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Revealing electronic state-switching at conical intersections in alkyl iodides by ultrafast XUV transient absorption spectroscopy.

  • Author(s): Chang, Kristina F
  • Reduzzi, Maurizio
  • Wang, Han
  • Poullain, Sonia M
  • Kobayashi, Yuki
  • Barreau, Lou
  • Prendergast, David
  • Neumark, Daniel M
  • Leone, Stephen R
  • et al.
Abstract

Conical intersections between electronic states often dictate the chemistry of photoexcited molecules. Recently developed sources of ultrashort extreme ultraviolet (XUV) pulses tuned to element-specific transitions in molecules allow for the unambiguous detection of electronic state-switching at a conical intersection. Here, the fragmentation of photoexcited iso-propyl iodide and tert-butyl iodide molecules (i-C3H7I and t-C4H9I) through a conical intersection between 3Q0/1Q1 spin-orbit states is revealed by ultrafast XUV transient absorption measuring iodine 4d core-to-valence transitions. The electronic state-sensitivity of the technique allows for a complete mapping of molecular dissociation from photoexcitation to photoproducts. In both molecules, the sub-100 fs transfer of a photoexcited wave packet from the 3Q0 state into the 1Q1 state at the conical intersection is captured. The results show how differences in the electronic state-switching of the wave packet in i-C3H7I and t-C4H9I directly lead to differences in the photoproduct branching ratio of the two systems.

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