Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Josep Taron Roca
Quantum Mechanics are used to describe how hydrogen ground state is split in two when the interaction between electron and proton's spins are considered. Using perturbation theory, the energetic difference between those levels is calculated. The corresponding wavelength is found to be close to = 21 cm. Lifetime of the decay is also calculated considering Fermi's Golden Rule. Some applications are discussed.