RFM File Formats

.cia File: Collision-Induced Absorption Data

06JUL17

Type
Input(s), mandatory if CIA Flag enabled.

Description
Collision-Induced Absorption cross-sections [cm5/molec2] for pairs of molecules, tabulated for particular wavenumber ranges at different temperatures.

Filename(s)
Specified in *CIA section of the Driver Table.

Structure
Note that this is the HITRAN file format, although the initial comment records are an RFM extension.
!CMNT [optional comment record(s)]
MOLEC WNOLOW WNOUPP NPT TEM CIAMAX RESLN COMMENTS REF [C*100 Header]
WNO(i) CIA(i) [Repeat for i=1:NPT]
The structure is then repeated for different temperatures within the same wavenumber range, and then for different wavenumber ranges.

Fields
FieldTypeDescriptionRange
!CMNT A80 Comment record(s) (optional) Record starts with '!'
MOLEC A20 Chemical Formula, right justified eg 'N2-O2'
WNOLOW F10.3 Lower Wavenumber [cm-1] for tabulation >0
WNOUPP F10.3 Upper Wavenumber [cm-1] for tabulation >0
NPT I7 No. of Wavenumber points >0
TEM F7.1 Temperature [K] of tabulation >0
CIAMAX E10.3 Max value of CIA [cm5/molec2]
RES F6.3 Resolution [cm-1] >0 or '-.999'
COMMENT A27 Comment
REF I3 Reference index
WNO R*4 Wavenumber axis [cm-1] WNOLOW:WNOUPP
CIA R*4 CIA value [cm5/molec2] ≤ CIAMAX

Notes
  1. The HITRAN data are arranged in separate files for each molecule pair, divided into spectral ranges in ascending order, each divided into temperature tabulations in increasing order. However, as far as the RFM is concerned, the data are just a series of tabulations in arbitrary order.
  2. !CMNT The RFM format allows for (optional) initial comment records at the start of the file
  3. The RFM only reads the following fields from the Header records: MOLEC, WNOLOW, WNOUPP, NPT, TEM
  4. On input, the RFM will extract the subset of the tabulated spectral ranges which overlaps the min/max wavenumbers required for the RFM calculations (as specified in the *SPC section). A message appears in the rfm.runlog file specifying the range used, as well as the number of temperature tabulations, eg:
    I-CIAFIL: 2199.9000 - 2300.0600 cm-1 read 9 Temps from 228.2 - 362.5 K
  5. CIA values are of the order of 1E-45, which is smaller than can be stored as a FORTRAN REAL variable. Therefore, internally, the RFM multiplies these values by (Avogadro's number ~ 6E26)2, converting units from cm5/molec2 to cm5/kmol2.
  6. CIA values are also often negative (representing noise on the measurement). These values are set to zero on input.

Example
Extract from HITRAN file O2-O2_2011.cia
O2-O2 1150.000 1950.000 4002 193.4 8.767E-45 0.500 P up to 4atm 2 1150.0000 -6.497E-48 1150.2000 -5.749E-48 1150.4000 -7.841E-48 1150.6000 -1.043E-47 ...