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Optical transmission measurements were carried out on Pb 1Ϫx Sr x Se samples, grown by molecular beam epitaxy, with different Sr compositions ͑x͒ ranging from 0 to 1. Refractive indices were calculated for all the samples at room temperature and at 77 K by fitting the transmittance data. Bandgap energies of all compositions were calculated by fitting the absorption coefficients to theoretical models of direct and indirect transitions. A distinct bandgap inversion from the direct to the indirect was observed at a Sr composition of approximately xϭ0.20. The direct and indirect bandgaps of SrSe calculated from the experimental results were found to be 3.81 and 1.82 eV, respectively.

We present experimental verification of predicted resonance structure in the energy dependence of the H+D2 reaction. Specifically we predict and observe a broad resonance in the H+D2-->HD(v(') = 0,j(') = 7)+D reaction at a collision energy of 0. 94 eV. This resonance structure is roughly Gaussian with a full width at half maximum of 0.1 eV. These results represent the first experimentally observed resonance structure in the fundamental H+H2 reaction system.

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