Galactic cosmic rays (CRs) are a ubiquitous source of ionisation of the interstellar gas. Along with UV and X-ray photons as well as natural radioactivity they determine the fractional abundance of electrons, ions and charged dust grains in molecular clouds and circumstellar discs, and thus substantially impact the dynamical and chemical processes occurring in these objects. One of the principal aims of the CAS-Theory group is to understand the physics of CRs in clouds and disks, by combining advanced theoretical methods of the kinetic theory and plasma physics and applying available observational constraints. more
Protoplanetary disks (PPDs)—the cradle of young planets—are the crucial link between the large scale cloud cores and the origin of solar system and life. However, the formation and evolution of PPDs have encountered great challenges in the past decades. Our CAS-Theory group aims to solve the puzzles of early formation of PPDs and its subsequent evolution as well as grains growth in PPDs, in both of which the magnetic field plays a key role. more
We developed the CAS deuterium chemistry model, which includes detailed treatment of spin-states of chemical species. The simultaneous studies of deuterium fractionation and spin-state chemistry yield important information on the properties of star-forming material and the initial conditions of star formation. Our model is successfully applied to constraining the chemical age of the envelope surrounding the prostellar system IRAS 16293-2422 A/B to ~1 million years. more

Astrochemical Modelling: Complex organic molecules

We couple the reactive desorption scheme with a detailed treatment of time-dependent ice composition. In this case, the energy released in a chemical reaction may lead to the immediate desorption of a reaction product on the grain surface, depending on the surface composition. Our model predicts relatively high gas-phase abundances for many COMs in dark cloud conditions, and also highlights the important role of the hydroxyl radical OH in the formation pathways of several COMs.

Couple Chemistry Models with (Magneto-)Hydrodynamics

In order to self-consistently study the chemical and physical processes in star formation, we couple the chemistry with hydrodynamic (HD) and magnetohydrodynamic (MHD) models from GMC to protoplanetary disk scales, adopting techniques such as multi-fluid and tracer particles. We aim to provide constraints on the observed chemical differentiations of various species in different star-forming environments.
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