 |
| Titel |
Effects of column density on I2 spectroscopy and a determination of I2 absorption cross section at 500 nm |
| VerfasserIn |
P. Spietz, J. Gómez Martín, J. P. Burrows |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 8 ; Nr. 6, no. 8 (2006-06-20), S.2177-2191 |
| Datensatznummer |
250003926
|
| Publikation (Nr.) |
 copernicus.org/acp-6-2177-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| 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. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|