EXPERIMENTAL-DETERMINATION OF REAL ELEMENTS OF THE DENSITY-MATRIX ANDTHE DIPOLE-MOMENT OF H(N=3) ATOMS PRODUCED FROM 20-100 KEV H+ ON AR

Diagonal and real off-diagonal coherence elements of the density matri x for H(n = 3) atoms produced in 20- 100-keV electron-capture collisio ns of protons with Ar atoms are experimentally determined. Balmer-alph a light from the decay of H atoms from the (n = 3) state to the (n = 2 ) state is observed. The intensity and polarization of the light as a function of an axially symmetric electric field in the collision regio n are fitted to a numerical model of the H atom in an electric field i n order to extract density-matrix elements. A new polarimeter, using a photoelastic modulator in conjunction with photon-counting techniques , is used in the experiment, and its efficacy is analyzed and compared to that of a rotating quarterwave plate polarimeter previously used i n similar experiments. The diagonal elements of the density matrix yie ld relative capture cross sections for the H(31) angular-momentum subs tates, while the coherence terms are used to determine the dipole mome nt of the atoms produced. Results are compared to those for protons co lliding with & He target and the differences are discussed.