1. Model systems

The two simplest atomic and molecular systems are, respectively, the hydrogen atom and the molecular ion ${\mathrm{H}}_2^{+}$ . Their study is of great importance, as they are the only systems that can be treated without approximation, and for which exact solutions are known.

Historically, these two systems have demonstrated the validity of quantum mechanics, thanks to the perfect convergence between experimental results and theoretical predictions. While Bohr's model of the atom led to satisfactory results overall, there were still a few unexplained points that Schrödinger's theory was able to integrate. These systems also have the major advantage of serving as models for the study of more...