FY2010 - Oak Ridge National Laboratory

Seed Money Fund—
Chemical Sciences Division
The FTIR spectrometer used for the measurements was a modified Bomem MR254 with a ZnSe
beamsplitter. It was anticipated that the reflectance measurements would push the limits of the system
sensitivity, with reflected signal levels less than 1% of the total energy hitting the samples. To eliminate
scattered light due to the optics and maximize the signal to the detectors, the input collimator was
removed. The detector field of view was 45 milliradians, with a 1 in. beam diameter at the beam splitter.
A folding mirror was used to enable horizontal operation of the instrument, with the samples and
calibration source located on the floor just in front of and below the instrument. The folding mirror was
an 8-in.-square, 3.2-mm-thick aluminum mirror (ThorLabs Item Number ME8S-G01). The calibration
source was a custom Bodkin Engineering extended source blackbody with 3-in.-diameter circular surface
area. Blackbody calibration data was taken both before and after each sample measurement. A two-point
calibration (at 25°C and 50°C) was used.
The folding mirror and instrument were fixed in place for all data collection. A careful alignment was
made so that the center of the instrument’s field of view was over the center of the blackbody, and the
blackbody position was marked on the floor of the test chamber so that it could be removed and replaced
with the test sample in the same position. Spectral resolution was set to 8 cm -1 and sweep speed was set to
32 kHz. The detector preamps were set to auto-ranging mode to achieve maximum signal for each data
point.
193