Ultrafast Vibrational Dynamics of Water and Confined Water in Reverse Micelles

183 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.A fast vibrational energy transfer across the surfactant layer of AOT reverse micelles has been measured in small AOT reverse micelles (AOT/water/CCl 4). Most of the vibrational energy from nanodroplet water is transferred to the AOT head group and then out to the CCl4 within 10 picoseconds. The vibrational relaxation of confined water in AOT reverse micelles is also investigated by varing the pump frequency and the size of the reverse micelles. The nuOH of interfacial water shows a slower VR dynamics while that of bulk-like water shows the same VR as bulk water. The subsequent cooling process of the heated nanodroplet after the completion of VR is investigated with transient anti-Stokes and Stokes Raman measurements. The exact quantum yield of the symmetric sulfonate stretch nSO-3 of AOT head group is measured using controlled mid-IR excitations and spectral measurements. The sulfonate quantum yield, ranging between 0.025 and 0.002, mainly depends on the size of reverse micelles; it increases gradually when the size of AOT reverse micelles decreases and then shows a steep increase near the smallest micelle size (rH < 2.5 nm). The nSO-3 quantum yield is independent of the excitation frequency and is explained by a fast vibrational excitation transfer between bulk-like and interfacial water molecules in AOT reverse micelles.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD