Hyperfine structure and isotope shift of high-lying metastable states of rhenium

Fourteen transitions in ReI, starting from high-lying metastable states belonging to the configurations (5d+6s)⁷, have been studied by laser-induced fluorescence in a collimated atomic beam, and accurate values for the isotope shifts in these transitions as well as for the hyperfine structure constants of 13 metastable and 9 excited states have been obtained. In addition, high precision measurements of the hyperfine structure of the states 5d ⁵ 6s ^{2 4} D _7/2 and 5d ⁶ 6s ⁶ D _{1/2, 3/2, 5/2, 9/2} have been performed using the atomic beam magnetic resonance technique coupled with laser-induced state-selective detection of metastable atoms. The analysis of the hyperfine structure data yields experimental evidence for far configuration mixing effects on the off-diagonal spin-dipole matrix elements. The phenomenological interpretation of the isotope shifts shows the significance of off-diagonal field-shift effects.     

High resolution measurements of hyperfine structure and isotope shifts in 9 spectral lines of Nd I

Nine transitions in Nd I, originating from various levels belonging to the 4f ⁴6s ² ground state configuration, have been studied with high resolution using an actively stabilized C.W. ring dye laser in a crossed laser-atomic-beam set-up. Accurate values for the isotope shifts in all transitions as well as for the hyperfine structure constants of 7 excited states have been obtained.     

A muonic X-ray study of the charge distribution of 144, 148, 150, 152, 154Sm

We report the measurement of the energies of the 4f → 3d, 3d → 2p and 2p → Is muonic atomic transitions in separated isotopes of ^{144, 148, 150, 152, 154}Sm, and that of the 2s → 2p transitions of ¹⁵²Sm as well. Using these transition energies as well as the hyperfine splittings of the 2p levels, we have interpreted our data in terms of a deformed Fermi distribution for the charge density and obtained good fits. A model independent analysis of the isotope shifts in terms of generalized R_h moments has been made and is in good agreement with electronic X-ray and optical isotope shifts. The static quadrupole moments and the isomer shifts of the first excited state of ^{152, 154}Sm have been determined from the 2p hyperfine structure.     

A high resolution study of the transitions 4f 76s 2→4f 76s6p in the Eu I-spectrum

Eight transitions in the Eu I-spectrum connecting the ground state with configuration 4f ⁷ 6s ² with states of the configuration 4f ⁷ 6s6p were studied with high resolution laseratomic-beam spectroscopy. CW dye lasers operating in the wavelength regions 435–470 nm and 560–630 nm were used for this study. New data for the hyperfine structure in¹⁵³Eu were obtained as well as new and more accurate values for the isotope shifts between¹⁵¹Eu and¹⁵³Eu. The existing data for the hyperfine structure in¹⁵¹Eu were reproduced with an exception for the levelz ⁶ P _7/2.     

High resolution spectroscopy of rydberg states in indium I

Two-photon laser spectroscopy in a dense indium vapour allowed to investigatenp ² P _{1/2, 3/2} states (n=27–35) for^{113, 115}In with a thermionic diode. Precise data on the fine structure splitting of these states and the isotope shift of the two photon transitions have been obtained. The fine structure splitting shows a hydrogenic behaviour. By using the result of our isotope shift measurement in combination with literature values, level isotope shifts with reference to the ionization limit are deduced and analysed with respect to the different contributions.     

Stark effect,hyperfine structure and isotope shifts in highly excited states of BaI and CaI

The electric dipole polarizabilities of 9 even-parity barium states (6s8s ¹ S ₀,³ S ₁; 6s7d ¹ D ₂,³ D _1,2; 5d7s ¹ D ₂ and 6p ^{2 3} P _0,1,2) in the interval 33,800–35,800 cm^?1 have been measured with high resolution laser-atomic-beam spectroscopy. Simultaneously, values of isotope shifts and hyperfine coupling constants for theJ=1 states have been obtained. Comparison of the experimental polarizabilities with calculated values as well as inspection of the data on isotope shifts and hyperfine structure from the present and earlier work strongly suggests erroneous assignments of theJ=2 states, with an exception for the 5d 7s ¹ D ₂ state. The influence of an electric field on the 3d ^{2 3} P _0,1,2 states of calcium has also been studied. A marked departure from a quadratic Stark effect has been observed at relatively small field strengths. This can be attributed to the large polarizabilities of neighbouring Rydberg states. The low field data allow the determination of admixtures of Rydberg states into the 3d ^{2 3} P-states as small as 0.02%.     

Isotope shifts and hyperfine structure in calcium 4snp and 4snf F Rydberg states

Isotope shifts and hyperfine structure have been measured in 4snp ¹ P₁ and Rydberg states for all stable calcium isotopes and the radioisotope ⁴¹Ca using high-resolution laser spectroscopy. Triple-resonance excitation via Rydberg state was followed by photoionization with a CO₂ laser and mass selective ion detection. Isotope shifts for the even-mass isotopes have been analyzed to derive specific mass shift and field shift factors. The apparent isotope shifts for ⁴¹Ca and ⁴³Ca exhibit anomalous values that are n-dependent. This is interpreted in terms of hyperfine-induced fine-structure mixing, which becomes very pronounced when singlet-triplet fine-structure splitting is comparable to the hyperfine interaction energy. Measurements of fine-structure splittings for the predominant isotope ⁴⁰Ca have been used as input parameters for theoretical calculation of the perturbed hyperfine structure. Results obtained by diagonalizing the second-order hyperfine interaction matrices agree very well with experimentally observed spectra. These measurements allow the evaluation of highly selective and sensitive methods for the detection of the rare ⁴¹Ca isotope. Received 17 December 1999 and Received in final form 29 March 2000     

Isotope shifts in transitions between low-lying levels of Sr I by laser-atomic-beam spectroscopy

High-resolution laser-atomic-beam spectroscopy has been used to determine isotope shifts in five transitions between low-lying states of Sr I. With these results and existing data a parametric analysis of level isotope shifts has been performed. The transition isotope shifts have been separated into field shift and mass shift contributions with a King-plot procedure using model-independent nuclear charge equivalent radiiR _k from muonic x-ray measurements. Values for the mean-square nuclear charge radiiδ〈r ₂ 〉 have been calculated from the field shifts in the optical transitions 5s ^{2 1} S ₀-5s5p ³ P ₁ and 5s5p ³ P ₀-5s6s ³ S ₁ and compared with correspondingδ〈r ² 〉 values evaluated from muonic x-ray data.     

Isotope shift in Ni I and changes in mean-square nuclear charge radii of the stable Ni isotopes

The isotope shift in the Ni I spectrum was studied in 17 lines for all stable isotopes by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. The measured isotope shifts were separated into mass shift and field shift by comparing the optical isotope shift with model-independent δ〈r ²〉 values derived from a combined elastic electron scattering and muonic x-ray data analysis. The ratios of the observed field shifts in different types of transitions could be explained quantitatively by Hartree-Fock calculations. The relative changes in mean-square nuclear charge radii were found to be: [58, 60] 1.293(15); [60, 62]1; [62, 64] 0.641(16); [60, 61] 0.382(9). The absolute value δ〈r ²〉^60,62=0.170(35) fm² was derived using fine structure as well as hyperfine structure data for the determination of the change in the electron charge density at the nucleus in 4s-4p transitions.     

Hyperfine structure and isotope shift of highly excited barium-I states

High-resolution laser-spectroscopy measurements of hyperfine structure and isotope shifts were performed for the 6snd ¹ D ₂ sequence of Ba-I in the regionn=12–24. Stepwise laser excitations of a collimated atomic beam were used. A strong influence on the hyperfine structure is observed at the perturbation atn=14, caused by interaction with the 5d7d configuration. Whereas the isotope shift for the even isotopes stays essentially constant with increasingn, the odd isotopes exhibit a strong change, indicating hyperfine-induced shifts.     

Changes in nuclear mean square charge radii of stable Krypton isotopes

The isotope shifts of stable even Kr isotopes (A=78 throughA=86) in the optical transitions at 432 nm and 557 nm were measured by means of polarization laser spectroscopy. The observed shifts are consistent with earlier results for other transitions. From the isotope shifts the changes in the nuclear mean square charge radiiδ〈r ²〉 were inferred using preliminary muonic isotope shift data. Starting from⁷⁸Kr, a monotonic decrease of 〈r ²〉 with increasing mass number is found throughout theg _9/2 neutron shell. The effect onδ〈r ²〉 of nuclear deformations as well as possible contributions due to changes in the skin thickness of the nuclear charge distribution are discussed.     

Isotope shifts and hyperfine structure in the transitions in calcium II

The isotope shift and hyperfine structure in the three - transitions in Ca II have been studied by fast ion beam collinear laser spectroscopy for all stable Ca isotopes. The metastable 3d states were populated within the surface ionization source of a mass separator with a probability of about 0.1%. After resonant excitation to the 4p levels with diode laser light around 850 nm the uv photons from the transitions to the ground state were used for detection. Hyperfine structure parameters A and B for the odd isotope ⁴³Ca, as evaluated from the splittings observed, agree well with theoretical predictions from relativistic many-body perturbation theory. Field shift constants and specific mass shift constants were extracted from the measured isotope shifts and are discussed in comparison with expectation values from theory. Received: 19 September 1997 / Revised: 5 December 1997 / Accepted: 27 January 1998     

Precision two-photon spectroscopy of alkali elements

In this paper, we have briefly reviewed the work on two-photon spectroscopy of alkali elements and its applications. The technique of Doppler-free two-photon spectroscopy is briefly summarized. A review of various techniques adopted for measuring absolute frequencies of the atomic transitions and precision measurements of isotope shifts and hyperfine structures (HFS) is presented. Some of the recent works on precision measurements of HFS constants of 6s ² S _1/2 level of ³⁹K and ⁴¹K, 9s ² S _1/2level and 7d ² D _3/2 level of ¹³³Cs are also discussed.     

Isotope shifts of the ground state of neon: Refining the measurement results

Abstract—It has been revealed that the published results of measurements of the isotope shift of the ground state of even neon isotopes contain systematic errors. The errors are caused by the use of erroneous data regarding the absolute values of specific mass shifts of excited states and by the measurement errors of the isotope shifts themselves for transitions to the ground state. The isotope shift of the 2p⁵4s[3/2]₁ → 2p⁶(¹S₀) transition has been measured to be 2305 ± 20 MHz, the absolute specific mass shift of the 3p[3/2]₂: (2_р9) level has been determined to be 647 ± 10 MHz, and the isotope shift of the ground state has been found to be–3156 ± 30 MHz.     

Hyperfine structure and isotope shifts in 733.2 nm mixed forbidden line of Pb I

Studies of the hyperfine structure and isotope shifts in 733.2 nm mixed (M1+E2) multipole line of Pb I are presented. As a light source the electrodeless discharge tube was used. The high resolution spectral apparatus consisted of a silver coated Fabry-Perot etalon and a grating spectrograph combined with a CCD camera used as a detector. In the analysis of the spectra a computer simulation technique was used. The experiments with the isotope ²⁰⁷Pb yielded the hyperfine structure splitting constant A for the ³P₁ and ¹D₂ levels of the 6s²6p² ground configuration. In the experiment with natural lead the isotope shifts between four stable isotopes (204, 206, 207, 208) were measured.     

Nuclear radii of thorium isotopes from laser spectroscopy of stored ions

Isotope shifts and hyperfine splittings in optical transitions for atomic ions of the thorium isotopes²²⁷Th to²³⁰Th and²³²Th have been measured by laser spectroscopy on stored ions. From the isotope shift data, changes of the mean square charge radii are determined. A continuous increase of the charge radius with mass numberA is observed, in agreement with droplet model calculations. The results indicate that the odd-even staggering for Th is different from that one of the neighbouring isotones of Fr and Ra. There is some empirical evidence from systematics for an inversion of the staggering and the appearance of an octupole deformation atN ≦137. The hyperfine splitting for²²⁹Th for 3 electronic levels is given.     

Optogalvanic spectroscopy of metastable states in Yb+

The metastable ²F_7/2 and ²D_3/2 states of Yb⁺ are of interest for applications in metrology and quantum information and also act as dark states in laser cooling. These metastable states are commonly repumped to the ground state via the 638.6 nm ²F_7/2–¹D[5/2]_5/2 and 935.2?nm ²D_3/2–³D[3/2]_1/2 transitions. We have performed optogalvanic spectroscopy of these transitions in Yb⁺ ions generated in a discharge. We measure the pressure broadening coefficient for the 638.6 nm transition to be 70±10?MHz?mbar^?1. We place an upper bound of 375 MHz/nucleon on the 638.6 nm isotope splitting and show that our observations are consistent with theory for the hyperfine splitting. Our measurements of the 935.2 nm transition extend those made by Sugiyama et al., showing well-resolved isotope and hyperfine splitting (Sugiyama and Yoda in IEEE Trans. Instrum. Meas. 44: 140, 1995). We obtain high signal-to-noise, sufficient for laser stabilisation applications (Streed et al. in Appl. Phys. Lett. 93: 071103, 2008).     

Relativistic J-dependence of the isotope shift in the 6s-6p doublet of Ba II

The collinear laser-ion beam technique has been used to measure the isotope shift and hyperfine structure in the 6s-6p doublet (4,934Å, 4,554Å) of Ba II for all seven stable isotopes. The influence of the excited² P _1/2 and² P _3/2 states on the field shift leads to a difference of 2.5(3)% in the electronicF factors. The specific mass shifts differ by {A′-A} 2.2(3) MHz which corresponds to about 12% of the normal mass shift.     

Dye laser saturation spectroscopy of the 23 S 1-23 P transition in6, 7Li+ ions

The metastable 2³ S ₁ state and the short lived 2³ P states of the helium-like^{6, 7}Li⁺ ion spectra have been investigated by dye laser saturation spectroscopy in a low-energy Li⁺ ion-beam and fluorescence light detection. The hyperfine structure splittings of all the levels, the 2³ P fine structure intervals and the isotope shift of the 2³ S ₁-2³ P transitions have been measured. These measurements were made by application of a specially constructed tunable dye laser system capable of single-mode laser scans over more than 60 GHz.     

Precision spectroscopy of metastable hydrogen and antihydrogen with a Lamb-shift polarimeter

A spinfilter, the most important component of a Lamb-shift polarimeter, can be used to produce a beam of metastable hydrogen (deuterium) atoms in one hyperfine state (α1, α2 and together with the Sona transition β3). As function of a magnetic field separated transitions between the 2S _1/2 metastable hyperfine states seem to be observable as well as single transitions into the short-lived 2P _1/2 and 2P _3/2 states. The Breit-Rabi diagrams for these states can be measured with good precision. Furthermore, the hyperfine splittings and the Lamb shift can be observed as well. Application of this method to anti-hydrogen atoms are suggested.