Picosecond Transient Infrared Study of the Ultrafast Deactivation Processes of Electronically Excited B‐DNA and Z‐DNA Forms of [poly(dG‐dC)]2

Very fast: UV excitation of the right-handed B form or the left-handed Z form of [poly(dG-dC)]2 results in transient IR absorption bands that remain long after the 1ππ* state is predicted to have decayed (see picture). A biexponential decay is observed for B-DNA, which is assigned to the vibrationally excited ground state and the 1nNπ* state. The decay of Z-DNA is dominated by single-exponential decay, which is assigned to an exciplex state.