Séminaire

Vendredi 19 Septembre 2025 à 11h00.

A versatile instrument to study the reactivity and spectroscopy of isomer-selected molecular ions

Ugo JACOVELLA
(Institut des Sciences Moléculaires d’Orsay)

Salle de séminaires RDC LIppmann

Invité(e) par
Luke MAC ALEESE

présentera en 2 heures :

''Distinguishing the chemical reactivity of isomers remains a fundamental challenge in chemistry, particularly in cluster chemistry, where the number of possible structures increases rapidly with cluster size. I will present a novel instrument designed to measure the kinetics of ion-molecule reactions of laser-ablated species with isomer-specific resolution. This is achieved by combining drift-tube ion mobility spectrometry with mass spectrometry, enabling shape-based selection of ions prior to probing their chemical reactivity. The capabilities of this approach are demonstrated through the determination of isomer-specific reaction rate coefficients for the C40+ cluster, a system known to exhibit multiple coexisting isomers. In addition to kinetic measurements, the instrument also enables the acquisition of electronic spectra of cryogenically cooled molecular ions that have been both mass- and shape-selected. These spectra are recorded via action spectroscopy techniques and are particularly relevant for the ongoing effort to identify the carriers of the diffuse interstellar bands (DIBs), a series of absorption features observed in the spectra of starlight passing through diffuse interstellar clouds. The ion mobility spectrometer serves a dual purpose: (i) it highlights ``magic structures'', particularly stable species that are likely to withstand the harsh ultraviolet conditions of the interstellar medium, and (ii) it enables isomer-specific electronic spectroscopy. The capabilities of the setup will be illustrated through the electronic spectra of carbon cluster rings. ''