Europlanet Strategic Workshop

I3 (Integrated Infrastructure Initiative) on Planetology (in FP7)

ESA/ESTEC, The Netherlands, 26-27 February 2007

Laboratory studies of gas-phase neutral reactions of planetary relevance

using the “Crossed Molecular Beams” scattering technique with mass spectrometric detection

and also LIF (Laser-Induced-Fluorescence) and REMPI (Resonance-Enhanced-Multi-Photon-Ionization)

Casavecchia P., Balucani N., Leonori F., Petrucci R., Volpi G. G.Dipartimento di Chimica, Università degli Studi di Perugia

06123 Perugia, Italy

To be included in a model a reaction must be:

thermodynamically feasible relatively fast (small activation

energy) of known branching ratios of

products

What can a reaction dynamics study tell us about

neutral reactions which are relevant in planetary atmospheres?

reaction kinetic studies provide us with the rate constants, but are rarely able to determine the reaction products

the experimental investigation of the elementary processes at the microscopic level provides us with the most detailed knowledge of gas-phase reactions

and aims to verify whether a specific reaction pathway is accessible by the system

Reaction Dynamics elementary processes under single

collision conditions

crossed molecular beams the colliding species are confined in distinct beams which cross each other at a specific angle and collision energy the species of each beam are made to collide only with the molecules of the other beam and the formed products fly undisturbed towards the detector

this allows us to observe the consequences of a single molecular collision, preventing secondary collisions and wall effects

atomic beam source molecular

beam source

detector

crossed molecular beams + mass spectrometric detection

P < 10-5 Pa

primary beam

source

Crossed beam method + "universal" mass spectrometric

detection and time-of-flight analysisPerugia

secondary beam source

tunable electron impact ionizer

- crossing angle: 90° (45°, 135°)- continuous beams

TOF spectra at LAB angle =34°

(17 eV electron energy) By using soft EI in a CMB experiment at Ec=54.0

kJ/mol we have been able to unambiguously detect the following radical and molecular products:7 CH2CHO (vinoxy) CH3CO (acetyl) CH2CO (ketene) CH3 (methyl)

CH2 (methylene)

CH3 + HCO 43% (major channel)

CH2CHO + H 27%

CH2CO + H2 13% (1st time established)

CH3CO + H 1% (1st time observed)

CH2 + HCHO 16%

J. Phys. Chem. A (2005)

Branching Ratios:

The reaction O(The reaction O(33P)+CP)+C22HH44

The reactions N(2D)+CH4

N(2D)+C2H2

N(2D)+C2H4

N(2D)+H2O

N(2D)+H2

Laboratory studies on N(2D) reactions of relevance to the

chemistry of planetary atmospheres

(Titan)A suite of N-bearing organic molecules: HCCN, CH2NH, CH3CN, CH2CHN, HNO, NH, have been identified as products

Vuitton et al.ApJ (2006)

“Critical review of N*, N+, N2+, N2

++ production and loss processes of relevance to Titan’s atmosphere”

in collaboration with O. Dutuit et al.,

Planetary and Space Science (in preparation)

Laboratory studies on the dynamics of neutral-neutral

gas-phase reactions of O, N, C atoms and OH, CN and C2

radicals with inorganic and organic molecules of relevance in planetary atmospheres and

prebiotic chemistry

Our laboratory activity can fit into the following categories:

● JRA (Joint Research Activities)

with other teams (e.g., Rennes, Orsay, Grenoble, Trento, Basel, ……) tackling in a synergistic way the kinetics/dynamics/spectroscopy of gas-phase chemical processes relevant to planetary atmospheres

● TNA (Trans-National-Access)

within Task and sub-Tasks in

- in Missions support / development (Spectrometry, Astrobiology)

- in Observation / Measurements (Laboratory data for modelling the atmospheres of Planets)

● NA (Networking activities)