Hydrogen atom (non relativistic) hydrogen atom was solved for the first time within Feynman's path integral formulation of quantum mechanics. This work greatly extended the range of applicability of Feynman's method. Hydrogen atom A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. In everyday life on Earth, isolated hydrogen atoms (called "atomic hydrogen") are extremely rare. Instead, hydrogen tends to combine with other atoms
Atom laser semiconductors. Another application, which might also benefit from atom lasers, is atom interferometry. In an atom interferometer an atomic wave packet is coherently split into two wave packets that follow different paths before recombining. Atom interferometers, which can be more sensitive than optical interferometers, could be used to test quantum theory, and have such high precision that they may even be able to detect changes in space-time. This is because the de Broglie wavelength of the atoms is much smaller than the wavelength of light, the atoms have mass, and because the internal structure of the atom can also be