A mass-selective ion transfer line coupled with a uniform supersonic flow for studying ion-molecule reactions at low temperatures

Baptiste Joalland (1) , Nour Jamal-Eddine (1) , D. Papanastasiou (2) , A. Lekkas (2) , Sophie Carles (1) , Ludovic Biennier (1)

1 IPR - Institut de Physique de Rennes
2 NCSR - National Center for Scientific Research "Demokritos"

A new approach based on the uniform supersonic flow technique-a cold, thermalized de Laval expansion offering the advantage of performing experiments with condensable species-has been developed to study ion-molecule reactions at low temperatures. It employs a mass-selective radio frequency transfer line to capture and select ions from an adaptable ionization source and to inject the selected ions in the core of the supersonic expansion where rate coefficients and product branching can be measured from room temperature down to similar to 15 K. The transfer line incorporates segmented ion guides combining quadrupolar and octapolar field orders to maximize transmission through the differential apertures and the large pressure gradients encountered between the ionization source (similar to mbar), the quadrupole mass filter (similar to 10(-5) mbar), and the de Laval expansion (similar to mbar). All components were designed to enable the injection of cations and anions of virtually any m/z ratio up to 200 at near ground potential, allowing for a precise control over the momentum and thermalization of the ions in the flow. The kinetics and branching ratios of a selection of reactions have been examined to validate the approach. The technique will be instrumental in providing new insight on the reactivity of polyatomic ions and molecular cluster ions in astrophysical and planetary environments.

Domaines: Chimie-Physique [physics.chem-ph]; Chimie théorique et/ou physique

Baptiste Joalland, Nour Jamal-Eddine, D. Papanastasiou, A. Lekkas, Sophie Carles, et al.. A mass-selective ion transfer line coupled with a uniform supersonic flow for studying ion-molecule reactions at low temperatures. Journal of Chemical Physics, 2019, 150 (16), pp.164201. ⟨10.1063/1.5086386⟩. ⟨hal-02149464⟩