NMR-ON on196,197m,198,198m,200mAu in Fe and Ni

The zero-field hyperfine splitting frequencies of a series of Au isotopes in Fe and Ni have been determined with nuclear magnetic resonance on oriented nuclei. The results are:. For¹⁹⁸Au(2^–) in Fe the quadrupole splitting could be resolved. The results are ¦g_NB_HF/h|=259.48 (3) MHz and e²qp/h=–2.08(4) MHz. Our measurements show that most hyperfine splittings published on these isotopes have been incorrect. The quadrupole splitting of¹⁹⁸AuFe disagrees in magnitudeand sign from the value reported by single-passage NMR on oriented nuclei. The following nuclear quantities are deduced: (^197mAu,11/2^–)=5.98(9) _N; (^198mAu, 12^–)=5.85(9) _N; (^200mAu, 12^–)=5.90(9) _N; Q(¹⁹⁸Au,2^–)/Q(¹⁹⁹Au, 3/2⁺)=1.37(3). Our measurements show further that the non-contact hyperfine field for Au in Ni is smaller than assumed previously, and that the magnetic hyperfine splitting frequency of¹⁹⁷AuFe known from NMR is inconsistent with the magnetic hyperfine splitting frequencies of^{198, 199}AuFe.     

Deformation change in light iridium nuclei from laser spectroscopy

Laser spectroscopy measurements have been performed on neutron-deficient and stable Ir isotopes using the COMPLIS experimental setup installed at ISOLDE-CERN. The radioactive Ir atoms were obtained from successive decays of a mass-separated Hg beam deposited onto a carbon substrate after deceleration to 1kV and subsequently laser desorbed. A three-color, two-step resonant scheme was used to selectively ionize the desorbed Ir atoms. The hyperfine structure (HFS) and isotope shift (IS) of the first transition of the ionization path 5d ⁷6s ²⁴ F _9/2 → 5d ⁷6s6p ⁶ F _11/2 at 351.5nm were measured for ^182-189Ir, ¹⁸⁶Ir ^m and the stable ^{191, 193}Ir. The nuclear magnetic moments μ_I and the spectroscopic quadrupole moments Q_s were obtained from the HFS spectra and the change of the mean square charge radii from the IS measurements. The sign of μ_I was experimentally determined for the first time for the masses 182≤A≤189 and the isomeric state ¹⁸⁶Ir ^m . The spectroscopic quadrupole moments of ¹⁸²Ir and ¹⁸³Ir were measured also for the first time. A large mean square charge radius change between ¹⁸⁷Ir and ¹⁸⁶Ir ^g and between ¹⁸⁶Ir ^m and ¹⁸⁶Ir ^g was observed corresponding to a sudden increase in deformation: from β₂ ≃ + 0.16 for the heavier group A = 193, 191, 189, 187 and 186m to β₂≥ + 0.2 for the lighter group A = 186g, 185, 184, 183 and 182. These results were analyzed in the framework of a microscopic treatment of an axial rotor plus one or two quasiparticle(s). This sudden deformation change is associated with a change in the proton state that describes the odd-nuclei ground state or that participates in the coupling with the neutron in the odd-odd nuclei. This state is identified with the π3/2⁺[402] orbital for the heavier group and with the π1/2^-[541] orbital stemming from the 1h _9/2 spherical subshell for the lighter group. That last state seems to affect strongly the observed values of the nuclear moments.     

Half-life measurements and gamma spectroscopy in the decay184Re m →184W

The half-lives of the intrinsic states at 1,285.8 and 1,502.2 keV in¹⁸⁴W have been measured in the decay of¹⁸⁴Re ^m to be 8.33±0.18Μs and 2.35±0.10 ns, respectively. These half-lives determine absolute gamma-ray transition probabilities of eight transitions and yield upper limits for three transitions. The decay scheme of¹⁸⁴Re ^m →¹⁸⁴W is improved through measurements of delayed gamma-ray spectra with a Ge(Li) detector. Spin and Nilsson model interpretations are discussed.     

Low-lying states of 184W and 184Os nuclei

The energy levels, transition energy, B （E2） values,intrinsic quadrupole moment Q₀ and potential energy surface for even-even ¹⁸⁴W and ¹⁸⁴Os nuclei were calculated using IBM-1. The predicted energy levels, transition energy, B（E2） values and intrinsic quadrupole moment Q₀ results are reasonably consistent with the experimental data. A contour plot of the potential energy surfaces shows that two interesting nuclei are deformed and have rotational characters.     

New isotope184Pb

The new isotope¹⁸⁴Pb has been produced through⁴⁰Ca +^147,148Sm reactions, and detected by its a radioactivity (E_α = 6618 ± 10 keV). The detection technique involves thermalization of recoil nuclei in a gas and electrostatic collection onto the active surface of a solid state detector. The identification is made on the basis of the (⁴⁰Ca,xn) excitation functions, and of the time correlation with the α-decay of the daughter¹⁸⁰Hg.     

Magnetic hyperfine field of Hg in nickel and the sign of magnetic moment of 197mAu by NMR-ON

Nuclear magnetic resonance on oriented nuclei (NMR-ON) measurements were performed on the successive decay of ^197mHg–^197mAu in Ni. The NMR-ON resonance spectra of ^197mHgNi were obtained by detecting the 134 keV γ-ray from the decay of ^197mHg and the 279 keV γ-ray from the decay of ^197mAu. The magnetic hyperfine splitting frequency of ^197mHgNi in an external magnetic field of 0.2 T has been determined as 16.55(6) MHz. With the known g-factor of ^197mHg the hyperfine field of B₈₂(^197mHgNi)= -13.53(6) T was deduced. The anisotropy of the 279 keV γ-ray (^197mAu to ¹⁹⁷Au) increased at the resonance. This phenomenon was explained using the spin inversion process including the lifetime of the isomer and the spin–lattice relaxation time. The sign of the g-factor of ^197mAu was determined to be positive. This revised version was published online in August 2006 with corrections to the Cover Date.     

Band crossing in184Pt

The levels in the ground band of¹⁸⁴Pt are identified up to the member with spin 20 in an in-beam spectroscopy experiment on theγ-rays following the¹⁷⁷Hf(¹²C, 5n)¹⁸⁴Pt reaction. In contrast to the situation in the heavier Pt isotopes, where the 10⁺ to 12⁺ level spacing is very small, the transition energies in¹⁸⁴Pt show a monotonie increase with spin. However, between spin 10⁺ and 14⁺ the moment of inertia grows quite rapidly and this appears to be reminiscent of the much more pronounced irregularity encountered in the isotopes of larger mass. This property of the moment of inertia is discussed within a model where twoi _13/2 neutron quasiparticles or twoh _9/2 orh _11/2 proton quasiparticles may be excited and coupled to the rotation of the core.     

Possible phase change between itinerant ferromagnetism and superconductivity

It is pointed out theoretically that a single electron band model is able to exhibit the interchange of two phases: itenerant band ferromagnetism and superconductivity. Our theory is based on the molecular field approximation applied for a simplified electron-electron interaction. Possible phase changes are discussed in connection with two phase transitions of ferromagnetism and superconductivity in the intermetallic compound Y₄Co₃.     

Die relative Isotopenlage des Os184

Using 3 mg of an Osmium sample, enriched in Os¹⁸⁴ to 2.25%, the isotopic shiftΔν(Os¹⁹²?Os¹⁸⁴) has been measured in two Os I-lines with a recording Fabry-Perot interferometer. The relative isotopic shift of Os¹⁸⁴ has been found to be\(\frac{{\Delta v(Os^{192} - Os^{184} )}}{{\Delta v(Os^{192} - Os^{190} )}} = 4.79 \pm 0.05\).     

Direct neutron scattering from 182W and 184W

Differential elastic and inelastic neutron scattering cross sections for ¹⁸²W and ¹⁸⁴W have been measured at incident energies 4.87 and 6.00 MeV. Cross sections for the first (0⁺, 2⁺, 4⁺, 6⁺), second (0⁺, 2⁺), and some higher excitations are presented. Angular distributions exhibit direct reaction characteristics, suggesting that compound cross sections for these states are small. This is supported by statistical-model calculations. Coupled-channel calculations of cross sections are made using a phenomenological deformed optical potential. Quadrupole and hexadecapole deformations have been searched to optimize fits. The necessity of introducing a β₆ deformation is investigated. Electric multipole transition matrix elements, used in the coupled-channel analysis, are obtained from the rotation-vibration model and the dynamic-deformation theory.     

Relationship between efficiency and predictability in stock price change

In this study, we evaluate the relationship between efficiency and predictability in the stock market. The efficiency, which is the issue addressed by the weak-form efficient market hypothesis, is calculated using the Hurst exponent and the approximate entropy (ApEn). The predictability corresponds to the hit-rate; this is the rate of consistency between the direction of the actual price change and that of the predicted price change, as calculated via the nearest neighbor prediction method. We determine that the Hurst exponent and the ApEn value are negatively correlated. However, predictability is positively correlated with the Hurst exponent.     

Low-spin states of doubly odd 184Au

Low-spin states of ¹⁸⁴Au have been studied using the β⁺/EC decay of ¹⁸⁴Hg. γ-ray and conversion-electron singles spectra were recorded with ¹⁸⁴Hg mass-separated sources. For γ-γ-t and X-γ-t coincidence measurements, mercury nuclei were produced in the ¹⁴⁸Sm + ⁴⁰Ar reaction and transported by a He-jet system. The electron spectra were recorded from ¹⁸⁴Hg sources produced at ISOLDE. A level scheme of ¹⁸⁴Au including 48 transitions is proposed. The experimental results are interpreted in the frame of a semi-microscopic axial-rotor-plus-two-quasiparticle model developed in the context of the HF+BCS approximation.     

Vibrational band structure in 184W populated in the decay of 184Re

The decay of ^184mRe has been investigated through γ-ray and conversion electron studies. The band head of the K^π = 2^? octupole band has been established at 1130.0 keV. The E2/M1 mixing ratios of three transitions from the γ-vibrational band to the ground state band have been determined by angular correlation measurements. A mixing of El, M2 and E3 multipolarity has been derived for the 921 keV transition combining angular correlation and conversion electron data. A value B(E3, 0⁺ → 3^? = (25 ± 5) × 10⁴e² · fm⁶ was obtained from the measured E2/M1 mixing of the 91 keV 3^? → → 2^? transition and γ-branchings. The data are discussed in terms of the collective model taking into account band mixing.     

Nuclear orientation of183Re and184Re in iron

The temperature dependence of the anisotropy of γ-rays from the decay of oriented¹⁸³,¹⁸⁴Re nuclei situated in an iron matrix was measured between 14 and 33 mK. Magnetic hyperfine splitting constants ofgH _HF=5.04(9) × 10^?18 erg andgH _HF=3.21 (13) × 10^?18 erg were determined for the groundstates of¹⁸³Re and¹⁸⁴Re, respectively. With the previously known hyperfinefield of ?760(15) kG for Re in iron the followingg-factors were deduced:¹⁸³Reg=1.32 (5) and¹⁸⁴Reg=0.84 (5). The E2/M1 mixing ratio of the 793 keV 2⁺ ?2⁺ transition in¹⁸⁴W was accurately determined to δ (793 keV)=+16.65 (85).     

The scattering of fast neutrons from W184

Neutrons with energies of 0.3 to 1.5 MeV are scattered from W¹⁸⁴. Pulsed-beam fast time-of-flight techniques including a magnetic bunching system are utilized to resolve the elastically scattered neutrons from those inelastically scattered. The differential elastic cross section is measured at 50 keV intervals with an ≈20 keV incident neutron energy spread. The differential cross sections for inelastic scattering resulting in the excitation of residual nuclear levels at 111±5, 365±10, 690±40, 900±25, 1000±30, and 1120±30 keV are determined. In all instances the inelastically scattered neutrons are emitted, within experimental error, isotropically. The experimental results are compared with those obtained in previous work and with the predictions of theory.     

Multi-quasiparticle states in 184 W via multi-nucleon transfer

A multi-nucleon transfer reaction using an 850 MeV ¹³⁶Xe beam incident on a ¹⁹⁸Pt target was used to populate high-spin states in ¹⁸⁴W, 14 nucleons from the target. A 4-quasiparticle isomer with ns has been observed for the first time and its de-excitation through collective and intrinsic structures studied. The results are compared with predictions of blocked BCS Nilsson calculations. Observation of this metastable state completes the tungsten 4-quasiparticle isomer systematics from A = 176 to 186. Mapping out the most yrast 4-quasiparticle isomers in these even-even tungsten isotopes suggests the existence of a highly favoured state in ¹⁸⁸W, within reach of current experimental set-ups.Received: 14 October 2003, Revised: 14 November 2003, Published online: 18 May 2004PACS: 21.10.Tg Lifetimes - 23.20.Lv transitions and level energies - 27.70. + q