Experimental determination of the density matrix describing collisionally produced H(n=3) atoms

An experimental technique and analysis procedure is described for determining the axially symmetric density matrix for collisionally produced H(n=3) atoms by measuring the Stokes parameters which characterize the emitted Balmer-α radiation as a function of axial and transverse electric fields applied in the collision cell. The electric fields induce strong characteristic variations in the Stokes parameters. The 14 independent elements of the density matrix are determined by fitting the observed Stokes parameters with signals calculated from a theoretical analysis of the experiment. The physical interpretation of the density matrix is presented in terms of graphs of the electron probability distribution and the electron current distribution. Examples of the determination of the density matrix are given for 40-, 60-, and 80-keV ${\mathrm{H}}^{+}$+He electron-transfer collisions.