3C4 - Two-quantum photoionization of Cs and I-

This paper will review briefly a recent experiment which measured the photodetachment probability for I
^-
ions due to simultaneous absorption of two ruby quanta. We have calculated the two-quantum photoionization rate for atomic cesium as a function of wavelength. The "transition" from the initial state to the bound intermediate state is expressed in terms of oscillator strengths. The second "transition," from these excited valence states into the coulomb continuum is expressed as a cross section. We have observed what appear to be genuine two-photon ionization signals in three cases: 1) near resonance in the
10P_{3/2}
state using the second-harmonic of
Q
-switched ruby, 2) away from resonances, using the 5300 Å second-harmonic of
Q
-switched neodymium laser, and 3) away from resonances using the first anti-Stokes line at 5750 Å from ruby-pumped D
2
gas. Present experiments aim at scanning the interesting range near resonance, e.g., by thermally tuning the ruby.