Wide-field, Femtosecond Infrared Spectroscopic Imaging

Vibrational spectroscopy is sensitive to molecular structure and dynamics. This has made it an attractive candidate as a microscopic contrast agent. We are developing wide-field, femtosecond infrared spectroscopic imaging methods that provide temporal and spatial resolution. Using the Ge AOM pulse shaper pioneered by the Zanni group and a state-of-the-art IR focal plane array (FPA), we have successfully collected FTIR images of metal carbonyls absorbed in polystyrene beads. This demonstrates that femtosecond IR laser sources are viable candidates for new infrared imaging methods and can spatially resolve distinct chemical species.

New experiments are underway to combine 2D IR spectroscopy and wide-field infrared imaging.

Figure 1: Diagram of the experimental setup showing the (a) Ge-AOM based pulse shaper, (b) the optional diffuser/recollimating device used for incoherent imaging and (c) the microscope.

Figure 2: Images of a mixture of Mn2(CO)10 or W(CO)6 soaked polystyrene beads suspended in water. (a) Transmitted light image of bead sample. (b) Fourier transform infrared (FTIR) absorption spectra of different beads, as indicated by pixel numbers. (c) False color FTIR absorption image. The W(CO)6 (1971 cm-1) absorption is mapped to red while the Mn2(CO)10 (2004 cm-1) is colored in cyan.