Divita GUPTA
Physikalisches Institut – Cologne
The molecular inventory of the interstellar medium is now almost 340 identified species, over a hundred of which are complex organic molecules (COMs) containing six or more atoms. Understanding how these carbon-rich molecules form, evolve, and are destroyed under the extremely low temperatures of space requires a focus on neutral–radical reaction kinetics. Neutral–neutral reactions, particularly those involving abundant radicals such as CN, often deviate from Arrhenius behaviour and can proceed at fast rates in cold environments, providing key pathways for the synthesis or destruction of COMs and potential prebiotic precursors. Accurate low-temperature rate coefficients for such reactions are critical for astrochemical models, yet remain sparse and are frequently extrapolated from room-temperature data.
In parallel, molecular ions are crucial drivers of chemistry in these cold environments. Ions act as indispensable intermediates and tracers of chemical evolution, linking the formation of hydrocarbons to their photodestruction in diffuse clouds and photodissociation regions. Recent advances in cryogenic ion-trap methods, notably leak-out spectroscopy (LOS) and double-resonance techniques, now deliver high-resolution rovibrational and pure rotational spectra of astrochemically relevant ions. These precise spectroscopic fingerprints enable unambiguous identification of ions with facilities like JWST, ALMA, and IRAM. Leak-out spectroscopic technique further opens the door to isomer- and quantum-state–specific reaction studies.
In this talk, I will discuss these two experimental approaches of low-temperature reaction kinetics of neutral–radical systems and high-resolution ion spectroscopy as powerful laboratory astrophysics tools. Together they provide a framework for constraining the formation and destruction routes of complex species and for modeling the chemical evolution of interstellar matter from simple precursors to the complex organics that may seed planetary systems.