A slice imaging and multisurface wave packet study of the photodissociation of CH3I at 304 nm

The role of the conical intersection between the 1Q1 and 3Q0 excited states in the photodissociation of CH 3I at 304 nm is investigated drawing a comparison between the adiabatic - through direct absorption to the 3Q1 state - and non-adiabatic - via the 1Q1 → 3Q 0 conical intersection - production of I atoms in the ground 2P3/2 state. The versatility of the slice imaging technique in combination with resonance enhanced multiphoton ionization (REMPI) detection of I(2P3/2) atoms allow distinct measurements of the competing processes. The I(2P3/2) atom kinetic energy distributions (KEDs) obtained in both cases reflect inverted vibrational progressions of the ν2 umbrella mode of the CH3 co-product. The experimental results show a satisfactory agreement with multisurface wave packet calculations using a reduced dimensionality (pseudotriatomic) model carried out on the available ab initio potential energy surfaces. © 2011 the Owner Societies.L.R.-L. thanks to Consejo Superior de Investigaciones Cientı´ficas (CSIC) for a JAE-DOC contract under the Unidad Asociada ‘‘Quı´mica Fı´sica Molecular’’ between Departamento de Quı´mica Fı´sica I of UCM and CSIC. J.D.R. acknowledges financial support from the Spanish Ministry of Science and Innovation (MCINN) for a FPI fellowship. G.A.A. and M.G.G. are supported by research contracts from Consolider program ‘‘Science and Applications of Ultrafast Ultraintense Lasers’’ CSD2007-00013 from MCINN. This work has been supported by the MCINN through Grants CTQ2008-02578/BQU, FIS- 2007-62002 and Consolider program ‘‘Science and Applications of Ultrafast Ultraintense Lasers’’ CSD2007-00013.Peer Reviewe