Hg(II) Coordination Studies in Penicillamine Enantiomers by 199mHg-TDPAC

In order to study the binding of the toxic heavy metal ion Hg²⁺ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction of ¹⁹⁹Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold, three-fold and four-fold coordinations. This revised version was published online in September 2006 with corrections to the Cover Date.     

Experimental study of 199Hg spin anti-relaxation coatings

We report on a comparison of spin relaxation rates in a ¹⁹⁹Hg magnetometer using different wall coatings. A compact mercury magnetometer was built for this purpose. Glass cells coated with fluorinated materials show longer spin coherence times than if coated with their hydrogenated homologues. The longest spin relaxation time of the mercury vapor was measured with a fluorinated paraffin wall coating.     

Hg-coordination studies of oligopeptides containing cysteine,histidine and tyrosine by 199mHg-TDPAC

In order to study the interaction of histidine- and tyrosine-containing peptide chains with Hg(II), the nuclear quadrupole interaction (NQI) of ^199mHg in the Hg complexes of the oligopeptides Alanyl–Alanyl–Histidyl–Alanyl–Alanine-amid (AAHAA–NH₂) and Alanyl–Alanyl–Tyrosyl–Alanyl–Alanine-amid (AAYAA–NH₂) was determined by time differential perturbed angular correlation and is compared with previous data on Alanyl–Alanyl–Cysteyl–Alanyl–Alanyl (AACAA–OH). The ^199mHg–NQIs depend on the oligopeptide to Hg(II) stoichiometry and indicate that two-fold and four-fold coordinations occur for the bound Hg(II). This revised version was published online in August 2006 with corrections to the Cover Date.     

L II-electron-gamma correlation in199Hg

The(50L _II?158γ) directional correlation has been measured in¹⁹⁹Hg. The result isA ₂₂=+0.038±0.024, which gives the mixing ratio for the 50keV transition,δ=+0.017±0.006. The accuracy of the method is discussed.     

TDPAC studies of the intercalation compound Li x TiS2 in the region 0≤x≤1

The electrochemical intercalation of Li⁺ into hafnium-doped TiS₂ was studied using time-differential perturbed angular correlations (TDPAC). The¹⁸¹Ta nuclear quadrupole interaction was monitored as a function of the charge transfer,n _F. For low uptakes, 0≤n _F≤0.03, a two-phase region was found with an empty host interaction, characterized byV _q=458(4) MHz, η=0.19(3) and δ-0.083(5), and a second interaction corresponding to lithiated material withv _q=597(5) MHz, η=0.13(4) and δ=0.061(5). No evidence was found for intermediate phases.     

Electric hyperfine interaction in199Hg fluorides

With the current integration technique, the Mössbauer effect on the 158 keV, 5/2^–1/2^– transition in¹⁹⁹Hg was studied using the cubic HgF₂ and the tetragonal Hg₂F₂ as absorbers; in the latter, a quadrupole splittingeQV _zz=}- 9.0(2) mm/s was observed. Electron densities were calculated with the self-consistent-charge-extended-Hueckel-molecular-orbital method and r ²=(3.26±0.11) fm² derived. From the quadrupole splitting and the calculation, an effective antishielding factor almost twice that of the neutral Hg atom is derived.Dedicated to Professor B. Elschner on the occasion of his 60th birthday.     

Gammastrahlung vom Einfang thermischer Neutronen in Hg 199

103 gamma transitions in Hg 200 have been observed. 37 of them were fitted into a level scheme which comprises 17 states. The energy of the one-phonon vibrational stateI=2⁺ has been determined to be 367.970±0.020 keV, that of the two-phonon vibrational triplet 947.34±0.07 keV, 1029.37±0.05 keV and 1254.20±0.10 keV. Further levels have been found at energies of 1570.30±0.10 keV, 1571.7±0.6keV, 1594.3±0.4 keV, 1631.5±0.2 keV, 1641.5±0.3 keV, 1718.5±0.2 keV, 1730.8±0.2 keV, 1775.7±1.1 keV, 1842.9±0.8 keV, 1882.9±0.3 keV, 2062.6±0.5 keV and 2082.9±1.0 keV.     

Lithium intercalation in cubic TiS2

Synthesis of TiS₂ in cubic defect spinel (c-TiS₂) by oxidation of CuTiS₄ with Br₂ in acetonitrile is reported. Intercalation of Li by chemical reaction with n-BuLi or in electrochemical cells Li/LiAsF₆, propylene carbonate/ c-TiS₂ yields a homogeneous single phase with stoichiometry c-TiS₂ (0≤×≤1). The system is compared with the classical layerd Ti_xTiS₂ (0≤×≤1) system. Extensions to other spinels are discussed.     

199Hg spin-lattice relaxation and chemical shift anisotropy in diphenylmercury

¹⁹⁹Hg spin-lattice relaxation times (T₁) have been measured for diphenylmercury at magnetic fields of 2.35 and 7.05 T. T₁ was nine times shorter at the higher field (0.033 sec at 310 K) than at the lower field (0.30 sec), showing relaxation by chemical shift anisotropy (CSA) to be the dominant mechanism even at the lower field. Variable-temperature ¹³C T₁ measurements at 6.35 T made it possible to determine a value for the correlation time for motion perpendicular to the axis of the molecule (50 psec at 300 K), which with the ¹⁹⁹Hg data allowed a value of 6800 ± 680 ppm to be calculated for the mercury chemical shift anisotropy. The activation energy for rotational motion was 13.3 kJ · mole⁻¹. Previous data on dimethylmercury have been reassessed and the importance of the CSA mechanism for ¹⁹⁹Hg at high fields is pointed out.     

Plasma assisted CVD of TiS2

Fine powder and highly oriented thin film TiS₂ were prepared by a reaction between TiCl₄ and H₂S in low-pressure glow discharge at low substrate temperatures (450°C). The products were investigated by changing the reaction conditions, e.g. the substrate temperature, the applied rf power between electrodes, and the reactant ratio ([H₂S]/[TiCl₄]). The fine powder product was an aggregate of plate-like crystallites of some ten nm in width and less than ten nm in thickness. Lithium batteries using the fine TiS₂ powder showed a flat discharge voltage around 2.2 V up to 100% utilization. Submicron TiS₂ crystallites had their lattice planes perpendicular to the substrate in the thin films having thicknesses greater than 1 m. This orientation is expected to be favorable for the application to lithium rechargable batteries.     

The magnetic moments and halflives of the 5/2− states in199Hg and197Hg and the discrepancies in the experimental hyperfine fields at Hg in Fe

The Larmor-precession frequencies for¹⁹⁷Hg in Fe have been determined to beω _L = 1291 ±25 MHz at 293 K andω _L = 1334±25 MHz at 105 K. For¹⁹⁹Hg in Feω _L =1372±50 MHz has been measured at 293 K. The half-lives of the 5/2^? states in¹⁹⁷Hg and¹⁹⁹Hg have been remeasured asT _1/2(¹⁹⁷Hg)=8.1±0.16 nsec andT _1/2(¹⁹⁹Hg)=2.45±0.05 ns, respectively. The magnetic moment of the 5/2^? 158keV state in¹⁹⁹Hg was redetermined by the integral perturbed angular correlation method in an external magnetic field of 47kG asμ(5/2 ^? ) = 0.905±0.091 nm. With this new value consistency for the magnetic hyperfine fields at Hg in Fe measured with the TDPAC-method and with the NMR/ON-method is obtained. This fact is used to determine theg-factors of the 5/2^? states in¹⁹⁷Hg and¹⁹⁹Hg more precisely fromω _L -values given above:g(¹⁹⁷Hg)=0.342(6);g(¹⁹⁹Hg)=0.352(13). The magnetic moments of the first excited 2⁺ states in^198–204Hg isotopes which rely on calibrations with the¹⁹⁹Hg-g-factor, are revised.     

The performance of Hg1−x Zn x Te photodiodes

This paper considers the Hg_1–x Zn _x Te alloy system as a potential material for the fabrication of infrared photodiodes. The influence of different junction current components (diffusion, tunneling and depletion layer currents) on the R ₀ A product of n⁺-pHg_1–x Zn _x Te photodiodes is analysed. The upper theoretical limits of the R ₀ A product and detectivity are determined. Results of calculations are compared with experimental data reported by other authors and those measured in our laboratory. Preliminary results on related technology and the properties of Hg_1–x Zn _x Te prepared by the ion-etching technique are presented.     

Thermalization of199Hg ion macromotion by a light background gas in an RF quadrupole trap

The largest systematic uncertainty in the performance of atomic frequency standards using a cloud of ions stored in an rf quadrupole trap is the second-order Doppler shift which depends on ion temperature and trapping parameters. This paper presents evidence that cooling the ions by collisions with atoms of a background gas light compared to the ions results in the condensation of the ions into a cloud of almost uniform density determined by space charge versus potential well forces. In this condition the second-order Doppler shift is simple to calculate and is found to depend only on readily measured characteristics of the ion cloud. This along with already observed good signal-to-noise ratio shows that the frequency standard we have constructed using the hyperfine splitting of singly ionized¹⁹⁹Hg, with helium cooling can have an order of magnitude better performance in accuracy, stability, and reproducibility than presently available commercial cesium beam standards.     

In-situ photoelectron spectroscopy study of a TiS2 thin film cathode in an operating Na intercalation electrochemical cell

TiS₂ thin films were prepared and intercalated in UHV either chemically or electrochemically and investigated by photoelectron spectroscopy. The chemical reaction was induced by Na evaporation. For the electrochemical reaction, the film was deposited on a Na solid electrolyte and the voltage between the TiS₂ and a graphite layer on the back of the plate was controlled during PES investigations. With both methods the same effects on the substrate are observed. The Na Auger peak appears and increases at a kinetic energy typical for intercalated Na. Due to the electron transfer to the conduction band an increase of the electron density at the Fermi level is clearly observed. The progressive filling of higher energy states shifts the Fermi level as reference for the PES spectra, and as a result the S 2p core levels and valence bands are shifted to higher binding energies. A shoulder appears at the lower binding energy side of the Ti 2p peak, indicating a higher negative charge density on the Ti atoms. It is also shown how the in-situ electrochemical intercalation allows experimentally to extrapolate the variation of the ionic contribution to the battery voltage. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Relativistic doppler effect in199Hg+ stored ions atomic frequency standard

RF traps are widely used nowadays in high resolution hyperfine spectroscopy. The spectrum of the microwave hyperfine transition at 40.5 GHz of the fundamental level² S _1/2 of¹⁹⁹Hg⁺ is phase modulated at the secular frequency of the stored ions and it consists of a narrow central line and lateral bands broadened by the ion trajectory and velocity distribution. The central line itself is shifted by the second-order Doppler effect which is the most important systematic error of stored ions frequency standards. In this paper the relativistic Doppler effect in the case of¹⁹⁹Hg⁺ stored ions is deduced applying a mathematical formalism and using physical parameters that we have measured experimentally.     

New limit on the permanent electric dipole moment of 199Hg

We present the first results of a new search for a permanent electric dipole moment of the 199Hg atom using a UV laser. Our measurements give d(199Hg) = -(1.06+/-0.49+/-0.40)x10(-28)e cm. We interpret the result as an upper limit absolute value [d(199Hg)]<2.1x10(-28)e cm (95% C.L.), which sets new constraints on theta bar;(QCD), chromo-EDMs of the quarks, and CP violation in supersymmetric models.