Multicharged Ions Team (Ions Multichargés :IONS)


Excitation and relaxation dynamics of molecular ions in the gas phase


Our team studies the excitation and relaxation, in the gas phase, of small molecular ions of biological or astrophysical interest up to nanometer scale systems such as fullerenes or PAH (Polycyclic Aromatic Hydrocarbon) and recently to proteins.

In our experiments, the single or multi-ionization and/or the excitation of the molecules are induced by collisions with low energy ions (<20keV/charge) or by photon absorption with laser excitation.


Using a multiscale approch on both the size of the studied systems and the time (from ns up to second) of the involved processes, our goals are to study and understand the various relaxation modes (ionization, fragmentation, radiative emission) of the molecule as a function of the internal energy .


The studied dissociation mecanisms present interests for multidisciplinary fields.

As an example, the adenine molecule, a building block of DNA is important for exobiology as the formation of this molecule of life still rises unresolved questions about the origin of life on Earth.

PAH laboratory studies are also important from the astrophysics point of view due to the abundance of these molecules in the interstellar medium and understanding their formation in such extreme medium is a challenging task.








Molecular fragmentation under energy control

Using the CIDEC method the internal energy of the molecular ion is measured for each fragmentation channel

C60 (Phys. Rev. Lett. 2007, Phys.Rev. A 2009)

Adenine (J.Chem.Phys. 2011)

W(CO)6 (J.Chem.Phys. 2011)
Anthracene (Phys.Rev. A 2012)


Relaxation of molecule over a large time scale

Experiments using a compact electrostatic storage ring, the MiniRing (ANR 2010–042601 "ANNEAU"; ITSLEIF)

Fast radiative cooling of anthracene cation was observed

Phys.Rev.Lett 2013Phys.Rev.A 2015


Deprotonation (DP) processes observed in collisions between Xe8+ and multiply protonated cytochrome-C

Experiments in collaboration with T. Schlathölter (KVI, The Netherland) and ILM Team SpectroBio of P. Dugourd. Supported by the COST Action MP1002 Nano-IBCT (Nanoscale insights into Ion Beam Cancer Therapy)

Phys.Rev. A 2014































 2015: PhD thesis of MingChao Ji and Céline Ortéga



Research activities


CIDEC (collision induced dissociation under energy control)

An original method to measure the excitation energy of a complexe system (C60,70, DNA bases, W(CO)6, PAH)


Cooling of PAH using the MiniRing

Evolution of the internal energy of stored PAH cations (anthracene,naphthalene, pyrene, coronne) is probed using laser induced dissociation


Molecule, Biomolecule, PAH fragmentation induced by collision with multicharged ions: multielectron capture and fragmentation processes

Collisionnal (electron capture) and post-collisionnal (fragmentation) processes are studied in collisions between multicharged ions and neutral molecules or clusters

Electron capture and fragmentation of molecules of biological interest (adenine, deoxyribose).

Deprotonation processes were observed in collisions between Xe8+ and multiply protonated cytochrome-C (Phys.Rev. A 2014)


Negative ion production

Production of negative ions are studied in collisions between multicharged ions and neutral molecules or clusters 



Experimental setups

ECR ion sources

Multicoincidence collision experiment:  recoil ions (Time-Of-Flight mass spectrometry) and ejected electron (number mesured with silicon detector PIPS) are detected in coïncidence with the energy and charge of the scattered projectile ions

Compact electrostatic storage ring: MiniRing

Double focusing mass spectrometer Finnigan MAT95XP

Nanosecond laser EKSPLA NT242: 532nm, 355nm; OPO 210nm - 2.6µm;  1kHz repetition rate



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