Absorption Cross Section Simulation: a Preliminary Study of Ultraviolet Absorption Spectroscopy for Ozone Gas Measurement

2013 ◽  
Vol 64 (3) ◽  
Author(s):  
Tay Ching En Marcus ◽  
Michael David ◽  
Maslina Yaacob ◽  
Mohd Rashidi Salim ◽  
Mohd Haniff Ibrahim ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Spectroscopy ◽  
Absorption Cross Section ◽  
Ultraviolet Absorption ◽  
Ultraviolet Region ◽  
Slight Variation ◽  
Absorption Cross ◽  
Peak Absorption ◽  
Ultraviolet Absorption Spectroscopy ◽  
Preliminary Study

Preliminary study to measure gaseous ozone concentration using ultraviolet absorption spectroscopy is presented. Firstly, background of ozone is introduced. Next, fundamental theory behind ultraviolet absorption spectroscopy is discussed based on Beer-Lambert’s Law and absorption spectrum of ozone. After that, absorption cross section of ozone is simulated via spectralcalc.com. Temperature of system is varied. Peak absorption cross section and peak absorption wavelength are found to be 1.166 ´ 10-21 m2 molecule-1 and 255.376 nm respectively at 300 K and 0 torr. Absorption cross section in ultraviolet region shows slight variation of at most 1.286 per cent when temperature is changed from 200 K to 300 K. Around room temperature, peak absorption cross section simulated in current work is consistent with previous work, because relative error is found to be small in between 1.630 per cent and 3.087 per cent. Unlike previous work, absorption of light by ozone is detected in ultraviolet region only due to weak absorption in visible region.

Vacuum ultraviolet absorption cross-section measurements in lead vapour

1969 ◽  
Vol 310 (1500) ◽  
pp. 35-42 ◽  
Keyword(s):  
Cross Section ◽  
Line Profile ◽  
Absorption Cross Section ◽  
Vacuum Ultraviolet ◽  
Ultraviolet Absorption ◽  
Experimental Curve ◽  
Ionization Threshold ◽  
Absorption Cross ◽  
A Value ◽  
Section Curve

The absorption cross-section curve for lead vapour has been determined from 1671 to 1470 Å. Three autoionization features corresponding to the transitions 6 s 2 6 p 2 3 P 0 → 6 s 2 6 p 6 d 3 P 1 0 , 1 P 1 Ɵ and 6 s 2 6 P 8 s 1 P 1 0 were investigated and their line profile parameters determined. The value of the cross-section at the series limit (1671 Å) was found to be 10 ±1 Mb and falls to zero within each of the autoionizing features. The unperturbed photoionization continuum, in the absence of autoionization, was inferred from the experimental curve and the autoionization parameters. It was found to decrease steadily from about 15 Mb at the ionization parameters. It was found to decrease steadily from about 15 Mb at the ionization threshold to a value of less than 5 x 10 -2 Mb at 1470 Å. It is suggested that this low value of the photoionization continuum can account for the missing 6 p 9 s autoionization feature which should otherwise appear at 1470 Å.

scholarly journals Effects of column density on I<sub>2</sub> spectroscopy and a determination of I<sub>2</sub> absorption cross section at 500 nm

2005 ◽  
Vol 5 (4) ◽  
pp. 5183-5221 ◽  
Author(s):  
P. Spietz ◽  
J. C. Gómez Martín ◽  
J. P. Burrows
Keyword(s):  
Optical Absorption ◽  
Cross Section ◽  
Absorption Spectroscopy ◽  
Absorption Cross Section ◽  
Column Density ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Reference Spectrum ◽  
Absorption Cross ◽  
Atmospheric Column

Abstract. The use of ro-vibronic spectra of I2 in the region of 543 nm to 578 nm as reference spectra for atmospheric Differential Optical Absorption Spectroscopy is studied. In this study it is shown that the retrieval of atmospheric column densities with Differential Optical Absorption Spectroscopy set-ups at FWHM at and above 1nm depends critically on the column density, under which the used reference spectrum was recorded. Systematic overestimation of the comparatively low atmospheric column density of I2 of the order of 13% is possible. Under low pressure conditions relevant in laboratory studies, the systematic deviations may grow up to 45%. To avoid such effects with respect to field measurements, new reference spectra of I2 were determined under column density of the order of 1016 molec/cm2 close to that expected for the atmospheric measurement. Thereby the described systematic deviations are avoided. Two typical configurations of Differential Optical Absorption Spectroscopy, which use grating spectrometers, were chosen for the spectroscopic set-up. One spectrum was recorded at similar resolution (0.25 nm FWHM) but finer binning (0.035 nm/pixel) than previously published data. For the other (0.59 nm FWHM, 0.154 nm/pixel) no previously published spectra exist. Wavelength calibration is accurate to ±0.04 nm and ±0.11 nm respectively. The absorption cross section for the recordings was determined under low column density with an accuracy of ±4% and ±3% respectively. The absolute absorption cross section of I2 at 500 nm (in standard air) in the continuum absorption region was determined using a method independent of iodine vapour pressure. Obtained was σI2(500 nm)=(2.186±0.021)·10−18 cm2·molec−1 in very good agreement with previously published results, but at 50% smaller uncertainty. From this and previously published results a weighted average of σI2(500 nm)=(2.191±0.02) ·10−18 cm2·molec−1 is determined.

scholarly journals Instrument intercomparison of glyoxal, methyl glyoxal and NO<sub>2</sub> under simulated atmospheric conditions

2015 ◽  
Vol 8 (4) ◽  
pp. 1835-1862 ◽  
Author(s):  
R. Thalman ◽  
M. T. Baeza-Romero ◽  
S. M. Ball ◽  
E. Borrás ◽  
M. J. S. Daniels ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Spectroscopy ◽  
Absorption Cross Section ◽  
Detection Limits ◽  
Ambient Air ◽  
Systematic Bias ◽  
Absorption Cross ◽  
Methyl Glyoxal ◽  
Ambient Concentrations ◽  
Uv Visible

Abstract. The α-dicarbonyl compounds glyoxal (CHOCHO) and methyl glyoxal (CH3C(O)CHO) are produced in the atmosphere by the oxidation of hydrocarbons and emitted directly from pyrogenic sources. Measurements of ambient concentrations inform about the rate of hydrocarbon oxidation, oxidative capacity, and secondary organic aerosol (SOA) formation. We present results from a comprehensive instrument comparison effort at two simulation chamber facilities in the US and Europe that included nine instruments, and seven different measurement techniques: broadband cavity enhanced absorption spectroscopy (BBCEAS), cavity-enhanced differential optical absorption spectroscopy (CE-DOAS), white-cell DOAS, Fourier transform infrared spectroscopy (FTIR, two separate instruments), laser-induced phosphorescence (LIP), solid-phase micro extraction (SPME), and proton transfer reaction mass spectrometry (PTR-ToF-MS, two separate instruments; for methyl glyoxal only because no significant response was observed for glyoxal). Experiments at the National Center for Atmospheric Research (NCAR) compare three independent sources of calibration as a function of temperature (293–330 K). Calibrations from absorption cross-section spectra at UV-visible and IR wavelengths are found to agree within 2% for glyoxal, and 4% for methyl glyoxal at all temperatures; further calibrations based on ion–molecule rate constant calculations agreed within 5% for methyl glyoxal at all temperatures. At the European Photoreactor (EUPHORE) all measurements are calibrated from the same UV-visible spectra (either directly or indirectly), thus minimizing potential systematic bias. We find excellent linearity under idealized conditions (pure glyoxal or methyl glyoxal, R2 > 0.96), and in complex gas mixtures characteristic of dry photochemical smog systems (o-xylene/NOx and isoprene/NOx, R2 > 0.95; R2 ∼ 0.65 for offline SPME measurements of methyl glyoxal). The correlations are more variable in humid ambient air mixtures (RH > 45%) for methyl glyoxal (0.58 < R2 < 0.68) than for glyoxal (0.79 < R2 < 0.99). The intercepts of correlations were insignificant for the most part (below the instruments' experimentally determined detection limits); slopes further varied by less than 5% for instruments that could also simultaneously measure NO2. For glyoxal and methyl glyoxal the slopes varied by less than 12 and 17% (both 3-σ) between direct absorption techniques (i.e., calibration from knowledge of the absorption cross section). We find a larger variability among in situ techniques that employ external calibration sources (75–90%, 3-σ), and/or techniques that employ offline analysis. Our intercomparison reveals existing differences in reports about precision and detection limits in the literature, and enables comparison on a common basis by observing a common air mass. Finally, we evaluate the influence of interfering species (e.g., NO2, O3 and H2O) of relevance in field and laboratory applications. Techniques now exist to conduct fast and accurate measurements of glyoxal at ambient concentrations, and methyl glyoxal under simulated conditions. However, techniques to measure methyl glyoxal at ambient concentrations remain a challenge, and would be desirable.

Nonadiabatic calculations of ultraviolet absorption cross section of sulfur monoxide: Isotopic effects on the photodissociation reaction

2014 ◽  
Vol 140 (4) ◽  
pp. 044319 ◽  
Author(s):  
Sebastian O. Danielache ◽  
Suzuki Tomoya ◽  
Alexey Kondorsky ◽  
Ikuo Tokue ◽  
Shinkoh Nanbu
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Ultraviolet Absorption ◽  
Absorption Cross ◽  
Sulfur Monoxide ◽  
Isotopic Effects

scholarly journals Effects of column density on I<sub>2</sub> spectroscopy and a determination of I<sub>2</sub> absorption cross section at 500 nm

2006 ◽  
Vol 6 (8) ◽  
pp. 2177-2191 ◽  
Author(s):  
P. Spietz ◽  
J. Gómez Martín ◽  
J. P. Burrows
Keyword(s):  
Optical Absorption ◽  
Cross Section ◽  
Absorption Spectroscopy ◽  
Absorption Cross Section ◽  
Column Density ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Reference Spectrum ◽  
Absorption Cross ◽  
Atmospheric Column

Abstract. The use of ro-vibronic spectra of I2 in the region of 543 nm to 578 nm as reference spectra for atmospheric Differential Optical Absorption Spectroscopy is studied. It is shown that the retrieval of atmospheric column densities with Differential Optical Absorption Spectroscopy set-ups at FWHM at and above 1 nm depends critically on the column density, under which the used reference spectrum was recorded. Systematic overestimation of the comparatively low atmospheric column density of I2 of the order of 13% is possible. Under low pressure conditions relevant in laboratory studies, the systematic deviations may grow up to 45%. To avoid such effects with respect to field measurements, new reference spectra of I2 were determined under column density of the order of 1016 cm-2 close to that expected for an atmospheric measurement. Two typical configurations of Differential Optical Absorption Spectroscopy, which use grating spectrometers, were chosen for the spectroscopic set-up. One spectrum was recorded at similar resolution (0.25 nm FWHM) but finer binning (0.035 nm/pixel) than previously published data. For the other (0.59 nm FWHM, 0.154 nm/pixel) no previously published spectra exist. Wavelength calibration is accurate to ±0.04 nm and ±0.11 nm respectively. The absorption cross section for the recordings was determined under low column density with an accuracy of ±4% and ±3% respectively. The absolute absorption cross section of I2 at 500 nm (wavelength: in standard air) in the continuum absorption region was determined using a method independent of iodine vapour pressure. Obtained was σI2 (500 nm)=(2.186±0.021·10-18 cm2 in very good agreement with previously published results, but at 50% smaller uncertainty. From this and previously published results a weighted average of σI2(500 nm)=(2.191±0.02)·10-18 cm2 is determined.

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