Coincidence momentum imaging of ultrafast hydrogen migration in methanol and its isotopomers in intense laser fields

Two-body Coulomb explosion processes of methanol (CH3OH, CD3OH, CH3OD) in an intense laser field (0.2 pW/cm(2), 60 fs) are investigated by the coincidence momentum imaging method. The dissociation pathways with hydrogen/deuterium migration or hydrogen/deuterium exchange prior to the C-O bond breaking are securely identified. From the anisotropic angular distributions and the relative yields of the fragment ions, it is revealed that the hydrogen migration process is terminated within the period of an intense ultrashort laser pulse. A comparison of the results obtained for CH3OH and those for the isotopomers shows that the hydrogen migration is decelerated by the isotope substitution. (c) 2006 Elsevier B.V. All rights reserved.