We report on the development of a microelectromechanical systems (MEMS)-scale photoacoustic sensor for the detection of trace gases. A mid-infrared quantum cascade laser (QCL) was used to determine detection limits for acetic acid, acetone, 1,4-dioxane, and vinyl acetate. The source was continuously tunable from 1015 cm(-1) to 1240 cm(-1), allowing for the collection of photoacoustic vibrationa...

Detection of moisture contamination in hydride gases, such as ammonia used for epitaxial growth, has become a significant concern for manufacturers of III-V compound semiconductors. The presence of moisture in NH3 can negatively affect device properties, such as minority-carrier lifetimes and luminescent efficiency in light-emitting diodes. Tunable diode laser spectroscopy (TDLAS) has emerged a...

A new edition of the AFGL trace gas compilation is now available. Absorption line parameters of positions, intensities, and halfwidths are given for the major bands of thirteen gases covering the spectral region from 0 to 10,000 cm(-1). In addition to updating the original gases (NO, SO(2), NO(2), and NH(3)), the molecules HNO(3), OH, HF, HC1, HBr, HI, CIO, OCS, and H(2)CO have been added to th...

We have developed an aerial mercury monitoring system whose operating principle is based upon gold amalgamation and flameless atomic absorption. A stable measurement of micro-trace mercury in the air becomes possible by preventing dirt from accumulating in the measuring system and minimizing interference from other gases occupying the same area. As a mercury collecting agent, a Chromosorb P coa...

The atmosphere is an oxidizing medium. Many environmentally important trace gases emitted from the Earth’s surface are removed from the atmosphere by oxidation. The list includes methane and other organic compounds, carbon monoxide, nitrogen oxides, and sulfur gases (Table 1). Understanding the processes and rates by which species are oxidized in the atmosphere, i.e., the oxidizing power of the...

[1] We explore possible mechanisms for the generation of warm, wet climates on early Mars as a result of greenhouse warming by both water vapor and periodic volcanic trace emissions. The presence of both water vapor (a strong greenhouse gas) and other trace greenhouse gases (such as SO2) in a predominantly CO2 atmosphere may act, under certain conditions, to elevate surface temperatures above t...

We investigate mass transfer during the isothermal absorption of atmospheric trace soluble gases by a single droplet whose size is comparable to the molecular mean free path in air at normal conditions. It is assumed that the trace reactant diffuses to the droplet surface and then reacts with the substances inside the droplet according to the first-order rate law. Our analysis applies a flux-ma...