This research activity focuses on solving fundamental physical and chemical processes at work in medium- to large-sized molecular systems, whether in the gas or condensed phase, using atomic simulations and dedicated experiments such as monitoring the infrared emission of isolated molecules. The systems studied range from isolated hydrocarbon molecules to clusters and biomolecules. Key problems such as the dynamics of carbon molecules in the interstellar medium or the ultrafast dynamics of biomolecules are addressed. Our simulations are directly motivated by experiments carried out within ISMO or our network of collaborators.
Competing radiative relaxation processes are at the core of several of our activities. These can be represented using the Jablonski diagram, including intramolecular relaxation processes and various radiative emission processes, from direct electronic fluorescence to recurrent (Poincaré) fluorescence to vibrational emission. The last two cases are statistical processes (ergodicity hypothesis) occurring at long times, i.e. well above a microsecond. Access to these relaxation pathways remains a challenge in the laboratory and, after a prediction in the 1980s, only recent measurements have begun to highlight recurrent fluorescence. The role played by this mechanism in the conditions of isolation of the interstellar medium appears increasingly appealing, and many studies are devoted to studying it.
In the team, we explore this process and its various possible manifestations through numerical simulation. For example, the expected emission from a set of carbon clusters is close to that of a blackbody-like emission for sizes of only a few dozen carbon atoms. Vibrational emission, observed experimentally through the C-H bond elongation modes, has made it possible to trace anharmonicity effects unattainable by other measurements. This experimental work is continued using the Nanograins and the Firefefly setups.
Anharmonicity ― Phenylacetylene-d1 ― as seen by time resolved IR emission after laser excitation at 193 nm
Contacts:
Cyril Falvo
Sabine Morisset
Pascal Parneix
Daniel Pelaez Ruiz
Thomas Pino
Nathalie Rougeau