Collisional rate coefficients in CO2 atmospheres

Collisional rate coefficients in CO2 atmospheres
Miguel Angel Lopez-Valverde
Instituto de Astrofísica de Andalucía (IAA/CSIC), Granada
Manuel López-Puertas
Bernd Funke
Maya García-Comas
Francisco Gonzalez-Galindo
“Astrophysical Group #4” of the ASTROMOL consortium
Expertise :
Terrestrial Planets' atmospheres , Radiative transfer , Molecular Spectroscopy,
Infrared Emissions (1-20 um) , Remote Sounding from ground/space,
Physical models (photochemistry, energy budget, dynamics, 1D & 3D GCM )
OUTLINE
Introduction to CO2 atmospheres and Non-LTE modeling
Importance of precise determination of energy transfer rate coefficients
Recent results which highlight need for laboratory colaboration
Three additional contributions :
Large Abundances of PAHs in the Upper Atmosphere of Titan
M. Lopez-Puertas, B. M. Dinelli, A. Adriani, B. Funke, M. Garcia-Comas,
M.L. Moriconi, E. DAversa, C. Boersma, L. J. Allamandola
Collisional rates relevant for the inversion of Titan upper atmosphere composition
M. López-Puertas, M. García-Comas, B. Funke, M. A. López-Valverde,
B. M. Dinelli, M. L. Moriconi and A. Adriani
A The Martian upper atmosphere: simulations with a General Circulation Model
F. González-Galindo, M.A. López-Valverde, and F. Forget
The CO2 atmospheres of the Solar System : Mars & Venus
Thermal Structure
Energy balance
Non-LTE models of the upper atmospheres of Mars & Venus
1st Complication : Radiative Transfer
Non-LTE models of the upper atmospheres of Mars & Venus
2nd Complication : Collisional Energy Transfer
2 types of collisional processes: V-V CO2(v) + M ↔ CO2(v-1) + M(v')
V-T CO2(v) + M ↔ CO2(v-1) + M + K.E.
V-V
V-T
Table of V-T rate coefficients used in the Mars / Venus NLTE models
from Lopez-Valverde and Lopez-Puertas, JGR, 1994
Table of V-V rate coefficients used in the Mars / Venus NLTE models
from Lopez-Valverde and Lopez-Puertas, JGR, 1994
Largest uncertainties: Isotopic processes
Higher energy states
Temperature dependece
15 m Cooling Rate : Importance of isotopic bands and V-V & V-T rates
Roldan et al, Icarus, 2000
Largest uncertainty:
V-T CO2(010) + O3P → CO2 + O3P
Impact of a factor 2 change in the V-T CO2-O3P rate coefficient
Mars
Venus
100 K/day
Roldan et al., Icarus, 2000
Gonzalez-Galindo, 2012, this conference
Solar Heating: Uncertain quenching routes of high energy states
Validation of NLTE models
Earth atmosphere :
Many missions obtained NLTE measurements
ATMOS/Spacelab 3 → rate V-T CO2-O3P
MIPAS/Envisat → correction factors to CO2(001) + N2 → CO2(v2) + N2
CO2(v3) + N2 → CO2(v3-1 + N2(1)
Mars : OMEGA and PFS on board Mars Express
Venus: VIRTIS on Venus Express
Lopez-Valverde et al., PSS, 2010
Remote Sounding requirements
Retrieval of VIMS/Cassini IR emissions permits derivation of many species but... rates uncertain!
Lopez-Puertas et al,
2012, this conference
Review of rates
uncertainties in the
Titan atmosphere
SUMMARY
Non-LTE models are powerful tools to study the atmospheres of Mars & Venus
Populations of vibrational states permit interpretation of IR measurements
Cooling/solar heating rates permit study of thermal structure
BUT ....
are subject to uncertainties due to the importance of collisional processes
in the upper atmosphere
Largest uncertainties in CO2 atmospheres: :
V-V relaxation of high energy CO2 vibrational states
V-T quenching of CO2(v2) states by O3P and CO2
V-V transfer between v3 - v2 modes of vibration
V-V & V-T rates involving isotopic species
Level of precision in the different rates depend on scientific objectives (remote sounding,
thermal balance, global circulation, etc).
There is a clear need of a narrow colaboration with laboratories capable to measure them.