FAILURES OF THE 4-WAVE-MIXING MODEL FOR CONE EMISSION

Strontium vapor is pumped by an unfocused, single-mode, pulsed dye las er tuned near the 461 nm resonance transition. With blue laser detunin g the previously reported red-shifted conical emission is present. We simultaneously resolve in angle and in frequency the emissions from th is intense, near-resonant pumping of a ''two-level'' atom. This quanti tative spectral and angular discrimination provides uniquely detailed measurements and demonstrates a serious lack of understanding of this highly nonlinear phenomenon.