The two-photon excitation and three-photon ionization of atomic cesium is investigated over the 6550-6950-Å wavelength region with a tunable-dye-laser source having a 0.06-0.08-Å linewidth and a space-charge ionization detector sensitive to a few ions per second. An online data-acquisition computer provides significant signal-to-noise recovery. The resulting dispersion curve for photoionization is interpreted in terms of the two-photon transitions from the ground level to resonant and intermediate states, and represents, to the authors' knowledge, the first such two-photon absorption spectrum of Cs. Transitions from have been recorded for the series and from for the series.
- Received 16 April 1973
©1974 American Physical Society