High-Harmonic Probing of Electronic Coherence in Dynamically Aligned Molecules

P. M. Kraus, S. B. Zhang, A. Gijsbertsen, R. R. Lucchese, N. Rohringer, H. J. Wörner
2013 Physical Review Letters  
We introduce and demonstrate a new approach to measuring coherent electron wave packets using high-harmonic spectroscopy. By preparing a molecule in a coherent superposition of electronic states, we show that electronic coherence opens previously unobserved high-harmonic-generation channels that connect distinct but coherently related electronic states. Performing the measurements in dynamically aligned nitric oxide (NO) molecules we observe the complex temporal evolution of the electronic
more » ... ence under coupling to nuclear motion. Choosing a weakly allowed transition to prepare the wave packet, we demonstrate an unprecedented sensitivity that arises from optical interference between coherent and incoherent pathways. This mechanism converts a 0.1 excitation fraction into a ∼20
doi:10.1103/physrevlett.111.243005 pmid:24483654 fatcat:qnzcojfkuzejbeyqagt4x2lxhy