scholarly journals Intercomparison of Hantzsch and fiber-laser-induced-fluorescence formaldehyde measurements

2014 ◽  
Vol 7 (1) ◽  
pp. 233-255 ◽  
Author(s):  
J. Kaiser ◽  
X. Li ◽  
R. Tillmann ◽  
I. Acir ◽  
F. Rohrer ◽  
...  
Keyword(s):  
Linear Regression ◽  
Fiber Laser ◽  
Gas Phase ◽  
Measurement Techniques ◽  
Laser Induced Fluorescence ◽  
Mixing Ratios ◽  
Wet Chemical ◽  
Simulation Chamber

Abstract. Two gas-phase formaldehyde (HCHO) measurement techniques, a modified commercial wet-chemical instrument based on Hantzsch Fluorimetry and a custom-built instrument based on Fiber-Laser Induced Fluorescence (FILIF), were deployed at the atmospheric simulation chamber SAPHIR to compare the instruments' performances under a range of conditions. Thermolysis of para-HCHO and ozonolysis of 1-butene were used as HCHO sources, allowing for calculations of theoretical HCHO mixing ratios. Calculated HCHO mixing ratios are compared to measurements, and the two measurements are also compared. Experiments were repeated under dry and humid conditions (RH < 2% and RH > 60%) to investigate the possibility of a water artifact in the FILIF measurements. The ozonolysis of 1-butene also allowed for the investigation of an ozone artifact seen in some Hantzsch measurements in previous intercomparisons. Results show that under all conditions the two techniques are well correlated (R2 ≥ 0.997), and linear regression statistics show measurements agree with within stated uncertainty (15% FILIF + 5% Hantzsch). No water or ozone artifacts are identified.

scholarly journals Intercomparison of Hantzsch and fiber-laser-induced-fluorescence formaldehyde measurements

2014 ◽  
Vol 7 (6) ◽  
pp. 1571-1580 ◽  
Author(s):  
J. Kaiser ◽  
X. Li ◽  
R. Tillmann ◽  
I. Acir ◽  
F. Holland ◽  
...  
Keyword(s):  
Fiber Laser ◽  
Gas Phase ◽  
Measurement Techniques ◽  
Laser Induced Fluorescence ◽  
Reaction Chamber ◽  
Mixing Ratios ◽  
Low Concentrations ◽  
Wet Chemical ◽  
Single Instrument ◽  
Instrument Sensitivity

Abstract. Two gas-phase formaldehyde (HCHO) measurement techniques, a modified commercial wet-chemical instrument based on Hantzsch fluorimetry and a custom-built instrument based on fiber laser-induced fluorescence (FILIF), were deployed at the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) to compare the instruments' performances under a range of conditions. Thermolysis of para-HCHO and ozonolysis of 1-butene were used as HCHO sources, allowing for calculations of theoretical HCHO mixing ratios. Calculated HCHO mixing ratios are compared to measurements, and the two measurements are also compared. Experiments were repeated under dry and humid conditions (RH < 2% and RH > 60%) to investigate the possibility of a water artifact in the FILIF measurements. The ozonolysis of 1-butene also allowed for the investigation of an ozone artifact seen in some Hantzsch measurements in previous intercomparisons. Results show that under all conditions the two techniques are well correlated (R2 ≥ 0.997), and linear regression statistics show measurements agree with within stated uncertainty (15% FILIF + 5% Hantzsch). No water or ozone artifacts are identified. While a slight curvature is observed in some Hantzsch vs. FILIF regressions, the potential for variable instrument sensitivity cannot be attributed to a single instrument at this time. Measurements at low concentrations highlight the need for a secondary method for testing the purity of air used in instrument zeroing and the need for further FILIF White cell outgassing experiments.

scholarly journals Measuring atmospheric naphthalene with laser-induced fluorescence

2004 ◽  
Vol 4 (2) ◽  
pp. 563-569 ◽  
Author(s):  
M. Martinez ◽  
H. Harder ◽  
X. Ren ◽  
R. L. Lesher ◽  
W. H. Brune
Keyword(s):  
New York ◽  
New York City ◽  
Gas Phase ◽  
Laser Induced Fluorescence ◽  
Integration Time ◽  
Mixing Ratio ◽  
Quenching Rate ◽  
Anthropogenic Pollutants ◽  
Mixing Ratios ◽  
Instrument Configuration

Abstract. A new method for measuring gas-phase naphthalene in the atmosphere is based on laser-induced fluorescence at low pressure. The fluorescence spectrum of naphthalene near 308 nm was identified. Naphthalene fluorescence quenching by N, O and HO was investigated in the laboratory. No significant quenching was found for HO with mixing ratio up to 2.5%. The quenching rate of naphthalene fluorescence is (1.980.18) 10cmmolecules for N, and (2.480.08)10cmmolecules for O at 297 K. Instrument calibrations were performed with a range of naphthalene mixing ratios between 5 and 80 parts per billion by volume (ppbv, 10. In the current instrument configuration, the detection limit is estimated to be about 20 parts per trillion by volume (pptv, 10 with 2 confidence and a 1-min integration time. Measurements of atmospheric naphthalene in three cities, Nashville, TN, Houston, TX, and New York City, NY, are presented. Good correlation between naphthalene and major anthropogenic pollutants is found.

scholarly journals Measuring atmospheric naphthalene with laser-induced fluorescence

2004 ◽  
Vol 4 (1) ◽  
pp. 343-363 ◽  
Author(s):  
M. Martinez ◽  
H. Harder ◽  
X. Ren ◽  
R. L. Lesher ◽  
W. H. Brune
Keyword(s):  
New York ◽  
New York City ◽  
Gas Phase ◽  
Laser Induced Fluorescence ◽  
Integration Time ◽  
Mixing Ratio ◽  
Quenching Rate ◽  
Anthropogenic Pollutants ◽  
Mixing Ratios ◽  
Instrument Configuration

Abstract. A new method for measuring gas-phase naphthalene in the atmosphere is based on laser-induced fluorescence at low pressure. The fluorescence spectrum of naphthalene near 308 nm was identified. Naphthalene fluorescence quenching by N2, O2 and H2O was investigated in the laboratory. No significant quenching was found for H2O with mixing ratio up to 2.5%. The quenching rate of naphthalene fluorescence is (1.98±0.18)×10−11 cm3 molecule−1 s−1 for N2, and (2.48±0.08)×10−10 cm3 molecule−1 s−1 for O2 at 297 K. Instrument calibrations were performed with a range of naphthalene mixing ratios between 5 and 80 parts per billion by volume (ppbv, 10−9. In the current instrument configuration, the detection limit is estimated to be about 20 parts per trillion by volume (pptv, 10−12) with 2σ confidence and a 1-min integration time. Measurement of atmospheric naphthalene in three cities, Nashville, TN, Houston, TX, and New York City, NY, are presented. Good correlation between naphthalene and major anthropogenic pollutants is found.

NOHSO4/HF – A Novel Etching System for Crystalline Silicon

2007 ◽  
Vol 62 (11) ◽  
pp. 1411-1421 ◽  
Author(s):  
Sebastian Patzig ◽  
Gerhard Roewer ◽  
Edwin Kroke ◽  
Ingo över
Keyword(s):  
Gas Phase ◽  
Chemical Etching ◽  
Silicon Surface ◽  
Crystalline Silicon ◽  
Etching Solution ◽  
Wide Range ◽  
Ft Ir ◽  
Wet Chemical ◽  
Wet Chemical Etching ◽  
Etching System

Solutions consisting of HF - NOHSO4 - H2SO4 exhibit a strong reactivity towards crystalline silicon which is controlled by the concentrations of the reactive species HF and NO+. Selective isotropic and anisotropic wet chemical etching with these solutions allows to generate a wide range of silicon surface morphology patterns. Traces of Ag+ ions stimulate the reactivity and lead to the formation of planarized (polished) silicon surfaces. Analyses of the silicon surface, the etching solution and the gas phase were performed with scanning electron microscopy (SEM), DR/FT-IR (diffusive reflection Fourier transform infra-red), FT-IR, Raman and NMR spectroscopy, respectively. It was found that the resulting silicon surface is hydrogen-terminated. The gas phase contains predominantly SiF4, NO and N2O. Furthermore, NH4+ is produced in solution. The study has confirmed the crucial role of nitrosyl ions for isotropic wet chemical etching processes. The novel etching system is proposed as an effective new way for selective surface texturing of multi- and monocrystalline silicon. A high etching bath service lifetime, besides a low contamination of the etching solution with reaction products, provides ecological and economical advantages for the semiconductor and solar industry.

scholarly journals Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006

2012 ◽  
Vol 12 (2) ◽  
pp. 5851-5880 ◽  
Author(s):  
B. H. Czader ◽  
B. Rappenglück ◽  
P. Percell ◽  
D. W. Byun ◽  
F. Ngan ◽  
...  
Keyword(s):  
Air Quality ◽  
Hydroxyl Radical ◽  
Gas Phase ◽  
Nitrous Acid ◽  
Organic Materials ◽  
Optical Absorption Spectroscopy ◽  
Ozone Formation ◽  
Mixing Ratios ◽  
Quality Study ◽  
Mist Chamber

Abstract. Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectroscopy) measurements at three different altitudes. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2*) hydrolysis, photo-induced formation from excited NO2* and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3) concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv), but significant increase in the hydroxyl radical (OH) and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

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