Surfaces are the last frontier for controlling chemical transformations. Yet probing surfaces – buried, high vapor pressure, and interfaces between dielectric materials – remains a challenge. Nonlinear spectroscopy has made great strides revealing secrets hidden within these interfaces, but nonlinear techniques bring their own challenge. Nonlinearity masks weak resonances beneath the noise, nearby resonances interfere, and lifetime data that reveals interactions is lost. Since the discovery of nonlinear techniques by Bloembergen in the mid-1960s, it has been known that overcoming these challenges requires measurement of the complex response. Over the intervening half-century, several techniques have been devised for this measurement, most popularly Fourier transform techniques based on ultrafast pulses. In this contribution, we present a nonlinear interferometer (dubbed a SBW interferometer) that is applicable in all time regimes. Significantly, the apparatus supports active stabilization over extended periods. Accuracy is improved due to direct, absolute measurement of the complex spectral components: both real and imaginary parts. We will present design and implementation details as well as spectra from several surfaces.

Poking surfaces: Absolute, interferometric, complex spectral measurement

255th National Meeting (2018)

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