Femtosecond dynamics of solvation at the air/water interface

The electronic excited-state solvation dynamics of coumarin 314 (C314) adsorbed at the air/water interface was investigated by femtosecond time-resolved surface second-harmonic generation (TRSHG). This Letter presents the first use of TRSHG to measure solvation dynamics and presents the theoretical basis for monitoring electronic excited-state solvation with TRSHG. The interfacial electronic excited solvation time of C314 was measured to be 790±30 fs. This is close to bulk results and is in agreement with simple dielectric continuum models of solvation and the predictions of molecular dynamics simulations.