Visiting Fellow Seminar - Marie-Aline Martin-Drumel

Title: Enabling new molecular detections in the interstellar medium using rotational spectroscopy.

Speaker: Marie-Aline Martin-Drumel

Abstract: The identification of new molecules in the interstellar medium (ISM) is intrinsically linked to their prior laboratory study, especially at high spectral resolution where their rotational spectra serve as molecular fingerprints. Yet current astronomical surveys, using instruments such as ALMA and the GBT, display a wealth of transitions that cannot be assigned to any known molecule, making accurate laboratory rest frequencies more than ever needed.

Candidates for interstellar detection fall into two broad categories:

stable and reactive species. The recent detections of the first PAH-type molecules (benzonitrile, cyanonaphthalenes, indene) after decades of unsuccessful searches have renewed interest in larger stable compounds and the need for new laboratory data on related species. Reactive species, though representing more than 50% of known interstellar molecules, remain undercharacterized — particularly at higher frequencies — because they are inherently more challenging to produce and study in the laboratory. For many, existing data are limited to below 300–400 GHz, while ALMA operates up to ~1 THz.

In our group, we exploit chirped-pulse millimeter-wave and frequency-multiplication-based (sub)millimeter spectroscopy to record rotational spectra of known and postulated interstellar species, providing accurate rest frequencies up to the terahertz domain. I will present an overview of our experimental capabilities, illustrated by results on a range of stable and reactive species — including our work on the methyl cation (CH3+) that led to its first detection in a protoplanetary disk.