Identification of a Previously Unobserved Dissociative Ionization Pathway in Time-Resolved Photospectroscopy of the Deuterium Molecule

Wei Cao, Guillaume Laurent, Itzik Ben-Itzhak, C. Lewis Cocke
2015 Physical Review Letters  
A femtosecond vacuum ultraviolet (VUV) pulse with high spectral resolution (<200 meV) is selected from the laser-driven high order harmonics. This ultrafast VUV pulse is synchronized with an infrared(IR) laser pulse to study dissociative ionization in deuterium molecules. At a VUV photon energy of 16.95 eV, a previously unobserved bond-breaking pathway is found in which the dissociation direction does not follow the IR polarization. We interpret it as corresponding to molecules predissociating
more » ... es predissociating into two separated atoms, one of which is photoionized by the following IR pulse. A time resolved study allows us to determine the lifetime of the intermediate predissociation process to be about 1 ps. Additionally, the dissociative ionization pathways show high sensitivity to the VUV photon energy. As the VUV photon energy is blueshifted to 17.45 eV, the more familiar bond-softening (BS) channel is opened to compete with the newly discovered pathway. The interpretation of different pathways is supported by the energy sharing between the electron and nuclei.
doi:10.1103/physrevlett.114.113001 pmid:25839264 fatcat:6h4rtspggjgabbflc3hg25x5hm