Posts Tagged ‘reactivity’
STSM by Jan Zabka, J. Heyrovsky Institute of Physical Chemistry of the ASCR, v. v. i., Prague (CZ), with Christian Alcaraz, Laboratoire de Chimie Physique, Orsay (FR)
On October 7th, 2014 (7 days)
From CZECH REPUBLIC to FRANCE
State-selected reactivity of CO2+ with CH4 of relevance for the modelling of plasma systems and the Earth atmosphere.
The purpose of the STSM was to perform a study the reactivity of CO2+ ions, generated in the electronic ground state with a known amount of vibrational excitation, with CH4. These reactions are of relevance for the modelling of plasma based dry reforming of methane and the chemistry of the Earth atmosphere.
The experiments was performed with the CERISES apparatus, (Collisions Et Réactions d’Ions Sélectionnés par Electrons de Seuil) an associated experiment to synchrotron SOLEIL. Vibrational state selection of CO2+ was performed via the Threshold Photoelectron Photoion Coincidence (TPEPICO) method using the cell ion source of CERISES and the DESIRS beamline. The photon energies were in the range from about 13.7 to 17.3 eV to produce the parent ion by photoionization.
Fig.1.: CERISES: Experimental setup
For the reactive systems described above, were obtaining an absolute cross sections (and hence branching ratios) and product velocity distributions for the various reaction pathways as a function of the vibrational excitation of CO2+ and at selected values of the collision energy within the 0.1 – 10 eV range.
From the dependences on the collision energy were get some insights onto the reaction dynamics, e.g. reaction mechanism or presence of energy barriers. The obtained cross sections and branching ratios will be useful to improve the predictability of chemical models for plasma based reforming of hydrocarbons and atmospheric chemistry.
Fig.2.: Exp. results: a) States of CO2+
Fig.2.: Exp. results: c) Collision energy dependences
The 1st Meeting of the Working Group 2 of the COST Action CM1204 XLIC took place at the Mercure Omaha beach Hotel situated in Port-en-Bessin, Lower Normandy, France from 24th to 27th February 2014. This meeting brought together experts from different disciplines (physics, chemistry, experience, theory) to discuss aspects of the stability of highly excited and highly charged molecules in the gas phase and their reactivity (for example interaction with other molecules and formation of new species through isomerization and/or fragmentation).
The format of the meeting was based on 24 talks (20’) with long discussion time (10’), 2 poster sections (with 23 posters) and free time for discussion. Seven talks were given by young researchers. The number of participants was around 50 persons.
We hope that this Meeting gave the opportunities exchange scientific ideas and results, to initiate new collaborations and to integrate in particular young researchers in the research community.Alicja Domaracka and Henning Zettergren
The Meeting Chairs
- 1st WG2 meeting (Port-en-Bessin, Feb. 2014) - Book of abstracts (2434 downloads)
- WG2 meeting web site
Post-transition state chemical dynamics for gas phase reactivity of dications
Our aim is to understand reaction mechanisms that characterize reactivity of dications in the gas phase, in particular complexes formed by a divalent metal (Ca, Sr for example) and an organic molecule. Two general pathways are possible, Coulomb explosion and neutral loss and chemical dynamics simulations are performed to understand weather and when reactivity proceeds through a statistical or to a non-statistical mechanism, and how the metal affects the reactivity.
Post-transition state dynamics were able to explain the difference in reactivity found between the two systems, in particular the Sr2+ + formamide reaction channel was found to be much more probable than the analogous Ca2+ + formamide one when starting from a particular transition state. Another particular result was obtained by analyzing the reaction pathways dealing to [Ca(H2O)]2+ that proceeds to a different and fast pathway with respect to what obtained from PES study. This pathway was not observed for related Sr2+ system, confirming experimental results.
We are now planning to perform detailed analysis on wave-function character and bond character across the two reaction pathways to couple the dynamical differences with chemical differences. Furthermore, we decided to run a fourth (and probably last) set of chemical dynamics simulations from another transition state. Finally, we are setting up publications related to the project, and in particular thanks to the ad hoc analysis tools provided during the visit, we are rationalizing all post-transition state dynamics results to show how this approach can be complementary to the usual PES approach.