Hyperfine structure investigations in the configuration 4f 125d6s 2 of Tm I by laser-atomic-beam spectroscopy

High resolution laser-atomic-beam spectroscopy has been applied to study the hyperfine structure of transitions starting from metastable states of the configuration 4f¹²5d6s² of Tm I. Precise values for the hyperfine constants of 8 levels belonging to the configuration 4f¹²5d6s² and 9 levels belonging to excited odd levels have been determined.     

Tm Mössbauer effect and magnetic study of Tm6Mn23 and its ternary hydride

The magnetic properties and the lattice constants of Tm₆Mn₂₃ were determined before and after hydrogen absorption. The compound Tm₆Mn₂₃ is ferrimagnetic with an ordering temperature T_c = 404 K. After hydrogen absorption the magnetization is strongly reduced and does not point to the occurrence of magnetic ordering. The strongly increasing hyperfine splitting observed by means of ¹⁶⁹Tm Mössbauer spectroscopy in the hydride for temperature below 60 K, however, shows that the Tm sublattice becomes magnetically ordered after H₂ absorption as well. In uncharged and charged Tm₆Mn₂₃ the values of the Tm moments are close to the free ion values.     

Measurements of the hyperfine structure constants of all the 5d 2 and 5d6s levels in139La II using the high-resolution spectroscopy on collinear laser-ion-beams

The hyperfine structure constants A and B of all¹³⁹La II even levels with 5d ² and 5d6s configurations have been measured, mainly by high-resolution spectroscopy on collinear laser-ion-beams. Morover some A and B constants of odd-parity levels have been obtained.     

169Tm Mössbauer effect and magnetic study of Tm6Mn23 and its ternary hydride

The magnetic properties and the lattice constants of Tm₆Mn₂₃ were determined before and after hydrogen absorption. The compound Tm₆Mn₂₃ is ferrimagnetic with an ordering temperature T_c = 404 K. After hydrogen absorption the magnetization is strongly reduced and does not point to the occurrence of magnetic ordering. The strongly increasing hyperfine splitting observed by means of ¹⁶⁹Tm Mössbauer spectroscopy in the hydride for temperature below 60 K, however, shows that the Tm sublattice becomes magnetically ordered after H₂ absorption as well. In uncharged and charged Tm₆Mn₂₃ the values of the Tm moments are close to the free ion values.     

The magnetic hyperfine field at Cd nuclei in the rare earth ferromagnets Gd,Tb, Dy,Ho, Er and Tm

The time differential perturbed angular correlation technique has been used to study the combined magnetic and electric hyperfine interactions at the site of a¹¹¹Cd impurity in the rare earth ferromagnets Gd, Tb, Dy, Ho, Er, and Tm at 4.2 °K. The following magnetic hyperfine fields at the site of¹¹¹Cd have been found: ¦H _hf ¦=340(7) kG in Gd, 275 (5) kG in Tb, 221 (4) kG in Dy, 116 (3) kG in Er and 60 (6) kG in Tm. In Ho two magnetically different sites were observed with magnetic fields of 159 (3) and 139 (3) kG. Both sites are equally populated. The coupling constantJ _5f of the conduction electron-4f interaction has been calculated for the different rare earth metals from the measured hyperfine fields by means of the RKKY theory.     

Rotational spectra, nuclear quadrupole hyperfine tensors, and conformational structures of the mustard gas simulent 2-chloroethyl ethyl sulfide

Rotational spectra have been recorded for both the ³⁵Cl and ³⁷Cl isotopic forms of two structural conformations of 2-chloroethyl ethyl sulfide (CEES). The rotational constants of the ³⁵Cl and ³⁷Cl isotopomers were used to identify the conformational isomers. A total of 236 hyperfine transitions have been assigned for 47 rotational transitions of the ³⁵Cl isotope of a GGT conformer, and 146 hyperfine have been assigned for 37 rotational transitions of the ³⁷Cl isotopomer. For the second conformer, a total of 128 (110) hyperfine and 30 (28) rotational transitions have also been assigned to the ³⁵Cl (³⁷Cl) isotopes of a TGT conformation. The extensive hyperfine splitting data, measured to high resolution with a compact Fourier transform microwave spectrometer, were used to determine both the diagonal and off-diagonal elements of the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors in the inertial tensor principal axis system. The experimental rotational constant data, as well as the ³⁵Cl and ³⁷Cl nuclear quadrupole coupling tensors, were compared to the results from 27 optimized ab initio (HF/6-311++G^∗∗ and MP2/6-311++G^∗∗) model structures.     

Application of the laser ion source for isotope shift and hyperfine structure investigation

The study of nuclei far from stability requires high sensitivity of the experimental technique. The method of Resonance Ionization Spectroscopy in a Laser Ion Source (RIS/LIS) allows one to carry out measurements of the isotope shifts and hyperfine splittings for isotopes at the production rate about 10² atoms per second. The sensitivity of this method is determined by the high efficiency of the laser ion source and the low background of the detection system afforded by characteristic α particle registration. The isotope shifts and hyperfine structures of ¹⁵⁵Yb, ¹⁵⁴Tm (I=9 and I=2) and ¹⁵³Tm (I=11/2) have been measured and the isotopic changes in mean square charge radii and nuclear electromagnetic moments have been determined. The further development of this experimental method – enhanced Target Ion Source system aimed to suppress thermionic background – enables direct detection of the photoions and widens the range of the applicability of the RIS/LIS method. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

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.     

Magnetic and electric hyperfine interactions of181Ta implanted in thulium

The magnetic and electric hyperfine interaction at the site of dilute¹⁸¹Ta impurities in the rare earth metal Tm has been investigated as a function of temperature by TDPAC measurements. The samples were prepared by ion implantation of radioactive¹⁸¹Hf. In the paramagnetic phase between 100 K and 700 K the electric fieldgradient is a linear function of temperature: V_zz(T)=V_zz(O)·(1-A·T) with A=4.6·10^?4K^?1 and V_zz(293K)=6.4 (4)·10¹⁷v/cm². The TDPAC spectrum observed at 4.2 K reflects the 4 magnetically non-equivalent sites for an impurity in magnetically ordered Tm. The relative values and amplitudes of the corresponding 4 magnetic hyperfine fields are consistent with the predictions of the RKKY theory.     

The hyperfine structure and hyperfine anomaly of 161Dy and 163Dy

The hyperfine structure of ¹⁶¹Dy and ¹⁶³Dy for five transitions hasbeen measured with a tunable dye laser and a thermal velocity atomic beam. Values for the magnetic dipole and electric quadrupole coupling constants have been determined for the relevant excited states. The hyperfine anomaly parameters, Δ, which are extracted are interpreted in terms of available atomic wave functions.     

ESR- und ENDOR-Spektren von F-Zentren in RbCl und RbBr

ESR- and ENDOR-spectra of F-centers in RbCl and RbBr have been measured, giving the hyperfine constants for 5 resp. 6 shells of neighbouring ions. The resolved structure with a characteristic distance of 36 G in the ESR-spectrum of RbCl is due to the interaction with the nearest Rb⁸⁵ nuclei. All results fit well with the properties of F-centers in other alkali halides.     

The lattice location and hyperfine field of implanted Yb in Fe as a function of annealing temperature

A combined study has been made of the lattice location and hyperfine field of Yb implanted into Fe single crystals. The location has been determined by ion channeling and back-scattering, the hyperfine field by perturbed angular correlation (PAC) measurements on¹⁶⁹Yb (decaying to excited states in¹⁶⁹Tm). The channeling experiments indicate that initially about 60% of the Yb atoms occupy substitutional sites in the Fe lattice, while the remaining atoms are not in any specific crystallographic site. On annealing, Yb migrates from substitutional to non-substitutional sites. No Yb atoms remain substitutional after a 600°C anneal. By making PAC measurements at two temperatures for two - cascades in¹⁶⁹Tm, it is found that the PAC pattern can be described using a combined static and time-dependent magnetic interaction. The PAC results show that the average hyperfine field and relaxation parameter decrease on annealing, and that the field disappears after a 600°C anneal. The correlation between the location and the hyperfine field is discussed. A comparison of the results with previous Mössbauer results for¹⁵¹Gd implanted in Fe, together with relaxation parameter measurements on a¹⁶⁹Yb₂O₃ source, suggests that the non-substitutional Yb is internally oxidized in the Fe host.Work partly carried out while at the Clarendon Laboratory, Oxford, England and Nuclear Physics Division, AERE, Harwell, England.     

Nuclear shielding and magnetic hyperfine structure of hydrogen cyanide

A millimeter-wave molecular beam maser has been used to resolve the magnetic hyperfine structure of hydrogen cyanide. The spin-rotation interaction constants have been measured for the three nuclei ¹⁴N, ¹³C, and H. The paramagnetic nuclear shielding factors have been calculated for the three nuclear sites. The spin-rotation constants for ¹⁴N in H¹²C¹⁴N, for H in H¹²C¹⁴N and for ¹³C in D¹³C¹⁴N are + 10.4 kHz, −3.7 kHz, and +15.0 kHz, respectively. The respective paramagnetic shielding factors are −408.98 × 10⁻⁶, −73.40 × 10⁻⁶, and −249.52 × 10⁻⁶.     

High-Resolution Visible Laser Spectroscopy of Cobalt Monochloride

The electronic spectrum of cobalt monochloride has been investigated from 415 to 725 nm using a laser-ablation/molecular-beam laser-induced fluorescence spectrometer. Two separate electronic systems with origins near 483.3 and 470.3 nm were observed. Data have been recorded for these two transitions at both low and high resolution. These transitions are now characterized as the [20.7]³Φ₄−X³Φ₄ and [21.3]³Φ₄−X³Φ₄ transitions. A low-resolution vibrational analysis and a high-resolution rotational analysis have been carried out for each system, resulting in accurate values for the ground and excited state vibrational spacings and effective rotational constants. In addition, the magnetic hyperfine structure resulting from the spin of the Co nucleus was resolved and the hyperfine constants were determined. Comparison of the CoCl spectrum with that of CoH and CoF has allowed the ground state electron configuration of (core)(10σ)²(4π)⁴(1δ)³(5π)³(11σ)² to be determined. The hyperfine constants support the electron promotion 11σ→12σ for the observed transitions.     

Saturated absorption experiments using a free running CW dye laser

The hyperfine structure of some new iodine lines has been observed over the tuning range of Rhodamine 6G (5800–6200 Å), using a free running, single mode cw dye laser. The resolution obtained in this experiment allowed to calculate the hyperfine constants of the excited state (³π₀⁺) of iodine with an accuracy of 2% for the quadrupole coupling constant and 50% for the magnetic one.     

The contribution of 5d electrons to the saturation magnetic moments and magnetic hyperfine fields in the heavy rare earth metals

The main results of a model for 5d electrons in the heavy rare earth metals are presented. The model involves the use of wave functions based on published analyses for 4fⁿ5d6s² atomic configurations, and the spreading of each of these energy levels uniformly over a band of width W in the metals. Excess saturation magnetic moments above those of the tripositive ions can be explained by the model with W in the range 0.84±0.16eV in the five metals Gd, Tb, Dy, Er and Tm. The magnetic hyperfine fields in the metals include negative contributions from the 5d electrons which have been shown to amount to about ?250koe in Gd, Er and Tm.     

High-resolution LIF measurements on hyperfine structure and isotope shifts in various states of Lu I using the second and third harmonic of a cw Ti:sapphire laser

With the second and third harmonic of a tunable single-mode cw Ti:S laser, generated inside external enhancement cavities, high-resolution LIF measurements on several states of Lu I in various parts of the electromagnetic spectrum are performed. From these measurements, hyperfine structure A and B constants for both ¹⁷⁵Lu and ¹⁷⁶Lu as well as isotope shifts have been determined for all levels observed in the single-step excitation process. From the measured A constants, the magnetic hyperfine structure anomaly has been derived for various states. Received 14 January 2002 Published online 19 July 2002     

57Fe and 166Er Mössbauer and magnetic studies of RFe4B (R = Er,Tm, Lu) compounds

Magnetic and Mössbauer studies have been carried out on a series of ternary borides RFe₄B (R = Er, Tm, Lu) which have the hexagonal CeCo₄B type structure. These compounds are found to be magnetically ordered at room temperature. Magnetization studies in the temperature range from 5 to 300 K reveal the presence of compensation temperatures in Er and Tm compounds and indicate antiferromagnetic coupling between the rare earth and Fe moments. Room temperature ⁵⁷Fe Mössbauer studies yield values of hyperfine fields at the two Fe sites as 246 and 185 kOe in ErFe₄B and TmFe₄B, and 204 and 145 kOe in LuFe₄B. The ¹⁶⁶Er Mössbauer studies give nearly free-ion hyperfine field at the Er sites which indicates that the exchange interaction in ErFe₄B is much stronger than crystal field interaction.