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Studies of the growth of crystals of energetic materials under conditions of high acceleration in an ultracentrifuge are reported. When a saturated solution is accelerated in an ultracentrifuge, the solute molecules move individually through the solvent molecules to form a crystal at the outer edge of the tube if the solute is more dense than the solvent. Since there is no evaporation or temperature variation, convection currents caused by simultaneous movement of solvent and solute are minimized and crystal defects are potentially minimized. Crystal growth is controlled by the g-level of the acceleration. We present results of TNT, RDX, and TNAZ grown at high g from various solutions. Crystals grown at high g were free of solution inclusions and gas bubbles.

Many researchers have studied the noise properties of optical amplifiers and have shown that all nonlinear optical amplifiers introduce noise into the amplified beam.1 In our research, we have conducted a theoretical and experimental investigation of the quantum noise generated by a phase-conjugate mirror (PCM) obtained using four-wave mixing in potassium vapor. An ideal PCM will generate light that exhibits excess quantum noise that is inherent to the phase conjugation process.2 Additional noise can be introduced as a result of fluctuations (e.g., collisions) in the nonlinear medium, as has been predicted for the nonlinear process of two-beam coupling in an atomic vapor.3 These sources of noise determine the fundamental limit on the smallest signal that can be phase-conjugated.

Studies of the growth of crystals of energetic materials under conditions of high acceleration are reported. This new way of growing crystals of energetic materials by using a concentration gradient is different than the usual procedure of crystal growth by solvent evaporation at constant temperature or by temperature variation with slow cooling. When a solution is accelerated in an ultracentrifuge, the solute molecules concentrate at the outer edge of the tube if the solute is more dense than the solvent. If the solution is initially saturated, then the solution at the outer edge of the tube becomes supersaturated and crystal growth can occur. Results are presented for growth of TNT and RDX crystals at high g in an ultracentrifuge using no seed crystals for most of the samples.

We discuss applications of an ultra-high vacuum TEM to the study of clean Si surfaces and in-situ deposited films. For the Nisi2 on Si system, we show the importance of metastable phases during growth. For native oxidation of Si, the behavior of individual atomic steps is viewed. In summary, moderate resolution TEM and diffraction is shown to have a great deal to contribute to semiconductor surface science primarily because of the kinematical diffraction by monolayers and the penetration to view sub-surface phenomena.