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Inelastic Collisions of H2O and O2 Molecules at Low Temperature by Raman Spectroscopy

Autor Fernández Sánchez, José María ; Tejeda, Guzmán ; Moreno, Elena ; Gámez, F.; Carmona-Novillo, Estela ; Hernández, Marta I. ; Montero, Salvador
Fecha de publicación 27-oct-2014
Citación 8th International Meeting on Photodynamics and Related Aspects (PHOTODYNAMICS) (2014)
ResumenRaman spectroscopy of supersonic gas jets has been employed along the last ten years [1-5] to study rotationally-inelastic collisions of a number of small molecules at temperatures below 100 K. Number densities and rotational populations can be directly measured along the jet axis from the rotational and/or vibrational Raman spectra. From these primary data, rotational and translational temperatures can be obtained, the latter from conservation of mass, momentum, and enthalpy along the jet. These measurements can be linked to calculations of state-to-state rate coefficients (sts-rates) by means of the kinetic Master Equation, which accounts for the time evolution of the rotational populations. A careful analysis of the Master Equation, which combines experimental and theoretical data, allows one to assess the accuracy of the calculated sts-rates and, in turn, of the potential energy surface (PES). After an introduction to the experimental technique, we will show our recent measurements in jets involving O2 and H2O(gas) molecules diluted in He. Oxygen molecules are cooled down to ~2 K, showing the relaxation among the fine structure triad of the ground rotational state. The rotational populations of H2O progressively deviate from the Boltzmann distribution, preventing to define a proper rotational ¿temperature¿ and affecting the collisional dynamics to a significant extent. Our results will be compared with calculated sts-rates for O2:He [6], and H2O:He collisions with three different PES¿s [7-9]. References 1. B. Maté, F. Thibault, G. Tejeda, et al., J. Chem. Phys. 2005, 122, 064313. 2. S. Montero, F. Thibault, G. Tejeda, et al., J. Chem. Phys. 2006, 125, 124301. 3. J.P. Fonfría, A. Ramos, F. Thibault, et al., J. Chem. Phys. 2007, 127, 134305. 4. G. Tejeda, F. Thibault, J.M. Fernández, et al., J. Chem. Phys. 2008, 128, 224308. 5. J. Pérez-Ríos, G. Tejeda, J.M. Fernández, M.I. Hernández, S. Montero, J. Chem. Phys. 2011, 134, 174307. 6. F. Lique, J. Chem. Phys. 2010, 132, 044311. 7. S. Green, S. Maluendes, A.D. McLean, Astrophys. J. Supp. Ser. 1993, 85, 181. 8. M.P. Hodges, R.J. Wheatley, A.H. Jarvey, J. Chem. Phys. 2002, 116, 1397. 9. K. Patkowski, T. Korona, R. Moszinski, et al., J. Mol. Struct. THEOCHEM 2002, 591, 231.
Descripción 8th photodynamics, Oaxaca, México, Oct 26-31, 2014 ; conferencia invitada ; http://www.photodynamics.hol.es/
URI http://hdl.handle.net/10261/111088
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