CIRI beamline; Chemical InfraRed Imaging; is a specialized research installation using infrared light. CIRI will ultimately be equipped with three end stations for imaging in micro- and nanometric spatial resolution.
The first end station is an FT-IR microscope with two types of detectors. MCT detector (mercury-cadmium-telluride detector) is used for single-point measurements and mapping. FPA detector (Focal Plane Array) for imaging is made of arrays of MCT detectors. Thanks to this type of construction, in a single measurement thousands of spectra are collected simultaneously. Measurements in different modes are possible on the microscope: transmission, reflection, transflection, and attenuated total reflectance (ATR) technique. Pixel size depends on the objective used and its numerical aperture. For standard Bruker objective 15x is 2,7 μm, and for 36x – 1,1 μm.
The second end station – microscope sSNOM/AFM-IR- is dedicated to experiments with spatial resolution below the diffraction limit of infrared light. The microscope construction is based on an atomic force microscope (AFM). AFM-IR and sSNOM are complementary techniques. The sSNOM scanning optical near-field microscopy enables imaging with spatial resolution at the nanoscale by detection of scattered light under the AFM probe. The AFM-IR technique is suggested when a full IR spectrum is desirable. The absorbed IR light is detected by the AFM tip which “reacts” to the thermal expansion of the sample.
The third planned end station is the O-PTIR microscope (Optical Photothermal Infrared). The microscope has two light sources - a laser with a wavelength in the visible range (532 nm) and an infrared radiation source. If the frequency of the IR wave matches the frequency of the molecule’s vibrations, absorption occurs, and as a result, the photothermal expansion of the sample in the place of illumination. The expansion changes the intensity of the elastically scattered light (Rayleigh scattering) of the green laser. The obtained signal is used to generate the spectroscopic infrared spectrum. The O-PTIR method allows, thanks to the use of a green laser, to obtain both infrared and Raman signals at the same time. The spatial resolution is specified by green laser wavelength.
|Available energy range||
500 meV – 12,5 meV (4000 cm-1 – 100 cm-1)
|Energy resolution ΔE/E||Station number 1:
Max. 0.5 cm-1 for mapping (MCT)
Max. 2 cm-1 for imaging (FPA)
Station number 2:
Station number 3:
|Beam size at sample (H x V)||Diffraction limit of IR – about 10 μm|
|Photon flux at sample||1013 (photons/s/0.1% BW)|
|IR microscope with FPA and MCT detectors end station||available|
|sSNOM and AFM-IR end station||available|
|O-PTIR end station||not available|