Term Symbols
Term symbols are used to represent the states and spectral transitions of atoms, they are found from coupling of angular momenta mentioned above. When the state of an atom has been specified with a term symbol, the allowed transitions can be found through selection rules by considering which transitions would conserve angular momentum. A photon has spin 1, and when there is a transition with emission or absorption of a photon the atom will need to change state to conserve angular momentum. The term symbol selection rules are. ΔS = 0, ΔL = 0, ±1, Δl = ± 1, ΔJ = 0, ±1
The expression "term symbol" is derived from the "term series" associated with the Rydberg states of an atom and their energy levels. In the Rydberg formula the frequency or wave number of the light emitted by a hydrogen-like atom is proportional to the difference between the two terms of a transition. The series known to early spectroscopy were designated sharp, principal, diffuse and fundamental and consequently the letters S, P, D, and F were used to represent the orbital angular momentum states of an atom.
Read more about this topic: Angular Momentum Coupling
Famous quotes containing the words term and/or symbols:
“No—is a term very frequently employed by the fair, when they mean everything else but a negative. Their yes is always yes; but their no is not always no.”
—Anonymous, U.S. women’s magazine contributor. M, Weekly Visitor or Ladies Miscellany, p. 203 (April 1803)
“The use of symbols has a certain power of emancipation and exhilaration for all men. We seem to be touched by a wand, which makes us dance and run about happily, like children. We are like persons who come out of a cave or cellar into the open air. This is the effect on us of tropes, fables, oracles, and all poetic forms. Poets are thus liberating gods.”
—Ralph Waldo Emerson (1803–1882)