만나보세요
새로운 프레젠테이션 도우미가 기다리고 있어요.
뎌욱 빠르게 컨텐츠를 다듬고, 보강하고, 편집하고, 원하는 이미지를 찾고, 시각자료를 편집하세요.
트렌드 검색
Basic principles of IR/Raman spectroscopy
9
Basic principles of IR/Raman spectroscopy
Introduction
Raman Spectroscopy, in its most general classification, is a form of vibrational spectroscopy, which involves emission and absorption of infrared (IR) and visible light (as the form of light-based interaction with the molecule).
Raman spectroscopy is a photonic technique of high resolution that provides in a few seconds chemical and structural information of almost any organic and / or inorganic material or compound allowing its identification.
Elluz Pacheco Cabrera
Prof: Vladimir Makarov
Principles
Consider an incident photon against a molecule. This interaction either involves the absorption or emission of a phonon. Thus, two conservation equations immediately arise:
The Raman spectrum consists of a main band or Rayleigh and two series of secondary bands corresponding to the Raman Stokes and Anti-Stokes bands located symmetrically on both sides of the Rayleigh band
where G is the reciprocol lattice vector and primes denote the final frequency
(ω) and the final photon wave vector (q), respectively, while ¯hk can be regarded as a quasi-momentum, as befits phonons, and according to the eigenvalue of the momentum operator in the position basis
The phenomenon known as Raman effect was described by the Indian physicist Chandrasekhara Venkata Raman in the year 1928.
He named the inelastic phenomenon of the dispersion of light that allows the study of rotations and molecular vibrations.
Raman spectroscopy is concerned with the absorption and emission of visible light; moreover, unlike Rayleigh scattering (the frequency invariant phenomenon which makes the sky blue), Raman scattering requires a change in frequency; hence, it is actually the inelastic scattering of light.
Energy diagram in which each energy state is represented by a horizontal line
Ramman Vs Rayleigh
Note that the energy
levels are with respect
to the molecule, rather
than the photon.
The Raman phenomena, Stokes (emission of phonon by photon) and
Anti-Stokes (absorption of phonon by photon) .
k
- One can derive for from either phonon absortion (anti-Stokes) or phonon emission (Stokes)