Laser-initiated shuttling of a water molecule between H-bonding sites

The two-step laser excitation scheme of stimulated emission pumping (SEP) induces shifts of a single water molecule between two remote hydrogen bonding sites on trans-formanilide. This reaction can be initiated by selective excitation of. either isomer (C=O-bound or NH-bound) with different SEP excitation wavelengths. Energy (E) thresholds for isomerization in both directions have been measured [796 wave numbers less than or equal to E(C=O-->NH) less than or equal to 988 wave numbers and 750 wave numbers less than or equal to E(NH-->C=O) :S 988 wave numbers], and the energy difference DeltaE between the C=O-bound and NH-bound isomers was extracted (-238 wave numbers less than or equal to DeltaE less than or equal to +192 wave numbers).