Photoacoustic infrared spectroscopy at the Canadian Light Source: commissioning experiments.

The commissioning of synchrotron radiation (SR) photoacoustic (PA) infrared spectroscopy at the Canadian Light Source is described in this article. Aperture tests demonstrated an exponential relationship between the wavenumber where SR and thermal-source PA intensities are equal and beam diameter. Total PA intensity increased linearly with aperture size up to 1.5 mm (SR) or 3 mm (thermal source). At larger apertures, this intensity approached a limiting value. The SR beam diameter in the spectrometer was estimated to be about 0.8 mm in these tests. The low-frequency noise and dc offset that characterize SR PA spectra are suppressed through the calculation of average interferograms prior to Fourier transformation.