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. (C) 1999 Elsevier Science B.V. All rights reserved.