Measurement of small absorptions in liquids

We use the recently developed technique of pulsed dye-laser optoacoustic spectroscopy of liquids to study the weak 607-nm absorption band of benzene dissolved in various concentrations in CCl(4). The technique involves the use of submersed piezoelectric transducer and gated detection of the transient acoustic signal. With increasing dilution, the peak of the 607-nm band is observed to be more blue-shifted, and the linewidth and asymmetry of the band decrease. We verify that the present technique can detect absorption coefficients of 10(-6) cm(-1) and absorbed energy of 10(-9) J. With these high sensitivities, we show that nonlinear optical processes such as multiphoton absorption and stimulated Raman scattering in liquids should be readily observable with our optoacoustic method.

CO2 laser in vitreoretinal surgery: 1. Quantitative investigation of the effects of CO2 laser radiation on ocular tissue

Scleral, lens, and vitreoretinal tissue was incised using CO2 laser radiation in a controlled and predictable fashion without producing untoward effects on neighboring ocular tissue. The penetration depth of infrared radiation into normal human vitreous was measured and was found to be exceedingly small. A quantitative correlation was observed between the CO2 laser power and the depth of penetration in scleral-chorio-retinal wall incisions and in lens tissue from human eyebank eyes. The results of this investigation suggest that the CO2 laser may be useful in intravitreal surgery, full-thickness scleral-chorio-retinal wall resections, transvitreal chorioretinal biopsy, and even dissolution of cataracts.

Laser Detection of Pollution

Spectroscopic analysis is a useful technique for identifying and quantitatively determining the presence of specific gaseous constituents. Development of high-power tunable lasers has made the spectroscopic technique for detection of trace constituents in the atmosphere very attractive for practical applications. In this article three of the currently used modes for laser detection of pollution are reviewed: (i) long-path measurements, (ii) laser Raman (differential absorption) measurements, and (iii) optoacoustic detection. Progress in the field has been extremely rapid in the last few years and very useful and reliable data on air pollution can now be obtained routinely with the techniques described.

Hydrogen Cyanide Production During Reduction of Nitric Oxide over Platinum Catalysts: Transient Effects

The formation of hydrogen cyanide during the catalytic reduction of nitric oxide (NO) with carbon monoxide and hydrogen was studied with a bench-scale flow reactor. The previously reported inhibition by sulfur dioxide of the formation of hydrogen cyanide was found to be counteracted by transient admission of oxygen to the catalyst. These results are discussed in the context of the control of automotive emissions of NO and the prevention of hydrogen cyanide production during such control.

Stratospheric Nitric Oxide: Measurements during Daytime and Sunset

Measurements of the temporal variation in the stratospheric nitric oxide concentration covering a time period from 11:00 to 20:30 local time show the effect of solar ultraviolet sunset. The experimental results strongly support the theorized role of nitric oxide as a catalyst in the destruction of ozone and its importance in the stratospheric ozone balance.

Spectroscopic Measurements of Stratospheric Nitric Oxide and Water Vapor

Spectroscopic measurements have been made of the nitric oxide and water vapor concentrations in the stratosphere at an altitude of 28 kilometers. The measurements, carried out in situ with the use of a spin flip Raman laser, represent the first accurate determination of nitric oxide as a function of time (as the sun rose) from about 6: 30 to 14: 00 C. D. T.

Air pollution: sensitive detection of ten pollutant gases by carbon monoxide and carbon dioxide lasers

Detection sensitivities of a few parts per billion for ten gaseous pollutants have been evaluated by measuring the strength of the absorption of infrared radiation from carbon monoxide and carbon dioxide lasers. Ethylene concentrations as small as 5 parts per billion have been detected in air. The measured absorption strengths indicate that in mixtures of pollutants, such as nitrogen dioxide and water vapor, the sensitivity is reduced by overlapping absorption bands. However, calculations indicate that it should be possible to detect nitrogen dioxide concentrations of 0.01 part per million in the presence of water vapor concentrations of 105 parts per million.

Nitric oxide air pollution: detection by optoacoustic spectroscopy

Nitric oxide is detected by a new technique in which tunable infrared radiation from a spin-flip Raman laser is used to measure the absorption spectrumn of a gas sample by optoacoustic spectroscopy. This technique is sensitive enough to detect a concentration of 0.01 part per million of nitric oxide pollution in air samples.