title: Direct Observation of the Transition-State Region in the Photodissociation of CH3I by Femtosecond Extreme Ultraviolet Transient Absorption Spectroscopy.
abstract: Femtosecond extreme ultraviolet (XUV) pulses produced by high harmonic generation are used to probe the transition-state region in the 266 nm photodissociation of CH3I by the real-time evolution of core-to-valence transitions near the iodine N-edge at 45-60 eV. During C-I bond breaking, new core-to-valence electronic states appear in the spectra, which decay concomitantly with the rise of the atomic iodine resonances of I((2)P3/2) and I*((2)P1/2). The short-lived features are assigned to repulsive valence-excited transition-state regions of (3)Q0 and (1)Q1, which can connect to transient core-excited states via promotion of 4d(I) core electrons. A simplified one-electron transition picture is described that accurately predicts the relative energies of the transient states observed. The transition-state resonances reach a maximum at ∼40 fs and decay to complete C-I dissociation in ∼90 fs, representing the shortest-lived chemical transition state observed by core-level, XUV, or X-ray spectroscopy.
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Attar
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Aditi
authors.initials: A
authors.lastname: Bhattacherjee
authors.affiliation: Department of Chemistry, University of California , Berkeley, California 94720, United States.|Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.|Department of Physics, University of California , Berkeley, California 94720, United States.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Leone
keywords: XUV absorption spectroscopy; photodissociation; transition state