Laboratoire Interuniversitaire des Systèmes Atmosphériques
CMC, faculté des Sciences, 61 avenue du Général de Gaulle
94010
Créteil cedex, FRANCE
Presentation 1 : None
Polyynes spectroscopy to support observation and modeling of Titan
Y. Bénilan(1), P. Chaquin(2), C. Crépin(3), M.-C. Gazeau(1), et al.
Polyynes spectroscopy to support observation and modeling of Titan’s atmospheric chemistry
Y. Bénilan(1), P. Chaquin(2), C. Crépin(3), M.-C. Gazeau(1), J.-C. Guillemin(4), A. Jolly(1), F. Shindo(1), F. Raulin(1), and V. Vuitton(1)
(1) LISA, UMR 7583 du CNRS, Universités Paris VII et XII, 94010 Creteil Cedex, France ;
(2) LCT, UPR 9070 du CNRS, Université Paris VI, 75252 Paris Cedex, France ;
(3)LPPM, Université Paris XI, 91405 Orsay Cedex, France ;
(4) LCOB, ESA 6052 du CNRS, ENSCR, 35700 Rennes Beaulieu, France.
The photochemistry occurring in the N2/CH4 Titan's atmosphere is known to produce many organic compounds. Among them, polyynes (C2nH2) are of prime interest since (1) they link the gaseous and the solid phase, (2) they play a role in the balance of molecular/atomic hydrogen control , and (3) they are involved in the indirect dissociation of CH4 that occurs in the stratosphere. Diacetylene (C4H2) has been observed and its relative abundance measured while triacetylene (C6H2) has been detected in laboratory simulation. We present spectroscopic studies (coupling experimental and theoretical approaches) developed in order to determine fundamental parameters : absorption characteristic in both UV and IR range and radiative lifetime of metastable states. These data will be used to improve the description of the chemistry in models as well as to interpret observations.
Presentation 2 : None
Experimental study of the degradation of polymers. Application to the origin of extended sources in cometary atmospheres.
N. Fray (1), H. Cottin (1), M.-C.Gazeau (1), B. Minard (2) F. Raulin(2) and Y. Bénilan (1)
Experimental study of the degradation of polymers. Application to the origin of extended sources in cometary atmospheres
N. Fray (1), H. Cottin (1), M.-C.Gazeau (1), B. Minard (2) , F. Raulin (2)and Y. Bénilan (1)
(1) LISA, UMR 7583 du CNRS, Universités Paris VII et XII, 94010 Creteil Cedex, France
(2) Organic Instructional Labs, Chemistry Department, Penn State University, USA
The distribution of some compounds in cometary atmosphere cannot be explained by a direct sublimation from the nucleus, but rather by a production in the coma. HCN polymers or polyoxymethylene [-CH2-O-)n] in solid state on cometary grains could release volatiles through thermal and photolytic degradation. These processes could explain the "extended sources" of CN and H2CO respectively. Photodegradation quantum yields or the thermodegradation kinetics of both species have been determined. Those data are then included into a model of the outer coma in order to interpret observations.These studies have shown that the degradation of organic polymers is a possible source of molecules and radicals which present an extended source.