Vertical electric field waveforms of leader‐return stroke sequences measured 500 m and 30 m from rocket‐triggered lightning are presented. The 500‐m data were recorded during the summer of 1986, the 30‐m data during the summer of 1991, both at the NASA Kennedy Space Center, Florida. The 40 leader‐return stroke field waveforms at 500 m and the 8 waveforms at 30 m all appear as asymmetrical V‐shaped pulses, the bottom of the V being associated with the transition from the leader to the return stroke. Only two waveforms at 30 m were suitable for quantitative analysis. The widths of the V at half of peak value for these are 1.8 and 5.0 μs, while for the 500‐m data they are 1 to 2 orders of magnitude greater, with a median value of 100 μs. Applying a widely used and simple leader model to the measured leader electric fields at 500 m, we infer, for the bottom kilometer or so of the leader channel, leader speeds between 2×106 and 2×107 m/s and leader charges per unit length of 0.02×10−3 to 0.08×10−3 C/m. From the two measured leader electric field changes at 30 m we infer, using the same leader model, for the bottom 100 meters or so of the leader channel, speeds of 3×107 and 1×107 m/s (the corresponding measured waveform half widths are 1.8 μs and 5.0 μs) and charges per unit length of 0.14×10−3 and 0.02×10−3 C/m (the corresponding measured leader field changes are 81 kV/m and 12 kV/m). The corresponding measured return stroke peak currents for the above two cases are 40 kA and 7 kA, respectively. A positive correlation is observed between the magnitude of the leader field change at 500 m and the ensuing return stroke current peak.

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Thermal oxidation of normalGaP and normalGaAs by oxygen has been studied. normalGaP on oxidation undergoes a violent exothermic reaction at 1130°±20°C . The products of the oxidation of normalGaP are the christobalite form of GaPO4 as a primary product and β‐Ga2O3 as a secondary product (about 5 w/o). normalGaAs on oxidation undergoes a mild exothermic reaction at 840°±10°C . The products of this reaction are β‐Ga2O3 as a primary product and the low quartz form of GaAsO4 as a secondary product (about 10 w/o). The GaAsO4 at temperatures higher than 1000 °C decomposes to As2O5+β‐Ga2O3 . The above statements are made on the basis of x‐ray diffraction data, change in weight data, and wet chemical analyses. On the basis of this data, it is concluded that thermal oxide masking should be readily applicable to normalGaP and that thermal oxide masking should not be applicable to normalGaAs .

The preparation of single crystals of black monoclinic and red tetragonal ZnP2 from the elements is described. The crystals contain 50 to 100 ppm Si as an impurity. The melting point of monoclinic ZnP2 is 992±1°C and of tetragonal ZnP2 is 985±1°C. Interplanar spacings are presented for both the red and black polymorphs of ZnP2. Two bands have been observed in the near-bandgap luminescence of tetragonal ZnP2 at low temperatures. Both bands exhibit sharp lines, respectively, near 2.144 and 2.020 eV, due to no-phonon decay of bound excitons, and contain much fine structure due to associated phonon-assisted transitions. These spectra are identical with luminescence bands reported by Akopyan et al., but are attributed to recombinations in the ternary compound semiconductor ZnSiP2. Preliminary measurements of the indirect-type absorption-edge spectrum at low temperatures indicate that the energy gap of tetragonal ZnP2 is close to 2.220 eV at 4.2°K and ∼2.14 eV at 300°K.

The epitaxial synthesis of gallium arsenide utilizing a flow system was achieved using gallium trichloride, arsenic, and hydrogen as reactants, and oriented single crystals of normalGaAs as substrates. Under the conditions of these experiments, there is almost no difference in growth rates between the “A” orientation of the {111} surface and the “B” orientation of a false{true1¯true1¯true1¯false} surface. The rate of growth on a {110} surface is more than twice as great as on a {111} surface, and the rate of growth on a {100} surface is slower by a factor of 1.4 than on a {111} surface.