Spectroscopy

Spectroscopy is the study of the interaction between matter and electromagnetic radiation, serving as a powerful tool to probe the properties of a substance. It operates by measuring the spectrum—the intensity of radiation as a function of its wavelength or frequency—that is absorbed, emitted, or scattered by atoms and molecules. Because each element and compound has a unique spectral "fingerprint," analyzing these spectra allows scientists to determine a sample's chemical composition, physical state, temperature, and atomic or molecular structure, making it an indispensable technique in fields ranging from astrophysics and materials science to chemistry and medicine.

1. Fundamentals of Spectroscopy
   1. Nature of Spectroscopy
      1. Definition and Scope
      2. Historical Development
      3. Classification of Spectroscopic Methods
         1. Atomic Spectroscopy
         2. Molecular Spectroscopy
         3. Magnetic Resonance Spectroscopy
   2. Electromagnetic Radiation
      1. Wave Properties
         1. Wavelength
            1. Units of Measurement
            2. Relationship to Energy
         2. Frequency
            1. Units of Measurement
            2. Relationship to Wavelength
         3. Wavenumber
            1. Definition and Units
            2. Use in Spectroscopy
         4. Amplitude
            1. Physical Meaning
            2. Relation to Intensity
         5. Velocity
            1. Speed of Light in Vacuum
            2. Effect of Medium
      2. Particle Nature of Light
         1. Photons
            1. Energy Quantization
         2. Planck-Einstein Relation
            1. Planck's Constant
            2. Energy Calculations
      3. Electromagnetic Spectrum
         1. Overview and Regions
         2. Radio Waves
            1. Frequency Range
            2. Wavelength Range
            3. Applications in Spectroscopy
         3. Microwaves
            1. Frequency Range
            2. Wavelength Range
            3. Rotational Spectroscopy Applications
         4. Infrared
            1. Near-Infrared
            2. Mid-Infrared
            3. Far-Infrared
            4. Vibrational Spectroscopy Applications
         5. Visible Light
            1. Frequency Range
            2. Wavelength Range
            3. Color Perception
         6. Ultraviolet
            1. Near-UV
            2. Far-UV
            3. Electronic Transitions
         7. X-rays
            1. Soft X-rays
            2. Hard X-rays
            3. Core Electron Transitions
         8. Gamma Rays
            1. Frequency Range
            2. Nuclear Transitions
   3. Interaction of Radiation with Matter
      1. Fundamental Processes
         1. Absorption
            1. Mechanism
            2. Absorption Spectra
            3. Absorption Cross-Section
         2. Emission
            1. Spontaneous Emission
            2. Stimulated Emission
            3. Emission Spectra
         3. Scattering
            1. Elastic Scattering
               1. Rayleigh Scattering
            2. Inelastic Scattering
               1. Raman Scattering
         4. Fluorescence
            1. Mechanism
            2. Fluorescence Lifetime
         5. Phosphorescence
            1. Mechanism
            2. Phosphorescence Lifetime
      2. Quantum Mechanical Principles
         1. Quantized Energy Levels
            1. Electronic Energy Levels
               1. Ground State
               2. Excited States
            2. Vibrational Energy Levels
               1. Normal Modes
               2. Harmonic Oscillator Model
            3. Rotational Energy Levels
               1. Rigid Rotor Model
               2. Rotational Quantum Numbers
            4. Nuclear Spin States
               1. Spin Quantum Number
               2. Magnetic Sublevels
         2. Transitions Between States
            1. Absorption Processes
            2. Emission Processes
            3. Energy Conservation
            4. Transition Probabilities
         3. Born-Oppenheimer Approximation
            1. Separation of Electronic and Nuclear Motion
            2. Implications for Spectroscopy
         4. Selection Rules
            1. Allowed Transitions
            2. Forbidden Transitions
            3. Symmetry Considerations
         5. Transition Dipole Moment
            1. Electric Dipole Transitions
            2. Magnetic Dipole Transitions
            3. Role in Transition Probability