Automated rapid triple-isotope (N, O, O) analyses of nitrate by Ti(III) reduction and NO laser spectrometry.

The nitrogen and oxygen (N, O, O) stable isotopic compositions of nitrate () are crucial tracers of nutrient N sources and dynamics in aquatic and atmospheric systems. Methods to reduce aqueous to NO gas (microbial or Cd method) before N and O isotope analyses require multi-step conversion or toxic chemicals, and O in NO cannot be disentangled by IRMS due to isobaric interferences. This technical note describes the automation of the stable-isotope analyses of nitrate by coupling the new Ti method with a headspace autosampler and an NO triple-isotope laser analyzer based on off-axis integrated cavity output spectroscopy.

Fast in situ airborne measurement of ammonia using a mid-infrared off-axis ICOS spectrometer.

A new ammonia (NH3) analyzer was developed based on off-axis integrated cavity output spectroscopy. Its feasibility was demonstrated by making tropospheric measurements in flights aboard the Department of Energy Gulfstream-1 aircraft. The ammonia analyzer consists of an optical cell, quantum-cascade laser, gas sampling system, control and data acquisition electronics, and analysis software.

Direct analysis of δ2H and δ18O in natural and enriched human urine using laser-based, off-axis integrated cavity output spectroscopy.

The stable isotopes of hydrogen (δ(2)H) and oxygen (δ(18)O) in human urine are measured during studies of total energy expenditure by the doubly labeled water method, measurement of total body water, and measurement of insulin resistance by glucose disposal among other applications. An ultrasensitive laser absorption spectrometer based on off-axis integrated cavity output spectroscopy was demonstrated for simple and inexpensive measurement of stable isotopes in natural isotopic abundance and isotopically enriched human urine. Preparation of urine for analysis was simple and rapid (approximately 25 samples per hour), requiring no decolorizing or distillation steps.

Use of laser spectroscopy to measure the 13C/12C and 18O/16O compositions of carbonate minerals.

The stable carbon and oxygen isotope compositions of carbonate minerals are utilized throughout the earth and environmental sciences for various purposes. Here, we demonstrate the first application of a prototype instrument, based on off-axis integrated cavity output laser spectroscopy, to measure the carbon and oxygen isotope composition of CO(2) gas evolved from the acidification of carbonate minerals. The carbon and oxygen isotope ratios were recorded from absorption spectra of (12)C(16)O(16)O, (13)C(16)O(16)O, and (12)C(16)O(18)O in the near-infrared wavelength region.

Ammonia Monitoring Near 1.5 mum with Diode-Laser Absorption Sensors.

We investigated ammonia spectroscopy near 1.5 mum to select transitions appropriate for trace ammonia detection in air-quality and combustion emissions-monitoring applications using diode lasers. Six ammonia features were selected for these trace-gas detection applications based on their transition strengths and isolation from interfering species.

In Situ Combustion Measurements of CO(2) by Use of a Distributed-Feedback Diode-Laser Sensor Near 2.0 mum.

High-resolution absorption measurements of CO(2) were made in a heated static cell and in the combustion region above a flat-flame burner for the development of an in situ CO(2) combustion diagnostic based on a distributed-feedback diode laser operating near 2.0 mum. Calculated absorption spectra of high-temperature H(2)O and CO(2) were used to find candidate transitions for CO(2) detection, and the R(50) transition at 1.

In situ combustion measurements of CO with diode-laser absorption near 2.3 microm.

In situ measurements of CO concentration were recorded with tunable diode-laser absorption spectroscopy techniques in both the exhaust and the immediate post-flame regions of an atmospheric-pressure flat-flame burner operating on ethylene air. Two room-temperature cw single-mode InGaAsSb/AlGaAsSb diode lasers operating near 2.3 microm were tuned over individual transitions in the CO first overtone band (v' = 2 <-- v" = 0) to record high-resolution absorption line shapes in the exhaust duct [79 cm above the burner, approximately 470 K; R(15) transition at 4311.

Multiplexed continuous-wave diode-laser cavity ringdown measurements of multiple species.

Rapid cavity ringdown measurements of multiple broadband absorbing species (methanol and isopropanol) in gas mixtures have been recorded with two multiplexed continuous-wave distributed-feedback diode lasers operating near 1.4 mum. A measurement sensitivity of 2.

Diode-Laser Absorption Measurements of CO(2) Near 2.0 mum at Elevated Temperatures.

A diode-laser sensor system based on absorption spectroscopy techniques has been developed for nonintrusive measurements of CO(2) in high-temperature environments. Survey spectra of the CO(2) (20 degrees 1,04 degrees 1)(I)-00 degrees 0 and (20 degrees 1,04 degrees 1)(II)-00 degrees 0 bands between 1.966 and 2.

Diode laser sensor for measurements of CO, CO(2), and CH(4) in combustion flows.

A diode laser sensor has been applied to monitor CO, CO(2), and CH(4) in combustion gases with absorption spectroscopy and fast extraction-sampling techniques. Survey spectra of the CO 3nu band (R branch) and the 2nu(1) + 2nu(2)(0) + nu(3) CO(2) band (R branch) near 6350 cm(-1) and H(2)O lines from the nu(1) + 2nu(2) and 2nu(2) + nu(3) bands in the spectral region from 6345 to 6660 cm(-1) were recorded and compared with calculated spectra (from the HITRAN 96 database) to select optimum transitions for species detection. Species concentrations above a laminar, premixed, methane-air flame were determined from measured absorption in a fast-flow multipass absorption cell containing probe-sampled combustion gases; good agreement was found with calculated chemical equilibrium values.

Off-axis cavity ringdown spectroscopy: application to atmospheric nitrate radical detection.

Atmospheric nitrate radicals (NO3) are detected using off-axis cavity ringdown spectroscopy (CRDS) for the first time to our knowledge with a room-temperature continuous-wave (cw) diode laser operating near 662 nm. A prototype instrument was constructed that achieved a 1sigma absorption sensitivity of 5 x 10(-10) cm(-1) Hz(-1/2), corresponding to a 1.4 part per trillion by volume 2sigma detection limit in 4.

Cavity-enhanced quantum-cascade laser-based instrument for carbon monoxide measurements.

An autonomous instrument based on off-axis integrated cavity output spectroscopy has been developed and successfully deployed for measurements of carbon monoxide in the troposphere and tropopause onboard a NASA DC-8 aircraft. The instrument (Carbon Monoxide Gas Analyzer) consists of a measurement cell comprised of two high-reflectivity mirrors, a continuous-wave quantum-cascade laser, gas sampling system, control and data-acquisition electronics, and data-analysis software. CO measurements were determined from high-resolution CO absorption line shapes obtained by tuning the laser wavelength over the R(7) transition of the fundamental vibration band near 2172.

Quantitative detection of singlet O2 by cavity-enhanced absorption.

A method for the practical determination of the absolute concentration of single (a1delta(g)) oxygen is discussed. The method is based on sensitive off-axis integrated-cavity-output spectroscopy (ICOS). Off-axis ICOS allows narrowband, continuous-wave lasers to be used in conjunction with optical cavities to record sensitive absorption measurements.

High-Resolution Measurements of HBr Transitions in the First Overtone Band Using Tunable Diode Lasers.

High-resolution absorption lineshapes of the R(7) and P(2) transitions in the first overtone (v = 0-2) band of H(79)Br have been recorded at room temperature using a pair of distributed feedback diode lasers operating near 1.95 and 2.00 µm, respectively.

Diode-Laser Measurements of He-, Ar-, and N2-Broadened HF Lineshapes in the First Overtone Band.

High-resolution lineshapes of the HF P(3) and P(6) transitions (2-0 band) have been recorded in a 14.9-cm long absorption cell (T = 296 K) using a pair of (InGaAsP)-distributed feedback diode lasers operating near 1.31 and 1.

Spectral Intensity and Lineshape Measurements in the First Overtone Band of HF Using Tunable Diode Lasers.

High-resolution absorption lineshapes for the P(3) and P(6) transitions of the first overtone (v = 2-0) band of HF at 296 K have been measured using a pair of distributed feedback diode lasers operating near 1.31 and 1.34 µm, respectively.

Diode laser absorption measurements of CH(3)Cl and CH(4) near 1.65 microm.

Two distributed-feedback (InGaAsP) diode lasers were used to record high-resolution absorption spectra of the parallel and the perpendicular components of the 2nu(4) band of methyl chloride (CH(3)Cl) and the 2nu(3) band of methane (CH(4)) near 1.65 mum. The room-temperature absorption measurements, which were conducted in a multipass cell with a variable path length (878-1020 cm), were used to determine the mole fractions of the constituent gases and thus demonstrate species-specific, nonintrusive concentration measurements of species with overlapping spectra.

Tunable diode-laser absorption measurements of NO(2) near 670 and 395 nm.

Two single-mode diode lasers were used to record high-resolution absorption spectra of NO(2) (dilute in Ar) near 670.2 and 394.5 nm over a range of temperatures (296 to 774 K) and total pressures (2.

Tunable diode-laser absorption measurements of methane at elevated temperatures.

A diode-laser sensor system based on absorption spectroscopy techniques has been developed to monitor CH(4) nonintrusively in high-temperature environments. Fundamental spectroscopic parameters, including the line strengths of the transitions in the R(6) manifold of the 2ν(3) band near 1.646 μm, havebeen determined from high-resolution absorption measurements in a heated static cell.

Dual diode-laser fiber-optic diagnostic for water-vapor measurements.

We present a novel diode-laser diagnostic for water-vapor measurements based on absorption spectroscopy. Two InGaAsP diode lasers were used to record H(2)O absorption line shapes near 1395 nm at a 3-kHz repetition rate along a single path through a water-vapor flow field generated in a shock tube. The use of two lasers permits simultaneous line-shape measurements in different spectral regions and facilitates the selection of appropriate line pairs for thermometry.

Semiconductor laser-based measurements of quench rates in an atmospheric pressure plasma by using saturated-fluorescence spectroscopy.

Plasma diagnostics based on saturated fluorescence and absorption spectroscopy with a semiconductor (diode) laser are developed to probe the 4s(3)P(1) ? 4p(3)D(2) transition (8425 A) of argon in an atmospheric pressure plasma produced by an inductively coupled plasma torch. Spatially resolved measurements of saturation intensity, nonradiative collisional transfer (quench) rate, and fluorescence yield (Stern-Volmer factor) are inferred from variations of spectral profile characteristics (line shape, line-center value, and frequency-integrated signal) with laser intensity. The results obtained by using fluorescence and absorption spectroscopy are mutually consistent in the analytical region 10 mm above the induction coil.

Fertility, maternal care, and offspring behavior in mice prenatally treated with tobacco smoke.

Female mice from lines selectively bred for differences in open-field activity were exposed to tobacco smoke during gestation. Smoke-treated females were less likely than controls to have produced litters by 23 days after observation of a vaginal plug. Within the high-active line, fewer pups of smoke-treated dams survived to weaning.

Fertility and offspring survival in mice selected for different sensitivities to alcohol.

The LS (long-sleep) and SS (short-sleep) selected lines of mice exhibit relatively high and low sensitivity to alcohol, respectively, because of their previous history of selective breeding. The present study identifies other differences between the two lines. SS animals are almost twice as fertile as LS animals.