Atomically Thin Transition Metal Dichalcogenide Monolayers (Brief Review)

JETP Letters - The main aspects of physical phenomena associated with the optical orientation of the spin and valley degrees of freedom in transition metal dichalcogenide monolayers and in van der...     

Ground-state energy of uranium diatomic quasimolecules with one and two electrons

Ground-state energies of the one- and two-electron uranium dimers are calculated for internuclear distances in the range D=40–1,000 fm and compared with the previous calculations. The generalization of the dual-kinetic-balance approach for axially symmetric systems is employed to solve the two-center Dirac equation without the partial-wave expansion for the potential of two nuclei. The one-electron one-loop QED contributions (self-energy and vacuum polarization) to the ground-state energy are evaluated using the monopole approximation for the two-center potential. Interelectronic interaction of the first and second order is taken into account for the two-electron quasimolecule. Within the QED approach, one-photon-exchange contribution is calculated in the two-center potential, whereas the two-photon-exchange contribution is treated in the monopole approximation.