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

Abstract

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 l s 3d 1D and 3D-levels of He I have been performed. From our measurements we deduced: z(31D)=(15.3 +0.3)ns, z(33D)=(14.2_+0.6)ns.

Analysis of impact-excited HeI states by applying magnetic and electric depolarization techniques

“…In this case, one may assume that the promoted electron at least partly adapts its velocity to the intermediate molecular system during the close encounter and has finally to return to the target atom. In accord with this picture, various experimental results [34,35] indicate that cascade feeding, is less pronounced for the ~D than for the 3D states of HeI.…”

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

“…The spectral line intensities have been investigated in dependence on magnetic and electric fields ~ and gz directed perpendicular to the ion beam and the direction of observation. The fields ~ and gz have been produced using Helmholtz coils and a pair of plane parallel, circular electrodes as described in [13]. Only for the measurements on the 33D level a special electric field set-up has been developed (Fig.…”

“…He + ions are axially extracted from a hot cathode penning discharge, electrostatically accelerated and focussed on a He-gas target (pressure ~10 -+ Torr). The details of the ion-beam apparatus have been described earlier [13]. In a first step the spectrum of the impact radiation emitted perpendicular to the ion beam has been registrated using a grating monochromator (Perkin Elmer, model 98B) and a photo-multiplier (EMI9558BQ).…”

Excitation of He—41 D-substates by He+- and Ne+-projectiles investigated by level-crossing techniques

“…This correction was confirmed by the analysis of electric field levelcrossing signals. Since alignment transfer due to cascades is strongly suppressed by electric fields [20], the sum of the three amplitudes AI_2,o, AI_I, 1 and AIo, 2 divided by Ioo should equal the cascade-corrected H.…”