Fractional revivals of vibrational wave packets in the NaK A1∑+ state

The real-time vibrational dynamics of NaK molecules excited to the electronic A1∑+ state has been studied isotipe-selectively by means of time-resolved three-photon ionization. For 23Na39K and 23Na41K vibrational periods of TA(23,39) ≊ 441 fs and TA(23,41) ≊446 fs are determined. A detailed Fourier analysis proofs a weak perturbation of the wave packet caused by spin-orbit coupling of A and b3ν states. Pronounced fractional revivals of the fundamental oscillation occur at Tfrev1,2(23,39) ≊ 75 ps and Tfrev1,2(23,41) ≊ 68 ps. Spectrograms of the real-time data nicely reveal a strong fractional revival at Tfrev1,4 = 12Tfrev1,2. Further revivals of weaker intensity at Tfrev1,6(23,39) ≈ 25 ps and Tfrev1,3(23,39) ≈ 50 ps are found for the lighter isotope.