Σu and Πu states of the hydrogen molecule: Nonadiabatic couplings and vibrational levels

Nonadiabatic coupling matrix elements are computed for six lowest and four lowest ¹Π_u electronic states of H₂ in a wide range of internuclear distances. These matrix elements are used together with the adiabatic potentials to determine the bound ro-vibrational levels of the 10 electronic states for rotational quantum numbers J ? 10. The computed energies agree quite well with existing experimental term values. However, some of the experimental levels should be assigned differently.     

Synthesis and gas sensing characteristic based on metal oxide modification multi wall carbon nanotube composites

A new type of gas sensing material based on metal oxide modification multi wall carbon nanotube (MO/MWCNT) composites is presented since the interface between the composites enhance the carrier density so as to improve the gas sensitivity. Three kinds of MO/MWCNT composite materials, such as ZnO/MWCNT, SnO₂/MWCNT and TiO₂/MWCNT, have been acquired in situ growth using catalytic pyrolysis method. The MO nano particles have decorated on side of MWCNTs, whereas the introduction of SnO₂ nano particles makes part of MWCNT showing two-dimensional form of carbon nano-wall structure. Among four kinds of cathode of ZnO/MWCNTs, SnO₂/MWCNTs, TiO₂/MWCNTs and pure MWCNT composite film, TiO₂/MWCNTs composite has the lowest threshold electric field required to draw current of 12 μA has been found to be ∼1.2 V/μm, and also TiO₂/MWCNTs composite has the highest sensitivity of 16% to ethanol. The TiO₂/MWCNTs composite is superior to the others both in vacuum electron transportation and gas sensitivity.     

Thermal and optical investigation of EuF3-doped lead fluorogermanate glasses

Europium-doped lead germanate and lead fluorogermanate glasses are studied by using differential thermal analysis, X-ray diffraction, photoluminescence and fluorescence lifetimes measurements of the ⁵D_j, j = 0, 1, 2 levels. PbF₂ addition increases the thermal stability of the lead germanate glass, while Eu³⁺ ions promote the crystallization of β-PbF₂:Eu³⁺ nano-crystals embedded in a glassy matrix. In the lead fluorogermanate glasses, Eu³⁺ ions exhibit a strong affinity for F⁻ ions although oxygen ions are much more numerous. It appears that luminescence concentration quenching is not important, while cross relaxation is very efficient in the glasses. The results allow to propose for these glasses a molecular model in which small fluorine rich island, incorporating the Eu³⁺ ions in low symmetry sites, are separated from each other by chains of germanate (GeO₄)⁴⁻ ions linked together.