The GEISA-2015 sub-database of absorption cross-sections

Besides the line transition parameters data catalog itself, GEISA includes, a second catalog, providing, at various temperatures and pressures, the cross-sections of molecules for which spectral line parameters are incomplete or unavailable; generally these are ‘large’ molecules for which the generation of line parameters is very difficult.

As in the previous editions of GEISA, the absorption cross-sections σ (ω), expressed in cm² molecule^-1 , at a given wavenumber ω, are determined through the following expression:

σ (ω)= ( ln [ I0(ω) / I(ω) ] ) / n*l   and where :

ln is the natural logarithm ω is the wavenumber (cm-1) I0(ω) and I(ω) are the intensities at wavenumber ω , of the incident and transmitted radiation, respectively n is the number of absorbing molecules (molecule cm-3) l is the optical path length (cm)

Starting from the previous GEISA 2011 archive as described in Jacquinet-Husson et al. (2008, 2011), the 2015 version has been enriched by several molecular species in a larger spectral range Cross-sections are available in two spectral regions: the infrared and the ultraviolet/visible.

It should be noticed that pressure and temperature ranges depend on the molecular species and on the data sources.

 

• In the Infrared :

Unchanged:
In the spectral range 200 – 6500 cm^-1, 39 molecular species already archived, in GEISA-2011, were kept, i.e.: CFC-13, CFC-113, CFC-114, CFC-115, CFC11, CFC12, CFC14, HCFC22, HCFC123, HCFC124, HFC125, HFC134a, HCFC141b, HCFC142b, HFC152a, HCFC225ca, HCFC225cb, HFC32, HFC143a, HFC134, N₂O₅, SF₆, ClONO₂; HFC-143, HCFC-21, CCl₄, C₂F₆, C₂H₂, C₂H₄, C₂H₆, C₃H₈, C₄H₈, HNO₄, SF₅CF₃, HCH-365mfc, C₆H₆, CH₃CN, C₂H₃NO₅, (CH₃)₂CO.

Updated:
Five molecular species, already present in GEISA-2011, were updated, i.e.: in the TIR (Thermal InfraRed): CFC-12, C₂ H₆ , C₃ H₈ (Propane), (CH₃)₂CO (Acetone); in the TIR and in the NIR (Near InfraRed), CH₃CN (Acetonitrile).

New :
In the spectral range 25 – 7497 cm^-1, 41 new molecular species were included in GEISA-2015:
– In the spectral interval 25 – 4800 cm^-1, 35 molecular species, i.e.: CF₂=CF₂ (PFC-1114), CF₃CF=CF₂ (PFC-1216), CF₂=CFCF=CF₂, CHF₂OCF₂CF₂OCHF₂ (HFE-338pcc13), HF₂OCF₂OCHF₂ (HFE-236ca12), (CF₃)₂CHOCH₂F (Sevoflurane), CHF₂OCHClCF₃ (Isoflurane), (CF₃)₂CFC(O)CF₂CF₃ (Perfluoro(2-methyl-3-pentanone), CHF₂CF₂CH₂OCH₃, CF₃CF₂CH₂OCH₃, CF₃CH₂OCH₂CF₃, (CF₃)₂CHOCH₃, CHF₂CHFOCF₃, CF₃CHFOCF₃, CHF₂OCHFCF₃, CF₃CHFCF₂OCH₂CH₃, CF₃CF₂CF₂OCHFCF₃, CHF₂OCH₂CF₃, CF₃CH₂OCH₃, CF₃CFHCF₂OCF₂H, CH₂FCH₂OH, CHF₂CH₂OH, CF₃CH₂OH, CF₃CF₂CH₂OH, CHF₂CF₂CH₂OH, CF₃CF₂CF₂CH₂OH, CF₃CHFCF₂CH₂OH, CF₃CH₂CH₂OH, CF₃(CH₂)₂CH₂OH, CF₃CHO, CF₃CH₂CHO, CF₃(CH₂)₂CHO, CH₃OH (Methanol), CHF₃ (HFC-23), CH₃CHO (Acetaldehyde)

– In the near infrared (NIR), spectral interval 6600 – 7497 cm^-1, 6 molecular species, i.e.: CH₃I (Methyl iodide), CH₃O₂ (Methyldioxidanyl), H₂CO (Formaldehyde), HO₂ (Hydroperoxy radical), HONO (Nitrous acid), NH₃ (Ammonia).

 

• In the Ultraviolet/Visible :

No update occurred in this spectral region. The GEISA 2011 database content has been kept, in the spectral range 7750 cm^-1 to 51282 cm^-1, for the following molecules and radicals: NO₂, CS₂, O₃, SO₂, O₂, O₂-O₂, O₂-N₂, OClO, H₂CO, OBrO, BrO, IO, OIO, and aromatic hydrocarbons; these are C₆H₆, C₇H₈ and the three isomers of (C₆H₄(CH₃)₂, as well.