Introduction:

Here we present a digital twin of a real experiment - a programmable digital reproduction of an already realized experiment, where the selected inputs activate the execution of the corresponding measured experimental results with accompanying videos and monitoring of the experimental realization. The user can select combinations of specific inputs that will activate the execution of already performed experiments for those inputs.

Experiment:

Raman spectroscopy (RS) measures the energy difference between incident (Ultraviolet/Visible/Infrared region) and scattered electromagnetic radiation and gives information about the molecular vibrations.
Raman frequency shift Δν = |ν0 ± ν| depends on the molecular species. Raman spectra provide information on chemical structures and identify substances based on characteristics, i.e., unique spectral patterns. It is non-destructive, with no contact with the sample, and no sample preparation needed.
 

Samples:

The rocks in the Earth`s crust are composed of mineral grains combined in different ways and with various properties. Minerals are naturally occurring chemical compounds in which atoms are arranged in three-dimensional patterns. The kind of elements and their arrangements lead to a particular appearance and certain properties for each mineral. The same chemical elements arranged in different patterns exhibit different characteristics. RS offers the possibility to identify minerals based on their specific spectrum, which is unique for every mineral. 
The sample from Cer Mt. represents a typical pegmatite (this type of rock generally consists of quartz, orthoclase and mica; a mineral from the garnet group may also be present in that sample). The pegmatites are attractive rocks for two reasons: some rarer minerals can appear in them, and more importantly, minerals occur in their rocks in large crystals that can be metered in size.
The sample from the Stari Trg-Trepca mine, located in the vicinity of Kosovska Mitrovica, represents a world-famous Pb-Zn deposit, not only because of the large ore reserves but also because the minerals in this mine occur in the form of well-developed crystals. For this reason, many samples from this deposit adorn the showcases of museums and private collectors worldwide. The most important minerals are sphalerite, galena, quartz, calcite, rhodochrosite, arsenopyrite, pyrrhotite, pyrite, and chalcopyrite. Samples provided by courtesy of Professor Aleksandar Pačevski, University of Belgrade-Faculty of Mining and Geology.

Geological setting: Select image below to see geographical location where it got collected

Image 1

Cer - The granitoid massif of Cer Mt. is situated in western Serbia, 80 km from Belgrade

Image 2

Trepča - The Trepča Pb-Zn-Ag metamorphic rock-skarn is located in the Kopaonik block of the western Vardar zone.

Region 01 Region 11

Sample from location Cer (video)

Sample from location Trepca (video)

Laser location indicator

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Micro-Raman spectrometer - A Raman spectrometer connected to a microscope. It allows us to observe a small area of the sample, and record the spectrum of the selected part.

Slides are changing every few seconds. Click on image to slow down, and select an image (will appear below), as well as sample point and location

Raman spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules.

laser

Select mode of operation for Raman spectroscopy

The selection of the laser wavelength is essential for obtaining meaningful Raman data.
Sensitivity-Raman scattering intensity is proportional to λ-4, where λ is the laser wavelength.
  Spatial resolution is partially dependent on the choice of laser. For example, with a 532 nm laser, and a 0.90/100x objective, the theoretical spot diameter will be 0.72 µm – with the same objective, a 785 nm laser would yield a theoretical spot diameter of 1.1 µm.
The choice of laser depends on type of sample. For example, green lasers can be suitable for inorganic materials, and red or near-infrared is good for fluorescence suppression.

Please select laser wavelength:

   
   
   

Raman signal strength is directly proportional to the power of the Raman laser (milliwatts) exciting the sample. This is why the first best practice is to use full laser power whenever possible. One drawback to this recommendation is that some samples will carbonize when exposed to full laser power. Usually, such samples are dark in colour or have an absorption band close to the excitation wavelength. With valuable samples, the laser power should be low and potential sample damage monitored. The laser power should be increased incrementally to prevent sample damage.

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Laser-induced fluorescence can be a side effect in Raman measurements and can also be detected in the Raman spectrum background. Fluorescence is not a problem for many minerals, but it can come from the surrounding matrix and may be overcome through background subtraction.

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