Nuclear moments and the change in the mean square charge radius of neutron deficient thallium isotopes

The hyperfine structure, isotope and isomeric shifts in the atomic transition 6p ² P _3/2–7s ² S _1/2, =535 nm have been measured for theI=7 andI=2 states of^{190, 192, 194, 196}Tl; theI=1/2 andI=9/2 states of¹⁹¹Tl and the I=7 isomer of¹⁸⁸Tl. The thallium isotopes were prepared as fast atomic beams at the GSI on-line mass separator following fusion reactions and — in some cases — subsequent-decay. The nuclear dipole moments, electric quadrupole moments and the change in the nuclear mean square charge radius are evaluated. Theuu-isotopes show an isomeric shift which changes sign between¹⁹²Tl and¹⁹⁴Tl.Dedicated to P. Armbruster on the occasion of his 60th birthday     

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.     

Forbidden lines in the hyperfine spectrum of the electron paramagnetic resonance of Mn++ in BaTiO3

The hyperfine spectrum of Mn⁺⁺ in powder BaTiO₃ was studied at 8740 MHz andT=80°K. The measured lines appearing as doublets between the hyperfine lines of Mn⁺⁺ are explained as forbidden transitions of the typeM=±1,m=±1. A theoretical expression for the position of these doublets is given and some of the constants of the spin Hamiltonian are determined:g=2.001±0.001, ¦A¦=86 Oe,D 40 Oe.     

Precise measurement of the quadrupole moment of β-emitting12B

Hyperfine interactions of¹²B(I ,T _1/2=21 ms) implanted in the substitutional site of B atoms (stable) in a (single crystal like) BN (hexagonal) was studied by use of a -NMR detection. For efficient and simple measurements, the conventional -NMR has been modified as a new nuclear quadrupole resonance technique (NNQR). For the present case with the nuclear spinI=1 the detection efficiency is improved about 30 times compared with the one with the old method. The quadrupole moment of¹²B was determined precisely as ¦Q(¹²B; 1⁺)¦=13.21±0.26 mb.     

Hyperfine field of samarium in europium monoxide

The hyperfine magnetic field at samarium in europium monoxide at 4.2 K was measured using the time-differential perturbed angular correlation technique. The resultH _hf=147.9±9.7 T indicates a 4f contribution of 130±20 T which is 60% less than the free ion value for Sm³⁺. It is suggested that there exists crystal plus exchange field interactions causing admixtures of the first excited state of Sm³⁺ with its ground state.     

The nuclear magnetic moment of182Ta

The nuclear magnetic moment of¹⁸²Ta has been measured with the aid of the NMR-ON technique, using the hyperfine fieldB=–65.6±1.3T in iron. Its value =298±0.06 _N is in excellent agreement with that calculated for a Nilsson configuration, using proper parametersg _K andg _R derived from neighbouring odd-A nuclei. Agreement is also found between experimental and calculated nuclear magnetic moments of¹⁸⁴Re, which has the sameK=1/2 neutron state as¹⁸²Ta.     

Precise measurement of quadrupole moment of8B by use of a modified β-NMR

The nuclear quadrupole moment of⁸B(I =2⁺,T _1/2=769 ms) has been determined by use of a modified -NMR detection as |Q(⁸B)|=68.3±2.1 mb. A field gradient was obtained in a single crystal Mg at room temperature.     

Magnetic moment of23Mg

The magnetic moment of the²³Mg (I =3/2⁺, T_1/2=11.3 s), has been determined as |(²³Mg)|=0.5364±0.003 µ_N by use of -NMR detection with the recoil polarization obtained through a low energy nuclear reaction.     

Output power enhancement of the 632.8 nm monomode He-Ne/I2-laser

For the He-Ne/I₂-laser, a stable monomode operation has been realized when the tube pressure exceeds a certain level. An output power of more than 1 mW has been obtained at the 632.8 nm laser transition. Within the monomode tuning range of the laser, the d, e, f, g, and h, i, j iodine hyperfine components of the R(127) line of the 11–5 band of the B ³ II ⁺ _0u–X ¹⁺ _0g electronic transition have been observed. The mode selection method used makes it possible to increase the contrast of the iodine hyperfine components.     

Precise measurement of the magnetic moment of doubly closed shell + 1 nucleon nucleus17F(I π=5/2+,T 1/2=64.5 s)

Hyperfine interactions of -emitting¹⁷F implanted in single crystals of NaF and CaF₂ were studied. The nuclear magnetic moment of theI =5/2⁺ state was determined with improved precision to be |(¹⁷F;I =5/2⁺,T _1/2=64.5s)|=4.72130±0.00025 µ_N.     

Muon knight shift in platinum and in β-PdHx (x=0.70, 0.75, 0.86)

The ⁺ Knight shift in Platinum has been measured between 20 K and 785 K. It shows a strong temperature dependence and scales with the magnetic bulk susceptibility. A temperature independent contribution of +53±15 ppm and a d-electron induced hyperfine field per unpaired d-electron per atom of B _hfd ^a =–5.03 kG(±8.5%) are obtained. The ⁺ Knight shift in PdH_0.70, PdH_0.75 and PdH_0.86 shows no dependence on temperature between 20 K and RT and increases from K=–(8±3) ppm for x=0.70 to K =+(6.5±3) ppm K=+(6.5±3) ppm for x=0.86, in good agreement with proton Knight shift measurements.     

Decay of Cs134m

The decay of the isomeric state of Cs¹³⁴ was studied. The decay half-timeT _1/2=2·93±0·05 hours was determined. From measurements carried out by means of a spectrometer with short lens, scintillation measurements and chemical separations, the non-existence of the weak decay of this state was proved, contrary to statements found previously in the literature (maximum possible intensity 0·02%, compared to the value of 1% found in the literature). The spectrum of conversion electrons was measured by a double-focusing spectrometer, and the following transition energies were determined: 127·3±0·3 keV (E3) and 138·4±0·4 keV (M4) (K:L:M+N is 92 100 27 for the 127·3 keV transition, and 206 100 31 for the 138·4 keV transition). The conversion coefficient of the 127 keV transition was measured, resulting in a value of _k =2·55±±0·4. The ratio of transition intensities isI ₁₃₈ I ₁₂₇=5·7 1000.     

NMR properties of hcp Ru metal — first detection of the99Ru and101Ru NMR in a paramagnetic solid

Results of nuclear magnetic resonance (NMR) measurements on hexagonal close-packed Rumetal are presented. The field spectra of both isotopes, having a nuclear spinI of 5/2, show a shape characteristic for quadrupolar disturbed NMR. From a simulation of these spectra, the electric field gradientV _zz has been determined to be (37±0.5)×10^–13 esu/cm³ in agreement with recent band structure calculations. The Knight shift tensor elements deduced from the spectra areK _x =K _y =0.46±0.02% andK _z =0.56±0.02%. These rather high and positive shifts are completely in line with that of the neighboring elements in the periodic system and have primarily to be ascribed to the Van Vleck contribution. This part of the Knight shift is also responsible for the rather strong anisotropy, that has been found.     

Muon Knight shift in platinum and in β-PdHx (x=0.70, 0.75)

The ⁺ Knight shift in platinum has been measured between 20 K and 785 K. It shows a strong temperature dependence and scales with the magnetic bulk susceptibility. A temperature independent contribution of +40 to +60 ppm and a d-electron induced hyperfine field per unpaired d-electron per atom ofB _hf,d =–5.03 kG (±8.5%) are obtained. The ⁺ Knight shift in PdH_0.70 and PdH_0.75 shows no dependence on temperature between 20 K andRT and increases fromK ppm forx=0.70 toK ppm forx=0.75, in good agreement with proton Knight shift measurements.     

Measurements of magnetic moments of Tc isotopes and the hyperfine field of Tc in Fe and Ni

We report measurements of nuclear magnetic resonance on oriented nuclei (NMR-ON) on⁹⁴Tc (I=7⁺,T _1/2=4.9 h),⁹⁵Tc (I =9/2⁺,T _1/2=20 h) and⁹⁶Tc (I =7⁺,T _1/2=4.3 d) in Fe and on⁹⁵Tc and⁹⁶Tc in Ni. In order to elucidate the discrepancies on the hyperfine field of TcFe in the literature, the resonances were measured with high precision as a function of the external magnetic field B_ext up to 2.0 T. In addition, TDPAC measurements were performed on⁹⁹TcFe at T=300 K and 13 K. TheT=0 K hyperfine fields of Tc in Fe and Ni were determined to be –314(3) kG and –51.8(5) kG, respectively. The g-factors of⁹³Tc,⁹⁴Tc,⁹⁵Tc,⁹⁶Tc and⁹⁹Tc(E=181 keV;I =5/2⁺) are redetermined as g(⁹³Tc)=1.405(14), g(⁹⁴Tc)=0.731(7),g(⁹⁵Tc)=1.321(13), g(⁹⁶Tc)=0.727(7), g(⁹⁹Tc)=1.390(17).We wish to thank E. Smolic and G. Seewald for experimental help. This work was funded by the German Federal Minister for Research and Technology (BMFT) under the contract number 06TM353/TP 4, by the Deutsche Forschungsgemeinschaft (DFG) under the contract numbers Ha 1282/3-1,2, and, partly, by the Kernforschungszentrum, Karlsruhe.     

Absolute frequency measurements and comparisons in iodine at 735 nm and 772 nm

We report frequency measurements at the rovibronic transition P(42)1-14 (772 nm) and R(114)2-11 (735 nm) from the electronic transition of the iodine molecule ¹²⁷I₂ with the help of a frequency comb as a reference. By using Doppler-free saturation spectroscopy a frequency precision in the 7 × 10⁻¹⁰ region is reached and two iodine cells both operated at 550-600 °C are compared. To relate our results to other measurements, the absolute transition frequency of the hyperfine structure line P(148)1-14 a₁ at 780 nm with an already known transition frequency was also determined.     

Molecular field effects in Mössbauer spectra of FeSb2O4

Mössbauer effect measurements have been made using⁵⁷Fe in FeSb₂O₄. At liquid helium temperature a combined electric quadrupole and magnetic hyperfine interaction is observed withH _eff=185±2 kOe, 1/2e ² qQ=2.94±0.09 mm/sec and =0.37±0.09. The direction ofH _eff is perpendicular to thec axis of the crystal and at 33° to the <110> direction. Thec axis is determined to be the direction of the intermediate principal EFG tensor axis. Calculations are made using a molecular field term in the Hamiltonian for the Fe²⁺ orbitals. The results of these calculations are used to explain the observed values of 1/2e ² qQ and and permit a determination of the ordring of the T_2g orbitals among the T_2g energy levels.     

Giant quadrupole moment andproton halo discovered in8B

The nuclear quadrupole moment of⁸B(I =2⁺,T _1/2=769 ms) has been determined by use of a modified -NMR detection as |Q(⁸B)|=68.3±2.1 mb, which is twice the prediction of the Cohen-Kurath shell model calculation. The anomalous quadrupole moment which is carried mainly by the protons in the nucleus, has been accounted for by the proton halo effect.