Chemistry Notes for B.Sc. and M.Sc.

Gross selection rule   tells whether a molecule will be active or inactive in a particular Spectroscopy.   Specific selection rule tells about the allowed changes in the magnitude of energy when it is active in a particular Spectroscopy.     Rotational or Microwave Spectroscopy Gross selection rule: permanent dipole moment  Specific selection rule: ∆J = +1 or -1 ( for rigid rotor) 2. Vibrational or IR Spectroscopy Gross selection rule: change in dipole moment during vibrations Specific selection rule: ∆v = +1 or -1 ( for harmonic oscillator) 3. Raman Spectroscopy Gross selection rule: change in polarizability  Specific selection rule:   ∆J = 0, +2 or -2   ∆v = +1 or -1  4. Electronic or UV-Visible Spectroscopy Gross selection rule: No stringent rule Specific selection rule: ∆s = 0  and ∆l = +1 or -1 5. Nuclear Magnetic  Resonance or Radio waves Spectroscopy Gross selection rule: nuclear spin should be no zero  Specific se...