Sumit Ashtekar

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Optical absorption can detect individual molecules and nanostructures even in dissipative or strongly quenching environments where fluorescence signals are weak. Here we image optical absorption of individual carbon nanotubes with subnanometer resolution. We show that we can discriminate adjacent nanotubes on a length scale far below the diffraction limit.(More)
Theory predicts, and experiments have shown, that dynamics is faster at glass surfaces than in the bulk, allowing the glass to settle into deeper energy landscape minima, or "age more." Is it possible that a glass surface could survive at temperatures where the bulk crystallizes, or that it could remain glassy after the bulk is heated all the way to its(More)
Cooperatively rearranging regions (CRRs) play a central role in the temperature dependence of glass dynamics. We record real-time atomic resolution movies of individual CRRs, while ramping their temperature. Between 295 and 326 K, well below the bulk glass transition temperature T(g), the rate coefficient for two-state hopping of CRRs increases over(More)
Amorphous silicon is an important material, amidst a debate whether or not it is a glass. We produce amorphous Si surfaces by ion bombardment and vapor growth, and image discrete Si clusters which hop by two-state dynamics at 295 K. Independent of surface preparation, these clusters have an average diameter of ∼5 atoms. Given prior results for metallic(More)
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