The Far InfraRed (FIR) & High Resolution (HR) branch of the IR Beamline is coupled to a Brüker IFS 125/HR spectrometer. This instrument can achieve ultra high spectral resolutions of up to 0.00096 cm^-1, which is necessary when examining the rotationally resolved spectra of gaseous species. The instrument can also be connected to a multitude of accessories and components, allowing a variety gas and condensed phase experiments to be conducted across a wide spectral range: THz – visible frequencies.

The Australian Synchrotron IR Beamline Hutch

The Far Infrared & High resolution Infrared Hutch

The Brüker IFS 125/HR FTIR spectrometer

Who would benefit by using this beamline?

Synchrotron light has a number of unique properties:

• Wide spectral coverage: synchrotron light is emitted with energies ranging from microwave to hard x-rays.
• High brightness: synchrotron light is extremely intense (hundreds of thousands of times more intense than that from conventional x-ray tubes or Globar sources), enabling quick experiments on low concentration/thin samples, e.g. weak IR absorbers, gases with low vapor-pressures, thin films, isotopes in small abundances.
• Collimated: a synchrotron light source can essentially be treated as a point source. The beam can therefore easily be collimated and/or focused to diffraction limited spot sizes (<10 µm), allowing for high spatial resolution (IR microscopes) &/or high spectral resolution (FIR & HR beamline).
• Highly polarised: the synchrotron emits highly polarised radiation (elliptical for the bend magnet radiation and radial for the edge radiation); linear, circular or elliptical. This minimises background scattering, improves sensitivity and enables measurement of circular dichroism and ellipsometry.
• Emitted in very short pulses: pulses emitted are typically around 2 nanoseconds (a billionth of a second), enabling time-resolved studies.

Combining a Fourier spectrometer capable of achieving ultra high spectral resolutions with the highly collimated and intense source of the synchrotron therefore creates an ideal instrument to measure the rotationally resolved spectra of gases. The high intensity of the source also means it is ideal for the study of thin samples in transmission or reflection, where the optical path of interaction is very small. In addition, as the beam displays a high level of polarisation, it is also perfect for the study of samples with oriented IR absorbing bonds (these studies require sample holders with angle adjustments; see Samples).

Far IR studies using synchrotron radiation therefore involve the study of:

• Molecules with small absorption coefficients or with weak modes of vibration
• Gases with low vapour-pressures, or cases where only small amounts of gas can be obtained either because they are hard to synthesise or they are expensive
• Isotopes with low natural abundances
• Thin films
• Samples with oriented bonds
• Chemical reactions or samples which evolve with time
• Circular dichroism