*SHP Section

RFM Driver Table Sections: Spectral Lineshapes

18MAR25
Type
Secondary Section, requires SHP Flag.

Description
User-selected (ie non-Voigt) spectral line shapes.

Format
Multiple records, any order
Record Structure
SHP GAS(1) GAS(2) ...
Fields
FieldTypeDescription
SHP C3 Lineshape to be used, any of: [1]
'VOI' Voigt Lineshape[3]
'LOR' Lorentz Lineshape
'DOP' Doppler Lineshape
'VAN' or Van Vleck Weisskopf Lineshape[4]
'VVW'
'CHI' Voigt plus Chi-factor[5]
GAS(:) C7 Molecule(s) to which lineshape is applied, or '*'[2]
Type: Cn=character string, length n.

Notes
  1. Only the first 3 characters of SHP are tested so, for example, LORENTZ can be used for LOR.

  2. An asterisk (*) may be substituted for GAS once in this section, in which case it is taken to represent all required gases not explicitly allocated other shapes.

  3. In the absence of an asterisk, any absorbers not explicitly assigned a shape will use the Voigt lineshape (subject to CHI modifications for CO2)

  4. The VVW lineshape specified here is an explicit calculation of the Van Vleck Weisskopf lineshape, i.e., the Lorentz lineshape with low-wavenumber correction terms (recommended for calculations in microwave region).
    • Alternatively, the VVW Flag can be used for applying the same correction to all lineshapes, i.e. VVW lineshape specified in this section is equivalent to LOR lineshape + VVW Flag.
    • If both the VVW Flag and VVW lineshape are specified, a warning is generated but the VVW correction is ignored for lines already generated with the VVW lineshape.

  5. Currently the CHI shape can only be used with CO2 (representing the sub-Lorentzian wings of CO2) — see CHI flag for a shorter way of invoking this. The RFM uses the model of Cousin et al (1985).

Example
(Unrealistically complicated, just for illustrative purposes)
*SHP Chi-factor CO2 ! Use CO2 sub-Lorentzian wings LORENTZ H2O CH4 ! Use Lorentz shape for H2O and CH4 LORENTZ N2O ! Also N2O VOI * ! Voigt shape for other gases [default anyway] DOPP CO ! Doppler shape for CO

Bugs
[none reported]