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Raman spectroscopy belongs to the big family of molecular bonding analysis techniques, in which interaction between electromagnetic waves and bonding vibration modes is used to identify unknown molecular bonds inside a given sample, and as a result recognize the sample's chemical nature.
Due to the reasons that stem from the fundamental physics laws, all molecular bonds at any temperature above zero Kelvin vibrate continuously in the modes of stretching, bending and/or rotational. A physicist named C. V. Raman was the one who first reported in details that traversing light (as an electromagnetic waves) through material may cause to some sorts of interactions with the aforesaid bonding vibration modes, causing to change in frequency of the reflected light. These interactions called inelastic scattering and/or Raman scattering and is the key element of Raman spectroscopy. However, when a monochromatic light source (like laser) is radiated into a material, the most part of light photons is reflected, scattered and/or traversed without any change in energy and frequency of photons, which, this case is called elastic scattering. This type of scattering, which its proportion is very high relative to the Raman scattering, does not say anything about sample's structure, so in the Raman spectroscopy they must be filtered out. Only light photons caused by Raman (inelastic) scattering must be kept and its frequency changes relative to the incident primary light photon (famously known as Raman shift) have to be recorded. In the Raman spectroscopy, therefore, the intensity of secondary light photons (caused by Raman scattering) is plotted against frequency shift, giving a continuous spectrum of intensity variation over the frequency shift (expressed in unit of inverse length mostly cm-1 known as wavenumber). According to the position of a peak in the spectrum, the respective type of molecular bonding inside the sample can be recognized and in that way the sample's chemical nature will be identified.
There are, of course, some molecular bondings that could not be detected by Raman Spectroscopy, in other word, they are not Raman active. Mathematically, for a given molecular bonding to be Raman active, the first derivative of polarizability with respect to vibration at the equilibrium position must not be zero. Some of those molecular bondings that are not Raman active, could be detected by other vibrational molecular bonding-based spectroscopy like Fourier transform infrared spectroscopy (FTIR). This is why the infrared (FTIR) and Raman spectroscopy are sometimes regarded complementary to one another.
Raman spectroscopy is used in chemistry to identify molecules and study chemical bonding. Because vibrational frequencies are specific to a molecule’s chemical bonds, each peak is used as a fingerprint of respective molecular bonding.
The specifications of the Raman spectroscopy apparatus offered by the manufacturer have been fully described in the Table.
In nanotechnology, a Raman microscope can be used to analyze a wide variety of nanoparticles in suspension solutions precursor as well as final products like various polymeric nanocomposites. Studying some carbon allotropes like graphene and analyzing molecular properties of nanoscale layers and surface are some examples of Raman microscopy applications in the nanotechnology.
- Use the proper power cable with UPS.
- Frequently check the integrity of electrical connectivity in high V cable.
- Avoid staring directly or indirectly into the laser beam. Using safety laser glasses is strongly recommended.
- The ambient temperature for optimum operating is between 5 and 30°C. Prolonged use beyond 30°C deteriorates the apparatus functions and may cause to irreversible damage.
- Before connecting the Raman microscopy into the computer, install the associating software onto the computer (use the CD accompanied with the apparatus).
- Use extreme caution when carrying the apparatus, and be careful that the apparatus never experience any impact, electrical and/or mechanical shock.
- Liquid samples can be poured into the transparent container for analyzing – the higher the liquid volume exposed to the laser beam, the stronger the resulting Raman scattering.
- For obtaining stronger Raman scattering and also better protection of objective lenses, first prepare the powder sample in form of compacted disc, and then begin to analyze.
- Be attentive that during analyzing of solid, corrosive and sticky sample, any contact with objective lenses must be avoided.
Install the apparatus in a place free of vapor and dust (preferably clean room).
Vibration and oscillation may cause to disturb apparatus' setting and calibration. So the apparatus must be installed in a place without any vibration (preferably in basement and/or ground floor).
The ambient temperature must not exceed beyond 40°C.
Avoid installing the apparatus near heat sources, air conditioner, and windows.
Avoid placement of light-emitting objects inside the apparatus.
Avoid unnecessary displacement of the apparatus as much as possible.
Apparatus must be carried by the handhold attached to the outside apparatus's body. Remember, during displacement, the apparatus must remain in its horizontal and vertical alignment.
Standard Date : 2017/03/08
Expire Date : 2020/03/07