Multi-channel Electronic and Vibrational Dynamics in Polyatomic   High-order Harmonic Generation
  High-order harmonic generation in polyatomic molecules generally involves multiple channels, each associated with a different orbital. Their unambiguous assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach, using unaligned SF$_6$ molecules as an example, where we combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Channel-resolved above-threshold ionization measurements reveal that strong-field ionization opens four channels. Two of them, identified by monitoring the ellipticity dependence of the high-harmonic emission, are found to dominate the harmonic signal. A switch from the HOMO-3 to the HOMO-1 channel at 26 eV is confirmed by a phase jump in the harmonic emission, and by the differing dynamical responses to molecular vibrations. This study demonstrates a modus operandi for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected. 
A. Ferr\'e, A.E. Boguslavskiy, M. Dagan, V. Blanchet, B. Bruner, F.   Burgy, A. Camper, D. Descamps, B. Fabre, N. Fedorov, J...
physics.chem-ph physics.atom-ph