Existence of pressure induced resonances in fluorescence spectroscopy

Wulfhard K. Lange

A. Jabeoński

Rudolf Grimm, J. Mlynek

G. Grynberg, P. R. Berman

We present three examples of pressure-induced extra resonances that can be observed in nonlinear spectroscopy: fluorescence of a ``three-level atom'' driven by two laser fields, two-photon ionization of a ``three-level atom'' (plus continuum) driven by two laser fields, and excitation of a ``four-level atom'' driven by four laser fields. We show that all these extra resonances can be interpreted in terms of quantum pathways, each pathway involving a collisionally aided excitation. We also demonstrate that the two first extra resonances can be obtained with incoherent fields, while relatively coherent fields are required in the last example.

George William Series

A. K. Mollema, L. W. Wansbeek, Lorenz Willmann +3 more

We demonstrate a spectroscopy method that can be applied in an atomic beam, light-pressure-induced spectroscopy (LiPS). A simple pump and probe experiment yields a dispersivelike spectroscopy signal that can be utilized for laser frequency stabilization. The underlying principles are discussed and compared to Monte Carlo simulations. The shape of the dispersive signal is well described by the simulations. The zero crossing point of the signal is redshifted with respect to the atomic resonance by $\ensuremath{\sim}3\text{ }\text{MHz}$ (one-tenth of the natural linewidth) and depends slightly on the laser intensity. The shift of the zero crossing is determined by laser-induced fluorescence and compared with results of Doppler-free saturation spectroscopy. To check the potential of LiPS for frequency stabilization purposes, it was used to frequency-stabilize the laser for 400 min. Frequency fluctuations of only 0.12 MHz were measured.