Reference Spectra
High-resolution reference spectra at atmospheric temperatures (203-293K) and pressures (100-1000 mbar), recorded using Fourier-Transform spectroscopy, in the UV-visible-NIR spectral regions (240-850 nm)
Motivation
- O3 and other atmospheric trace gases are currently monitored by spectroscopic techniques in the UV-visible spectral range.
- Very accurate laboratory reference spectra are needed for the data analysis.
- Fourier-Transform spectroscopy has the great advantages of covering a broad spectral range with very high wavelength accuracy and of a well-known instrumental line shape (the "sinc" function).
- Everybody who needs accurate O3 reference spectra can use the new spectra by convolution with the appropriate instrumental line shape (e.g. grating spectrometers).
Experiment
- instrument: Bruker IFS-120 HR Fourier-Transform spectrometer
- broadband white light sources: 75 W Xenon arc (Hamatsu Super-Quiet), 50 W QTH (Osram Xenophot)
- beamsplitter: UV-grade quartz (for all spectral regions)
- detectors: Si diode, GaP diode, UV (solar-blind) photodiode
- absorption cell: White coolable type multipass cell, pathlengths of 120 cm, 505 cm, and 985 cm
Results
- O3 absorption cross sections in the spectral range between 240-850 nm O3 sample temperatures: 203 K, 223 K, 246 K, 280 K, 293 K
- total sample pressures: 100 mbar and 1000 mbar (N2 as buffer gas)
- spectral resolution: 5.0 cm-1 (0.028 nm at 240 nm and 0.36 nm at 850 nm)
- spectral accuracy: ca. 0.01 cm-1 (0.00006 nm at 240 nm and 0.0007 nm at 850 nm)
- uncertainty of absorption cross sections: wavelength dependent, in many regions better than 5%