文档介绍：Lecture Notes: Electronic Spectroscopy
Electronic Spectroscopy: Using light absorption to change charge distribution of
electrons about molecule (a lot of energy: often can break bonds)
At equilibrium, molecule is in ground electronic state → lowest energy electronic
state and typically in v=0.
Transitions to higher lying electronic states are panied by changes in v, J.
Selection Rules — Even for diatomics, this plicated
→ conservation of nuclear/spin/total angular momentum.
(In larger molecules: tough to predict.
∂µ
Again absorption requires ≠ 0
∂q
→ change of parity: u ↔ g , change of inversion symmetry to orbitals.
Types of electronic transitions:
Organics: Involving π, σ, n electrons
pounds
σ→σ∗, n →σ∗: deep UV (<250 nm)
−−+
Double bonds/unsaturated systems— C C C C
∗
less energy to π+ + −
π→π∗, n →π∗ transitions : UV and
visible (200-700 nm) + + −
C O C O
−−+
anics: Additionally, transitions between d orbitals split by presence of
ligand field.
d-d transition
Charge transfer transition: Electron moves between ligand and metal.
One must act as donor and other as acceptor
−
MnO4
Electronic Spectra of Diatomics
• Electronic absorption also carries vibrational and rotational structure.
• Typically in a ground electronic state with v=0, you have transitions to excited
electronic