Refractive index measurements of poly(methyl methacrylate) (PMMA) from 0.4-1.6 μm.

Using a transmission-spectrum-based method, the refractive index of a 50 μm thick sample of poly(methyl methacrylate) (PMMA) was measured as a function of wavelength. To mitigate the effects of nonplane-parallel surfaces, the sample was measured at 16 different locations. The technique resulted in the measurement of index at several thousand independent wavelengths from 0.

Thin sample refractive index by transmission spectroscopy.

Transmission spectroscopy and a small number of refractometer index measurements are combined to provide refractive index measurements of transparent samples ~50 um thick at hundreds of wavelengths with absolute accuracies <1 x 10(-4). Key to the technique is the use of independent index measurements to circumvent the need for an independent thickness measurement of the sample. The method was demonstrated on glass samples where fits to Cauchy curves had RMS accuracies <3 x 10(-5) from 415 to 1610 nm.

n-Alkane adsorption to polar silica surfaces.

The structures of medium-length n-alkane species (C(8)-C(11)) adsorbed to a hydrophilic silica/vapor interface were examined using vibrational sum frequency spectroscopy. Experiments sampling out-of-plane orientation show a clear pattern in vibrational band intensities that implies chains having primarily all-trans conformations lying flat along the interface. Further analysis shows that the methylene groups of the alkane chains have their local symmetry axes directed into and away from the surface.

Ti:sapphire, broadband vibrational sum-frequency generation spectrometer with a counter-propagating geometry.

We report the development of a counter-propagating, broadband vibrational sum-frequency generation spectrometer based on a Ti:sapphire regenerative amplifier. We present simple procedures for aligning the spectrometer and for setting the timing of the IR and visible pulses. We demonstrate that the use of this geometry offers a number of important advantages over a co-propagating geometry, including a high dynamic range, reduced nonresonant background signal at buried interfaces, and minimal beam deviation upon changing samples.

Hydrogen-bonding molecular ruler surfactants as probes of specific solvation at liquid/liquid interfaces.

Resonance-enhanced, second harmonic generation (SHG) is used to measure the electronic structure of solutes sensitive to specific solvation adsorbed to liquid/liquid and liquid/solid interfaces. Here, specific solvation refers to solvent-solute interactions that are directional and localized. N-methyl-p-methoxyaniline (NMMA) is a solute whose first allowed electronic transition wavelength remains almost constant (approximately 315 nm) in non-hydrogen-bonding solvents regardless of solvent polarity.