Excited state absorption spectra and intersystem crossing kinetics in the naphthaldehydes

Picosecond time resolved, excited state absorption spectra following excitation at 355 nm are reported for 1-naphthaldehyde (1-NA) and 2-naphthaldehyde (2-NA) in room temperature solutions. The kinetics of the lowest excited singlet state (S₁) decay are determined for each. The S₁ lifetimes in cyclohexane are ∼26 ps for 1-NA and ∼55 ps for 2-NA. Both S_n←S₁ and T_n←T ₁ spectra are reported. Molecular orbital model calculations based on the INDO formalism predict excited state singlet-singlet spectra and spin-orbit coupling matrix elements that are consistent with the observed spectra and kinetics.