TY - JOUR
T1 - Line shape parameters for the H2O–H2 collision system for application to exoplanet and planetary atmospheres
AU - Renaud, Candice L.
AU - Cleghorn, Kara
AU - Hartmann, Léna
AU - Vispoel, Bastien
AU - Gamache, Robert
N1 - Funding Information:
The authors are pleased to acknowledge support of this research by the National Science Foundation through grant no. AGS-1622676 . Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
Publisher Copyright:
© 2017 Elsevier Inc.
PY - 2018/5/15
Y1 - 2018/5/15
N2 - Water can be detected throughout the universe: in comets, asteroids, dwarf planets, the inner and outer planets in our solar system, cool stars, brown dwarfs, and on many exoplanets. Here the focus is on locations rich in hydrogen gas. To properly study these environments, there is a need for the line shape parameters for H
2O transitions in collision with hydrogen. This work presents calculations of the half-width and line shift, made using the Modified Complex Robert–Bonamy (MCRB) formalism, at a number of temperatures. It is shown that this collision system is strongly off-resonance. For such conditions, the atom–atom part of the intermolecular potential dominates the interaction of the radiating and perturbing molecules. The atom–atom parameters were adjusted by fitting the H
2O–H
2 measurements of Brown and Plymate (1996). Several techniques were used to extract lines for which there is more confidence in the quality of the data. The final potential yields results that agree with the measurements with ∼0.3% difference and a 5.9% standard deviation. Using this potential, MCRB calculations were made for all transitions in the pure rotation, ν
2, ν
1, and ν
3 bands. The structure of the line shape parameters and the temperature dependence of the half-width, as a function of the rotational and vibrational quantum numbers, are discussed. It is shown that the power law model of the T-dependence of the half-width is inadequate over large temperature ranges.
AB - Water can be detected throughout the universe: in comets, asteroids, dwarf planets, the inner and outer planets in our solar system, cool stars, brown dwarfs, and on many exoplanets. Here the focus is on locations rich in hydrogen gas. To properly study these environments, there is a need for the line shape parameters for H
2O transitions in collision with hydrogen. This work presents calculations of the half-width and line shift, made using the Modified Complex Robert–Bonamy (MCRB) formalism, at a number of temperatures. It is shown that this collision system is strongly off-resonance. For such conditions, the atom–atom part of the intermolecular potential dominates the interaction of the radiating and perturbing molecules. The atom–atom parameters were adjusted by fitting the H
2O–H
2 measurements of Brown and Plymate (1996). Several techniques were used to extract lines for which there is more confidence in the quality of the data. The final potential yields results that agree with the measurements with ∼0.3% difference and a 5.9% standard deviation. Using this potential, MCRB calculations were made for all transitions in the pure rotation, ν
2, ν
1, and ν
3 bands. The structure of the line shape parameters and the temperature dependence of the half-width, as a function of the rotational and vibrational quantum numbers, are discussed. It is shown that the power law model of the T-dependence of the half-width is inadequate over large temperature ranges.
KW - H O–H
KW - Half-widths
KW - Line shifts
KW - Temperature dependence of half-widths
UR - http://www.scopus.com/inward/record.url?scp=85033455315&partnerID=8YFLogxK
U2 - 10.1016/j.icarus.2017.10.016
DO - 10.1016/j.icarus.2017.10.016
M3 - Article
SN - 0019-1035
VL - 306
SP - 275
EP - 284
JO - Icarus
JF - Icarus
ER -