Observation of exciplex emission from the mixed dimer of naphthalene and 2-methoxynaphthalene: A laser-induced fluorescence study in supersonic jet

Exciplex formation in the van der Waals mixed dimer of naphthalene and 2-me thoxynaphthalene has been investigated by using laser-induced fluorescence spectroscopy in supersonic jet. In contrast to the barrierless excimer form ation in the S-1 state of naphthalene homodimer, the exciplex formation in the mixed dimer occurs with a vibrational energy barrier of 466 cm(-1). The energy gap between the S-1 states of two molecules in the mixed dimer is 1 000 cm(-1). Therefore, the contribution of the exciton resonance interactio n to the stability of the exciplex state is considered to be insignificant. Charge transfer interaction and the mixing of the charge transfer state wi th the locally excited state due to orbital overlap between two molecules a t suitable geometry are proposed to be the decisive factors in formation of the exciplex. (C) 2001 American Institute of Physics.