Time-resolved photoelectron spectroscopy of adenosine and adenosine monophosphate photodeactivation dynamics in water microjets

The excited state relaxation dynamics of adenosine and adenosine monophosphate were studied at multiple excitation energies using femtosecond time-resolved photoelectron spectroscopy in a liquid water microjet. At pump energies of 4.69-4.97 eV, the lowest pi pi* excited state, S-1, was accessed and its decay dynamics were probed via ionization at 6.20 eV. By reversing the role of the pump and probe lasers, a higher-lying pi pi* state was excited at 6.20 eV and its time-evolving photoelectron spectrum was monitored at probe energies of 4.69-4.97 eV. The S-1 pi pi* excited state was found to decay with a lifetime ranging from similar to 210 to 250 fs in adenosine and similar to 220 to 250 fs in adenosine monophosphate. This lifetime drops with increasing pump photon energy. Signal from the higherlying pi pi* excited state decayed on a time scale of similar to 320 fs and was measureable only in adenosine monophosphate. Published by AIP Publishing.