The Center for Chemistry at the Space-Time Limit (CaSTL) is a multi-institutional NSF Center for Chemical Innovation. Its central goal is to develop the science and technology necessary to directly visualize the inner workings of individual molecules as they undergo chemical change. By tracking structural changes within molecules in real-time, the aim is to capture and control chemistry in the act.
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The image of the unpaired electron recorded on a single radical anion shows an orbiting orbital (hoop) driven by pseudo-rotation of the molecular frame (waist). The entangled motion ensures that the vibrational wavefunction (0.1 Å scale) is completely specified by the measured image of the electron (~10 Å orbit).
The movie is the tomographic reconstruction of the motion of the Br-Br bond in phase space, Wigner distribution function (WDF), at the quantum uncertainty limit of resolution in position and momentum, recorded at a frame every 5 fs. The negative hole in the distribution function (inside white contour) is the unique signature of quantum interference (cattiness of a state).
This research proves the feasibility of recording single molecule chemistry using ultrasmall electronic devices. The project built devices out of single lysozyme molecules, and then watched the electrical signal that resulted as the enzyme went about its normal activity of chopping apart bacteria.
CaSTL researchers have combined scanning tunneling microscopy (STM) with tip-enhanced Raman spectroscopy (TERS) to image polyatomic molecules adsorbed on metal surface. They show that Raman spectra, which report on the molecular bonding structure, can be recorded with sub-nm spatial resolution.
CaSTL researchers have joined forces to constructing a new type of sum-frequency generation (SFG) microscope. SFG microscopy provides detailed information on molecular structure due to its vibrational sensitivity. This laser scanning microscope has the potential to reveal precise chemical information about molecules at interfaces with sub-micrometer spatial resolution.
This study has successfully used an STM to probe the luminescence of a single molecule at the submolecular scale, reaching the ultimate resolution in real space. The atomic scale resolution in the optical emission is achieved by taking advantage of using tunneling electrons as the excitation source that is spatially confined to Ångström dimensions.
This research demonstrates a “global positioning system” for tracking single molecules in 3D space by equipping them with nano-dumbbell antennae; and the use of Raman spectra as a voltmeter to characterize AC and DC fields on nanometric scale.