Isotope-selective femtosecond wave packet dynamics: The rare molecule

Abstract:

For the first time, the femtosecond real-time vibrational dynamics of the rare ^41,41K₂ isotope, excited to the electronic state, could be selectively studied by means of time-resolved three photon ionization. A vibrational period of fs is determined. Superimposed, a beat structure with a period of 20 ps is observed. A detailed Fourier analysis reveals a strong band of three lines centered around 65.5 cm^-1. A significant perturbation of the wave packet caused by spin-orbit coupling of the A and the crossing state is found. This perturbation is the reason for the fast dephasing of the initially generated wave packet within about 10 ps. The spectrogram of the real-time data shows total revivals of the wave packet at 20 ps and 40 ps. Fractional revivals are found for times around 10 ps and 30 ps. Due to high intensity effects a remarkable slightly broadened line at 90 cm^-1 appears and can be assigned to the wave packet propagation generated in the dimer's ground state by impulsive stimulated Raman scattering. Revivals of this ground state wave packet are found at 17ps and 34ps. A comparison with other isotopes of K₂ is given.