Collision Spectroscopy of Quartet and Doublet Transitions in doubly excited Ne⁷⁺

Abstract

We present the observation of VUV transitions between doubly excited states of Ne7+. Spectra were selectively produced by single electron capture in a cesium vapor by Ne8+ ions prepared in the metastable state 1s2s 3S by a previous collision of a Ne9+ beam with a gas target. The observed lines were assigned to 1s2l2l' → 1s2lnl'' and 1s2l3d → 1s2lnf electric dipole transitions. Furthermore, the forbidden electric quadrupole transition 1s2s2p 4Po-1s2p3d 4Fo has been identified at 78.71Å.

Low-lying quartet states in Li-like neon

“…Denis et al [20] previously observed Ne VIII 1s2s2p 4 P o -1s2s4d 4 D at 64.7 Å. We enhance the accuracy to 64.42 ± 0.03 Å, in agreement with the predicted value of 64.43 ± 0.09 Å.…”

“…Not only does the low transition probability preclude our observing this transition in our spectra, it is blended with strong lines coming from Ne VI 1s 2 2s2p 2 4 P -1s 2 2s2p4d 4 D o [32] and with an unknown line from Ne VII ions at 97.25 ± 0.02 Å which could come from a quintet transition [33]. Denis et al [20] observed this two-electron transition at 97.03 Å. This value does not correspond to the usual deviation from our SOCHFR calculations.…”

“…The linear regressions along the isoelectronic sequence give for these transitions, 92.21 ± 0.03 Å without considering Mg X, 83.77 ± 0.03 Å and 86.85 ± 0.03 Å without Si XII. Denis et al [20] observed this latter line at 86.89 Å in first order and at 86.86 Å in second order. Generally, their third and second order observations are the closest to our results.…”

“…Nevertheless as previously discussed for lifetime measurements, the shape of the decay curve of this line does not show strong non-linear behaviour caused by the picosecond lifetime of the doublet on a semi-logarithmic graph (figure 8) as does the one for 1s2s3d 4 D in figure 7. In electron-transfer collision spectroscopy, Denis et al [20] did not mention any of these doublet transitions even though the n = 3 electrons with high angular momenta are favoured as suggested by the absence of the quartet transition discussed previously.…”

“…Mg X, Al XI and Si XII by Blanke et al [13] and Si XII, S XIV and Ar XVI by Khardi et al [14] and even the triply excited state 2p 3 4 S o from He − to C IV [15][16][17] have also been investigated. Nevertheless, studies of the transitions from the low-lying states in Li-like neon are still scarce [18][19][20], although Rydberg ISEQUAS in UV and visible beam-foil spectra have been recently reported [21]. Whereas transition wavelength calculations already exist [22], systematic studies to be published have been undertaken only for transitions Ne VIII 1s2l3d 4 L-1s2l4f 4 (L + 1); l = s, p [23].…”