In well studied examples of multi-photon driven hybrid resonances, a resonant or near resonant transition in a simple molecule or in atoms during collision, leads to a “product” which subsequently is further excited.
A new, simple method for the generation of Xe(6s[3/2]1) and Xe(6s′[1/2]1) atoms is described. The method involves resonant two-photon excitation of Xe(6p[1/2]0 and 6p′[3/2]2) states followed by amplified spontaneous emission (ASE) to the Xe(6s[3/2]1 and 6s′[1/2]1) states. The vacuum ultraviolet transitions, Xe(6s[3/2]1→5p6(1S0)) at 147 nm and Xe(6s′[1/2]1→5p6(1S0)) at 129.6 nm, were used to monitor the time dependence of the resonance state atom concentrations. The quenching rate constants of these resonance atoms with ten molecules were measured at 300 K. The quenching cross-sections of the Xe(6s and 6s′) resonance atoms are compared to the cross-sections of the metastable Xe(6s[3/2]2) atoms and Xe(6p[3/2]2) atoms. The correlation between quenching cross-sections and photoabsorption cross-section of the molecules predicted by the resonance dipole–dipole energy transfer model is discussed. The applicability of the two-photon driven ASE method for the generation of other resonance state atoms is considered.
By using a multiphoton ionization technique, we observed a laser-induced energy-transfer process of fifth order in Xe–Ar atoms. Through four-photon excitation of the 4f[5/2]J = 2 level of Xe in collision with a ground-state Ar atom and the absorption of one additional photon, the 5s[3/2]J = 1 level of Ar is excited and subsequently ionized. By coincidence the same photon energy required for four-photon excitation of the chosen state in Xe is also adequate for absorption by Ar during the Xe*–Ar collision, thus permitting observation of a fifth-order laser-induced energy transfer in a simple one-color experiment.
Through multiphoton ionization measurements, we have observed the interference of five-photon and internally generated fifth-harmonic excitation processes in \ensuremath{\Delta}J=1 even-odd parity resonant transitions in Xe and Ar. In agreement with theory, these five-photon resonances are not observable in single-pass laser beams, but are convincingly observed in counterpropagating beams. In the negatively dispersive regions of the 5d[3/2]0J=1 level of Xe, tunable fifth-harmonic light is generated by phase matching with various buffer-gas mixtures. The fifth-harmonic profiles are in good agreement with calculated phase-matching curves.