A significant enhancement of beam-spectroscopy diagnostics is proposed: it is shown that polarization analysis of Lα emission from a neutral hydrogen or deuterium beam allows to measure both the magnetic field pitch angle γp and an effective charge Zeff simultaneously. The suggestion is based on a novel, generalized semiclassical theory of ion impact broadening in high-temperature, magnetized plasmas. A series of generalized theories that the authors had developed recently, represented a significant advancement in accuracy over the standard semiclassical theories. This was achieved by using symmetries of the hydrogenlike quantum systems in electromagnetic fields and treating one component of the dynamic electric microfield much more precisely that the standard theories did. The novelty of the present generalized theory is that the ion impact broadening of magnetically splitted levels of beam atoms is highly anisotropic, resulting in a pronounced angular dependence of widths of π- and σ-components of spectral lines. © 1997 American Institute of Physics.