Hyperfine structure and absolute frequency measurements of <Superscript>127</Superscript><Emphasis Type="Italic">I</Emphasis><Subscript>2</Subscript> transitions with monolithic Nd:YAG 561-nm lasers

The precision hyperfine structures of the ¹²⁷ I ₂ transitions at 561.4 nm are measured by the heterodyne beat between two home-made ¹²⁷ I ₂-stabilized Nd:YAG lasers. The theoretical distributions of the observed transitions’ hyperfine sublevels are used to identify the two transitions. High-accuracy hyperfine constants are obtained by fitting the measured hyperfine splittings to the four-term Hamiltonian, which includes the electric quadruple, spin-rotation, tensor spin–spin and scalar spin–spin interactions. The absolute frequencies of the observed four transitions are measured by an optical frequency comb based on a mode-locked erbium-fiber laser.     

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585 nm

The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in ¹²⁷I₂ are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a₁₅ and P(80)21-1 a₁₀ are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.     

Widely usable interpolation formulae for hyperfine splittings in the 127I2 spectrum

Based on new systematic high precision measurements of hyperfine splittings in different rovibrational bands of ¹²⁷I₂ in the near infrared spectral range between 778 nm and 816 nm, and the data in the range from 660 nm to 514 nm available from literature, the quantum number dependence of the different hyperfine interaction parameters was reinvestigated. As detailed as possible parameters were re-fitted from the reported hyperfine splittings in literature, considering that the interaction parameters should vary smoothly with the vibrational and rotational quantum numbers, and follow appropriate physical models. This type of consistency has not been sufficiently taken into account by other authors. To our knowledge it is now possible for the first time to separate the hfs contributions of the two electronic states B ³ and X ¹ Σ ⁺ _g for optical transitions in a very large wavelength range. New interpolation formulae could be derived for both states, describing the quantum number dependences of the nuclear electric quadrupole, of the nuclear spin-rotation and also of the nuclear spin-spin interactions. Using these new interpolation formulae the hyperfine splittings for the components with the quantum number condition F - J = 0 can be calculated with an uncertainty of ≤30 kHz for transitions in the wavelength range between 514 nm and 820 nm. Received 17 July 2001 and Received in final form 17 October 2001     

Microwave optical double resonance of NO2 with a tunable cw dye laser: Spin-rotation and hyperfine interactions in the 2B2 excited electronic state

Various spin and hyperfine components of the 6₁₆ → 7₀₇ microwave transition in the ²B₂ electronic excited state were observed by microwave optical double-resonance spectroscopy using a tunable cw dye laser near 593 nm. Spin splittings and the hyperfine structure of two levels were precisely determined. Spin-rotation and hyperfine interactions in the ²B₂ state are discussed using these and the previously reported results on the 8₁₈ → 9₀₉ transition. From the hyperfine splittings of the K_a = 0, N = 7 and 9 levels, a value for the Fermi contact interaction constant, (0)_I, of ～50 MHz was determined.     

Frequency measurements on optically narrowed Rb-stabilised laser diodes at 780 nm and 795 nm

Laser diodes, optically narrowed using the technique of resonant optical feedback, have been frequency stabilised to hyperfine transitions of the two Rb D lines at 780 nm and 795 nm. The best frequency stability of the beat between two similar lasers was 1.5 kHz (4 parts in 10¹² of the optical frequency) observed for an averaging time of 10 s. A frequency reproducibility of 44 kHz (one standard deviation) was observed on strong isolated hyperfine components, and possible causes of frequency shift were investigated. Values for the Rb hyperfine intervals were obtained, leading to an improved determination of the excited state hyperfine constants of ⁸⁵Rb and ⁸⁷Rb, and the isotope shift. The absolute frequencies of the hyperfine transitions of the two D lines were determined interferometrically by comparison with an ¹²⁷I₂-stabilised He-Ne laser at 633 nm. Measurements were made on component c at 795 nm and the d/f level crossing at 780 nm. The frequencies were found to be 377106271.6 MHz and 384227981.9 MHz respectively under the chosen conditions, with an uncertainty of ±0.4 MHz, limited by knowledge of the reference frequency. These results represent the most accurate and complete characterisation to date of laser diodes stabilised to Doppler-free Rb spectra.     

Proton hyperfine interactions in the gas-phase E.P.R. spectra of SH (2Π3/2) in two lowest rotational levels

Gas-phase E.P.R. spectra of the SH radical (²Π_3/2) in the J = 5/2 and J = 3/2 rotational levels are described. Analysis of the hyperfine splittings gives the values of axial and non-axial components of the proton hyperfine interaction and the value of the constant d. The frequencies of the two strong lines in the zero-field spectrum are estimated by the use of the observed value of the hyperfine interaction constant d.     

Theg-factor of the 2+ state of180W and quadrupole moment ratios observed for180W and180Hf by the Mössbauer technique

By Mössbauer absorption experiments the magnetic hyperfine splitting has been observed for the 2+ states of¹⁸⁰W and¹⁸²W in a tungsten iron alloy (3.6 at%W). Since theg-factor of the 2+ state of¹⁸²W is known the measured splitting of the¹⁸²W line could be used for the calibration of the magnetic hyperfine field and the measurement with¹⁸⁰W gave then for the unknowng ₂₊-factor of¹⁸⁰W: $$g_{2 + } (^{180} W) = 0.260 \pm 0.017.$$ By use of a WO₃ absorber the electric quadrupole splittings in the same states were measured. The ratio of the quadrupole moments was derived $$\frac{{Q_{2 + } (^{180} W)}}{{Q_{2 + } (^{182} W)}} = 0.983 \pm 0.022.$$ This ratio is somewhat smaller, but more accurate than the weighted means of previous results and in disagreement with the theoretical prediction. A similar measurement with¹⁷⁸Hf and¹⁸⁰Hf and a HfO₂ absorber gave $$\frac{{Q_{2 + } (^{178} Hf)}}{{Q_{2 + } (^{180} Hf)}} = 1.052 \pm 0.021.$$ This result is larger than the average of previous measurements and agrees with theory. The isomer shifts of the Mössbauer lines of¹⁸⁰W and¹⁸²W were measured for sources in a tantalum metal environment and for absorbers of metallic tungsten. Different signs were observed which indicate that the mean squared charge radius of the 2+ state of¹⁸²W is larger than that of the ground state whereas for¹⁸⁰W the ground state has the larger 〈r ²〉-value.     

Sub-Doppler laser absorption spectroscopy of the AΠi − XΣ (1, 0) band of CN: Measurement of the N hyperfine parameters in AΠ CN

Measurements of multiple rotational lines in the (1, 0) band of the A²Π_i − X²Σ⁺ “red” system of the cyanogen radical (CN) at sub-Doppler resolution are reported. The CN radical was produced by 193 nm photodissociation of NCCN (ethane dinitrile) and detected with a Ti:sapphire ring laser operating near 10 900 cm⁻¹. The sample was exposed to a weak, frequency-modulated probe beam and a strong, counterpropagating bleach laser beam. Demodulated probe laser signals display absorption and dispersion features derived from Doppler-free saturation of the hyperfine components as the laser scans across the central region of a Doppler-broadened rotational line spectrum. Hyperfine-resolved transition frequencies were combined with known ground-state X²Σ hyperfine term values to determine A²Π state hyperfine term values, which were analyzed in terms of an effective Hamiltonian for the A²Π state. All the expected hyperfine and ¹⁴N quadrupolar parameters were determined and their values analyzed in terms of a simple molecular orbital picture of the bonding in the radical. Higher sensitivity obtained with 400 kHz amplitude modulation of the bleach laser and additional phase-sensitive detection allowed hyperfine splittings in some rotational lines of ¹³C¹⁴N to be observed in natural abundance. Excited state hyperfine splittings were determined for a selection of rotational states, but not enough to determine the ¹³C hyperfine parameters.     

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.     

Derg-Faktor des 364 keV-Zustandes von184W und die Hyperfeinfelder von Wolfram in Eisen,Kobalt und Nickel

Theg-factor of the 364 keV state of¹⁸⁴W was measured by the time integral angular correlation method using the high hyperfine fields at the tungsten nucleus in iron. The same experiment was performed with the 111 keV state giving the ratiog(364 keV)/g(111 keV)=1.02(14). Using this ratiog(364 keV-level)=0.286(35) was deduced. For the hyperfine fields of W in Fe, W in Co and W in Ni at 300 K ?610(35) kG, ? 358(23) kG and ?80(3) kG respective have been determined.     

Nonlinear UV-laser spectroscopy of the 2 3S−5 3P transition in 3He and 4He

We report the production of stable CW single mode UV radiation around 295 nm at powers exceeding 50 mW, using a passive enhancement cavity for second harmonic generation. With this laser we have investigated the 2 ³S?5 ³P transition at 294.5 nm in ³He and ⁴He by intermodulated fluorescence spectroscopy. The measurements of the hyperfine splittings of the 5 ³P levels agree with semi-empirical calculations.     

Isotope shifts and hyperfine structure of the 6s-7p transitions in the cesium isotopes 133, 135, and 137

The 6s-7p transitions in cesium at 459.3 nm (7² P _1/2) and 455.5 nm (7² P _3/2) have been investigated by saturation spectroscopy in vapor cells, using a laser spectrometer with 500 kHz bandwidth in the blue spectral range. Isotope shifts as well as hyperfine splittings were determined for the isotopes 133, 135 and 137.     

Goldanskii-karyagin effect at mössbauerE2-transitions

Investigations of anisotropic Debye-Waller factors have been carried out mainly using the M1-transitions of⁵⁷Fe and¹¹⁹Sn. For this case the theory of the Goldanskii Karyagin effect is well established. Mössbauer studies of electric quadrupole interactions in hafnium and tungsten compounds made it necessary to extend the theory to the more complex case of E2-transitions. As the investigated compounds show a strong axial anisotropy of the electric field gradient, a similar behaviour has to be expected in principle for the tensor of the mean-square displacements, which determines the Debye-Waller factor immediately. A fitting procedure taking into account an axial asymmetric Debye Waller factor is worked out and applied to measurements performed with several complex hafnium and tungsten fluorine compounds. With NaWO₂F₃ the quadrupole interactions of¹⁸²W,¹⁸³W, and¹⁸⁴W have been measured yieldingQ ^5/2+(¹⁸³W)/Q ²+(¹⁸²W)=0-86(6) andQ ²+(¹⁸⁴W)/Q ²+(¹⁸²W)=0.955 (3).     

Substituted barium ferrites; sources of anisotropy

Ar-ion sputtering is successfully used to produce intense atomic beams of refractory elements. The population in the ground and low metastable states of Ta 1 is investigated for the sputtered atoms. Isotope shifts and hyperfine structures of seven transitions have been measured for the stable isotopes of Hf, Ta and W. The hyperfine coupling constantsA andB are determined for eight atomic levels of^177,179Hf,¹⁸¹Ta and¹⁸³W.     

Spectral signatures of hyperfine and isotopic effects and of Tm-Tm pairs in LiYF4:Tm

We report on the high-resolution optical Fourier-transform spectroscopy of the LiYF₄:Tm³⁺ crystals. Splitting of several lines in the optical low-temperature polarized spectra was observed. We show that these splittings are caused by (i) the hyperfine interaction, (ii) the isotopic disorder in the lithium sublattice, and (iii) the interionic interaction between neighboring Tm ions. It is the first observation of the hyperfine splitting in the spectra of the Tm³⁺ ions in crystals. From the experimentally measured hyperfine splitting we evaluate the magnetic field at the thulium nucleus and calculate the magnetic g-factors of the excited crystal-field levels.     

Relaxation effects in the Mössbauer hyperfine structure of amorphous Fe70Co10B20 at 125°C

A new approach was attempted in following the irreversible relaxation effects in the hyperfine structure of amorphous Fe₇₀Co₁₀B₂₀. Room temperature transmission⁵⁷Fe Mössbauer spectra were measured in the course of interrupted isothermal annealing. For the data fitting, a model of pseudo-three-dimensional distribution of correlated hyperfine parameters was adopted and the corresponding spectrum modelled by a FFT-based procedure. In addition to commonly used hyperfine parameters, the second order quadrupole splitting was also considered. The time dependences of the average magnetic and the second order quadrupole splittings show two relaxation stages interpreted as the relief of quenched-in stresses and the free volume shrinking.     

The inversional dependence of hyperfine quadrupole coupling in 14NH3

A simple theoretical model explaining the inversional dependence of hyperfine quadrupole coupling in ¹⁴NH₃ is presented. The model, when related to available experimental hyperfine splittings, can be used to predict the effective hyperfine quadrupole coupling constants for all (low-lying) ro-inversional levels. The actual predictions reveal that the inversional dependence of the coupling constants is not only rather strong but also non-monotonic.     

Charge radii and moments of strontium nuclei by laser spectroscopy

The isotope shifts and hyperfine splittings for 11 strontium isotopes (A=80–90) and two isomers for the optical transition λ=293.2 nm were measured. The magnetic dipole and electric quadrupole moments and the changes of the mean square charge radii are derived. The results are discussed with respect to the increasing nuclear deformation and the anomalous coupling scheme of light Sr nuclei.     

The magnetic hyperfine structure in the rotational spectrum of H2CNH

The hyperfine structure in the ground-state rotational spectrum of methanimine was studied in the frequency range of 64-172 GHz by means of the Lamb-dip technique. This allowed to resolve, in some hyperfine components due to the ¹⁴N nucleus, doublets separated by only some tenth of kHz. We explain the splittings as due to magnetic interactions of the three protons with their molecular environment. The analysis of the experimental spectrum has been guided by quantum-chemical calculations of the hyperfine parameters.     

Nuclear orientation of156Tb in gadolinium matrix

The anisotropy of the angular distribution of gamma-rays from the decay of¹⁵⁶Tb, oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ¹⁵⁶¦=(9·6±1·3)×10^?27 J/T and the electric quadrupole momentQ ¹⁵⁶=(2·9±0·9)×10^?28 m² of the¹⁵⁶Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in¹⁵⁶Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models.