Spectroscopy of francium in a magneto optical trap

The francium atom offers an excellent laboratory to study electron-nucleus interactions. As the heaviest alkali, its atomic properties can be calculated with high precision, and laser trapping methods now allow precision optical spectroscopy of many isotopes. Recent measurements of the 7P_1/2 hyperfine structure, when coupled with previous measurements of the ground state hyperfine structure reveal a hyperfine anomaly. The change in anomaly between an even-N isotope and an odd-N isotope is sensitive to the radial distribution of the neutron magnetization. This revised version was published online in August 2006 with corrections to the Cover Date.     

Change of hyperfine and transferred hyperfine interaction of Eu2+ in CdF2, CaF2, SrF2, and BaF2

ENDOR measurements of the hyperfine and transferred hyperfine interaction of Eu²⁺ in CdF₂, SrF₂, and BaF₂ were performed. Compared with measurements on CaF₂, there is a radial shifting of the next fluorine ligands in CdF₂∶ +5.4%, CaF₂∶ + 3.5%, and BaF₂∶ ?3.9%. Since the SrF₂ and EuF₂ lattice constants are approximately equal, a shifting in SrF₂ was not assumed. In both europium isotopes (151 and 153) a change of hyperfine fields at the nucleus was observed. This can be explained qualitatively by the difference in radial distribution of the different europium orbitals. Also noticed was a small change of the hyperfine anomaly, which indicates contributions of the zero-point vibration.     

Confirmation of the giant hyperfine anomaly of the system184W2+-183W g by new spin-echo experiments with183WFe and remarks on possible explanations

Spin-echo measurements on¹⁸³W were performed with dilute alloys of W (0.1, 0.25, 0.5 and 1 at %) in Fe. The result for the hyperfine field:B _4.2K ^hf =(?)62 · 54 (3) T agrees with the old data of Kontani and Itoh, but the accuracy is much better. The giant hyperfine anomaly of¹⁸³W with respect to¹⁸⁴W₂₊ observed by Alzner et al. is thus confirmed and the errors are reduced to:¹⁸⁴W₂₊Δ¹⁸³W_g=+0.150(31). This is the first case of a very large hyperfine anomaly in electronic hyperfine fields which is not caused by the pathological cancellation of orbital and spin magnetism in jackknifep _1/2 ord _3/2 single proton configurations. A detailed discussion shows that the large hyperfine anomaly may be related to the anomalously small magnetic dipole moment of¹⁸³W. Our result should stimulate further theoretical work with the aim to understand this magnetic moment as well as the giant hyperfine anomaly.     

Hyperfine magnetic anomaly in isotopic pairs <Superscript>151, 152</Superscript>Eu and <Superscript>152, 153</Superscript>Eu

High-resolution laser spectroscopy measurements of optical hyperfine splitting on the ^{151, 152, 153}Eu isotopes were performed on the atomic transition 4f ⁷6s ^{2 8} S _7/2 → 4f ⁷6s6p ⁶ P _5/2 at λ ≈ 564.58 nm. Values of the nuclear magnetic dipole and electric quadrupole moments are obtained from the measured hyperfine splitting and the magnetic hyperfine anomalies in the isotope pairs ^{151, 152}Eu and ^{152, 153}Eu are deduced. The absolute values of the hyperfine anomaly in both cases are unusually large: 5 (1)%. The possible sources causing these anomalies are discussed.     

Hyperfine splitting constants in the optical transition \boldsymbol{{4{f}^{7}} {6{s}^{2}} \;{^{8}{\rm S}_{7/2}} \to {4{f}^{7}} {6{s}6{p}}\; {^{6}{\rm P}_{5/2}} \ {\rm of} \ {^{151-155}{\rm Eu}}} isotopes and hyperfine anomaly

Using the method of laser-induced fluorescence in an atomic beam we have measured the hyperfine splitting constants, A and B, of the ground and excited states of the optical transition 4f ⁷6s ^{2 8}S $_{1/2}\to 4f^{7}$ 6s6p ⁶P_5/2 (564.58 nm) for ^151???155Eu isotopes. For all isotopes, the magnetic dipole constants of the ⁶P_5/2 atomic level are determined to a precision better than 0.04%. The A and B constants for the ground state ⁸S_7/2 of the radioactive ^152,154,155Eu were obtained for the first time with a precision better than 0.5%. Our data along with previous ground state hyperfine structure measurements for the stable europium isotopes allow us to determine the hyperfine anomaly for mentioned Eu isotopes.     

Magnetic hyperfine anomaly in muonic193Ir

The nuclear decay of the 5/2⁺ 139 keV state to the 3/2⁺ ground state was observed in muonic¹⁹³Ir. The hyperfine splitting of the 3/2⁺ state and 5/2⁺ state was determined to be 640±100 eV and 1280±160 eV, respectively. The ground state splitting is about twice that of a point nucleus, an anomaly never observed this large. This is mainly due to the different radial distribution of spin and orbital magnetization of a d_3/2 proton configuration for which these contributions nearly cancel to zero in the magnetic moment. But calculations including configuration mixing and coupling to a vibrating or a deformed core show deviations. The groundstate anomaly is in line with that observed by the Mössbauer technique.     

Hyperfine and Zeeman studies of low-lying atomic levels of181Ta and the nuclear electric quadrupole moment

The hyperfine structure of the atomic levels 5d ³ 6s ^{2 4} F _{7/2, 9/2} and⁴ P _1/2 in¹⁸¹Ta has been studied by atomic-beam magnetic-resonance. Using intermediate coupling wave functions derived for the configurations (5d+6s)⁵ the hyperfine structure data of six low-lying metastable states have been analyzed with respect to the effective operator formalism. The effective radial parameters for the magnetic dipole and electric quadrupole interactions are determined from these measurements and compared with relativistic calculations. The value obtained for the spectroscopic quadrupole moment of the¹⁸¹Ta nuclear ground state is Q_hfs=3.44(17) barn (uncorrected for configuration interaction effects).     

Precise measurement of hyperfine structure in the 52P1/2 state of Rb

We have measured hyperfine structure in the 5 ²P_1/2 state of Rb using a frequency-stabilized diode laser, which is locked to one hyperfine transition, and an acousto-optic modulator, whose frequency is locked to the interval of interest. We check for optical-pumping errors by repeating the measurement at different values of pump power in the saturated-absorption spectrometer. We obtain precise values of the hyperfine constant: A=120.645(5) MHz for ⁸⁵Rb and A=406.119(7) MHz for ⁸⁷Rb. The values resolve a large discrepancy between two earlier high-accuracy measurements on this state.     

Effective hyperfine temperature in frustrated Gd 2Sn 2O 7: two level model and 155Gd Mössbauer measurements

Using ¹⁵⁵Gd M?ssbauer spectroscopy down to 27 mK, we show that, in the geometrically frustrated pyrochlore Gd₂Sn₂O₇, the Gd³⁺ hyperfine levels are populated out of equilibrium. From this, we deduce that the hyperfine field, and the correlated Gd³⁺ moments which produce this field, continue to fluctuate as T ↦ 0. With a model of a spin 1/2 system experiencing a magnetic field which reverses randomly in time, we obtain an analytical expression for the steady state probability distribution of the level populations. This distribution is a simple function of the ratio of the nuclear spin relaxation time to the average electronic spin-flip time. In Gd₂Sn₂O₇, we find the two time scales are of the same order of magnitude. We discuss the mechanism giving rise to the nuclear spin relaxation and the influence of the electronic spin fluctuations on the hyperfine specific heat. The corresponding low temperature measurements in Gd₂Ti₂O₇ are presented and discussed. Received 17 October 2001 Published online 6 June 2002     

Apparent giant hyperfine anomaly of nuclear levels in the indium isotopes — A puzzle

The magnetic hyperfine fields of In in Fe, Co and Ni were measured by PAC using¹¹⁷In, and by NMR-ON using^114mIn and¹¹⁴In. There is a disparity of about 8% (4%) between the fields derived from PAC on¹¹⁷In (NMR-ON on¹¹⁴In) and the values that have been measured using isomeric 1g_9/2 proton states in^109,111,115In. This is tentatively attributed to a giant hyperfine anomaly.     

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.     

161Dy Mössbauer study on magnetic properties in DyZn2 intermetallics

The magnetic properties of the DyZn₂ have been studied by¹⁶¹Dy Mössbauer effect measurements at temperatures from 5.0 to 77.4 K. The spectra are interpreted with a single set of hyperfine parameters. The magnetic hyperfine field is 837 MHz at 5 K, which is very close to the value of Dy³⁺ free ion. Since the relaxation rate increases rapidly as the temperature increases, no accurate hyperfine parameters are obtained analytically nearT _N. The width of the Lorentizian absorption lines increases at the temperatures at which the magnetic structure is an incommensurable moment-modulated one. Anomalies in the -ray transmission rate at zero velocity are observed at 29 and38 K which are the commensurate-incommensurate transition andthe Néel temperatures, respectively. Another anomaly observed around 60 K may originate in a short-range order of Dy moments.     

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).     

The radial dependence of the magnetic hyperfine field for Sn atoms in the ferromagnetic Heusler alloys

The magnetic hyperfine fields,B _hf, for impurity¹¹⁹Sn atoms in Z sites of ferromagnetic Heusler alloys Co₂MnZ (Z=Si, Ge) are measured by the Mössbauer effect. At 77 KB _hf=–1.43±0.04 T in Co₂MnSi andB _hf=+1.05±0.05 T in Co₂MnGe. From the comparison between the values ofB _hf for Sn atoms in Co₂MnZ (Z=Si, Ge, Sn), it follows that the negative contribution toB _hf drops as the interatomic distance begins to increase. This radial dependence also manifests itself in the anomalies of the temperature dependences of the hyperfine fields. The temperature anomaly is positive for Sn in Co₂MnGe and negative for Sn in Co₂MnSi.     

Hyperfine spectroscopic study of the metal-insulator transition in V2O3

The metal-insulator (M-I) transition in vanadium sesquioxide V₂O₃ has been investigated by time differential perturbed angular correlation measurements of the electric fieldgradient (EFG) and the magnetic hyperfine field at dilute¹¹¹Cd impurities. The EFG undergoes a first-order change at the M-I transition at T_t=160 K, but does not reflect the high temperature resistivity anomaly. The increase of the EFG with temperature in the metallic phase can be attributed to thermal variations of the oxygen sublattice. The temperature dependence of the magnetic hyperfine field in the insulating phase follows a Brioullin function with a saturation value of H_hf(O)=15 KOe and an extrapolated Neel temperature, which, depending on the impurity concentration, varies between 188 and 230 K.     

Tabulation of hyperfine splittings in rotational F1 and F2 levels of the ground vibrational state of 12CH4 for J ≤ 20

To a good approximation, hyperfine splittings for F₁ and F₂ rotational levels of the ground vibrational state of ¹²CH₄ depend linearly on three hyperfine interaction parameters. Coefficients in these linear expressions have been computed in a relatively simple manner and tabulated for levels with 1 ≤ J ≤ 20. The hyperfine pattern for the $\text{J = 7 F}{}_2{}^{\mathrm{(2)}}$ level computed from these expressions using values for the three hyperfine interaction parameters reported recently by Yi, Ozier and Ramsey (1) agrees well with the pattern obtained from new HeNe laser measurements of Hall and Bordé (2) on the $\text{P(7) F}{}_2{}^{\mathrm{(2)}}$ line of the ν₃ band of methane.     

Paramagnetic fluctuations in Yb3Ga5O12 investigated with 172Yb PAC probe

¹⁷²Yb PAC measurements were carried out on Yb₃Ga₅O₁₂ at temperatures ranging from 14 to 1100 K. The time dependent hyperfine interaction is clearly evident below room temperature. It is attributed to spin fluctuations of Yb ion in the ground state of the ²F_7/2 multiplet. Above 500 K, the temperature dependence of the electric field gradient is shown to result from a varying population of the crystal electric field levels. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Nuclear ground state spins of short-lived strontium isotopes

Nuclear ground state spins of the odd-mass strontium isotopes between A=79 and 97 were determined by measurements of the hyperfine structure in the ionic transition 5s²S_1/2?5p²P_3/2. The spins of⁹³Sr and⁹⁷Sr are revised to I=5/2 and I=1/2, respectively, while assignments for the remaining isotopes are confirmed.     

Hyperfine Interactions at 181Ta in Hf2Co7

In this paper we report a time differential perturbed angular correlation (TDPAC) study of hyperfine interactions at ¹⁸¹Ta in Hf₂Co₇ compound. The TDPAC measurements have been performed in the temperature range 77–1023K. The measured spectra showed broad distribution of hyperfine interactions up to 388K. Above this temperature, in a reversible manner, two nuclear electric quadrupole interactions (EQI) have been observed: at 393K, _Q1=449.0(27)MHz, ₁=0.00(4) and _Q2=144.7(41)MHz, ₂=0.44(2). Since the Curie temperature for this compound is known from the literature to be around 420K, only magnetic order transition could be responsible for such an observation. However, the measurements of magnetization did not exhibit any drastic change in this temperature range.