Cationic complex-enhanced C–H stimulated Raman scattering in naphthalene–benzene solution

Abstract

Ring skeleton vibrations of aromatic series are dominant in Raman spectroscopy compared with the C–H stretching vibrations. When a laser-induced plasma (LIP) was generated in a mixed solution of naphthalene and benzene, an anomalous enhancement was observed in stimulated Raman scattering (SRS) of aromatic C–H stretching vibrations of naphthalene (3055 cm−1). However, SRS of C–H stretching vibrations of benzene at 3060 cm−1 disappeared. The LIP produced electrons and cations, and the transient production of ionized material contributed to the enhancement of SRS of C–H vibrations of naphthalene. Density functional theory calculations showed that the C–H Raman activity of the naphthalene molecules in (naphthalene–benzene)+ heterodimer was significantly enhanced compared with neutral naphthalene. In addition, SRS pulse durations were better compressed in pure benzene and naphthalene due to the self-focusing effect.