Rabi's method was an improvement over Stern-Gerlach. As shown in the figure, the source emits a beam of neutral atoms, having spin angular momentum ℏ ℏ / 2 . The beam passes through a series of three aligned magnets. Magnet 1 produces an inhomogeneous magnetic field with a high gradient ∂ ∂ B ∂ ∂ z (as in Stern–Gerlach), so the atoms having 'upward' spin (with S z = ℏ ℏ / 2 ) will deviate downward (path 1), i.e. to the region of less magnetic field B, to minimize energy. Atoms with 'downward' spin with S z = − − ℏ ℏ / 2 ) will deviate upward similarly (path 2). Beams are passed through slit 1, to reduce any effects of source beyond. Magnet 2 produces only a uniform magnetic field in the vertical direction applying no force on the atomic beam, and magnet 3 is actually inverted magnet 1. In the region between the poles of magnet 3, atoms having 'upward' spin get upward push and atoms having 'downward' spin feel downward push, so their path remains 1 and 2 respectively. These beams pass through a second slit S2, and arrive at detector and get detected.