Non-Markovian dynamics of the vibrations of ions in water from femtosecondinfrared three-pulse photon echoes

The first femtosecond three-pulse photon echo experiment of a vibrational t ransition is presented. A mode of the azide ion N-3(-) at 2043 cm(-1) is us ed to probe the impulsively excited vibrational energy distribution and hen ce the dynamics of the water around the ion. The vibrational frequency corr elations decay on time scales of about 80 fs and 1.3 ps, while a small part remains for longer than about 10 Ds. The 1.3 ps decay is the residence tim e for hydrogen bonds to the ion. Major differences between vibrational and optical three-pulse echoes are addressed.