Ramanspectroscopy instrumentation

The principle behind Raman spectroscopy is that the monochromatic radiation is passed through the sample such that the radiation may get reflected, absorbed, or scattered. The scattered photons have a different frequency from the incident photon as the vibration and rotational property vary. This results in the change of wavelength,, which is studied in the IR spectra.

The difference between the incident photon and the scattered photon is known as the Raman shift. When the energy associated with the scattered photons is less than the energy of an incident photon, the scattering is known as Stokes scattering. When the energy of the scattered photons is more than the incident photon, the scattering is known as anti-Stokes scattering.

What is raman spectraused for

Raman scattering is defined as the scattering of photons by excited molecules at higher energy levels. It is also known as the Raman effect. The photons are inelastically scattered, which means that the kinetic energy of an incident particle is either lost or increased and is composed of Stokes and anti-Stokes portions.

Ramaneffect

Around 50% of the Sun's energy to the Earth is in the form of infrared,[6] therefore the balance of this radiation in the atmosphere is crucial to keep a stable temperature and climate. Carbon dioxide in the atmosphere produces a greenhouse effect, because CO2 is able to absorb and re-emit infrared radiation as seen in Figure 2, unlike the gasses that make up most of the atmosphere (molecular oxygen, O2 about 21% and nitrogen, N2, about 78%).[7] This greenhouse effect is necessary for the livable temperatures on Earth, however an increasing level of greenhouse gases is contributing to an unstable warming of the Earth which is a cause for great concern. Read more about this imbalance here.

Ramanspectroscopy diagram

C.V. Raman discovered Raman spectroscopy in 1928 to study the vibrational, rotational, and low-frequency modes of the molecules. It finds application mainly in chemistry to get the information related to fingerprints.

With the help of the Raman scattering, one can easily say why the sky is blue. This depends on the scattering of blue light because of the presence of the air molecules in the atmosphere. Learn more about applications of Physics concepts with BYJU’S.

For Raman scattering, 3 N is the DOF (for any given chemical compound), where N is the number of atoms in the compound 3 N is DOF because each atom moves in x, y, and z-direction ie; they possess translational, rotational, and vibrational motion.

Since the infrared spectrum is of lower energy than visible light, this limits the amount of solar energy that can be harnessed with standard photovoltaic cells.

What is raman spectrain chemistry

Raman spectrometer is an instrument that consists of one or more single-coloured light sources and lenses and filters to focus the light and to differentiate the reflected and scattered light, respectively. A prism is used for splitting the light into its components which has a detector to detect the weak light. Later the spectrum is obtained on the monitor to analyze the information.

LASER, considered intense monochromatic light in Raman scattering, can give rise to scattered light, which contains one or more sidebands offset by rotational or vibrational energy differences. The sidebands produced include frequencies containing information about the scattering medium, and hence they are used in remote sensing.

Infrared radiation (IR) is a type of radiant energy, with longer wavelengths than the visible light humans can see, but shorter wavelengths than radio waves. Its range extends from fairly small wavelengths near the color red, 700x10-9 m, to nearly a millimeter, 3x10-4 m.[2]

The degree of freedom (DOF) is defined as a number of independent parameters that determine the configuration of the physical system. Following is the degrees of freedom formula:

Ramanspectroscopy PDF

What is raman spectraand how does it work

To analyse the Raman effect, the wavelength of the scattered photon is converted to wavenumber. These wavenumbers are plotted on the x-y plane. The wavenumbers are taken along the x-axis and the Raman intensity is taken on the y-axis. The difference between the wavenumbers and the intensity is known as the Raman spectrum.

Inelastic scattering of photons is similar to the concept of an inelastic collision, which states that the total microscopic kinetic energy is not conserved. In an elastic collision, the transfer of kinetic energy occurs, but the scattering will still be inelastic like in Compton scattering.

similar to Rayleigh scattering, Raman scattering also depends on the polarizability of the molecules. The intensity of Rayleigh scattering is about 10−3 to 10−4 compared to the intensity of the exciting source. The photon’s energy and the state of the molecule after the scattering events are unchanged. In Raman scattering, the frequency of photons presents in the monochromatic light changes when interacted with the vibrational states, or modes, of a molecule.

Raman scattering produces scattered photons with a different frequency depending on the source and the vibrational and rotational properties of the scattered molecules. Raman spectroscopy works on the principle of Raman scattering. It is used to study materials by chemists and physicists. In the olden days, to record spectra, a mercury lamp and photographic plates were used; in modern days, lasers are used. Sir CV Raman was awarded the Nobel Prize for Physics in the year 1930. C V Raman, along with his student K S Krishnan, discovered Raman’s scattering.

Even though infrared radiation cannot be seen by the human eye, it can definitely be felt. Infrared energy is felt as heat because it interacts with molecules by exciting them, causing them to move faster which increases the internal temperature of the object absorbing the infrared energy. Although all wavelengths of radiant energy will heat surfaces that absorb them, infrared radiation is most common in daily life because of the "ordinary" objects that emit it as radiant heat (see blackbody radiation and Wien's Law for more information on this).[3] For example, humans at a temperature of 37°C[4] emit most of their radiant heat in the infrared range, as can be seen in Figure 1.