Excited-state detachment dynamics and rotational coherences of C2− via time-resolved photoelectron imaging

Time-resolved photoelectron imaging (TRPEI) is used to investigate the effect of time-evolving alignment on the photoelectron angular distribution (PAD) from anion photodetachment. The B←X 000 transition in C2− is pumped with a femtosecond laser pulse at 541 nm and probed by femtosecond photodetachment at 264 nm. The pump pulse produces rotational coherences in the upper state that exhibit partial and full revivals, as evidenced by modulation of the PAD anisotropy moments. From these, one can extract the excited state rotational constant of C2− and information regarding the molecular frame PAD.