Ion pair dissociation of highly excited carbon clusters

May 18, 2016, 3:10 PM



Mr Thibaut LAUNOY (Université Libre de Bruxelles)


Carbon-chain molecules have been detected in many astrophysical environments such as interstellar medium (ISM) and circumstellar envelopes. These molecules can be formed in different processes, such as neutral-neutral, ion-neutral or ion-ion collisions and the demand for accurate molecular data concerning these processes is very strong.

We will present measurements of ion pair dissociation of carbon clusters formed in high velocity collisions of Cq+n projectiles with atoms in the AGAT set-up [1], situated nearby the Tandem accelerator in Orsay (France).We propose a theoretical interpretation to the ion pair relaxation experiment of C+2 into C++/C−. Ion pair dissociation is a relaxation process in which anionic and cationic fragments are simultaneously emitted. Even if it is a minor process which requires a high excitation of the molecule, the strongly varying probabilities found in the literature (from 10−4 to a few %) is not completely understood.

Using multi-configurational ab initio methods (CASSCF/MRCI + Davidson correction) with different basis sets, we were able to obtain the potential energy curves for the fifty low-lying 4A2 electronic states arising from various molecular dissociation channels and to characterize the ionic channels C++(1S)/C−(4S∘) which interact with valence electronic states resulting in a large number of avoided crossings.

Based on that information and with a statistical approach depending on the dipole excitation selection rules, we propose an interpretation of the measured branching ratio.


[1] Béroff, K. et al 2013 J. Phys. B At. Mol. Opt. Phys. 46 015201.

Primary author

Mr Thibaut LAUNOY (Université Libre de Bruxelles)


Prof. Nathalie VAECK (Université Libre de Bruxelles) Xavier Urbain (Université catholique de Louvain)

Presentation materials