Analysis of level-crossing signals after impact excitation of 1snd ³ D levels of He I by He⁺-He collision

Abstract

Level-crossing signals of impact radiation of He I have been analyzed with regard to the determination of excitation matrices. The signals have been registered at various electricfield strengths by sweeping a magnetic field strength ℋ_z through the positions ofΔm=2 crossings of Zeeman substates ofn ³ D ₂ andn ³ D ₃ levels (n=4 and 5) of He I excited by 35keV-He⁺-He collisions. We analyzed the signal amplitudes and signal shapes with regard to a spin-dependence of the excitation matrix usually discarded by theoretical arguments. To this end a parametrization of spin-dependent excitation matrices has been performed, and the dependence of the level-crossing amplitudes on the 19 parameters obtained have been studied. It turned out that the observed relative signal amplitudes can satisfactorily be explained by only two parameters, the two multipole components of orderk=2 andk=4 of the alignment of the orbital angular momentum. Thus in agreement with theoretical estimations no spin-dependence must be taken into account.