Heisenberg has discussed the coupled double harmonic oscillator, and has shown that the ordinary rules of quantization lead to two non-combining sets of states in one of which the electrons are in phase and out of phase. The energy of the system is successively transferred from one to the other - resonance!
Linus PaulingWe may, I believe, anticipate that the chemist of the future who is interested in the structure of proteins, nucleic acids, polysaccharides, and other complex substances with high molecular weight will come to rely upon a new structural chemistry, involving precise geometrical relationships among the atoms in the molecules and the rigorous application of the new structural principles, and that great progress will be made, through this technique, in the attack, by chemical methods, on the problems of biology and medicine.
Linus Pauling