Force-Detected Single Molecule Absorption Spectroscopy

Abstract: Single molecule manipulation and optical detection have been revolutionary tools for biophysics, but find limited application at the chemical level due to a lack of structural resolution. We propose that the technical difficulties associated with observing the change in light transmission affected by a single molecule can be circumvented by encoding absorption spectroscopy into a force signal. The optical trap is used to isolate a single molecule and to position it near a metallic microsphere, which functions as nanoscale electrostatic force sensor and replaces the spectrometer. Model calculations and ongoing experiments are described.