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 (1s3d ¹ D-1s 2p ¹ P) 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 1s 3d ¹ D (53%), cascade excitation through 1s4f (26%), 1s 5g (12%), and 1s5f-levels (6%) contributes significantly to the magnetic depolarization signal. From the signal widths the radiative lifetimes of the 1s4f-levels and 1s5g-levels have been deduced: τ(1s4f)=(74±3)ns, τ(1s5g)=(230±20)ns.     

Fine-structure and tensor polarizabilities of 1snd 3 D levels of He I (n=3 to 7)

Zeitschrift für Physik A Hadrons and nuclei - Using level crossing techniques the fine-structure splittings and tensor polarizabilities of the 1snd 3 D levels of He I withn=3 to 7 have been...     

Radiative lifetimes and tensor polarizabilities of 1s4f 1 F and 1s5f 1 F level of He I

He atoms have been excited by Ne⁺ ion impact and the depolarization of the fluorescence lines at 668 nm and 492 nm by magnetic and electric fields has been studied. The Ne⁺ ion energy could be chosen such that pure cascade level crossing signals were observed. From the widths of magnetic depolarization signals the radiative lifetimes τ(1s4f ¹ F)=74(2) ns and τ(1s5f ¹ F)=133(5) ns have been determined. By investigating the electric field splitting of the magnetic depolarization signals the tensor polarizabilities ¦α _ten(1s4f ¹ F)¦=0.58(1) kHz/(V/cm)² and ¦α _ten(1s5f ¹ F)¦=4.2(1) kHz/(V/cm)² have been deduced. From the latter value a mean frequencyv(1s5g?1s5f)=14.4 GHz of the transitions between the levels of the 1s5f configuration and those of the 1s5g configuration has been derived.α _ten(1s4f ¹ F) depends sensitively on the singlet-triplet mixing in the 1s4f configuration and thus a mixing coefficient could be deduced for this configuration.     

Cascade-free lifetime measurements on the 1s3d-levels of He I

He-atoms have been excited using 35 keV-He⁺-ion-He-atom-collisions. Investigating the electric and magnetic depolarization of fluorescence light, cascade-free lifetime measurements on the 1s 3d ¹ D and³ D-levels of He I have been performed. From our measurements we deduced:τ(3¹ D)=(15.3±0.3)ns,τ(3³ D)=(14.2±0.6)ns.