The infrared spectrum of the matrix-isolated phenyl radical.

We have measured the infrared absorption spectrum of C(6)H(5), /X (2)A(1), in an Ar matrix at 10 K. The experimental frequencies (cm(-)(1)) and polarizations follow. a(1) modes: 3086, 3072, 3037, 1581, 1441, 1154, 1027, 997, 976, 605; b(1) modes: 972, 874, 706, 657, 416; b(2) modes: 3071, 3060, 1624, 1432, 1321, 1283, 1159, 1063, and 587. Three different methods have been used for the production of the phenyl radicals. Infrared absorption spectra of five deuterated isotopomers, C(6)D(5), p-C(6)H(4)D, p-C(6)HD(4), o-C(6)H(4)D, and m-C(6)H(4)D, were recorded to compare experimental frequency shifts with calculated (UB3LYP/cc-pVDZ) harmonic frequency shifts. The use of CO(2) or NO as internal standards enabled the experimental determination of absolute infrared intensities. The linear dichroism was measured with photooriented samples to establish experimental polarizations of each vibrational band. True gas-phase vibrational frequencies were estimated by considering the gas-to-matrix shifts and matrix inhomogeneous line broadening. The phenyl radical matrix frequencies listed above are within +/-1% of the gas-phase vibrational frequencies. The C(6)H(5) frequencies from this paper supersede our earlier values reported in J. Am. Chem. Soc. 1996, 118, 7400-7401. See also: http://ellison.colorado.edu/phenyl.

Characterization of biomass pyrolysis vapors with molecular beam, single photon ionization time-of-flight mass spectrometry.

A single photon ionization, molecular beam sampling, reflectron time-of-flight mass spectrometer (SPI/MBTOFMS) has been developed and used to study pyrolysis products from a selection of biomass materials. Spectra are characterized by high resolution and decreased fragmentation compared to electron-impact ionization mass spectra from related molecular beam mass spectrometer systems equipped with quadrupole mass analyzers.

Theory and laboratory demonstrations on the use of a nematic liquid-crystal phase modulator for controlled turbulence generation and adaptive optics.

We discuss the use of liquid-crystal phase modulators (LCPM's) both as a repeatable disturbance test source and as an adaptive optics corrector. LCPM's have the potential to induce controlled, repeatable, dynamic aberrations into optical systems at low cost, low complexity, and high flexibility. Because they are programmable and can be operated as transmissive elements, they can easily be inserted into the optical path of an adaptive optics system and used to generate a disturbance test source. When used as wave-front correctors they act as a piston-only segmented mirror and have a number of advantages. These include low operating power requirements, relatively low cost, and compact size. Laboratory experiments with a Meadowlark LCPM are presented. We first describe use of the LCPM as a repeatable disturbance generator for testing adaptive optics systems. We then describe a closed-loop adaptive optics system using the LCPM as the wave-front corrector. The adaptive optics system includes a Shack-Hartmann wave-front sensor operated with a zonal control algorithm.

Experimental measurements of the statistical properties of a monochromatic speckle pattern.

An experimental approach to the measurement of phase of a coherent optical field with a Shack-Hartmann sensor is presented. We demonstrate the usefulness of this sensor by verifying a theoretical model for the distribution of ray directions in a monochromatic speckle pattern.

Coherent image synthesis from wave-front sensor measurements of a nonimaged laser speckle field: a laboratory demonstrations.

We report what are to our knowledge the first coherent images recovered in the laboratory from measurements made with a Shack-Hartmann wave-front sensor of the phase and amplitude of a laser speckle wave front. We discuss the design of our wave-front sensor, which can obtain the phase and amplitude of an optical field with a single intensity measurement, and we point out a particular type of phase jump that cannot be detected by the Shack-Hartmann sensor. We also discuss implementations of this technique that may permit near-diffraction-limited imaging through turbulent media.

First astronomical application of postdetection turbulence compensation: images of alpha Aurigae, nu Ursae Majoris, and alpha Geminorum using self-referenced speckle holography.

We describe a postdetection turbulence compensation technique for obtaining high resolution imagery through the atmosphere. We present preliminary results fromfield experiments.