Summary of Molecular Spectroscopy, Phase Equilibria, and Computational Chemistry

Molecular Spectroscopy

  • Study of molecules using electromagnetic radiation.

  • Provides information on energy levels, shapes, and charge densities.

Energy Components

  • Energy includes: rotational, vibrational, and electronic components.

  • Energy spacing: rotational < vibrational < electronic.

Electromagnetic Spectrum

  • Divided into regions based on wavelength/frequency/energy.

  • Absorption: energy difference calculated as ( E = \frac{hc}{\lambda} ).

  • Emission occurs when transitioning from higher to lower energy levels.

Selection Rules

  • Essential for light absorption: pertain to molecular symmetry and wavefunctions.

  • Two types: gross selection rules; specific selection rules for transitions.

Spectral Types

  1. Raman Spectroscopy: Inelastic scattering of light; studies molecular vibrations.

  2. Microwave Spectroscopy: Probes rotational energies.

  3. Infrared Spectroscopy (IR): Studies vibrational transitions, requires change in dipole moment.

  4. Electronic Spectroscopy: Involves transitions between electronic energy levels.

Born-Oppenheimer Approximation

  • Total energy ( E = Et + Er + Ev + Ee ) (simplified to ( E = Er + Ev + E_e )).

Energy Quantization

  • Energy transitions lead to excitation or emission of spectrum.

  • For rotational levels: ( E_J = \frac{h^2}{8\pi^2I} J(J+1) ).

Vibrational Spectroscopy

  • Vibrational transitions follow: ( E_v = (\nu + \frac{1}{2})h
    u ).

  • Involves harmonic and anharmonic oscillators.

Phase Equilibria

  • Phases depend on temperature, pressure, and concentration.

  • Gibbs Phase Rule: ( F = C - P + 2 ) (Degrees of freedom).

Computational Chemistry

  • Uses simulations to predict molecular properties and reactions.

  • Aims for cost-effective experimental design and insights into molecular behavior.

Key Techniques

  1. Density Functional Theory (DFT): Studies electronic structure.

  2. Ab Initio Methods: Solve Schrödinger Equation.

Applications of Methods

  • Drug design, material science, spectroscopy simulations, and energy research.