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%
     
Institute of Environmental Physics (IUP)
Institute of Remote Sensing (IFE)
University of Bremen, Otto-Hahn-Allee 1
28359 Bremen Germany