Infrared spectrometers onboard satellites or airborne have been providing valuable information for the identification and characterization of the composition of the interstellar medium and planetary atmospheres. As new missions and satellites equipped with more advanced technologies are launched, like the James Webb Space Telescope (JWST) scheduled for 2018, a broader range of the IR spectrum can be recorded, at higher resolution. Analysis of the generated data can then be supported by laboratory and theoretical studies. To this end, accuracy becomes critical for the latter. For this reason, an important part of our work over the recent years has been the setup of a robust and reliable computational protocol, through a combination of new developments and state-of-the-art applications.[1]<br/>Band-shapes directly comparable to experiment are obtained by inclusion of anharmonic effect to the transition energies and intensities.[2] Here, the cost-effective second-order vibrational perturbation (VPT2) is used over a hybrid coupled-cluster/density functional theory electronic structure calculation scheme. The well-known problem of resonances in VPT2 will also be addressed, as well as ways to overcome it.[3] This will be illustrated through the examples of small-to-large semi-rigid and flexible molecular systems possibly present in the interstellar medium and exo(planets).[4] In addition to IR spectra, inclusion of anharmonic effects on thermodynamic properties is required for the proper evaluation of the stability of different conformers, which may exist at specific space conditions.[5]

Role of anharmonic effects in analysis of astrochemical observations: IR signatures and thermodynamics

254th National Meeting (2017)

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