Ultrafast Dynamics of the Isolated Adenosine-5′-triphosphate Dianion Probed by Time-Resolved Photoelectron Imaging

The excited state dynamics of the doubly deprotonated dianion of adenosine-5'-triphosphate, [ATP-H-2](2-), has been spectroscopically explored by time-resolved photoelectron spectroscopy following excitation at 4.66 eV. Time-resolved photoelectron spectra show that two competing processes occur for the initially populated 1 pi pi* state. The first is rapid electron emission by tunneling through a repulsive Coulomb barrier as the 1 pi pi* state is a resonance. The second is nuclear motion on the 1 pi pi* state surface leading to an intermediate that no longer tunnels and subsequently decays by internal conversion to the ground electronic state. The spectral signatures of the features are similar to those observed for other adenine-derivatives, suggesting that this nucleobase is quite insensitive to the nearby negative charges localized on the phosphates, except of course for the appearance of the additional electron tunneling channel, which is open in the dianion.

Automated summary

The excited state dynamics of the doubly deprotonated dianion of adenosine-5'-triphosphate have been investigated using time-resolved photoelectron spectroscopy. Two competing processes were observed for the initially populated 1 pi pi* state: rapid electron emission by tunneling through a repulsive Coulomb barrier and nuclear motion on the 1 pi pi* state surface. The spectral signatures of the features are similar to other adenine derivatives, indicating insensitivity to nearby negative charges except for an additional electron tunneling channel in the dianion.