Knowledge Bank

Multiphoton ionization (MPI) spectra of sodium and cesium were obtained in a crossed $N2$ pumped dye laser and alkali beam. Hybrid resonance were observed at the cesium $7d2D3/2-6p2P1/2$ and $7p2P3/2-6p2P1/2$ transitions and the sodium $4d2D3/2,5/2-3p2P1/2,3/2$ transitions together with the more common MPI via intermediate S, P and D states. Power dependences for these processes are presented together with and interesting case of a switch from red to blue Stark shifting in the sodium MPI spectrum.