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)

The synchrotron has a microtome onsite that you can access if requested as part of your beamtime. The microtome is used for samples that are in the form of a solid plastic-like material, or that can be embedded in an IR transmissive material like AgCl e.g. using a pellet press (the synchrotron also has a pellet press onsite). Microtoming involves taking transverse slices of the embedded sample into pieces ideally 5 µm thick (perhaps thinner if they are strongly absorbing) for analysis in transmission. In addition, if you have samples for use with the ATR, the microtome can be used to expose a smooth surface for analysis.

Site access can be granted earlier than your scheduled beamtime to prepare microtomed samples if arranged with beamline staff prior to your beamtime.

If you require microtomed tissue and/or cryosections, or your samples are tricky and you require expert help, we recommend contacting the Monash Histology Platform for advice.

This depends on the properties of your samples and the wavenumber region of interest. Different window materials will transmit different wavelengths to different extents in the mid-IR. We typically purchase our windows from Crystran, a company based in the UK, and recommend use of calcium fluoride or barium fluoride windows at 0.5 mm thick, or zinc selenide windows at 1 mm thick (due to issues with fringing across the baseline of spectra at 4 cm^-1 spectral resolution using 0.5 mm thick windows). Ideally, the diameter of the window should be between 12 - 22 mm. Extensive spectral properties are listed on the Crystran website for each material, however for a brief overview summary please see below or HERE :

The company we typically purchase our IR transmissive windows from is Crystran, a company based in the UK. We normally recommend using their calcium fluoride windows, 0.5 mm thickness by 13 mm or 22 mm diameter. These are stock items so are typically delivered very quickly (we've had them within a week if the order is urgent). Zinc selenide and barium fluoride are also popular materials (0.5 mm thickness again), depending on the wavelength region of analysis. Some windows can be washed and reused (see Table above), however they do have a finite lifetime.

Yes, if the windows are not made of barium fluoride. Windows have a finite lifetime but can be washed and reused a limited number of times before becoming excessively scratched. Use water and/or a mild detergent to wash them, and lens tissue to gently polish them.

Yes, the beamline has been used by several groups to examine soil particulates. If you require the spectra to be collected from individual microscopic sized grains or small particles of soil, this would be your primary argument in any proposal for your need to use synchrotron radiation. Remember however, that as the wavelength of mid-IR radiation is in the range 3-10 µm that this will be the approximate smallest sized objects that can be individually resolved.

Typical methods of sample preparation include using transmission mode by sandwiching the soil samples between diamond windows using our diamond window micro-compression cells. Many organic molecules are relatively strong absorbers of IR radiation so by flattening them between the windows, successful spectra of soil particulates can be collected. Water is however also a strong absorber and so you may need to consider whether you can dehydrate the soils without significantly disrupting the native chemistry. Some absorbed water can be worked with but it will mask spectral signatures coming from other O-H groups, C=O carboxylates etc., and to a lesser extent the C-O from carbohydrates etc.

Soil samples can also be embedded in an IR transmissive material like KBr. Previous groups have first gently pressed a thin KBr pellet (50 mg KBr, pressed at 7 tonnes for 2.5 minutes), then have sprinkled some particles selected with a fine needle on the top of the pellet before pressing again (7 tonnes for 2.5 minutes), to create thin pellets for transmission. A pellet press is available onsite for this purpose if required. An advantage of this method over use of the diamond window micro-compression cell is that the refractive index of KBr is close to that of soil, limiting any scattering effects around the edges of the particles. Disadvantages include a higher wavenumber cut-off closer to 900 cm^-1, when compared to that achieved when using the compression cell with a cut-off closer to 750 cm^-1.