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Molecular orientation and hydrogen bonding at aqueous interfaces

Event Details

Event Dates: 

Friday, January 19, 2018 - 4:00pm

Seminar Location: 

  • JILA Auditorium

Speaker Name(s): 

Alexander Benderskii

Speaker Affiliation(s): 

University of Southern California
Seminar Type/Subject

Scientific Seminar Type: 

  • Phys Chem/Chem Phys Seminar

Event Details & Abstract: 

Physical and chemical properties of interfacial water affect processes such as heterogeneous catalysis, electrochemistry, atmospheric, environmental chemistry, and biological self-assembly. The two sides of the puzzle describing water properties on the microscopic scale are hydrogen bonding and molecular orientation. Both of these reflect the asymmetry of the interfacial environment. In this talk, I will discuss applications of the surface-selective vibrational sum frequency generation (VSFG) spectroscopy to address the interplay between H-bonding and alignment of the water molecular, at the air/water interface, and in the presence of electric field at charged interfaces such as organic monolayers or transparent electrodes. Both vibrational modes of water (stretch and bend) were spectroscopically investigated by VSFG. We will discuss the spectral line shapes and polarization dependence of the VSFG spectra to extract the molecular orientation. Comparison of the stretch and bend spectra, together with theoretical calculations by our collaborators, aid the assignment of the spectral features to different hydrogen bonding motifs. Furthermore, polarization-dependent measurements of the stretch and bend vibrational modes are complementary, because their transition dipoles have different orientations in the molecular frame. Together, they help us understand the 3-dimensional orientation of the water molecules at the interface.