Our FTIR microscope typically operates in the mid-IR region from 750 cm^-1 up to 3800 cm^-1. The long wavelength range can also be extended to 550 cm^-1 if required using the wideband detector but with a 10× loss in sensitivity, and a larger aperture size is required, compromising spatial resolution. We recommend that this detector only be used if you are interested in specific bands within the 900-550 cm^-1 range.

Example spectra acquired with the narrowband and wideband detector on the same sample can be found HERE.

When preparing your beamtime proposal, it is important that you demonstrate that there is a genuine need for the high lateral spatial resolution achievable at the beamline.  The beam can be focused to a spot size ranging from ~1-20 µm, depending on the experimental configuration and is ideal for raster mapping complex heterogeneous polymeric samples, single cell, or complex biological tissue, for example. Ideally, you will specifically state the spatial resolution that you required, in microns. Remember that as the wavelength of mid-IR radiation is in the 3-10 µm range, this will thereby essentially limit the smallest sized objects that can be individually resolved using this beamline.  The size of the beam, according to the sampling mode as well as the objective and pinhole used, can be found HERE .

Experiments requiring a spot size of 20 µm or greater, or that require 'bulk' or average measurements per sample, will have no advantage using the synchrotron and can be carried out on a lab-based IR microscope. However, If you can show that desired results were unsuccessful using a lab-based IR microscopy, this can be advantageous for your application to use our beamline. Furthermore, we now offer time resolved IRM, or rapid scan analysis, with the ability to measure up to 65 spectra/sec at a resolution of 16 cm^-1, and a scanner velocity of 160 kHz.  Requirements of the time resolved spectroscopy could justify the requirement of the synchrotron IRM beamline without the need for spatial resolution.  Please contact an IRM team member  if you are unsure whether your experiment would benefit from use of the synchrotron.

The IRM beamline operates in the mid-IR region (typically 750-3800 cm^-1) and is ideal for studying condensed-phase, heterogeneous samples due to the high lateral spatial  resolution that can be achieved. The measurement area can be decreased to diffraction-limited spot sizes of around 3-5 µm , and the Bruker microscope stage can step across a sample in precise steps, less than 1 µm. This beamline is thus ideal for creating chemical maps of a sample by raster mapping along complex samples over regions of interest.

The THz/Far IR Beamline operates at much longer wavelengths, down to 10 cm^-1. At these longer wavelengths the larger minimum spot size means this beamline does not perform the same type of spatial mapping across a sample. Instead this beamline takes advantage of the synchrotron source and their Bruker spectrometer to measure:

• Gaseous samples at high spectral resolution, by which we mean the beamline can measure extremely detailed IR spectra of gases by stepping the IR wavelength in precise increments of down to 0.00096 cm^-1; &

• The THz spectrum of condensed phase, homogenous samples, by placing the sample in the beam path where the beam has a typical spot size of about 3 mm. Here, as with IRM condensed phase samples, there is no advantage to going to high spectral resolutions so samples are typically scanned at spectral resolutions of between 4-8 cm^-1

Please speak to a beamline scientist if you would like to conduct experiments across both beamlines. Each beamline requires its own, separate proposal application for beamtime. To contact both beamlines, email: as-ir@ansto.gov.au

This beamline cannot do depth profiling (axial mapping of a sample), however when operating in transmission mode the z-height of the microscope stage can be moved through the focus of your sample in a set step size.  So if your sample is thicker than 5 µm, e.g. you are working with a 30 µm polished wafer of rock with an inclusion in the middle, you can focus the beam into your inclusion. The lateral spatial resolution achievable does degrade from the diffraction limit however when you have thicker samples.

The ATR on our beamline is also of a fixed angle, so again cannot be used to profile depth.

IR analysis can be run using transflection, which requires sections to be laid onto IR reflective slides e.g. Kevley MirrIR slides or ITO coated glass, instead of straight transmission. MirrIR slides are much cheaper than IR transmissive slides such as calcium fluoride and have the larger dimensions of normal microscope slides (1 x 3 inches), so you can potentially lay 1-3 sections per slide. There are inherent problems with this method however, in that your sample e.g. if working with tissue sections, have to be extremely uniform and ideally 4 µm thick, rather than the 5-8 µm thick required for transmission with a bit more leeway in the uniformity. Results are also more difficult to interpret using this method. We recommend the following papers discussing the potential issues with transflection analysis for further information.

P. Bassan, J. Lee, A. Sachdeva, J. Pissardini, K.M. Dorling, J.S. Fletcher, A. Henderson, P. Gardner. Analyst, 138, 144 (2013)

K. Malek, B.R. Wood, K.R. Bambery. FTIR Imaging of Tissues: Techniques and Methods of Analysis; Chapter 15. in book M. Baranska (ed.), Optical spectroscopy and computational methods in biology and medicine. Springer Science, 2014.

M. Miljkovic, B. Bird, M. Diem. Analyst, 137, 3954 (2012)