Postdoc Fellow
NASA Ames Research Center
Greeting! I am a postdoc fellow working at NASA Ames with Dr. Mark Marley. I enjoy doing fundamental and
interdiciplinary science which explains why I had my education focused on chemistry and atmospheric astronomy.
This is why I called myself ExoAtmoSpectroscopist.
Peer-edited papers:
Selected Talks:
Selected Conference Abstracts:
Computing Opacity Data
Understanding the composition of exoplanetary atmospheresis the main objectives in exoplanetary science. In order to properly interpret observationaldata from either space-based telescopes or Earth-based observatories, we need to carry outthe radiative transfer modeling of exoplanetary atmospheres. The accuracy of the radiativetransfer modeling results depends upon the accuracy of molecular opacity data data. Opacities are strongly dependent on temperature, pressure, and background gases (broadeners).Laboratory Spectroscopy
Using the Bruker IFS 125HR spectrometer in LawrenceBerkeley National Laboratory, the high-resolution transmission spectra of CH4in H2bathgas are recorded forν3band at 300–700K. Since this is one of my primary dissertationprojects, I had the leading role in developing the experimental details including simulatingthe expected IR spectra, calculating the appropriate pressures of CH4and H2, and alsodiscussing the project details with my PhD advisers, my collaborators, and the beamlinescientist at Lawrence Berkeley National Laboratory who is in charge of Bruker 125HR spec-trometer. More than 200 lines are analyzed to extract the pressure-broadening coefficients(i.e., Lorentzian and temperature-dependence). We found that Lorentzian coefficients are inthe range of 0.055–0.08 cm−1/atm, and are strongly dependent on the rotational quantumnumbers J and on the symmetry of the transition. The results are important in modelinghot-Jupiters and classifying T-dwarfs Atmospheric Modelings Fully capitalizing on the information encoded in a spectrum requires a robust model interpretation. Models used to interpret thermal emission spectra (either from an isolated object like a brown dwarf, M-dwarf, or directly imaged planet, or a secondary eclipse spectrum for a transiting planet) and transmission spectra (for transiting planets) require some combination of chemistry and radiative transfer. Self-consistent models (either 1D or 3D) rely upon a detailed coupling between chemical processes (e.g., thermochemical equilibrium or chemical kinetics/photochemistry), radiative energy transport, convective/dynamical energy transport, and cloud/haze processes to determine the atmospheric state and subsequent observables. Retrieval models, on the other hand, are purely data-driven and attempt to leverage large numbers of free parameters (e.g., molecular abundances for select species, temperature profile parameterization) to adequately fit the observables to determine Bayesian constraints on composition, clouds, and thermal structures \citep{Line2014}. The adequacy of these methods, whether for predictions or parameter estimation, relies upon accurate and complete molecular and atomic opacities.Email:Ehsan.GharibNezhad@NASA.Gov