Resonant two-photon ionization and laser induced fluorescence spectroscopyof jet-cooled adenine

Electronic spectra of the jet-cooled DNA base adenine were obtained by the resonant two-photon ionization (R2PI) and the laser induced fluorescence (L IF) techniques. The 0-0 band to the lowest electronically excited state was found to be located at 35 503 cm(-1). Well-resolved vibronic structures we re observed up to 1100 cm(-1) above the 0-0 level, followed by a slow rise of broad structureless absorption. The lowest electronic state was proposed to be of n pi* character, which lies similar to 600 cm(-1) below the onset of the pi pi* state. The broad absorption was attributed to the extensive vibronic mixing between the n pi* state and the high-lying pi pi (*) state. (C) 2000 American Institute of Physics. [S0021- 9606(00)00246-4].