Hyperfine quenching and precision measurement of the 2P03-2

Abstract

The hyperfine-quenched transition 2 3 /Vl 'So has been observed in heliumlike gadolinium (Gd 62+ ) in the two isotopes ,55 Gd and ,57 Gd. The lifetime for the transition (to) has been measured for each isotope and found to be r 0 (l55) = 13.43(27)x 10" l2 sec and r 0 (l57) =7.65(55)x 10" ,2 sec. From the measured lifetimes a value is inferred for the absolute value of the 2 3 Po-2 3 P\ fine-structuring splitting |A£o-i| in Gd 62+ with the result |AEo-i| = 18.57(19) eV, where the error represents 1 standard deviation. This result is compared with calculations based on the multiconfiguration Dirac-Fock method and on the unified method. PACS numbers: 32.30.Rj, 12.20.Fv, 31.30.Jv, 32.70.FwThe splittings of the I s Pj levels [l] in two-electron ions (AEJ.J) are determined largely by the electron-electron interaction. The measurement of these splittings constitutes, therefore, a test of theories of this interaction in the simplest atomic system in which it can be observed. Because of the rapid scaling of the relativistic part of this interaction with atomic number Z, measurements at high Z provide a particularly sensitive test of the relativistic theory. Calculations of the fine-structure splittings generally include the effects of relativity by a perturbation expansion in the parameter (Z«) 2 . The problems associated with this approach at high Z are illustrated by the fact that in ordinary helium (Z=2) the calculations [2] are accurate at the ppm level, whereas the most elaborate calculations [3,4] at Z=64 are accurate at only the few percent level. Accurate experimental measurements performed at high Z can therefore act to stimulate further theoretical work in including relativistic effects in the calculation of two-electron energy levels.Accurate experimental measurements of the two-electron fine-structure splittings in the I s Pj multiplet have been performed in He and Li + using radio-frequency spectroscopy [5] and laser spectroscopy [6]. The extension of laser spectroscopy to the heliumlike ion F 7+ was achieved by Myers et al.[7], who measured the interval 2 3 / > i-2 3 / > 2 (AE1.2). However, extension of the laser method to much higher Z is experimentally not feasible. Indirect measurements using x-ray and UV spectroscopy have been performed and are summarized in review articles by Martin [8] and Desequelles [9], but such measurements have not been very precise. So far there have been no measurements reported with sufficient precision to examine the theoretical predictions at high Z. In thisLetter we describe the first measurement at high Z with a precision smaller than the current theoretical accuracy.The measurement reported here is of the interval AEo.\ in the two-electron ion Gd 62+ . Gadolinium has a number of stable even-even isotopes with nuclear spin 7=0. For these isotopes, the radiative decay 2 3 /Vl '-So is strictly forbidden and the 2 3 / > o state undergoes E\ decay to the 2 3 S1 state with a calculated lifetime [10] of r(2 3 / > 0 ) =0.339xl0~9 sec. Gadolinium also has two stable isotopes ( ,55 ...

Magnetic-field- and hyperfine-induced P03−S01 transitions in Be- and Ne-like ions

“…A number of recent papers present rates of HITs [3,[12][13][14][15][16][17][18][19][20] in the absence of magnetic fields. For HIT, experimental and theoretical studies for He-like ions [21][22][23][24][25][26][27][28][29] and Ni-like Xe [15,[30][31][32] are in good agreement. The resulting rate for Be-like N by Brage et al [33], obtained by modeling of a planetary nebulae, are also in agreement with theory, albeit with fairly large experimental uncertainty.…”

Storage-Ring Measurement of the Hyperfine InducedTi18+47(2s2p P0Schippers1, Ew2, Bernhardt3 et al. 2007Phys. Rev. Lett.802611View full textAdd to dashboardCite

“…However, in contrast to the present case they do not represent the only radiative decay path, but compete with allowed transitions such as 1s2p 3 P 0 -1s2s 3 S 1 . Moreover, the resulting lifetimes are generally much shorter than in a divalent system with comparable valence shell and nuclear charge; the HFI decay rate variations studied so far for the 1s2p 3 P 0 -1s 2 1 S 0 line are in the range of 10 7 -10 12 s −1 [13,14,15,16].…”

Two-photonE1M1decay of23P0s

“…Twophoton E1M1 rates are also expected to be significant for heavy two-electron ions other than U +90 and calculations are needed. To date, the only ion with Z > 50 for which a measurement of hyperfine quenching has been made is heliumlike gadolinium [2]; for the isotope 155 Gd, the E1M1 correction to the lifetime is only 0.08%.…”

“…In recent years, accurate calculations of decay rates of 2 3 P 0 states of heliumlike ions have been performed for nuclear charges Z ≤ 94, with [1,2] and without [3] consideration of hyperfine quenching. Single photon decay of the 2 3 P 0 state to the ground state is strictly forbidden by angular momentum selection rules and only a weak E1 decay to the 2 3 S 1 state or an even weaker M1 decay to the 2 3 P 1 state is possible for isotopes with nuclear spin I = 0.…”