Foil Angle Dependence of Anisotropic Excitation at Large Inclination Angles

The dependence of orientation and alignment parameters on foil inclination angle represents an important means of testing theories of the production of excited level anisotropy. Such dependences have been extended to angles of 80 degrees or more, usually at a constant incident ion energy. However, the increased target thickness arising from the foil inclination can significantly alter the mean energy and velocity distribution of the emerging ions. The energy dependence of the anisotropy generation process is sufficiently large to alter the angular dependence in certain cases. A study of the orientation and alignment of the 4d 1D2 level of fast helium atoms at several incident energies illustrates the significance of foil thickness effects.