Femtosecond Study of Multiphoton Ionization Processes in K2: From Pump−Probe to Control

Experimental and theoretical pump−probe studies are performed for the K 2 molecule. Special molecular spectroscopic properties combined with the dynamics induced by “femtosecond state preparation” facilitate the transition from pump−probe to control spectroscopy. Hereby, the intensity of the laser field serves as a control parameter in the observed multiphoton processes. In the monitored transient ion signal we can distinguish the effect of two processes, i.e., multiphoton ionization (MPI) and resonant impulsive stimulated Raman scattering (RISRS). As a consequence, the temporal evolution of the ion signal reflects the induced dynamics of either the first excited state A 1 Σ u + or the ground state X 1 Σ g + of the potassium dimer.