The Role of the Gouy Phase in the Coherent Phase Control of the   Photoionization and Photodissociation of Vinyl Chloride
  We demonstrate theoretically and experimentally that the Gouy phase of a focused laser beam may be used to control the photo-induced reactions of a polyatomic molecule. Quantum mechanical interference between one- and three-photon excitation of vinyl chloride produces a small phase lag between the dissociation and ionization channels on the axis of the molecular beam. Away from the axis, the Gouy phase introduces a much larger phase lag that agrees quantitatively with theory without any adjustable parameters. 
Vishal J. Barge (1), Zhan Hu (1 and 2), Joyce Willig (1) and Robert J.   Gordon (1) ((1) University of Illinois at Chicago, ...