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:
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 input files contain the wavenumber in double precision
(8 byte) and 15 polynomial coefficients in single precision (4 byte).
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
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: