Triplet-singlet interaction in the 1s 2s3S1 hyperfine splitting of he-like Li+

The hyperfine structure (hfs) interaction between the metastable 2³ S ₁ and 2¹ S ₀ states in^{6, 7}Li⁺ causes very small equal and opposite energy level shifts,δ, in the two levels having the same total angular momentum quantum numberF=I. This amounts to 12ppm with respect to the total hfs splitting of 30 GHz for the⁷Li⁺ 2³S₁ state and has been measured for the first time directly for the case of a core-free electronic system by combined laser-microwave spectroscopy. A new calculation ofδ with accurate integral-transform 2¹ S ₀ and 2³S₁ wave functions is reported. Configuration interactions and electron exchange and correlation effects, which differ for parallel (³ S ₁) and antiparallel (¹ S ⁰) spins, are treated in detail in order to obtain very good agreement between measured and theoretical values for this tiny perturbation. A complete understanding ofδ is indispensable for extracting fundamental constants from two-electron spectroscopic data.     

Shell model analysis of the magnetic hyperfine splitting in muonic thallium

The magnetic hyperfine splitting of the ground and first excited state in muonic²⁰³Tl and²⁰⁵Tl is calculated on the basis of the shell model with configuration mixing. Fair agreement with the recently measured ground state splitting is found.     

Precision measurement of the 2p-1s transition in muonic C: Search for new muon-nucleon interactions or accurate determination of the rms nuclear charge radius

The wavelength of the 2p3/2-ls1/2 transition in muonic ¹²C was measured with a crystal spectrometer as 16.473765 (88) pm. With an improved model-independent analysis we deduce an rms charge radius for ¹²C of 2.4829 (19) fm. A 2.4 standard deviation difference between our rms charge radius and that deduced from recent elastic electron-scattering experiments is tentatively attributed to a short-range additional interaction between muon and nucleons. A comparison is made with other experiments yielding information on such interactions.     

Measurement of the 8S hyperfine splitting in cesium

The Cs 8S level hfs splitting δ₈ has been measured. The experimental value δ₈ = (900 ± 60) MHz is in good agreement with both other experimental results and theoretical predictions.     

Search for the metastable 2s state in muonic hydrogen

Results of an experiment to search for the metastable 2s state in muonic hydrogen at 150 and 600 Torr are presented. About 6% of all ωp formed go to the 2s state. Most of these (ωp)_{2 s} decay in less than 100 nsec; assuming a calculated lifetime of 2 ωsec at 150 Torr (0.5 ωsec at 600 Torr) for the long-lived fraction f of all 2s states, we find f to be less than 4% (16%) with 90% confidence level.     

Self-energy correction to the hyperfine splitting of the 1 s and 2 s states in hydrogenlike ions

The one-loop self-energy correction to the hyperfine splitting of the 1 s and 2 s states of hydrogenlike ions is calculated for both point and finite nuclei. The results of the calculation are combined with other corrections to find the ground state hyperfine splitting in lithiumlike ²⁰⁹Bi⁸⁰⁺ and ¹⁶⁵Ho⁶⁴⁺. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 19–22 (10 July 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Long-lived population of the metastable 2s state in muonic hydrogen

Preliminary experimental results of the search for long-lived metastable μp(2s) are presented. The μp(2s) are identified via muon transfer to neon in a gas mixture of hydrogen and several percent of neon at mbar pressures. An energy-dependent 1s transfer rate to neon has been observed. The time spectra can only be explained assuming a nonzero μp(2s) population. This revised version was published online in August 2006 with corrections to the Cover Date.     

Spin exchange polarization and measurement of the hyperfine splitting of short-lived8Li

Free⁸Li (T _1/2=0.84 sec) atoms were polarized by spin exchange with optically pumped rubidium vapour. The⁸Li nuclei were produced by the reaction⁷Li(d, p)⁸Li in a thin LiF target. They recoiled into helium which was used as a buffer gas for optical pumping as well. Nuclear polarization up to 2% was detected by β-decay asymmetry. Rf transitions between hfs levels of the atomic ground state yielded the hfs separation ΔW=382.543(7) MHz. The nuclear spin assignmentI=2 was confirmed.     

Precise determination of the ground state hyperfine splitting of135Ba+

A microwave-optical double resonance experiment has been performed on¹³⁵Ba⁺ ions, confined in a r.f. quadrupole trap. Linewidths as narrow as 0.9 Hz have been obtained on the 7.18 GHz,F=1,m=0 toF=2,m=0 transition. Shifts of the resonance frequency due to magnetic stray fields and the electric trapping field have been observed. The final result, extrapolated to zero field strengths, isΔ υ _HFS=7183340234.90(0.57) Hz.     

Self-energy contribution to the ground state hyperfine splitting of Bi82+

The self-energy contribution to the hyperfine splitting of the ground state of Bi⁸²⁺ is calculated for a point nucleus. It is found that the theoretical value of the wavelength of the ground-state hyperfine-splitting transition of ²⁰⁹Bi⁸²⁺ is λ=244(1) nm and is in good agreement with experiment. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 309–310 (10 March 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Measurement of the hyperfine splitting of the 9 S1/2 level in Cesium by Doppler-free two-photon spectroscopy

The hyperfine splitting for the ¹³³Cs isotope for the 6s ²S_1/2 → 9s ²S_1/2 transition has been measured using Doppler-free two-photon fluorescence spectroscopy in a gas cell for the first time to our knowledge. The hyperfine splitting between the two components was measured to be 8754 (1) MHz and the magnetic dipole coupling constant (A) for the excited 9s ²S_1/2 level was determined to be 109.7 (3) MHz for the ¹³³Cs isotope. The measured values are in good agreement with the earlier reported results.     

Two-particle correlations and the origin of intermittency in muon-nucleon interactions

The relation between two-particle correlations, in particular the Bose-Einstein effect, and the intermittency signal is investigated in muon-nucleon scattering at 280 GeV using data of the European Muon Collaboration. From a comparison of the second factorial moments for unlike and negative charges with each other and with the predictions of the Lund model it is concluded that the observed intermittent behaviour is due to Bose-Einstein interference.     

铯原子7S1/2态磁偶极超精细常数的测量

在室温下的原子气室中, 基于铯原子6S_1/2-6P_3/2-7S_1/2(852.3 nm+1469.9 nm) 阶梯型能级系统, 利用电光调制器的主频和±1级边带分别产生的三套双共振吸收光谱, 当驱动电光调制器的信号源频率严格等于7S_1/2态超精细分裂的能级间隔时, 三套谱线中的一些超精细跃迁谱线重叠且线宽最窄, 利用这一现象很好地避免了激光器频率扫描时非线性效应的影响, 测量出了7S_1/2 态超精细分裂能级间隔: 2183.72 MHz±0.23 MHz, 并计算出该态的磁偶极超精细常数: A_hfs= 545.93 m MHz±0.06 MHz, 与文献中报道的测量结果一致.     

Measurement of the hyperfine structure splitting for the 4 and 52 P 1/2 states of sodium using radio-frequency spectroscopy

The hyperfine-structure splitting for the 4 and 5² P ^1/2 states of sodium was measured using step-wise laser excitation combined with rf-resonance techniques. The magnetic dipole interaction constants were found to be a(4² P _1/2)=30.4(5) MHz and a(5₂ P _1/2) =13.3(2) MHz. The results are compared with a theoretical calculation, taking polarization effects into account.     

A measurement of the ground state hyperfine splitting for Li-like fluorine ions by nuclear quantum beats

The technique of nuclear quantum beats (perturbed angular correlations) has been applied to the investigation of the hyperfine splitting of the²S_1/2 ground state in Li-like fluorine ions. Using the 197 keV state in¹⁹F as a probe, a value of 73.1 (1.5) GHz was found for the hf splitting. This result is compared with theoretical predictions.     

On the hyperfine structures of the ground state(s) in the <Superscript>6</Superscript>Li and <Superscript>7</Superscript>Li atoms

The hyperfine structure of the ground 2²S-states of the three-electron atoms and ions is investigated. By using our recent numerical values for the doublet electron density at the atomic nucleus, we determine the hyperfine structure of the ground (doublet) 2²S-state(s) in the ⁶Li and ⁷Li atoms. Our predicted values (228.2058 and 803.5581 MHz, respectively) agree well with the experimental values 228.20528(8) MHz (⁶Li) and 803.50404(48) MHz (⁷Li [R.G. Schlecht and D.W. McColm, Phys. Rev. 142, 11 (1966)]). The hyperfine structures of a number of lithium isotopes with short lifetimes, including ⁸Li, ⁹Li, and ¹¹Li atoms are also predicted. The same method is used to obtain the hyperfine structures of the three-electron ⁷Be⁺ and ⁹Be⁺ ions in their ground 2²S-states. Finally, we conclude that our approach can be generalized to describe the hyperfine structure in the triplet n³S-states of the four-electron atoms and ions.     

Anisotropy of hyperfine interactions as a tool for interpretation of NMR spectra in magnetic materials

Approach for interpretation of nuclear magnetic resonance (NMR) spectra in magnetic materials is presented, consisting in employing the anisotropy of hyperfine interaction. The anisotropic parts of hyperfine magnetic fields on ⁵⁷Fe nuclei are calculated ab initio for a model example of lithium ferrite and utilized to assign the experimental NMR spectral lines to iron sites in the crystal structure.