Width Narrowing Research Articles

The Orientational Freedom of Molecules in Crystals: I. Joint Interpretation of Thermal and N.M.R. Data in an “All or Nothing” Correlation of Orientation Theory

Abstract It is shown quantitatively that the Frenkel model (step reorientations among potential wells) is, in most cases, a very good approximation to the motion in crystals presenting a molecular orientational freedom. In contrast to n.m.r., thermodynamics is not sensitive to the dynamies of the motion, but rather to the appearance of the orientational disorder, whatever its rate of rearrangement. A classification accounting for the different observable temperature relations between n.m.r. line width narrowing and thermal data is proposed. This classification is based on the comparison between the symmetry of the molecule and the symmetry of its allowed orientations (potential wells). It applies to crystals of rigid molecules, in thermodynamic equilibrium, in which the correlation of orientation of the molecules is either very large (low temperature) or very small (high temperature).

Current mode second breakdown in epitaxial planar transistors

Current mode second breakdown is a type of voltage "switchback" observed in epitaxial transistors. The phenomenon is initiated when the emitter is injecting at a collector voltage in excess of the collector-emitter sustaining voltage, and is characterized by delay and voltage fall times on the order of a nanosecond. The device can be sustained in the low voltage state only as long as there is sufficient charge to produce conductivity modulation within the collector-base depletion region. When the available charge is exhausted, the collector voltage will recharge at a rate determined by the external circuit. At some critical current density, the collector-base depletion region collapses toward the high conductivity substrate. The electric field within the depletion region increases as the depletion region width narrows, until avalanche occurs. The sustaining voltage will be determined by the bulk base-to-collector avalanche voltage. A consequence of this behavior is that most epitaxial transistors cannot operate stably in the LV <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CER</inf> mode, and switching-off unclamped inductive circuits with the emitter-base junction terminated in some finite resistance will lead to second breakdown.

Giant Pulse Laser Action and Pulse Width Narrowing in Neodymium-Doped Borate Glass

Giant Pulse Laser Action and Pulse Width Narrowing in Neodymium-Doped Borate Glass