Hyperfine Structure Measurements Research Articles

Hyperfine structure and isotope shifts of the (4s2)S01→(4s4p)P11 transition in atomic zinc

We report absolute frequency, isotope shift, radiative lifetime, and hyperfine structure measurements of the (4s2)S01→(4s4p)P11 (213.8 nm) transition in Zn I using a cryogenic buffer gas beam. Laser-induced fluorescence is collected with two orthogonally oriented detectors to take advantage of differences in the emission pattern of the isotopes. This enables a clear distinction between isotopes whose resonances are otherwise unresolved, and a measurement of the Zn67 hyperfine structure parameters, A(Zn67)=20(2)MHz and B(Zn67)=10(5)MHz. We reference our frequency measurements to an ultralow expansion cavity and achieve an uncertainty at the level of 1 MHz, about 1 percent of the natural linewidth of the transition. Published by the American Physical Society 2024

Hyperfine structure measurements for neutral and singly ionized terbium by Fourier-transform spectroscopy

Fourier transform spectrum and its fit with the colored arrows indicating individual hyperfine structure components distinguished by the transition rules.

Improved Measurements of Muonic Helium Ground-State Hyperfine Structure at a Near-Zero Magnetic Field.

Muonic helium atom hyperfine structure (HFS) measurements are a sensitive tool to test the three-body atomic system and bound-state quantum electrodynamics theory, and determine fundamental constants of the negative muon magnetic moment and mass. The world's most intense pulsed negative muon beam at the Muon Science Facility of the Japan Proton Accelerator Research Complex allows improvement of previous measurements and testing further CPT invariance by comparing the magnetic moments and masses of positive and negative muons (second-generation leptons). We report new ground-state HFS measurements of muonic helium-4 atoms at a near-zero magnetic field, performed for the first time using a small admixture of CH_{4} as an electron donor to form neutral muonic helium atoms efficiently. Our analysis gives Δν=4464.980(20) MHz (4.5ppm), which is more precise than both previous measurements at weak and high fields. The muonium ground-state HFS was also measured under the same conditions to investigate the isotopic effect on the frequency shift due to the gas density dependence in He with CH_{4} admixture and compared with previous studies. Muonium and muonic helium can be regarded as light and heavy hydrogen isotopes with an isotopic mass ratio of 36. No isotopic effect was observed within the current experimental precision.

Hyperfine structure measurements on a forbidden transition of Bi I using fourier transform spectroscopy

Hyperfine structure (hfs) investigations have been performed on a forbidden transition of the Bi I emission spectral line in the visible region at 15,437.49 cm−1, between the levels 6p3 4S3/2 and 6p3 2D5/2, by means of a Fourier Transform spectrometer. Electrodeless discharge lamps (EDL) containing BiI3 were utilized to generate the bismuth plasma. In these observations, all the 6 components of electric quadrupole (ΔF = ±2) transitions have been detected for the first time, in addition to the 12 components of magnetic dipole (ΔF = 0, ±1) transitions. Magnetic dipole constant (A) and electric quadrupole constant (B) have been derived for the combining levels.

In-gas-jet laser spectroscopy with S[formula omitted]-LEB

The Super Separator Spectrometer-Low Energy Branch (S3-LEB) is a low-energy radioactive ion beam experiment under commissioning as part of the GANIL-SPIRAL2 facility. It will be used for the production and study of exotic nuclei by in-gas laser ionization and spectroscopy (IGLIS), decay spectroscopy, and mass spectrometry. We report recent results from the off-line commissioning of S3-LEB, including first laser spectroscopy measurements in both the gas cell and the supersonic gas jet, the determination of the transport efficiency of laser ions from the gas cell through the RFQ chain, and time-of-flight measurements with the multi-reflection time-of-flight mass spectrometer PILGRIM. The measurements were performed using erbium, introduced by evaporation from a heated filament in the gas environment. The reported laser spectroscopy results include a characterization of the pressure broadening in the gas cell, proof-of-principle isotope shift measurements, and hyperfine-structure measurements.

High-precision measurements of the hyperfine structure of cobalt ions in the deep ultraviolet range

High-precision hyperfine structure measurements were performed on stable, singly-charged ^{59}Co ions at the IGISOL facility in Jyväskylä, Finland using the collinear laser spectroscopy technique. A newly installed light collection setup enabled the study of transitions in the 230 nm wavelength range from low-lying states below 6000 cm^{-1}. We report a 100-fold improvement on the precision of the hyperfine A parameters, and furthermore present newly measured hyperfine B paramaters.

Status of the new muonic helium atom HFS measurements at J-PARC MUSE

Measurements of the muonic helium atom hyperfine structure (HFS) are a sensitive tool to test the theory of three-body atomic systems and bound-state quantum electrodynamics (QED) and to determine fundamental constants of the negative muon magnetic moment and mass. The world’s most intense pulsed negative muon beam at J-PARC MUSE brings an opportunity to improve previous measurements and test further CPT invariance by comparing the magnetic moments and masses of positive and negative muons. Test measurements at D-line are now in progress utilizing MuSEUM apparatus at zero field. The first results already have better accuracy than previous measurements in the 1980s. Also, the investigation of a new experimental approach to improve HFS measurements by repolarizing muonic helium atoms using a spin-exchange optical pumping (SEOP) technique was started. If successful, this would drastically improve the measurement accuracy.

New beamlines and future prospects of the J-PARC muon facility

At the J-PARC muon facility (MUSE), new beamlines started operation recently. H-line is a high-intensity pulsed muon beamline for fundamental physics experiments. The first beam of the H-line was delivered to its first branch (H1 area) in January 2022, where a precise measurement of the muonium hyperfine structure and a search for μ-e conversion will be conducted. Further extension of the second branch of the H-line for a muon g-2/EDM experiment and a transmission muon microscope project is also ongoing. In addition, the second branch of the surface muon beamline (S2 area of the S-line) was opened for a muonium 1S-2S spectroscopy experiment in FY2021. In this paper, the recent upgrade and present status of the J-PARC muon facility and its prospects are presented.

Survey of Hyperfine Structure Measurements in Alkali Atoms

The spectroscopic hyperfine constants for all the alkali atoms are reported. For atoms from lithium to cesium, only the long lived atomic isotopes are examined. For francium, the measured data for nuclear ground states of all available isotopes are listed. All results obtained since the beginning of laser investigations are presented, while for previous works the data of Arimondo et al. [Rev. Mod. Phys. 49, 31 (1977)] are recalled. Global analyses based on the scaling laws and the hyperfine anomalies are performed.

Doppler-free dual-excited state spectroscopy and its application for measurement of hyperfine structure of 6D5/2 level of 133Cs

Doppler-free dual-excited state spectroscopy and its application for measurement of hyperfine structure of 6D5/2 level of 133Cs

The effect of saturation on hyperfine and Zeeman spectra in laser absorption spectroscopy

Using laser absorption spectroscopy, i.e. techniques such as optogalvanic spectroscopy or laser-induced fluorescence, it is often possible to separate and register individual components of a hyperfine or Zeeman structure. If these components are well separated (i.e. the distances between them are greater than their FWHM), it is relatively easy to determine their frequency position. However, when the atomic structure is very rich and the individual components overlap, problems arise with the correct determination of the position of the respective intensity peaks. Usually, only the envelope curve can be fitted to the observed structure, hence assumptions about the relative intensity ratios of the overlapping components as well as assumption about the line profile of a single component are necessary. An additional problem is the saturation effect. The saturation effect changes the theoretically predicted relative intensity ratios between the line components. In the current work, we present a method of analyzing experimentally observed hyperfine structure (hfs) patterns without and with an external magnetic field (Zeeman-hfs), which considers the saturation effect and allows for a relatively precise determination of the position of the individual components. In addition, we point out that, because of the saturation effect, hyperfine structure measurements should be carried out in conditions where the polarization of the exciting light (relative to magnetic stray fields) is known and this fact should be reflected in computer simulations which adjust a model function based on theoretical predictions to the experimental spectrum.

Comment on: “Hyperfine structure measurements of Co I and Co II with Fourier transform spectroscopy” by Fu et al. [JQSRT 2021, 107590

This comment points out errors in the analysis of 61 magnetic hyperfine structure (A) constants of Co II energy levels by Fu et al. [JQSRT 2021, 107590]. The paper was published without full awareness of the extensive literature already available for Co II hyperfine A constants at the time; 57 of 58 A constants that were claimed to have been measured for the first time had already been measured by the prior work of Ding and Pickering [ApJS 2020, 251:24], who had published A constants for 292 levels of Co II. The A constant of 3d64s2 a5D4 has been determined by Fu et al. [JQSRT 2021, 107590] for the first time to be 12.0±1.8 mK (1 mK = 0.001 cm−1), which was found to agree with line profiles observed by Ding and Pickering [ApJS 2020, 251:24]. Discrepancies in 17 A constants of Fu et al. [JQSRT 2021, 107590] were found, which are likely due to the analysis of weak, experimentally unclassified transitions with Ritz wavenumbers 25453.966 cm−1 and 25149.948 cm−1 by Fu et al. [JQSRT 2021, 107590] for the A constants of the energy levels 3d7(2G)4s a3G5 and 3d7(2P)4s c3P2 respectively. Fewer transitions and poorer quality spectra analysed by Fu et al. [JQSRT 2021, 107590] are also concluded to have contributed to disagreements in the 17 A constants.

Proposal for new measurements of muonic helium hyperfine structure at J-PARC

The measurement of the ground state hyperfine structure of muonic helium has the potential to improve the precision of the mass of the negative muon by a factor of 50 or more. The mass of the negative muon is very important because it enables us to test the CPT theorem by comparison with positive muon mass. We aim to measure the hyperfine structure of muonic helium with a precision 1000 times higher than previous experiments [1,2] using the highintensity muon beam at J-PARC and have already obtained results better than the current precision in zero-field measurements in a test experiment in March 2021. To further improve the precision, we plan to measure in a high magnetic field and incorporate a technique that can produce highly polarized muonic helium atom [3]. In this paper, we will report on these developments.

Hyperfine structure measurements of Nb I and Nb II by Fourier transform spectroscopy

Some of the archival data derived from the Fourier transform spectrometer (FTS) at the US National Solar Observatory ranging from 0 − 36,947 cm−1 were investigated to study the hyperfine structure (HFS) patterns of Nb I and Nb II lines. The analysis of 155 lines in the FTS spectra was performed by a least squares fitting to derive values of the magnetic dipole HFS constant A. In total, the HFS constant A was determined for 68 levels of Nb I between 11,524.65 and 45,719.07 cm−1 and for 57 levels of Nb II between 2356.816 and 73,869.773 cm−1. 26 results for Nb I and 46 results for Nb II are reported for the first time, as far as we know.

Isotope shift and hyperfine structure measurements on triple resonance excitation to the autoionizing Rydberg state of atomic strontium

Triple resonance excitation to the autoionizing Rydberg state of atomic strontium was studied for the isotope-selective photoionization of strontium-90 (90Sr). We investigated a new resonance ionization scheme, namely, 689.4 nm–472.4 nm–404.2 nm that is less affected by the multiphoton ionization induced by the first (689.4 nm) laser compared to the scheme in our previous study, namely, 689.4 nm–487.4 nm–393.8 nm. The isotope shifts and hyperfine structure constants of stable Sr isotopes were measured for the second and third transitions of these two schemes. Thus, the 90Sr isotope shift for each of the four transitions was evaluated using the King plot analysis. Under the current laser conditions, no significant difference was observed in the measured 90Sr optical isotopic selectivity between these two schemes, but the new scheme could show better selectivity if the first (689.4 nm) laser output is increased to improve the ionization efficiency. Our spectroscopic data will be useful for future analysis of 90Sr in real samples and may also help promote studies in other fields, such as precision measurements using cold atoms in optical traps.

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

As a new method to determine the resonance frequency, Rabi-oscillation spectroscopy has been developed. In contrast to the conventional spectroscopy which draws the resonance curve, Rabi-oscillation spectroscopy fits the time evolution of the Rabi oscillation. By selecting the optimized frequency, it is shown that the precision is twice as good as the conventional spectroscopy with a frequency sweep. Furthermore, the data under different conditions can be treated in a unified manner, allowing more efficient measurements for systems consisting of a limited number of short-lived particles produced by accelerators such as muons. We have developed a fitting function that takes into account the spatial distribution of muonium and the spatial distribution of the microwave intensity to apply the new method to ground-state muonium hyperfine structure measurements at zero field. This was applied to the actual measurement data and the resonance frequencies were determined under various conditions. The result of our analysis gives $\nu_{\rm HFS}=4\ 463\ 301.61 \pm 0.71\ {\rm kHz}$, which is the world's highest precision under zero field conditions.

Resonance Fabry–Perot interferometer as instrument for investigation of fine and hyperfine mode structure of free electron lasers

Free electron lasers usually emit periodic sequences of short pulses, which are parts of pulses circulating inside an optical cavity. Due to the laser nature of the radiation, the output pulses generated by the same intra-cavity pulse are a priori coherent with each other. Under certain technical conditions, different intra-cavity pulses can be coherent too. The coherence of intra-cavity pulses gives rise to a fine structure of the laser emission spectrum, and the coherence of output pulses from one intra-cavity pulse gives rise to a hyperfine mode structure. The article describes a special device, the resonance Fabry–Perot interferometer, and methods for panoramic frequency measurements of the mode composition of radiation with a resolution of up to 5⋅ 10−8 and for practically unlimited-resolution time-domain measurements of the monochromaticity of lines of hyperfine structure. With this device, it was shown that there is no fine structure in the Novosibirsk free electron laser (NovoFEL), and its hyperfine structure was measured in detail. The measurement of hyperfine structure of an FEL was carried out for the first time. It is shown that under certain conditions, NovoFEL operates either in the generation regime of one Laguerre-Gaussian supermode or in the regime of several transverse supermodes. The measured relative linewidth of the NovoFEL hyperfine mode structure, defined by technical factors, is 2.2 × 10−8, which is about two orders of magnitude larger than its absolute physical quantum limit.

Development of microwave cavities for measurement of muonium hyperfine structure at J-PARC

Abstract The MuSEUM collaboration is planning measurements of the ground-state hyperfine structure (HFS) of muonium at the Japan Proton Accelerator Research Complex (J-PARC), Materials and Life Science Experimental Facility. The high-intensity beam that will soon be available, the H-line, allows for more precise measurements by one order of magnitude. We plan to conduct two staged measurements. First, we will measure the Mu-HFS in a near-zero magnetic field, and thereafter we will measure it in a strong magnetic field. We have developed two microwave cavities for this purpose. Furthermore, we evaluated the systematic uncertainties from such a fluctuation of microwave fields and confirmed the requirements for the microwave system; we use a microwave field distribution calculated with the finite element method.

Hyperfine structure measurements of Co I and Co II with Fourier transform spectroscopy

ABSTRACT We used some archival data from the Fourier transform spectrometer (FTS) at the US National Solar Observatory to study the hyperfine structure (HFS) patterns of Co I and Co II, and determined the HFS constants of Co I and Co II. In total, HFS constants A for 36 levels of Co I from 0.00 to 60,262.463 cm−1 and for 61 levels of Co II from 11,651.277 to 85,876.271 cm−1 were determined, of which 33 results for Co I and 58 results for Co II are reported for the first time, as far as we know. Our study increased the total number of HFS constants A to over 333 for Co I and over 86 for Co II.

New precise spectroscopy of the hyperfine structure in muonium with a high-intensity pulsed muon beam

A hydrogen-like atom consisting of a positive muon and an electron is known as muonium. It is a near-ideal two-body system for a precision test of bound-state theory and fundamental symmetries. The MuSEUM collaboration performed a new precision measurement of the muonium ground-state hyperfine structure at J-PARC using a high-intensity pulsed muon beam and a high-rate capable positron counter. The resonance of hyperfine transition was successfully observed at a near-zero magnetic field, and the muonium hyperfine structure interval of νHFS=4.463302(4)GHz was obtained with a relative precision of 0.9 ppm. The result was consistent with the previous ones obtained at Los Alamos National Laboratory and the current theoretical calculation. We present a demonstration of the microwave spectroscopy of muonium for future experiments to achieve the highest precision.