Local density augmentation around acetophenone N,N,N′,N′-tetramethylbenzidine exciplex in supercritical water

Local density augmentation around exciplex between acetophenone and N,N,N′,N′-tetramethylbenzidine (TMB) in supercritical water was measured by peak shift of transient absorption spectrum at 380 °C and at pressures from 6 to 37 MPa. Large local density augmentation was observed at lower densities. The excess density, defined by the difference between local density and bulk density, exhibited a maximum at approximately 0.15 g cm−3. Our results show that the degree of local density augmentation that exists in supercritical water is comparable to that observed in supercritical carbon dioxide in some system.