Nuclear Thomson scattering of 5.5–7.2 MeV photons

The elastic differential scattering cross section from carbon and magnesium targets was measured at θ = 140° using monoenergetic photons in the range 5.5–7.2 MeV. The contribution of nuclear Thomson scattering is shown to be dominant. The results are in good agreement with predicted values.     

Study of the 49Ti energy levels using the (γ, γ′) and the (γ, n) reactions

An unbound level in ⁴⁹Ti at 8884 keV was photoexcited using a γ-beam obtained from the Cr(n, γ) reaction. The γ-decay and n-decay properties of this level were studied using angular distributions and polarization measurements. Thus spin and parity assignments of some levels in ⁴⁹Ti were made. The neutron width and the total radiative widths of the 8884 keV level were determined to be: Γ_n = 0.25 ± 0.05 eV, Γ_γ = 2.55 ± 0.80 eV.     

Interference between nuclear resonance and nuclear Thomson scattering of photons

The elastic differential scattering cross section from ⁵⁵Mn has been measured at θ = 140° with E_γ = 5.5–11.4 MeV photons. Evidence for destructive interference between nuclear resonance (NR) scattering and nuclear Thomson (NT) scattering has been obtained.     

Electronic Properties of MoSi2-Type Hf2X Intermetallic Compounds (X=Pd,Ag, Cd)

The Hf z coordinate and the value of the electric field gradient (efg) main component (V _zz ), were calculated for three Hf₂X compounds (X = Pd, Ag, Cd) on a first-principle basis, using the full potential linear augmented plane wave (LAPW) method. Exchange and correlation effects were treated either by the local spine density approximation (LSDA) or by the more advanced generalized gradient approximation (GGA). The calculated V _zz values, in the Hf site, were in very good agreement with available ¹⁸¹Hf TDPAC experimental results. This revised version was published online in September 2006 with corrections to the Cover Date.     

XRD, TDPAC and LAPW study of Hf10B2 under high pressure

The crystallographic structure and electronic properties of Hf¹⁰B₂ were studied as a function of pressure by combining X-ray diffraction measurements with full potential linearized augmented plane wave (LAPW) calculations. No phase transition was observed up to a pressure of 30.8 GPa, with a total volume contraction of V/V ₀?=?0.85 and a bulk modulus value of B ₀?=?232 ±13 GPa. The calculated V _zz value at the hafnium site is linearly increasing as a function of the pressure induced volume reduction, while the V _zz value at the boron site stays almost zero. The major contribution to the V _zz value at the hafnium site comes from a p–p contribution next to the probe nucleus, with a relatively large d–d contribution of about 25%. This unusual large d–d contribution arises from the hafnium p–d electrons coupling.     

TDPAC study of the ZrCo-hydrogen system

The properties of the ZrCo-hydrogen system as a function of composition ratio H/ZrCo were investigated by combining TDPAC and X-ray diffraction techniques with the full potential linearized augmented plane wave (LAPW) band structure calculations. It was found that during hydrogenation ZrCo transferred directly into ZrCoH₃ and no transition phase existed. The z component V_zz of the efg and the asymmetry parameter η at the Zr and Co sites were calculated for ZrCoH₃ by using the structure parameters of Zr and Co, obtained in the present work, combined with the hydrogen structure parameters obtained from neutron diffraction on ZrNiH₃. The calculations are in good agreement with the measured values for V_zz and η. This agreement is consistent with the proposed 4c and 8f interstitial sites occupancy of the hydrogen atoms in ZrCoH₃. This revised version was published online in August 2006 with corrections to the Cover Date.     

An ion mobility spectrometry/mass spectrometry (IMS/MS) study of the site of protonation in anilines

Ion mobility spectrometry (IMS) and IMS/MS techniques were used to differentiate between nitrogenprotonated and carbon-protonated anilines, both of which coexist under the conditions of the IMS. Analysis of the results led to the conclusion that the former species had lower mobilities than the latter. This was attributed mainly to charge delocalization in the ring-protonated species, which results in a weaker interaction with the drift gas molecules. Furthermore,meta-alkyl substitution enhanced ring protonation, while in 2-chloroaniline the nitrogenprotonated species was predominant, as expected.     

The magnetic moment of the 4+, 3.55 MeV level of 18O

The magnetic moment of the 4⁺, 3.55 MeV level of ¹⁸O has been determined to be |g| = 0.62 ± 0.10 in a perturbed angular correlation measurement on nuclei recoiling into gas and vacuum. Analysis of the recoil-into-gas data using the Abragam-Pound model agrees with analysis of the recoil-into-vacuum data using a model for the electronic ensemble described in a previous communication. The value of the g-factor shows the 4⁺ wave function to consist mainly of the$\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}{}^2$ configuration.     

Study of magnetic moments of nuclear excited states at Tristan

Facilities at the TRISTAN mass separator for measurement of magnetic moments of nuclear excited states are described and recent results for the N=82 isotones are presented.