PHD
  1. Inorganic chemistry  1.1. Coordination chemistry  1.1.1. Ligand field theory  1.1.2. Crystal field theory  1.1.3. Molecular Orbital Theory for Coordination Compounds  1.1.4. Stability of Coordination Compounds  1.1.5. Electronic spectra of coordination compounds  1.1.6. Isomerism in Coordination Compounds  1.1.7. Kinetics and mechanism of coordination reactions  1.2. Organometallic Chemistry  1.2.1. Metal Carbonyls  1.2.2. Metal alkyl and aryl  1.2.3. Fischer and Schrock carbonaceans  1.2.4. Oxidative Addition and Reductive Elimination  1.2.5. Metal Hydrides  1.2.6. Catalysis by organometallic compounds  1.2.7. Metallocenes and Sandwich Complexes  1.2.8. CH activation  1.3. Solid state chemistry  1.3.1. Crystal structures and lattices  1.3.2. Band theory and electrical properties  1.3.3. Defects in the crystal  1.3.4. Synthesis of solid state materials  1.3.5. Magnetic and optical properties of solids  1.3.6. Superconductivity  1.3.7. Solid state ionics  1.4. Bio-inorganic chemistry  1.4.1. Metalloproteins and enzymes  1.4.2. Metal ion transport and storage  1.4.3. The role of metals in medicine  1.4.4. Bioinspired catalysis  1.4.5. Metal–DNA interactions  1.4.6. Metal Complexes in Medical Science  1.5. Lanthanides and Actinides  1.5.1. Electronic configuration and oxidation states in lanthanides and actinides  1.5.2. Spectral and Magnetic Properties in Lanthanides and Actinides  1.5.3. Separation and Extraction of Lanthanides and Actinides  1.5.4. Coordination chemistry of f-block elements  1.6. Main Group Chemistry  1.6.1. Chemistry of boron compounds  1.6.2. Chemistry of Silicon and Germanium Compounds  1.6.3. Chemistry of Phosphorus and Sulfur Compounds  1.6.4. Organosilicon chemistry  1.6.5. Noble Gas Chemistry
  2. Organic chemistry  2.1. Reaction mechanism  2.1.1. Nucleophilic substitution reactions  2.1.2. Electrophilic addition and substitution reactions  2.1.3. Elimination reactions  2.1.4. Rearrangement reactions  2.1.5. Radical reactions  2.1.6. Pericyclic Reactions  2.1.7. Photochemical reactions  2.2. Stereoscopic  2.2.1. Chirality and optical activity  2.2.2. Structural analysis  2.2.3. Stereoelectronic effects  2.2.4. Asymmetric synthesis  2.2.5. Dynamic Stereochemistry  2.3. Organometallic Chemistry in Organic Synthesis  2.3.1. Organolithium and organomagnesium reagents  2.3.2. Transition metal catalyzed coupling reactions  2.3.3. Palladium-catalyzed reactions  2.3.4. Olefin Metathesis  2.3.5. Gold and silver catalysis  2.4. Natural products chemistry  2.4.1. Alkaloids and terpenoids  2.4.2. Steroids and Flavonoids  2.4.3. Total synthesis of natural products  2.4.4. Biosynthesis of natural products  2.5. Supramolecular Chemistry  2.5.1. Host-Guest Chemistry  2.5.2. Self-assembly and molecular recognition  2.5.3. Supramolecular Catalysis  2.5.4. Molecular Machines
  3. Physical Chemistry  3.1. Thermodynamics  3.1.1. Laws of Thermodynamics  3.1.2. Chemical Potential and Equilibrium  3.1.3. Statistical thermodynamics  3.1.4. Non-equilibrium thermodynamics  3.2. Quantum Chemistry  3.2.1. Schrödinger equation and its applications  3.2.2. Molecular orbital theory  3.2.3. Density functional theory  3.2.4. Post-Hartree–Fock methods  3.3. Chemical kinetics  3.3.1. Reaction rate theory  3.3.2. Mechanism and rate laws  3.3.3. Catalysis and enzyme kinetics  3.3.4. Reaction dynamics  3.4. Spectroscopy and molecular structure  3.4.1. Infrared Spectroscopy  3.4.2. UV-visible spectroscopy  3.4.3. Nuclear Magnetic Resonance Spectroscopy  3.4.4. Mass Spectrometry  3.4.5. Raman Spectroscopy  3.5. Surface and Colloid Chemistry  3.5.1. Absorption and Catalysis  3.5.2. Surfactants and micelles  3.5.3. Colloidal Stability  3.5.4. Nanomaterials and Interfaces
  4. Analytical chemistry  4.1. Chromatography  4.1.1. Gas Chromatography  4.1.2. High Performance Liquid Chromatography  4.1.3. Thin Layer Chromatography  4.1.4. Ion Chromatography  4.2. Electroanalytical techniques  4.2.1. Voltammetry and Polarography  4.2.2. Conductometry and potentiometry  4.2.3. Colometry  4.3. Spectroscopic Methods  4.3.1. Atomic absorption spectroscopy  4.3.2. Fluorescence Spectroscopy  4.3.3. X-ray diffraction  4.3.4. Electron paramagnetic resonance spectroscopy  4.4. Chemometrics  4.4.1. Data processing and statistical methods  4.4.2. Multidisciplinary analysis  4.4.3. Machine Learning in Analytical Chemistry
  5. Theoretical and Computational Chemistry  5.1. Molecular dynamics simulation  5.2. Quantum chemistry methods  5.3. Computational drug design  5.4. Machine Learning in Chemistry  5.5. Ab initio molecular dynamics
  6. Biophysics and Medicinal Chemistry  6.1. Drug discovery and design  6.2. Enzyme kinetics and inhibition  6.3. Chemical biology approach  6.4. Protein-ligand interactions  6.5. Bioorthogonal chemistry
  7. Materials chemistry  7.1. Polymer chemistry  7.1.1. Polymerization mechanism  7.1.2. Functional Polymers  7.1.3. Biodegradable Polymer  7.1.4. Conducting and semiconducting polymers  7.2. Nano Chemistry  7.2.1. Nanoparticles and nanostructures  7.2.2. Carbon-based nanomaterials  7.2.3. Quantum dots  7.3. Energy and Environmental Chemistry  7.3.1. Battery and Fuel Cell Chemistry  7.3.2. Green chemistry and sustainable materials  7.3.3. Photocatalysis

PHD → Physical Chemistry → Spectroscopy and molecular structure ↓


Raman Spectroscopy


Raman spectroscopy is a powerful analytical tool in the field of physical chemistry used to study molecular structure. It is based on the inelastic scattering of photons, known as Raman scattering, which provides extensive details about molecular vibrations and chemical structure.

Basic principle of Raman spectroscopy

When light interacts with a molecule, most of the light is scattered elastically, which is called Rayleigh scattering. However, a small portion of the light is scattered inelastically, which occurs at frequencies different from the incident light. This inelastic scattering is called Raman scattering.

Raman spectroscopy measures the shift in the frequency of inelastically scattered light, giving information about the vibration modes of molecules. If the polarizability of the molecule changes during vibration, Raman scattering can be observed.

        Incident photon + molecule --> scattered photon + vibration energy of molecule

Raman Effect

The Raman effect is the basis of Raman spectroscopy. When light scatters inelastically, the scattered photon either gains or loses energy compared to the incident photon, causing a shift known as the Raman shift.

        Raman shift (in wave number) = (1/λ incident ) - (1/λ scattered )

Here, λ incident and λ scattered refer to the wavelengths of the incident and scattered light.

Process of Raman scattering

When a photon interacts with a molecule, it can be absorbed, causing the molecule to move into a virtual energy state. From this state, the molecule relaxes back into a different vibrational energy state, causing the emission of a photon of different energy. This process can have two outcomes:

  • Stokes scattering: The energy of the emitted photon is lower than that of the incident photon, resulting in vibrational energy in the molecule.
  • Anti-Stokes scattering: The energy of the emitted photon is higher than that of the incident photon, because the molecule was initially in an excited vibrational state.

In Raman spectroscopy, Stokes scattering is typically measured because it is stronger than anti-Stokes scattering.

incident light scattered light virtual energy state

Selection rules for Raman spectroscopy

Raman activity depends on the change in the polarizability tensor of the molecule during vibration. For a vibration to be Raman active there must be a change in the polarizability tensor of the molecule.

The selection rules are determined by the symmetry of the molecular vibrations. In general, vibrations that are symmetric with respect to the rotation axis of the molecule are Raman active.

Comparison with infrared spectroscopy

Raman spectroscopy and infrared spectroscopy are complementary techniques used for vibrational analysis.

Aspect Raman Spectroscopy Infrared Spectroscopy
Principle Inelastic scattering of light (Raman effect) Absorption of light (IR effect)
Sample preparation Minimum - Single Measurement Sample preparation may be required
Limit of detection Visible range IR Range
Selection Rules Changes in polarization Change in Dipole Moment

Applications of Raman Spectroscopy

Raman spectroscopy is used in a variety of fields because of its ability to provide detailed information about molecular vibrations and material structure. Some of its applications are as follows:

  • Chemical analysis: Identifying chemical bonds and functional groups.
  • Materials science: characterization of materials, especially carbon-based materials.
  • Biological studies: Non-destructive analysis of biological materials.
  • Forensics: Identifying pigments, explosives, and other substances.

In conclusion, Raman spectroscopy is a versatile tool that provides extensive insight into the molecular structure and composition of substances through the analysis of vibrational modes. Its non-destructive nature and minimal sample preparation make it an invaluable technique in physical chemistry and beyond.


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Raman Spectroscopy

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