Autoionizing rydberg states of. The Li2 molecule: Molecular constants for Li2+

Autoionizing Rydberg series of Li₂ have been observed in the two-step optical cxcitation of a supersonic lithium beam. The series limits are vibrational states of Li₂⁺. In the most probable assignment IP(Li₂) = 41236.4 ± 2.5 cm^?1 and for Li₂⁺ω_e = 263.45 ± 1.3 cm^?1; ω_eχ_e = 1.35 ± O.2 cm^?1; r_e = 3.032 ± 0.01 Å; D_e = 10807 ± 150 cm^?1.     

Megawatt VUV xenon laser employing coaxial electron-beam excitation

3 nsec laser pulses, of bandwidth 1.3 nm, are obtained from a 10 J, 600 keV coaxial diode electron-beam pumping arrangement. Uniform pumping, with a well defined cylindrical geometry, facilitates experimental investigation of the laser parameters. Gas heating limits the laser repetition rate. While mirror damage at present limits the peak power to ∽ 1 MW, higher powers seem available. The addition of helium results in a drastic reduction of peak molecular xenon fluorescence.     

Evolution of the dUTPase gene of mammalian and avian herpesviruses

Sequences of dUTPases encoded by Alpha- and Gammaherpesviruses resemble other dUTPases in their possession of five conserved motifs, but differ in having greater chain lengths (about twice as long) and in the location of Motif 3 at an N terminal location relative to the other motifs. It was proposed that the herpesvirus gene arose by intragenic duplication of a standard dUTPase coding sequence and subsequent loss of one copy of each motif from the double length chain, and that the resulting enzyme was active as a monomer. With knowledge of the trimeric 3D structure of standard dUTPases, it is possible to suggest transformations that occurred in evolutionary development of the herpesvirus dUTPase. The distinct location of Motif 3 can indeed be seen to be consistent with it contributing to a single intramolecular active site with the other motifs. Separately, the occurrence in herpesvirus dUTPases of around 20 to 40 additional residues between Motifs 4 and 5 allows the C-terminal Motif 5 to reach the active site intramolecularly. The driving force behind these evolutionary changes remains obscure. We speculate that they may have allowed acquisition of a novel, presently unknown function by the protein. Consistent with this idea is the observation that in Alpha- and Gammaherpesvirus dUTPases the original locus of Motif 3 is occupied by a distinct conserved sequence (Motif 6); perhaps this element constitutes part of a separate functional capability. Notably, the apparently orthologous protein in Betaherpesviruses lacks the standard motifs while Motif 6 is still present.     

Prism reflectors for high power lasers

A new type of laser reflector is described in which the laser beam is split by frustrated total internal reflection and the components combined again. It has the properties of high reflectivity, high damage resistance, wide bandwidth and variable reflectivity. The design of two particular reflectors is discussed and their performance evaluated. One of these reflectors has the property of lateral inversion of the reflected beam, which is found to aid transverse mode selection in a ruby laser. As an application of the reflectors, a damage free, single transverse mode, mode-locked ruby laser is described.     

Catalyst development for organocatalytic hydrosilylation of aromatic ketones and ketimines

A new family of Lewis basic 2-pyridyl oxazolines have been developed, which can act as efficient organocatalysts for the enantioselective reduction of prochiral aromatic ketones and ketimines with trichlorosilane, a readily available and inexpensive reagent. 1-Isoquinolyl oxazoline, derived from mandelic acid, was identified as the most efficient catalyst of the series, capable of delivering high enantioselectivities in the reduction of both ketones (up to 94% ee) and ketimines (up to 89% ee).     

Co-axially pumped,narrow band,continuously tunable,high power VUV xenon laser

High efficiency spectral narrowing to 0.13 nm and frequency tuning from 169 nm to 176 nm has been produced with a new design of coaxial-pumped xenon laser employing a single intra-cavity prism. The laser peak power is 3 MW (9 mJ) and becomes 0.7 MW (power density 10 MW cm^-2) when frequency narrowed.     

The Nike electron-beam-pumped KrF laser amplifiers

Nike is a recently completed multikilojoule krypton-fluoride (KrF) laser that has been built to study the physics of direct-drive inertial confinement fusion. The two final amplifiers of the Nike laser are both electron-beam-pumped systems. This paper describes these two amplifiers, with an emphasis on the pulsed power. The smaller of the two has a 20×20 cm aperture, and produces an output laser beam energy in excess of 100 J. This 20 cm Amplifier uses a single 12 kJ Marx generator to inject two 300 kV, 75 kA, 140 ns flat-top electron beams into opposite sides of the laser cell. The larger amplifier in Nike has a 60×60 cm aperture, and amplifies the laser beam up to 5 W. This 60 cm amplifier has two independent electron beam systems. Each system has a 170 kT Marx generator that produces a 670 kV, 540 kA, 240 ns Bat-top electron beam. Both amplifiers are complete, fully integrated into the laser, meet the Nike system requirements, and are used routinely for laser-target experiments     

Optimal sampling strategies for quicksort

A well-known improvement on the basic Quicksort algorithm is to sample from the subarray at each recursive stage and to use the sample median as the partition element. General sampling strategies, which allow sample size to vary as a function of subarray size, are analyzed here in terms of the total cost of comparisons required for sorting plus those required for median selection. Both this generalization and this cost measure are new to the analysis of Quicksort. A square-root strategy, which takes a sample of size Φ(√n) for a subarray of size n, is shown to be optimal over a large class of strategies. The square-root strategy has O(n^1,5) worst-case cost. The exact optimal strategy for a standard implementation of Quicksort is found computationally for n below 3000. © 1995 John Wiley & Sons, Inc.     

The production and measurement of ultrashort pulses in a ruby layer

The two-photon flourescence from a whole pulse train is measured photoelectrically for a variety of laser conditions. A compound mode-locking solution containing DDI and DCI is found to reduce pulse lengths. An etalon which cancels gain-narrowing also has this effect. Intensity-dependent variations are found in the two-photon fluorescence profile which suggest a threshold for self-phase modulation.