Since ocular aberrations above the Zernike fourth order are relatively insignificant in normal eyes, current scanning lasers with a beam diameter of 1.0 mm or less are theoretically capable of eliminating most higher-order aberrations.

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Rate coefficients of the reaction of hydroxyl (OH) radicals with CH3OCH3 (k 1) and CH3OC(CH3)3 (k 2) over an extended temperature range are reported. Measurements were performed using a laser photolysis−laser-induced fluorescence technique under slow flow conditions at a total pressure of 740 ± 10 Torr. Arrhenius plots of the data exhibited significant curvature and were fitted in the form of k(T) = AT B exp(−C/T). The resulting modified Arrhenius expressions (error limits ±2σ) that best described these extended temperature measurements and prior low-temperature measurements were (in units of cm3 molecule-1 s-1) k 1(295−650 K) = (1.05 ± 0.10) × 10-17 T 2.0 exp[(328 ± 32)/T] and k 2(293−750 K) = (1.15 ± 0.11) × 10-17 T 2.04 exp[(266 ± 41)/T]. Comparison of our measurements for k 1 with previous, overlapping low-temperature measurements indicated generally good agreement. Our measurements for k 2, although consistent with previous room temperature measurements, exhibited a larger temperature dependence than previously reported. High-temperature oxidation mechanisms for these oxygenated fuel components are proposed. Support for the mechanisms is presented in the form of product analysis studies in high-temperature tubular flow reactors. For CH3OC(CH3)3, these studies suggest that H abstraction from the tert-butyl group is an important high-temperature oxidation pathway.

A refracting system consisting of two lenses is designed to transform an annular Gaussian laser beam into a circular Bessel beam. The slopes of the input and output surfaces fit well with a sixth-order polynomial. A smooth variation of the radii of curvature of the resulting aspheric surfaces is very attractive for easy machining of the surfaces. The diffraction-free length for the designed system is 59.4735 m at 633 nm.