We report the first successful preparation of thin films of Y-Ba-Cu-O superconductors using pulsed excimer laser evaporation of a single bulk material target in vacuum. Rutherford backscattering spectrometry showed the composition of these films to be close to that of the bulk material. Growth rates were typically 0.1 nm per laser shot. After an annealing treatment in oxygen the films exhibited superconductivity with an onset at 95 K and zero resistance at 85 and 75 K on SrTiO3 and Al2O3 substrates, respectively. This new deposition method is relatively simple, very versatile, and does not require the use of ultrahigh vacuum techniques.

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The variation with temperature of the penetration depth of weak magnetic fields into niobium has been measured. The variation was more rapid than expected from the BCS theory of superconductivity, in contrast to the situation in previously measured superconductors where it was less rapid. Just as in the previous cases, the results here can be understood in terms of a variation of the energy gap different from that predicted by the BCS theory. A comparison with the energy gap deduced by Dobbs and Perz from their ultrasonic-attenuation measurements is given. The penetration depth at absolute zero, \(0), is estimated from the present results to be 470=1=50 A, while the London penetration depth XL(0) is 390=b50 A.

Experiments to measure the hydrogen uptake kinetics of DEB getter/Pd catalyst/activated carbon pellets have been performed under isothermal isobaric conditions. The extracted kinetics were then used to predict the performance of the getter pellets under different temperatures and pressures, including nonisobaric situations. For isothermal isobaric uptake at higher H2 pressure (666.6-2666.5 Pa), H2 solubility in the getter matrix is responsible for the uptake observed up to a 40-60% reacted fraction. Once the hydrogenated product becomes thicker, the diffusions of the reactants (atomic hydrogen and getter molecules) toward the reaction front become the rate limiting step. However, in a dynamic but very low H2 pressure, encountered in many vacuum electronic applications, the hydrogen spillover effect, over micrometer scale, becomes the dominant reaction mechanism. Despite such a complex dependence of the rate limiting mechanisms on the experimental environment, there is good agreement between kinetic prediction models and experiments. The investigation also reveals that the ultimate uptake capacity in the getter pellets scales inversely with the free volume of the vacuum vessel in which the DEB getter pellets are used, and that DEB getter pellets' performance greatly deteriorates during the final 10-15% capacity (as evidenced by the sharp bend in the slopes of the reacted fraction vs time curves at 85-90% reacted fraction).

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We have computed the potential energy surfaces for the low-lying electronic states of uranium hydrides, UHn (n=1–3), which are important in the uranium hydriding reactions. We have employed a number of computational methods including the complete active space multiconfiguration self-consistent field followed by multireference relativistic configuration interaction computations with spin–orbit coupling that included up to 6 million configurations. We find that the activation barrier to insert uranium into H2 is reduced substantially by spin–orbit coupling, and the product species UH2 in its A1 spin–orbit ground state is substantially stable over U(5L)+H2 dissociated products. We have found two electronic states for UH to be quite close to each other, and depending on the level of theory the relative ordering of the Λ6 and I4 states changes, I4 state being the lowest at the highest second-order configuration interaction level. The UH2 species also exhibits a similar feature in that the triplet state is favored at the single-reference second-order Møller–Plesset and coupled cluster levels, while the quintet state is favored at the multireference and density functional theory levels. The UH3 species is extremely floppy, exhibiting an inversion potential surface that has a barrier smaller than its zero-point energy. It is shown that the UH3 species is considerably more ionic than UH2 or UH, and UH3 is responsible for catalyzing the U-hydriding reaction as the highly positive U site in UH3 reacts with H2 spontaneously without an activation barrier. The results of our computations are compared with previous experimental results. The spin–orbit coupling is shown to be more important for energy activation than near the minima.

A silica-filled polydimethylsiloxane (PDMS) composite M9787 was investigated for potential outgassing in a vacuum/dry environment with the temperature programmed desorption/reaction method. The outgassing kinetics of 463 K vacuum heat-treated samples, vacuum heat-treated samples which were subsequently re-exposed to moisture, and untreated samples were extracted using the isoconversional and constrained iterative regression methods in a complementary fashion. Density functional theory (DFT) calculations of water interactions with a silica surface were also performed to provide insight into the structural motifs leading to the obtained kinetic parameters. Kinetic analysis/model revealed that no outgassing occurs from the vacuum heat-treated samples in subsequent vacuum/dry environment applications at room temperature (∼300 K). The main effect of re-exposure of the vacuum heat-treated samples to a glove box condition (∼30 ppm by volume of H2O) for even a couple of days was the formation, on the silica surface fillers, of ∼60 ppm by weight of physisorbed and loosely bonded moisture, which subsequently outgasses at room temperature in a vacuum/dry environment in a time span of 10 yr. However, without any vacuum heat treatment and even after 1 h of vacuum pump down, about 300 ppm by weight of H2O would be released from the PDMS in the next few hours. Thereafter the outgassing rate slows down substantially. The presented methodology of using the isoconversional kinetic analysis results and some appropriate nature of the reaction as the constraints for more accurate iterative regression analysis/deconvolution of complex kinetic spectra, and of checking the so-obtained results with first principle calculations such as DFT can serve as a template for treating other complex physical/chemical processes as well.