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Institute for Electronic Structure Dynamics

Infrared micro-spectroscopy

 

 

Benefit of the synchrotron radiation for IR microscopy

The use of the synchrotron radiation results in about one order of magnitude benefit in comparison to the internal Globar source due to the high brilliance of the sychrotron source.  This makes possible to achieve diffraction limited spatial resolution in the infrared experiments. Moreover the synchrotron radiation ensures significantly higher light flux in in the range below 600 cm-1 and enables the experiments in far-IR and THz spectral ranges.

Synchrotron IR Brilliance

Infrared micro-spectroscopy end-staion at IRIS / BESSY II

The micro-spectroscopy end-station at IRIS beamline is based on a Hyperion 3000 IR microscope and a Vertex 80 FTIR spectrometer (Bruker Optics GmbH, Ettlingen, Germany). The microscope ensures stable in time operation and the experiments in the mid-infrared spectral range can be done with the use of a single-point mercury cadmium telluride (MCT) detector enabling diffraction limited special resolution in the spectral range of 650-4000 cm-1. A focal plane array (FPA) detector can be used to complement the raster scan measurements and perform measurements faster over the larger areas of interest. 

 

Hyperion 3000 / Si Bolometer

Infrared micro-spectroscopy end-station at IRIS beam-line, BESSY II storage ring

Far-Infared capabilities

The microscope has an optical port for a Si-bolometer. This is a LHe cooled detector, which ensures high detectivy in the spectral range below 600 cm-1. Combined with the infrared radiation of the synchrotron this enables diffraction limited experiments in the far-IR and THz spectral ranges.  Use of the Si-bolometer  expands the spectral range available for the end station in the low wavenumber range to about 80 cm-1.

Microscopy in far-IR - enlarged view

Comparison of the fluxes in the far IR spectral range at the micro-spectroscopy end-station.  Using the infrared synchrotron radiation the signal intensity is about one order of magnitude higher than using the internal Globar source. An rms noise of better than 0.1% is achieved from the synchrotron source in the range of 150-550 cm-1

Experimental capabilities

Using the microscope, it is possible to perform transmission and reflection experiments in the spectral range 100-4000 cm-1 as well as attenuated total reflection measurements. The additional modalities available allow to carry out temperature dependent measurements in the range of 77 - 850 K; study anisotropy, in particular using  the vibrational linear dichroism modality (Schmidt et al., 2006). The step scan and the rapid scan techniques make the microscope suitable for time-resolved experiments.