Updates for GEISA-2015 Thermal and Near-InfraRed
absorption cross-sections sub-database Update

A: GEISA-2015 THERMAL INFRARED (TIR) ABSORPTION CROSS-SECTIONS

Thirty-nine molecules were represented by cross sections in GEISA-2011. The GEISA-2015 compilation has been updated with additional cross-section datasets, consisting of multiple temperature-pressure combinations, for new and existing molecules. This represents more than about 50% increase in information volume, with the introduction of 41 new molecular species. This update stems mainly from two sources:

1. CROSS-SECTION SET FROM THE University of Oslo [1,2] AND THE UNIVERSITY OF CASTILLA-LA MANCHA [3,4,5].

These compounds (halocarbons, bromocarbons, bromofluorocarbons, bromochlorofluorocarbons, halogenated alcohols, halogenated, fluorinated ethers and perfluorinated compounds) contribute to the global warming;

Updated IR absorption cross-sections for CFC-12 and 31 fluorinated
compounds, included in a recent review of Hodnebrog et al. [1] were
added to GEISA-2015 and are listed in Table 1, which provides for each
compounds: its chemical formula, common name, spectral information,
i.e.: spectral range, gas bath, foreign broadening pressure (Pa), and
references. These compounds (halocarbons, bromocarbons,
bromofluorocarbons, bromochlorofluorocarbons, halogenated alcohols,
halogenated, fluorinated ethers and perfluorinated compounds)
contribute to the global warming.

References

[1] Ø. Hodnebrog, M. Etminan, J.S. Fuglestvedt, G. Marston, G. Myhre,
C.J. Nielsen, K.P. Shine, T.J. Wallington, Global warming potentials
and radiative efficiencies of halocarbons and related compounds: A
comprehensive review, Reviews of Geophysics. 51 (2013) 300-378.

[2] C.J. Nielsen, Private communication, 2014

[3] E. Jiménez, M. Antinolo, B. Ballesteros, E. Martinez, J.
Albaladejo, Atmospheric Lifetimes and Global Warming Potentials of CF₃CH₂CH₂OH and CF₃(CH ₂)₂CH₂OH, Phys. Chem. Chem. Phys. 11
(2010) 4079-4087.

[4] M. Antiñolo, S. González, B. Ballesteros, J. Albaladejo, E.
Jiménez, Laboratory Studies of CHF₂CF₂CH ₂OH and CF₃CF₂CH₂OH: UV and
IR Absorption Cross Sections and OH Rate Coefficients between 263 and
358 K, J. Phys. Chem. A. 116 (2012) 6041-6050.

[5] M. Antiñolo, Fluoroalcohols and Fluoroaldehydes in the Troposphere:
Kinetics and Photochemistry in the Gas Phase sutdied by Pulsed Laser
Techniques, PhD Thesis, University of Castilla-La Mancha. 2011.

[6] G. Myhre, F. Stordal, I. Gausemel, C.J. Nielsen, E. Mahieu,
Line-by-line calculations of thermal infrared radiation representative
for global condition: CFC-12 as an example, J. Quant. Spectrosc.
Radiat. Transfer 97 (2006) 317-331.

[7] G. Acerboni, J.A. Beukes, N.R. Jensen, J. Hjorth, G. Myhre, C.J.
Nielsen, J.K. Sundet, Atmospheric degradation and global warming
potentials of three perfluoroalkenes, Atmos. Environ. 35 (2001)
4113-4123.

[8] G. Myhre, C.J. Nielsen, D.L. Powell, F. Stordal, Infrared
absorption cross section, radiative forcing, and GWP of four
hydrofluoro(poly)ethers, Atmos. Environ. 93 (1999) 4447-4458.

[9] S.M. Ryan, C.J. Nielsen, Global Warming Potential of Inhaled
Anesthetics: Application to Clinical Use, Anesth. Analg. 111 (2010)
92-98.

[10] B. D’Anna, S.R. Sellevag, K. Wirtz, C.J. Nielsen, Photolysis study
of perfluoro-2-methyl-3-pentanone under natural sunlight conditions,
Environ. Sci. Technol. 39 (2005) 8708-8711.

[11] N. Oyaro, S.R. Sellevag, C.J. Nielsen, Study of the OH and
Cl-initiated oxidation, IR absorption cross-section, radiative forcing,
and global warming potential of four C-4-hydrofluoroethers, Environ.
Sci. Technol. 38 (2004) 5567-5576.

[12] N. Oyaro, S.R. Sellevag, C.J. Nielsen, Atmospheric chemistry of
hydrofluoroethers: Reaction of a series of hydrofluoro ethers with OH
radicals and Cl atoms, atmospheric lifetimes, and global warming
potentials, J. Phys. Chem. A. 109 (2005) 337-346.

[13] S.R. Sellevag, C.J. Nielsen, O.A. Sovde, G. Myhre, J.K. Sundet, F.
Stordal, I.S.A. Isaksen, Atmospheric gas-phase degradation and global
warming potentials of 2-fluoro ethanol, 2,2-difluoroethanol, and
2,2,2-trifluoroethanol, Atmos. Environ. 38 (2004) 6725-6735.

[14] S.R. Sellevåg, B. D’Anna, C.J. Nielsen, Infrared Absorption
Cross-Sections and Estimated Global Warming Potentials of CF₃CH₂CH₂OH, CHF₂CF₂CH₂OH, CF₃CF₂CH₂OH, CF₃CHFCF₂CH₂OH, and CF₃CF₂CF₂CH₂OH, Asian
Chemistry Letters. (2007) 33-40.

[15] S.R. Sellevåg, T. Kelly, H. Sidebottom, C.J. Nielsen, A study of the IR and UV-Vis absorption cross-sections, photolysis and OH-initiated oxidation of CF₃CHO and CF₃CH₂CHO, Phys. Chem. Chem. Phys. 6 (2004) 1243-1252.

Table 1: Summary of GEISA-2015 infrared absorption cross-sections update. Data from University of Oslo [1,2] and the University of Castilla-La Mancha [3,4,5] at room temperature and spectral resolution of 1 cm^-1.

^a Each reference corresponds to a single T/P dataset.

^b Experiments performed with diluted compound in He provide the same infrared absorption cross-sections.

B: GEISA-2015 NEAR INFRARED (NIR) ABSORPTION CROSS-SECTIONS

The 1-3 µm near-infrared spectral region is of great interest for atmospheric remote-sensing and planetary science.

The sections below present and document a first set of seven high-resolution absorption cross-sections as reference data in the near-infrared region, for molecules and bands where no theoretical prediction is available.

An overview of its contents is given in Table 3. The common names of the molecules and their formula are listed in the two first columns. The spectral regions covered (cm^-1), the spectral resolution (cm^-1), the maximal uncertainties of the spectral position (cm ^-1) and absorption cross-sections (%), are given in columns two to five, and references in the final column.

Table 3: Summary of the molecules whose experimental absorption cross-sections in the NIR are newly implemented provided in GEISA-2015 database.

 

Acetonitrile (CH₃CN)

Absorption cross-sections of Acetonitrile between 6814 and 7067 cm^-1 were measured, by O’Leary et al. [1 ], with off-axis CW-CEAS at 5 mbar with a resolution of about 0.001 cm^-1. There are about 4630 absorption lines in this spectrum. Absorption features of H₂O in this region have been removed from the spectrum. Approximately 200 individual overlapping spectral segments have been concatenated to cover the entire spectral range.

Reference

[1] D.M. O’Leary, A.A. Ruth, S. Dixneuf, J. Orphal, R. Varma, The near infrared cavity-enhanced absorption spectrum of methylcyanide, J. Quant. Spectrosc. Radiat. Transfer 113 (2012) 1138-1147.

Methyl iodide, also called iodomethane (CH₃I)

Measurements, by Farag¢ et al. [2], of methyl iodide were made using CW-CRDS in the wavenumber range 7473–7497 cm^-1 at a total pressure of 50 Torr and a resolution of 0.001 cm^-1. CH ₃I was prepared as a diluted mixture in helium, and its concentration was determined from calibrated flowmeters. The spectrum was measured in several small portions in order to minimize a shift in the baseline between measurement of the spectrum with and without CH ₃I. There are small gaps in the spectrum at wavelength ranges corresponding to absorption lines of water where data have been erased because water was present in the cell.

Reference

[2] E.P. Faragó, B. Viskolcz, C. Schoemaecker, C. Fittschen, Measurement of
the absorption spectrum and of absolute absorption cross-sections of CH ₃O₂ Radicals and CH₃I in the near IR
Region, J. Phys. Chem. A 117 (2013) 12802-12811.

Methyldioxidanyl (CH₃O₂)

Measurements, by Farag¢ et al. [2], of methyldioxidanyl were made using CW-CRDS coupled to laser photolysis. The wavenumber range 7474–7493 cm^-1 was scanned at a resolution of 0.025 cm^-1. CH₃O₂ was generated by pulsed photolysis of CH₃I in the presence of O₂. Absolute CH₃O ₂ concentrations have been deduced by measuring the time-resolved absorbance following the photolysis pulse and adjusting the
decay rate to the well-known rate constant of the self-reaction of CH₃O₂ radicals [2]. Calibration of CH₃O ₂ concentration was obtained by measuring the time-resolved
evolution of the CH₃O₂ concentration and fitting the
kinetic decay traces of CH₃O₂ to a bimolecular
reaction. Using the well-known rate constant of the self-reaction allows
retrieval of the initial CH₃O₂ concentrations. A
generally broad absorption spectrum was obtained containing three striking
absorption features located at 7748.18, 7489.16 and 7493.33 cm^-1
. For these three characteristic lines absolute absorption cross-sections
of 3.41×10^-20, 3.40×10^-20 and 2.11×10^-20
cm² were established, respectively. The remainder of the broad
spectrum was scaled according to these cross-sections. Within the error
limit of the measurement the cross-sections were not affected by changes of
the pressure between 50 and 100 Torr. The error is estimated to be 30%,
mostly due to uncertainty in the rate constant for the self-reaction.

Reference

[2] E.P. Faragó, B. Viskolcz, C. Schoemaecker, C. Fittschen, Measurement of
the absorption spectrum and of absolute absorption cross-sections of CH ₃O₂ Radicals and CH₃I in the near IR
Region, J. Phys. Chem. A 117 (2013) 12802-12811.

Formaldehyde (H₂CO)

Absorption cross-sections for formaldehyde were measured, by Staak et al.
[3], with CW-CEAS at 2 mbar in the range 6547–7051 cm^-1 with a
resolution of about 0.001 cm^-1. The absorption cross-sections
were evaluated by comparison with the known measured line-intensities of CO ₂ and H₂O. H₂CO was prepared by pyrolysis
of paraformaldehyde under vacuum. The gaseous H₂CO was first
passed through a cooling trap below 200 K to remove water vapor and
polymerization products of H₂CO. The monomeric H₂CO
was trapped and stored at 77 K under vacuum. H₂CO gas was
introduced into the cavity by slowly heating the solid H₂CO from
the cooling trap; the temperature of the system was 291 ± 2 K. It was found
that the absorption cross-sections from Staak et al. [3]
were systematically a factor of 2 too large. A summary is given in Ruth et
al. [4] together with new absorption data on H₂CO between 6804
and 7051 cm^-1. GEISA-2015 contains the data from Ruth et al. [4]
and those of Staak et al. [3] corrected by a factor of 2 in the spectral
range 6547–7051 cm^-1.

References

[3] M. Staak, E.W. Gash, D.S. Venables, A.A. Ruth, The
rotationally-resolved absorption spectrum of formaldehyde from 6547 to 6804
cm^-1, J. Molec. Spectrosc. 229 (2005) 115-121.

[4] A.A. Ruth, U. Heitmann, E. Heinecke, C. Fittschen, The
rotationally-resolved absorption spectrum of formaldehyde from 6550 to 7050
cm^–1, Z. Phys. Chem. 229 (2015) 1609-1624.

 

Hydroperoxy radical (HO₂)

Measurements of the HO₂ radical were made by
Thiebaud et al. [5] and Ibrahim et al. [6] at a total pressure of 50 Torr.
HO₂ radicals were generated by reaction of Cl-atoms with CH ₃OH in the presence of O₂. Cl-atoms were generated either by photolysis of SOCl₂ at 248 nm or by photolysis of Cl₂ at 351 nm. The spectrum was measured in the 6604-6696 cm^-1 wavenumber range with a resolution of better than 0.003 cm ^-1. A few selected lines were calibrated by determining the absolute, initial HO₂ concentration in the same way as CH₃O ₂: time resolved HO₂ absorption decays were measured following their pulsed photolysis. As the decay is governed by a bimolecular reaction, the initial HO₂ radical concentration can be deduced from the shape of the decay. More details on the pressure broadening in HO₂ can be found in [7].

References

[5] J. Thiebaud, S. Crunaire, C. Fittschen, Measurements of line strengths
in the 2n₁ band of the HO₂ radical using laser
photolysis/continuous wave cavity ring-down spectroscopy (cw-CRDS), J.
Phys. Chem. A 111 (2007) 6959-6966.

[6] N. Ibrahim, J. Thiebaud, J. Orphal, C. Fittschen, Air-broadening
coefficients of the HO₂ radical in the 2n₁ band
measured using cw-CRDS, J. Mol. Spectrosc. 242 (2007) 64-69.

[7] H. Bouzidi, M. Djehiche, T. Gierczak, P. Morajkar, C.
Fittschen, P. Coddeville, A. Tomas, Low pressure photolysis of
2,3-pentanedione: quantum yields and reaction mechanism, J. Phys. Chem. A
119 (2015) 12781-12789.

Nitrous Acid (HONO)

Measurements of nitrous acid were made, by Jain et al. [8], in the
range 6623.6–6645.6 cm^-1 with a resolution of 0.005 cm ^-1, using CW-CRDS coupled to laser photolysis. HONO was
generated in situ by photolysis of H₂O₂ in
the presence of NO. Calibration of the HONO concentration (and hence the cross-sections) was achieved through modelling the kinetics of the time resolved concentrations of the OH and HO₂ radicals, which are generated in the H₂O₂ photolysis.

Reference

[8] C. Jain, P. Morajkar, C. Schoemaecker, B. Viskolcz, C. Fittschen,
Measurement of absolute absorption cross-sections for nitrous acid (HONO)
in the near-infrared region by the continuous wave cavity ring-down
spectroscopy (cw-CRDS) technique coupled to laser photolysis, J. Phys.
Chem. A 115 (2011) 10720-10728.

 

Ammonia (NH₃)

Absorption cross-sections, as a function of wavelength for NH₃ were measured by O’Leary et al. [9], with off-axis CW-CEAS at 0.2 mbar (6883–6997 cm^-1) and at 11.5 mbar (6850–6997 cm^-1). A total of 1117 NH₃ lines are contained in the spectrum.

It should be noted that 262 lines of the NH₃ line-by-line sub-database are present in this cross-sections spectral region. Among these lines, only 49 have been assigned. We retain the unassigned lines, which are useful for many purposes, and we have implemented the cross-sections, in addition, to provide the total absorption in that region.

Reference

[9] D.M. O’Leary, J. Orphal, A.A. Ruth, U. Heitmann, P. Chelin, C.E.
Fellows, The cavity-enhanced absorption spectrum of NH₃ in the
near-infrared region between 6850 and 7000 cm^-1, J. Quant. Spectrosc. Radiat. Transfer 109 (2008) 1004-1015.