CHEM 214 Study Guide - Final Guide: Internal Conversion, Photoexcitation, Singlet Oxygen
Document Summary
Spin: unlikely to change during radiative transition (no multiplicity change). This means that the spins for singlet states will remain paired even though the electrons are no longer in the same orbital. Overlap: orbitals involved in transitions must have spatial overlap. Symmetry: requirements on the types of states that can be coupled by light (tough to analyze: nuclear coordinates rules: franck-codon principle. Initial vibrational state: ground vibrational state is the ground electronic state (n=0) Final vibrational state: electronic transitions do not restrict change in n, can take any value. Less likely to do transition into higher vibrational states because nuclei are further apart in higher vibrational states. S0 n=0 => s1 n=0: equilibrium bond length in excited state is longer (shifted) Molecule ends up compressed after electronic excitation, and it vibrates significantly after photon absorption. When it emits light, the process produces an elongated ground state.