What is the study of Spectroscopy?

What is the study of Spectroscopy?

Spectroscopy is the study of interactions (= matter makes a transition from a quantum state to another quantum state) between electromagnetic waves and matter

-The subject of spectroscopy concerns the emission and absorption of electromagnetic radiation, when an atom or a molecule changes its energy state and as such, the wave nature of the radiation is discarded.

Diffraction on the other hand implies the wave side of the radiation.

-Spectroscopy is mainly the study of the interactions of a photon with matter.

-Spectroscopy provides:

-the energies corresponding to the transitions between them.

-the governing factors the possibility of these transitions under the effect of electromagnetic radiation.

The main types of spectroscopy 

1-Atoms

Atomic absorption spectroscopy (line spectra): it involves electronic excitation (AAS and AES)

2-The molecules

1_spectroscopy μ_ondes (rotational excitation)

2_ IR and Raman spctroscopy (vibrational and rotational excitation)

3_UV and visible (excitation e- accompanied by vibration and rotation)

4_RMN (excitation of atomic nuclei by a magnetic field)

5_RPE (excitation of electrons by a magnetic field)

6_Mass (bombardment of molecules and fragments by e- of medium energy. These transformations are not reversible)

Now let's  targeting the electromagnetic spectrum!

The most well-known region of the electromagnetic spectrum is by far the visible region. Historically, it was in this region that the first spectroscopic transitions were observed and measured. However, this region is a small part of the total electromagnetic spectrum.

We sometimes say that electromagnetic waves are an effect of light, we all have a fairly precise idea of what is light because we can see it, it comes from the sun or a bulb, the definition of electromagnetic waves cover a much wider spectrum of radiation than just visible light.

We know many other electromagnetic waves such as X-rays, UV, etc., we do everything that differentiates one electromagnetic wave from another is its wavelength, therefore its frequency, its energy.

Knowing that the wavelength is inversely proportional to the energy: E = hc / Lambda- L

The most energetic and most dangerous electromagnetic waves for us have a high energy and a weak wavelength at the center of the electromagnetic wave range we find visible light which is only 380 nm, or 380 nm at 760 nm.

Our eye can only detect these wavelengths and this is why we say that they are visible, the full spectrum of electromagnetic waves is approximately on wavelengths varies from 10 ^ -12 m to 10 ^ 3 m, we find on the left the rays with shorter wavelengths are the most energetic (gamma rays, X-rays, UV) these types of radiation as being powerful enough to cause cancer.

More in the center we find the visible spectrum going from purple to red around 380 and 760 nm. The set of visible wavelengths forms white light, these colors can be seen by passing white light through a prism.

When this white light is projected on a colored surface, part of this light will be absorbed by the color and the reflected part corresponds to the color that we see, we can approximately determine the color of an object if we know the length d wave that its surface absorbs by consulting the chromatic circle, the reflected light therefore that which we see located in the chromatic circle opposite to that absorbed by the object.

Beer_Lambert's law: light arriving on a sample can be transmitted, refracted, scattered or absorbed.

 C. Dean and Aspirant of the LRS project

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