Hyperfine Splitting of the 2s1/2 and 2p1/2 Levels

Abstract

High-resolution spectroscopy of the 2s(1/2)-2p(1/2) transition in the extreme ultraviolet region is shown to resolve the level splitting induced by the nuclear magnetic field of both the 2s(1/2) and the 2p(1/2) levels in lithiumlike (141)Pr(56+) and of the 2s(1/2)2p(1/2) (3)P(1) level in berylliumlike (141)Pr(55+). The (141)Pr ions are an ideal test of this measurement approach because their energy levels are known well from first principles and are unaffected by small energy contributions from QED and nuclear magnetization effects. The accuracy attained in the measured 196.5 ± 1.2 meV 2s(1/2) splitting is more than an order of magnitude better than that achieved before using crystal spectroscopy of the 2s(1/2)-2p(3/2) x-ray transition and at the level needed to implement a proposed scheme for disentangling the contributions from QED and nuclear magnetization effects in higher-Z ions, such as (209)Bi.

Highly charged ions: Optical clocks and applications in fundamental physics

“…As already mentioned, an important boost to the field of optical spectroscopy with HCI occurred as both ion storage rings (Klaft et al, 1994;Seelig et al, 1998) and EBITs (Beiersdorfer et al, 2001;Crespo López-Urrutia et al, 1996 reported HFS measurements in hydrogenlike ions of heavy elements. It was clear that scaling laws would shift the 21 cm microwave transition of atomic hydrogen into the optical region, and reduce its enormous 11 million years lifetime to milliseconds.…”

“…The first direct observation of a hyperfine splitting (HFS) in the optical range was achieved by resonant laser excitation of the M1 transition coupling the two hyperfine levels of the ground state of hydrogenlike 209 Bi 82+ ions circulating at relativistic velocities in the GSI heavy-ion storage ring ESR (Klaft et al, 1994), followed by spontaneous-emission measurements of 187 Ho 66+ (holmium, Z = 67) ), 185,187 Re 74+ (rhenium, Z = 75) ((Crespo López-Urrutia et al, 1998a)), and 203,205 Tl 80+ (thallium, Z = 81) (Beiersdorfer et al (2001)) ions trapped in an EBIT, and a further experiment on 207 Pb 81+ (Seelig et al, 1998) at ESR. In all those experiments, systematic effects, low resolution and statistics limited the relative wavelength accuracies to about 1 × 10 −4 .…”

“…Experiments are already approaching this level of accuracy, e.g. for the 2s 1/2 → 2p 1/2 EUV hyperfine transitions in Li-like and Be-like ions of 141 Pr (Beiersdorfer et al, 2014). Karpeshin and Trzhaskovskaya (2015) have proposed the opposite approach, namely to investigate the nuclear magnetization distribution based on the HFS experimental data for various isoelectronic sequences, as had been demonstrated by Beiersdorfer et al (2001); Crespo López-Urrutia et al (1998a) for the cases of Re and Tl HCI.…”

“…III.B, tests of QED in strong fields were the main interest of the community, and theoretical work aimed at disentangling contributions from two-loop QED, nuclear recoil effects and nuclear magnetization distribution in the measured transitions. Lacking sufficient accuracy, models of nuclear magnetization were deemed far more uncertain than the dominant first order QED contributions, thus leading to the application of the HFS data to determining nuclear magnetic radii (Beiersdorfer et al, 2001;Crespo López-Urrutia et al, 1998b).…”

Guest Editor’s Notes on the “Atoms” Special Issue on “Perspectives of Atomic Physics with Trapped Highly Charged Ions”

“…The team at GSI has tried to induce this transition for many years, and only recently a resonance has been seen, the frequency of which still needs to be located with accuracy in the rest frame of the speedy ion [49,50]. Concurrently the Livermore SuperEBIT has provided EUV/soft-x-ray spectra of 2s-2p 3/2 and 2s-2p 1/2 line multiplets in Bi and Pr from which the hyperfine splitting of the 2s 1/2 and the 2p 1/2 electrons could be determined [51][52][53]. The hyperfine intervals make up only a fraction of the EUV transition energy, and, consequently, the accuracy of the determination of the hyperfine interval is lower than what ultimately the direct laser resonance experiment should be able to achieve.…”