Excited-state relaxation of protonated adenine

Abstract

The excited state dynamics of protonated adenine in the gas phase were investigated by femtosecond pump-probe transient mass spectroscopy. Adenine was protonated in an electrosproy ionization source and transferred to a Paul trap. Two femtosecond laser pulses at 266 nm and 800 nm excited the lowest electronic pi pi* state and probed the excited-state dynamics by monitoring ion fragment formation. The measured excited state decay is monoexponential with a lifetime shorter than 161 fs. This agrees with a theoretical prediction of very fast internal conversion via a conical intersection with the ground state.