Spectroscopy Series VOL. 2: Components of a Raman Spectrometer

in steemstem •  9 months ago 

Hello friends who love science in this opportunity I want to present the continuation of my previous post where I talked about the theory involved in the phenomenon Raman. Where I am going to show the components used to describe the Raman spectroscopy and in the passing of days and I will explain different important spectroscopy techniques to measure this phenomenon and obtain spectra of different materials.

As mentioned in my previous post, Raman spectroscopy provides us with very important information about molecular vibrations within the crystalline structure of a material, which can be used both for the identification and for the quantification of samples of different materials that we wish to characterize.

The basic principle of this technique refers to the illumination by means of a monochromatic light source in the material and detecting said scattered light, this light has the same frequency as the source of excitation, that is, most of the scattered light and this is known as the Rayleigh line or elastic dispersion, the small portion of scattered light that remains moves in energy from the frequency of the laser light due to electromagnetic interactions or vibrations within the molecule of the characterized material. After having happened all this phenomenon and when the intensity of the light changes in function of the frequency, we obtain the spectrum that we are looking for, that is denominated Raman spectrum.

Next I will present the appropriate equipment to measure raman spectroscopy, explaining in detail each component that make up this device.

Components used in Raman spectroscopy

Laser

We can say that it is the main component for the operation of this technique, since it is the source of excitation, without it the light could not be dispersed. For this technique, it is recommended to use the Helium-Neon laser. although there is a great variety. This type of laser has a great power so it is the right one to produce the Raman scattering, since the intensity is very weak, this laser helps to intensify it even more so it needs a very powerful source of excitation, that is to say that the intensities are greater than the noise of the equipment. The He-Ne laser has a large wavelength of approximately 630 nm, making it the most used source, due to its high degree of phase coherence, which makes it very monochromatic. Other types of laser used are those of Ar that have a wavelength of around 500 nm.

Optical fiber


Optical fiber cable License CCO Pixabay by blickpixel

This element consists of the medium through which the laser light travels, towards the sample of the material that it is desired to characterize and later to excite it. There are two ways in which light travels through fiber optic cabling, the first is the light is guided to the optical head of the spectrometer, and the other is the one that collects and transports the laser light to the monochromator. Normally in the experiments when we assemble the equipment a length greater than 10 meters with a diameter of 110 μm is used.

Optical head

Presents various components that form the optical head:

Camera, This device allows to control the area where the incidence of the laser is correctly produced, it consists of a small camera that provides adequate information on the sample image of the material and presents a mirror where the operator can place it in the way he wishes and It is controlled through a movable screw.

The filter, where the wavelength interference occurs, its main function is to allow the laser to pass to the frequency that we want. It is composed of the nocht and edge filters, which eliminate all contact information during the procedure in order to avoid errors in the measurements.


Components of the optical head of a spectrometer

Lens, focuses the concentration of laser light in the area where the sample is analyzed, is also responsible for collecting all the scattered light and then perform the corresponding analysis.

The mirror, allows you to create the bidirectional path between light and excitation, its objective is to reflect the light that goes to the sample to be characterized, and then the information is collected again through the optical fiber.

Monochromator


Scheme of the spectrometer shows the function performed by the monochromatorLicensed Creative Commons by Sobarwiki

The main function of this component is to capture the signal sent by the laser, this happens when the light is captured by the optical head of the spectrometer, which is taken by means of the fiber optic cable, where the signal finally reaches the monochromator. This component is formed by input and output slots, mirrors and collimator.

Coupled charging device

It is a capacitor that converts the photons sent by the laser through the optical fiber, after passing through the mirrors in a similar signal, the CCD is responsible for capturing this signal, it receives it digitizes the sent data and finally sends it to a computer that shows the light spectra of the material.

Software


Example of a spectrum analyzer program CC BY-SA 3.0

Finally, after carrying out the entire process previously explained with the various devices that make up the spectrometer, we get to the computer software where we can obtain the spectrum and perform its subsequent qualitative analysis. Through this computer program you can visualize the obtained spectral pattern, there is a great variety of programs that help to analyze this type of information, the most used are the LabSpec or the SpectraPro, it allows to observe and identify bands in the vibrations modes , spectral lines, Fourier transforms, etc.

Soon to share with you all more interesting topics about the world of spectroscopy.

Until next time...

If you want more information about the subject you can visit the following links:

The Raman Spectrophotometer

Components of a Raman Spectrometer

Raman scattering

What is the Raman effect?

Raman spectroscopy

Article researchgate Raman


Video credits @gtg

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Nice to have found you (via @trufflepig, that is).
I have been majoring in solid state physics also.

Hey excellent if you specialize in this area can you share with us your knowledge that you think? @isarmoewe

do you know about @steemSTEM?

Of course I know about steemSTEM. :)
There's a German split-off actually which I used to publish some emergency medicine basics.

I once worked with or rather used an NMR spectrometer for some measurements on Calcium ionic conduction.
The issue(s) with my diploma thesis work are described here:
https://steemit.com/myshittiestmethod/@isarmoewe/throwback-times-my-shittiest-lab-method

Having all of this seen happening in my probably last chance to obtain a diploma at all, the fact, that this happened 9 years ago ( I never worked in a lab since) are the main root causes why I didn't write any other articles on physics topics so far.
On the other hand I just cannot find the strength to pull together a valuable article about, let's say, NMR basics. It's just too long ago to have all of it still available in my memory.

Excellent but you can write from your propiso knowledge or simply to inagar in the web, read books and collect information that help you remember and refresh to thenredactar a good text and share it with us.

It should be noted that we are not as demanding as a scientific journal at the time of evaluation, however we have our rules that a post must take to be taken into account by STEM.

Feel free to ask me what you need I am a healer of steemSTEM and I can guide you, in the same way we have many mentors in our discord channel https://discord.gg/edxs53S @isarmoewe

Thank you for the moment. :)
I'm currently busy with other stuff but I'm considering it. :)

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