Complete Reconstruction of the Wavefunction of a Reacting Molecule by Four-Wave Mixing Spectroscopy

Understanding the mechanisms of chemical reactions is a central goal of chemistry. Most photochemical reactions occur in excited electronic states and are governed by the excited potential energy surface. Except for very small molecules it is extremely challenging to know these potentials with any reasonable accuracy. 
We have recently shown that one can reconstruct the complete excited-state wavefunction (WF) of a reacting molecule [1,2]. Generally, WF reconstruction methods require a priori knowledge of the excited potential [3,4]. The WF reconstruction methodology we propose uses no a priori information on any excited state, but only of the ground state. We express the excited-state WF in the basis of the (assumed known) ground vibrational eigenstates. The superposition coefficients can then be extracted by inversion of a multi-dimensional CARS signal. The method applies to polyatomics, and to dissociative as well as bound excited potentials. Finally, the unknown excited potential can be recovered from the excited WF.

[1] D. Avisar and D.J. Tannor, PRL, 106, 170405, (2011).

[2] D. Avisar and D.J. Tannor, JCP, 136, 214107, (2012).

[3] M. Shapiro et al, PCCP, 12, 15760, (2010).

[4] J.A. Cina, Annu. Rev. Phys. Chem., 59, 319, (2008).