Observation of wave packets with simultaneous electronic, vibrational, and rotational degrees of freedom in Li2

Using ultrafast pump–probe spectroscopy, we observe quantum beats between rovibrational states located on the uncoupled bound G 1 Π g + and F 1 Σ g + electronic curves of Li2. From a pure launch state ( A 1 Σ u + v A , J A = 11 , 28 ) , a wave packet is prepared using the output from a visible ultrafast optical parametric amplifier and is photoionized by an 800 nm ultrafast pulse. As the OPA wavelength is scanned, a vibrational progression of rotational quantum beats on the G curve is observed. At energies around 35 000 cm−1, in addition to rotational beats on the G curve, vibrational, rotational, and electronic beating between the G and F curves is observed.