CASCADE-FLUORESCENCE SPECTROSCOPY ON IMPACT-EXCITED HE-ATOMS USING LEVEL-CROSSING TECHNIQUES

He atoms have been excited by 35 keV-Ne+ ions, and magnetic depolarization signals of the induced fluorescent light at 667.8nm (1 s3 d1D-1 s 2 p1P) have been investigated. By applying suitable electric fields in addition to the variable magnetic field, the complicated superposition structure of the depolarization signal resulting from cascade processes could be analyzed. Beside direct excitation of 1 s 3 d1D (53%), cascade excitation through 1 s4 f (26%), 1 s 5 g (12%), and 1 s5 f-levels (6%) contributes significantly to the magnetic depolarization signal. From the signal widths the radiative lifetimes of the 1 s4 f-levels and 1 s5 g-levels have been deduced: τ(1 s4 f)=(74±3)ns, τ(1 s5 g)=(230±20)ns. © 1979 Springer-Verlag.