Stark beats of Lyman-α emission of foil-excited hydrogen atom

The Stark beats of Lyman-α emission due ton=1 ? 2 transition of hydrogen atom have been studied by the beam-foil method. After passage through a thin carbon foil, the static electric field of 500 V/cm was applied to the beam in the direction either parallel to or anti-parallel to the the beam velocity. The linearly polarized emission was measured by using a toroidal mirror at a Brewster's angle reflection. When the direction of the applied electric field is reversed, an appreciable phase shift was observed. The analysis of the data leads to the complete determination of the density matrix of the H(n=2) atoms at the time of their production.