P. E. Toschek

Visible superfluorescence from atomic europium

Abstract Visible superfluorescence was observed on twenty lines of Eu I after two-photon excitation. The emission cascade 1961 nm (or 1926 nm), 605.7 nm is studied in detail. The yellow peak power varies as the square of the excitation number, N , pulse width and delay vary as N -1 in agreement with theory. When the emission overlaps with the excitation pulses, the ir emission is dominated by cooperative resonant Stokes radiation (“Raman superradiance”).

Two-photon light shift

Abstract We have made the first observation of a two-photon light shift: a shift of a two-photon resonance due to a third, non-resonant light field. The effect is observed in cross-saturation spectroscopy of neon pumped by a standing-wave saturator field, to which the neon is rendered transparent. A novel high-intensity theory gives a satisfactory fit to the spectrum.

Light-Assisted Collisional Energy Transfer

We have observed collisional energy transfer from europium atoms in the states to the 5p2 1D2 level of strontium, when light at λ2 = 657 nm; 651 nm, and 644 nm provides for the energy difference (s.Fig.1). Processes of this type have been discussed by GUDZENKO and YAKOVLENKO |l|; recently HARRIS, LIDOW, and collaborators |2| have given evidence for light-induced inelastic collisions between Ca and Sr.

Collisional effects upon optical coherences: Experimental study in a xenon three-level system

Laser induced nonlinear absorption profiles in a three-level system have been recorded to study the effect of elastic collisions upon optical coherences. In our particular system, the signal is due to a pure double-quantum term, where we have separated the effect of phase-interrupting collisions from the effect of velocity-changing collisions. Experimental results show that the effect of velocity-changing collisions is very small, and that broadening of the signal is due to phase-interrupting collisions mainly. We are able to determine the increase of the decay rate of the coherent superposition (the “coherence”) of two levels of same parity [Dγ13/dp=(6.5±1) MHz/Torr] and an upper limit for the mean velocity change (ũ≲5m/s).