Surface plasmon-polaritons and their uses

Surface plasmon-polaritons have been experimentally and theoretically studied for many years but in recent years interest has grown substantially due to their possible use in novel device applications. The aim of this review is to introduce the concept of surface plasmon-polaritons so that the reader will be able to appreciate the physics they can probe, and the device applications in which they may be utilized.     

Theoretical and experimental consideration of the reactions between VxOy+ and ethylene

We present joint theoretical and experimental results which provide evidence for the selectivity of V(x)O(y)(+) clusters in reactions toward ethylene due to the charge and different oxidation states of vanadium for different cluster sizes. Density functional calculations were performed on the reactions between V(x)O(y)(+) and ethylene, allowing us to identify the structure-reactivity relationship and to corroborate the experimental results obtained by Castleman and co-workers (Zemski, K. A.; Justes, D. R.; Castleman, A. W., Jr. J. Phys. Chem. A 2001, 105, 10237). The lowest-energy structures for the V(2)O(2)(-)(6)(+) and V(4)O(8)(-)(10)(+) clusters and the V(2)O(3)(-)(6)(+)-C(2)H(4) and V(4)O(10)(+)-C(2)H(4) complexes, as well as the energetics for reactions between ethylene and V(2)O(4)(-)(6)(+) and V(4)O(10)(+) are presented here. The oxygen transfer reaction pathway was determined to be the most energetically favorable one available to V(2)O(5)(+) and V(4)O(10)(+) via a radical-cation mechanism.The association and replacement reaction pathways were found to be the optimal channels for V(2)O(4)(+) and V(2)O(6)(+), respectively. These results are in agreement with the experimental results reported previously. Experiments were also conducted for the reactions between V(2)O(5)(+) and ethylene to include an energetic analysis at increasing pressures. It was found that the addition of energy depleted the production of V(2)O(4)(+), confirming that a more involved reaction rather than a collisional process is responsible for the observed phenomenon. In this contribution we show that investigation of reactions involving gas-phase cationic vanadium oxide clusters with small hydrocarbons is suitable for the identification of reactive centers responsible for selectivity in heterogeneous catalysis.     

Temporal criterion for single-frequency operation of passively Q-switched lasers

An analytical expression for the difference in buildup time between two longitudinal modes in a passively Q -switched laser resonator is developed and compared with experimental laser data. The results support the following temporal criterion for single-frequency, passively Q -switched operation: The difference in buildup time between any two longitudinal modes of the laser resonator should be comparable with or greater than the laser pulse duration to ensure single-frequency operation.     

The sequential analysis of long range fallout debris

A method for the determination of the principal radionuelides of Sr, Ba, Ce, Cs, Y, Zr, Nb, and W in single fallout samples containing bulk Si, Fe, and Ca is presented. The sample and added carriers are dissolved by fusion with sodium carbonate. The melt is leached first with hot water and then with hydrochloric acid. W and Cs are recovered from the water leach. Sr, Ba, Y, and the heavier rare earths appear in the hydrochloric acid leach. Ce is found in the leach residue and Nb in both the residue and the hydrochloric acid leach. The Zr and Nb in the residue are separated from Ce by absorption on an anion-exchanger from hydrochloric acid. The Zr and Nb in the hydrochloric acid leach are separated from Sr and Ba by precipitation of Sr and Ba as nitrates and then separated from Y and the heavier rare earths by absorption on the anion-exchanger. The combined Zr fractions are eluted with dilute hydrochloric acid and Nb with a hydrochloric-hydrofluoric acid mixture.     

Speckle statistics in imaging systems

We examine the statistical properties of speckle in ordinary imaging systems using a gaussian approximation. Expressions for the probability density and contrast of the pattern at an arbitrary axial point are derived and discussed. The principal features of the results are illustrated by examples in which the formulae are evaluated numerically.     

Photoassociation of a Bose-Einstein condensate near a Feshbach resonance

We measure the effect of a magnetic Feshbach resonance (FR) on the rate and light-induced frequency shift of a photoassociation resonance in ultracold 7Li. The photoassociation-induced loss-rate coefficient K_{p} depends strongly on magnetic field, varying by more than a factor of 10;{4} for fields near the FR. At sufficiently high laser intensities, K_{p} for a thermal gas decreases with increasing intensity, while saturation is observed for the first time in a Bose-Einstein condensate. The frequency shift is also strongly field dependent and exhibits an anomalous blueshift for fields just below the FR.     

Experimental studies of Bose-Einstein condensates in disorder

We review recent studies of the effects of disorder on an atomic Bose-Einstein condensate (BEC). We focus particularly on our own experiments with ⁷Li BECs in laser speckle. Both the interaction, which gives rise to the nonlinearity in a BEC, and the disorder can be tuned experimentally. This opens many opportunities to study the interplay of interaction and disorder in both condensed matter physics and nonlinear science.