In molecular physics, the molecular term symbol is a shorthand expression of the group representation and angular momenta that characterize the state of a molecule, i.e. its electronic quantum state which is an eigenstate of the electronic molecular Hamiltonian. It is the equivalent of the term symbol for the atomic case. However, the following presentation is restricted to the case of homonuclear diatomic molecules, or symmetric molecules with an inversion centre. For heteronuclear diatomic molecules, the u/g symbol does not correspond to any exact symmetry of the electronic molecular Hamiltonian. In the case of less symmetric molecules the molecular term symbol contains the symbol of the group representation to which the molecular electronic state belongs.
It has the general form:
where
- S is the total spin quantum number
- Λ is the projection of the orbital angular momentum along the internuclear axis
- Ω is the projection of the total angular momentum along the internuclear axis
- u/g is the parity
- +/− is the reflection symmetry along an arbitrary plane containing the internuclear axis
Read more about Molecular Term Symbol: Λ Quantum Number, Ω and Spin–orbit Coupling, Reflection Through A Plane Containing The Internuclear Axis, Reflection Through An Inversion Center: U and G Symmetry, Alternative Empirical Notation
Famous quotes containing the words term and/or symbol:
“As the term of my relief from this place [Washington, D.C.] approaches, it’s drudgery becomes more nauseating and intolerable, and my impatience to be with you at Monticello increases daily.”
—Thomas Jefferson (1743–1826)
“The symbol of perpetual youth, the grass-blade, like a long green ribbon, streams from the sod into the summer, checked indeed by the frost, but anon pushing on again, lifting its spear of last year’s hay with the fresh life below. It grows as steadily as the rill oozes out of the ground.... So our human life but dies down to its root, and still puts forth its green blade to eternity.”
—Henry David Thoreau (1817–1862)