In an investigation of the fundamental optical absorption edge of indium oxide at room temperature, transitions identified as direct-allowed have been observed with an energy gap (probably at k=0) of 3.75 eV. Indirect-forbidden transitions have also been observed with an energy gap of 2.619 eV and an assisting phonon of 0.069 eV. It is proposed that the minimum of the conduction band is at k=0 and the maximum of the valence band is at k≠0.

The n = 2 fine-structure transitions in positronium have been measured by observation of increased Lyman-a radiation at microwave induced resonances. We used an accelerator based slow positron beam to produce positronium in the 2 3 5'i excited state inside a waveguide. Our results are v 0 = 18499.65 ± 1.20±4.00 MHz, vi-13012.42±0.67±1.54 MHz, and v 2 =8 624.38 ±0.54 ± 1.40 MHz for the 2 3 S'i-* 2 3 Po,\,2 transition frequencies, respectively. The first error is statistical and the second is systematic. This is in agreement with recent bound state QED calculations.

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