Surface second harmonic generation SSHG

The study of surfaces and interfaces has always been hampered by the search of appropriate experimental tools. Optical surface second-harmonic generation (SSHG) has been shovm to be a powerful method and has thus been widely applied over the last decades in surface science. Phenomena like adsorption processes, surface reconstruction or interfacial chemical reactivity have been investigated at both solid and liquid surfaces and have already been extensively reviewed in the past [1-5]. At Uquid/ liquid interfaces experimental results are far less numerous, despite the growing interest for these interfaces which... 

Surface second harmonic generation (SSHG) is very nsefnl to measure the spectrum of interfacial species and therefore to do a pH titration in the interfacial layer that is not centrosymmetric. The concept of measnring a snrface pA"j was introduced by Zhao et al. [40] who showed that the surface pA"j of p-hexadecylaniline was 3.6 compared to a bulk value of 5.3, indicating that the interface prefers to accommodate neutral rather than charged species. 

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