Second Harmonic Generation-Based Coherent Vibrational Spectroscopy for a Liquid Interface under the Nonresonant Pump Condition

摘要

The molecular dynamics in the low-frequency region (0-500 cm~(-1)) sensitively reflects the intermolecular interactions in a liquid.The second harmonic generation-based coherent vibrational spectroscopy (SHG-CVS) was developed to monitor the low-frequency dynamics of molecules at a liquid interface,which was difficult to access by using the present spectroscopic techniques such as sum frequency generation or attenuated total reflection (ATR)-IR.Background-free detection with the transient grating (TG) optical configuration was adopted to obtain the weak signal under the electronically nonresonant pump condition.It was demonstrated that the S/N ratio of the SHG-CVS with the TG configuration was remarkably superior to that with the conventional time-resolved SHG configuration,and the improved detection limit enabled us to detect the low-frequency dynamics of coumarin 314 molecules at the air/water interface under the electronically nonresonant pump condition.