The low temperature electric quadrupole orientation of184Ir and185Ir in rhenium

The half-lives of¹⁸⁴Ir,¹⁸⁵Ir and¹⁸⁶Ir have been determined to be 3.14(2) h, 14.4(1) h and 16.64(3) h, respectively. The quadrupole frequenciesv _Q = e²qQ_s/h of¹⁸⁴Ir and¹⁸⁵Ir in rhenium single crystal have been determined to be Q_s(¹⁸⁴Ir) = + 2.0(3) b MHz and Q_s(¹⁸⁵Ir) = +2.0(3) b MHz. Adopting the value of –3.6(2)×10¹⁷ V·cm^–2 for the electric field gradient eq at T=0 K, the values of the ground-state spectroscopic quadrupole moments of these isotopes are determined to be Q_s(¹⁸⁴Ir)=+2.0(3) b and Q_s(¹⁸⁵Ir)=–2.5(3) b. The¹⁸⁵Ir moment is only consistent with the ground state Nilsson configuration , the¹⁸⁴Ir moment is consistent with K4 with a predominant K=4 component, in disagreement with K=0,1 found for¹⁸⁶Ir. Our analysis differs in detail from the recent nuclear orientation study by Hagn et al.[1].     

Double resonance NMR-on study on oriented188Ir in iron

The quadrupole splitting of oriented¹⁸⁸Ir in iron was studied at 8.6 mK using a double resonance NMR-ON method. With r.f. power applied at the strongest resonance frequency, a second frequency was used to simultaneously investigate the second resonance component, where the splitting is caused by an electric quadrupole interaction. The electric hyperfine splitting frequency ν_Q=e ² qQ/h was measured to be 3.37(11) MHz. With the known electric field gradient of −0.283(6)×10¹⁷ V/cm² at Ir in iron, the spectroscopic quadrupole moment of¹⁸⁸Ir was deduced to be 0.492(26)b. The present results show that the double resonance method is a powerful tool in establishing the quadrupole splitting, if it leads to well-resolved NMR-ON resonance components.     

Magnetic hyperfine field of Se in nickel measured by means of the DPAC method

The magnetic hyperfine field of Se in nickel was measured by means of the time-differential perturbed angular correlation (DPAC) technique, using the 755–250 keV γ-ray cascade fed in the decay of⁷⁷Br. A value ofB _hf(NiSe)=+15.11(35) T was obtained at room temperature. The half-life of the 250 keV state and the anisotropy of the 755–250 keV cascade were found to beT _1/2=9.68(6) ns andA ₂₂=−0.454(9), respectively.     

Investigation of the hyperfine interaction of the transition element impurity193Ir in gadolinium

The combined magnetic and electric hyperfine interaction of dilute¹⁹³Ir impurities in ferromagnetic Gd has been investigated by means of the Mössbauer effect. The magnetic hyperfine field of¹⁹³Ir in Gd at 4.2 K is: |H _hf(Ir:Gd)|=624(6) kG.The electric fieldgradient at the site of Ir in Gd is:V _zz (Ir:Gd)=+19.5(5.0) × 10¹⁷ V/cm².The fieldgradient is axially asymmetric with an asymmetry parameter of 0.53(2)1.     

Determination of the242m Am nuclear moments

The hyperfine structure of Am atoms was investigated in an atomic beam by laser spectroscopy. The observed splittings were evaluated with respect to the magnetic dipole and electric quadrupole moments of^242m Am. The results are: μ _I (^242m Am)=+0.97(5)nm,Q(^242m Am)=+6.5(2.0)b.     

Temperature dependence of quadrupole interaction of99Ru in Zn

The quadrupole interaction (QI) of⁹⁹Ru as a dilute impurity in Zn, Cd and Sn lattices was studied by using time differential perturbed angular correlation technique. The electric field gradients calculated from the measured quadrupole interaction frequencies at room temperature are 5.14 × 10¹⁷ volts/cm² for⁹⁹RuZn, 4.58 × 10¹⁷ volts/cm² for⁹⁹RuCd and 2.87 × 10⁹⁹ volts/cm² for⁹⁹RuSn. The temperature dependence of the QI studied in the case⁹⁹RuZn is similar to that of¹¹⁷InZn.     

NMR-ON measurements of187WFe,182,183,186ReNi,186ReFe and203PbFe

The magnetic hyperfine splitting frequencies of¹⁸⁷WFe,¹⁸²Re(j ^π=2⁺)Ni,¹⁸³ReNi,¹⁸⁶ReNi,¹⁸⁶ReFe and²⁰³PbFe in a zero external magnetic field have been determined by the NMR-ON method at about 7 mK as 225.56(6), 130.9(1), 98.17(4), 136.6(4), 1007.0(3) and 58.43(3) MHz, respectively. With the knowng-factors ofg(¹⁸⁶Re, 1⁻)=1.739(3) andg(²⁰³Pb, 5/2⁻)=0.27456(20), the following hyperfine fields were deduced:B _HF(¹⁸⁶ReNi)=−103.05(35) kG;B _HF(¹⁸⁶ReFe)=−759.7(13) kG;B _HF(²⁰³PbFe)=+279.18(25) kG. Taking hyperfine anomalies into account, theg-factor of¹⁸³Re was deduced as |g(¹⁸³Re, 5/2⁺)|=1.267(6). With the assumption of Knight shift factorK=0, theg-factors of¹⁸²Re and¹⁸⁷W and the hyperfine field of¹⁸⁷WFe were determined as |g(¹⁸²Re, 2⁺)|=1.63(5), |g(¹⁸⁷W, 3/2⁻)|=0.414(10) andB _HF(¹⁸⁷WFe) =−714(18) kG. The large hyperfine anomaly was deduced to be¹⁸³W Δ¹⁸⁷W =−0.124(22).     

Nuclear electric quadrupole interaction of implanted ions in graphite

A number of isotopes have been implanted into thin foils of highly oriented pyrolytic graphite in order to investigate the possibility of using this material as a catcher for on-line LT-NO experiments to measure the quadrupole interaction of short-lived nuclei. Pure nuclear electric quadrupole interaction of nuclei of^188,189Ir,²⁰³Hg,^69mZn,^182m,183Re and¹¹¹In has been observed. Values for the electric field gradient along theC-axis are: +10.0(3) +8.2(9), +5.4(2.6) and +1.5(1)·10²² V/m², respectively, for Ir, Hg, Re and In in graphite. A value ofQ=+0.79(6) b is deduced for the quadrupole moment of¹⁸⁹Ir. Two theoretical models provide a better understanding of the origin of the electric field gradient in graphite. The first is based on induced electric polarization of graphite atoms, while in the second one hybridization of impurity and graphite electronic wave functions is calculated.     

Electric quadrupole orientation of iridium isotopes in rhenium

The quadrupole frequenciese ² qQ/h, for^{186, 188–190}Ir in a Re single crystal have been determined by nuclear orientation at temperatures down to 2 mK. Using a modeldependent value of +1.0 b for the quadrupole moment of the ground state of¹⁸⁹Ir, the electric field gradient of IrRe at 0 K is found to be–3.6×10¹⁷ V·cm^–2. The value is consistent with systematics proposed by Raghavan et al. Using this EFG, quadrupole moments are deduced for^{186, 188, 190}Ir.     

The electric field gradient at188Os nuclei in Re metal

The electric quadrupole interaction of the first excited 2⁺ state of¹⁸⁸Os in hexagonal rhenium metal was investigated by means of the time-differential perturbed angular correlation technique. From the observed quadrupole frequencyV _Q=170(7) MHz, we deduce an electric field gradient value of |V_zz|=4.77(23)·10²¹V/m² for the system OsRe. The half-life of the 2⁺ state was measured to be 641(4)ps.     

The magnetic moment of103Ru

The nuclear magnetic moment of¹⁰³Ru has been determined using the technique of low-temperature nuclear orientation on¹⁰³Ru as a dilute impurity in Fe. The Fe lattice was cooled to 1.7 mK using a PrNi₅ enhanced nuclear demagnetisation stage precooled with a³He–⁴He dilution refrigerator. The¹⁰³RuFe system was observed to have a long nuclear spin-lattice relaxation time, but analysis of the relaxation indicates that the¹⁰³Ru nuclei are close to thermal equilibrium with the Fe lattice at times>200 min after demagnetising. From the near thermal equilibrium anisotropy of the 497 keV -ray in¹⁰³Rh we have deduced the nuclear magnetic moment as |(¹⁰³Ru)|=0.18(2)_N. This value is almost independent of the choice of spinI=3/2 or 5/2 for the nucleus, but is only consistent with systematics ifI(¹⁰³Ru)=3/2 and <0. UsingI=3/2 we obtain the E2/M1 mixing ratio of the 497 keV -ray as =–0.42(4). The sign of the anisotropy of the 610 keV -ray from the 650 keV level in¹⁰³Rh is only consistent with an allowed -decay to the state ifI(650 keV,¹⁰³Rh)=5/2. The E2/M1 mixing ratio of the 610 keV -ray is then =+0.15(3) or +60( _–40 ⁺ ), <–80. From the initial rise in -ray anisotropy following demagnetisation we determine the Korringa constant for¹⁰³RuFe to beC=5.7(5) K·s.     

Static electric quadrupole interaction of Ce and Pb ions in lead titanate

The static electric quadrupole interaction of¹⁴⁰Ce and²⁰⁴Pb has been studied in polycrystalline PbTiO₃ at the lead site with the time-differential perturbed angular correlation (TDPAC) method. The interaction frequencies areω _Q(2083 keV;¹⁴⁰Ce)=2.11 (17) MHz andω _Q(1274keV;²⁰⁴Pb)=3.60(3) MHz. The results are compared with the electric field gradient calculated in a point charge model. Under the assumption that the covalent contributions for Ce and Pb are equal, one can derive the quadrupole moment of the 1274 keV state of²⁰⁴Pb to be ¦Q¦=0.68 b.     

Mössbauer study of the electromagnetic properties of the 69.6-keV level in Os 189

The 69.6-keV level with spin 5/2^? in¹⁸⁹Os was investigated by the recoilless resonance absorption technique. Its magnetic moment was found to beμ (5/2)=(0.977±0.014)μ _N. From the measured ratio of the excited and ground-state electric quadrupole moments,Q(5/2)/Q(3/2)=?0.79±0.09, the excited-state quadrupole momentQ(5/2)=?(0.72±0.11)b could be derived. TheE2/M1 mixing parameter of the 69.6-keV ground-state transition was found to beδ=+0.69±0.10. The results are interpreted in terms of two low-energy rotational bands with strong Coriolis mixing.     

NMR studies on polarized12B implanted in highly oriented pyrolytic graphite

NMR measurements on¹²B nuclei implanted in a thin sheet of highly oriented pyrolytic graphite (Grafoil) have been made to study the magnitude of the polarization of¹²B and its electric quadrupole coupling. The magnitude of the residual polarization of¹²B held in carbon material is of crucial importance to the experiment measuring the average polarization of¹²B produced in the muon capture by¹²C. It was found that the polarization of¹²B can be maintained at 101.0±2.2% in Grafoil under a magnetic field of 3 kG. The electric quadrupole coupling was determined to bee ² qQ/h=+1207.3±8.2 kHz. From the magnitude and the sign of the electric field gradienteq, the location of¹²B was found to be a substitutional site in the carbon lattice. The anomalous B-C bond involving thesp ₂ hybrid orbitals with partially filledp _z electrons is also discussed.     

Nuclear quadrupole interaction of119mHg in mercury(I) and mercury(II) halides

The nuclear quadrupole interactions of^199mHg in the mercury(I) and mercury(II) halides with Cl, Br, I were determined by time differential perturbed angular correlation. The quadrupole moment of theI=5/2 state in¹⁹⁹Hg was redetermined to beQ _5/2=0.674(77) b. The nuclear quadrupole interaction in both mercurous and mercuric halides scales with the electronegativity. Electric field gradients at mercury and halogen sites were calculated by a full-potential linearized augmented plane wave method (WIEN code) and were found in good agreement with experiment. In some cases a total energy minimization for internal parameters was carried out and found to be essential.     

The g-factor and the electric quadrupole moment of the 7/2+ isomer in125Xe

The time differential perturbed angular distribution method (PAD) was used to measure theg-factor and the electric quadrupole interaction in a Cd single crystal for thet _1/2=140 ns,I ^π=7/2⁺ isomer in¹²⁵Xe. Theg-factor isg=+0.264(10) and the quadrupole coupling constante ² Qq/h=122.1 (6) MHz at 552 K. The lifetime of theI ^π=11/2⁺ state was measured to beτ=11.3 (1.1) ps by the recoil distance method (RDM). From an analysis of the spectroscopic data using the triaxial-rotor-plus-particle (TRPP) model the quadrupole moment of the 7/2⁺ isomer is deduced to beQ=1.40 (15) b yielding an electric field gradient (efg)eq=3.6(4)·10¹⁷ V/cm² for XeCd.     

Electric quadrupole interactions in Ru-Sc alloys

In TDPAC studies of the electric quadrupole interaction in Ru_xSc_1–x alloys two different electric fieldgradients (EFG) have been observed at the site of⁹⁹Ru: V_zz(I)=12.6·10¹⁷ V/cm² and V_zz(II)=18.9·10₁₇ V/cm². The corresponding relative fractions f(I) and f(II), respectively, vary with the Ru concentration x. For low concentrations x<0.01 most nuclei (f(I)0.8) experience the smaller EFG V_zz(I). At x=0.01, however, the fraction f(I) goes abruptly to zero and V_zz(II) becomes dominant. In view of these results the previous interpretation of V_zz(II) as the EFG of dilute Ru on substitutional Sc sites can no longer be maintained. The Ru-Sc configurations producing these EFG's have not yet been identified. In the intermetallic compound Ru₂Sc the interaction is completely different, in RuSc₃, however, similar values have been observed.     

Magnetic moment of the 5/2−1/2[541] ground state of 14h 185Ir

The magnetic and electric hyperfine splitting frequencies ¦gμ _N B _HF/h¦ ande ² qQ/h of the 5/2^?1/2[541] ground state of 14h ¹⁸⁵Ir in Ni were measured with nuclear magnetic resonance on oriented nuclei to be 360.8(7) MHz and +6.7(2.0) MHz, respectively. The ground state magnetic dipole moment and electric quadrupole moment of¹⁸⁵Ir are deduced to be ¦μ¦=2.601 (14)μ _N andQ=?1.9(5)b, taking values for the hyperfine field and electric field gradient of B_HF=?454.9 (2.3) kG and eq=?0.151(4) × 10¹⁷ V/cm², respectively. The negative quadrupole moment is in agreement with nuclear-orientation data and proves again theI ^π K=5/2^? 1/2 ground state configuration.     

LMR quadrupole interaction measurement on69mGe and71mGe in Zn

A new experimental set-up to perform in-beam LMR (Level Mixing Resonance) measurements is briefly outlined. The first results are reported here. The quadrupole interaction of^69mGeZn is measured and in good agreement with earlier measurements:v _Q=80.6(4) MHz; for^71mGeZn, the valuev _Q=33.1(30)MHz is found. In addition, the relaxation behaviour and radiation damage of Ge recoil implanted in Zn is studied.     

Quadrupole interaction of8Li and9Li in LiNbO3 and the quadrupole moment of9Li

The quadrupole interaction of nuclear spin polarized⁸Li (I=2) and⁹Li (I=3/2) in LiNbO₃ has been studied at room temperature. The polarization was achieved by optical pumping of a fast atomic beam with circularly polarized laser light. The atoms were implanted into a hexagonal LiNbO₃ single crystal and the quadrupole splitting ofβ-NMR spectra was measured. A ratio of ¦Q(⁹Li)/Q(⁸Li)¦=0.88(4) for the nuclear quadrupole moments was deduced, yielding a new value of ¦Q(⁹Li)¦=25.3 (9) mb for the quadrupole moment of⁹Li.