Atom of Ernest Rutherford, bombarded a metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.
Atom interferometer the group around Pritchard at MIT. Shortly afterwards, an optical version of Ramsey spectrometer typically used in atomic clocks was recognized also as an atom interferometer at the PTB in Braunschweig, Germany. The largest physical separation between the partial wave packets of atoms was achieved using laser cooling techniques and stimulated Raman transitions by S. Chu and coworkers in Stanford. The first team to make a working model, Pritchard's, which included D.W. Keith, prompted Keith to leave atomic physics after achieving success, in part because one of the most obvious applications for atom interferometry was in highly accurate gyroscopes for