IR Spectromicroscopy at the SRC
People to contact:
Carol Hirschmugl
University of WI-Milwaukee
email name: cjhirsch email address: @uwm.edu
414-229-5748
Bob Julian
Synchrotron Radiation Center
email name: rjulian email address: @src.wisc.edu
608-877-2158
About IR Spectromicroscopy at the SRC
IR spectromicroscopy combines the advantages of ir spectroscopy and ir microscopy in a single device. IR spectroscopy, a non-destructive method, is sensitive to functional groups of chemical species, including groups with (but not limited to) C, N, O, S and H.
The capabilities of IR microscopy are fully realized using a tunable source of bright IR radiation - a synchrotron radiation source, which provides the opportunity to obtain diffraction limited, spatially resolved IR images of small samples (approximately 10 microns).
IR spectromicrometers, microscopes using co-linear IR/visible reflective optics coupled to an interferometer, afford the opportunity to optically choose a sample area of interest and to collect an IR spectrum for the same area. At the Synchrotron Radiation Center, a NicPlan IR microscope is coupled with a Nicolet Magna Bench at the IR beamline. Infrared objectives (Swarzschild mirror objectives) are used to focus the IR beam to a 25 micron by 25 micron spot size at the sample position.
The spot size can be further limited by adjusting manual apertures for higher spatial resolution. A one hundred to one thousand-fold gain in photon density can be realized at the sample for small aperture sizes (below 25 x 25 microns). The sample is located on a motorized sample stage, with high spatial reproducibility, and surrounded by a nitrogen purged, plexi-glass enclosure. A large spectral range is measured for each measuring position in about 1 minute, depending on the absorptivity of the sample.
IR spectromicroscopy combines the advantages of ir spectroscopy and ir microscopy in a single device. IR spectroscopy, a non-destructive method, is sensitive to functional groups of chemical species, including groups with (but not limited to) C, N, O, S and H.
An example of a spectrum for one pixel within a sample of a single cell is shown, with corresponding IR images for two absorption bands. The contour maps are shown in 2 dimensions and 3 dimensions. White is maximum absorption and dark blue is minimum absorption strength.
In this example, one IR image shows a concentration of one component within a small area inside a single cell. The other IR image shows a lack of concentration in the center of the cell with a larger concentration towards the edges of the cell.
