There are 25 ascii files containing measured absorption cross sections without wavenumbers. In order to get the wavenumber axis, use:


These wavenumbers correspond to the uncalibrated spectrum. The calibration factor is 1.0000021512. All files have the same number of data points. The absorption cross sections were calculated according to:

To convert to cm2/molecule multiply by 5.5448e-21. This contains the conversion from pressure to particle density and the absorption path in the experiment.

The file MESSPAR.DAT contains information linked to the files:

Air pressure (mbar)
Spectral noise level
File name
Air pressure (mbar)
Spectral noise level
File name
00.00 189.58 0.433 190_000.xy
154.2 218.93 0.924 219_150.xy
12.74 189.70 0.717 190_012.xy
00.00 248.27 1.607 249_000.xy
24.57 189.58 0.542 190_025.xy
12.72 248.41 1.295 249_012.xy
44.96 189.58 0.382 190_050.xy
25.59 249.23 1.590 249_025.xy
94.59 189.58 0.573 190_100.xy
53.53 249.24 0.346 249_050.xy
155.8 189.70 0.480 190_150.xy
98.30 249.24 0.425 249_100.xy
00.00 219.00 0.761 219_000.xy
147.8 249.25 0.516 249_150.xy
05.225 218.95 0.752 219_005.xy
00.00 297.2 0.497 297_000.xy
12.83 218.95 1.060 219_012.xy
23.91 297.13 0.305 297_025.xy
26.10 218.94 0.940 219_025.xy
44.76 297.44 0.331 297_050.xy
53.40 218.95 1.504 219_050.xy
95.08 297.39 0.198 297_100.xy
95.42 219.24 0.285 219_100.xy

Only 23 files of the inital 25 measurements are used for polynomial expansion and are listed in the table above. 2 files had redundant information and were used for quality assurance.

We have fitted polynomial coefficients in ln(P+5) (order 4) and T (order 2). Using ln(P+5) instead of P gave a better uniform grid with respect to the strong changes at low air pressures which could be better represented with polynomials with low order. The Borland Pascal program abspolyfit.ppp was used to obtain the polynomial coefficients.

Background for calculation of absorption cross sections from polynomial coefficients:

Experimental absorption cross sections for various air pressures and temperatures were fitted by a polynomial matrix with first index pressure (order 4) and second index temperature (order 2). The names of the files are:
The range is ca. 700 - 1330 cm-1

The input files contain the wavenumber in double precision (8 byte) and 15 polynomial coefficients in single precision (4 byte).
( nu,p(P0,T0),p(P0,T1),...,p(P4,T2) )
where P0...P4 refer to ln(Pressure+5). (See above for the reasons) The data are currently binary for LINUX on IBM compatible PC (IEEE format). If you have problems with this format, please contact, or Note: The bytes by may be differently ordered for other than IBM compatible PCs.

The wavenumber grid is determined by the highest resolution experimental spectrum.

Supplied is also a Borland Pascal program calculating desired absorption cross sections for a given air pressure and temperature and spectral range: POL2ABS_CLONO2.PP

Furthermore, an ASCII input file named MODEL.INP is given.

689.999393 //start wavenumber 1330.000272 //end wavenumber
13.86 //air pressure in mbar
204.42 //temperature in K
204_012.model //output filename

This file is read by the Pascal program and gives the parameters for the desired absorption cross sections which are outputted in ASCII with calibrated wavenumber and absorption cross section in cm2/molecule in each line of the output file. Note that the frequency calibration is also carried out in this program.

Receipe for your own software:
1. Select wavenumber range, air pressure (in mbar) and temperature (in K) and calculate ln(pressure+5)
2. Read in frequency and the polynomial coefficients in the correct order (check "polkeofftype" in our code).
3. Calculate absorption cross sections according to our procedure "model".
4. Do frequency calibration. Calibration factor is given in our code and named "calfact".
5. Enjoy!

the files listed in the table above (*.xy) + 204_012.xy+190_075.xy