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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