New Coherent Cancellation Effect Involving Four-Photon Excitation and the Related Ionization

摘要

We describe here an effect which occurs when a first laser is tuned near a dipole allowed three-photon resonance and a second laser is used to complete a dipole allowed four-photon resonance between the ground state /vert bar/0 > and an excited state /vert bar/2 >. In this process three photons are absorbed from the first laser and one photon from the second; so that if the /vert bar/0 >--/vert bar/2 > transition is two-photon allowed the transition is also pumped resonantly by the third harmonic field due to the first laser and the second laser field. When the second laser is strong enough to cause strong absorption of the third harmonic light, and the phase mismatch, /DELTA/kappa is large and dominated by the nearby resonance, a destructive interference occurs between the pumping of the /vert bar/0 >--/vert bar/2 > transition by two- and four-photon process. 7 refs. (ERA citation 14:009776)