Gleichzeitige Messung von Hyperfeinstruktur,Starkeffekt und Zeemaneffekt des133Cs19F mit einer Molekülstrahl-Resonanzapparatur

An electric molecular beam resonance spectrometer has been used to measure simultaneously the Zeeman- and Stark-effect splitting of the hyperfine structure of¹³³Cs¹⁹F. Electric four pole lenses served as focusing and refocusing fields of the spectrometer. A homogenous magnetic field (Zeeman field) was superimposed to the electric field (Stark field) in the transition region of the apparatus. Electrically induced (Δ m _J =±1)-transitions have been measured in theJ=1 rotational state, υ=0, 1 vibrational state. The obtained quantities are: The electric dipolmomentμ _el of the molecule for υ=0, 1; the rotational magnetic dipolmomentμ _J for υ=0, 1; the anisotropy of the magnetic shielding (σ _⊥-σ‖) by the electrons of both nuclei as well as the anisotropy of the molecular susceptibility (ξ _⊥-ξ‖), the spin rotational interaction constantsc _Cs andc _F, the scalar and the tensor part of the nuclear dipol-dipol interaction, the quadrupol interactioneqQ for υ=0, 1. The numerical values are:

$$\begin{gathered} \mu _{el} \left( {\upsilon = 0} \right) = 73878\left( 3 \right)deb \hfill \\ \mu _{el} \left( {\upsilon = 1} \right) - \mu _{el} \left( {\upsilon = 0} \right) = 0.07229\left( {12} \right)deb \hfill \\ \mu _J /J\left( {\upsilon = 0} \right) = - 34.966\left( {13} \right) \cdot 10^{ - 6} \mu _B \hfill \\ \mu _J /J\left( {\upsilon = 1} \right) = - 34.823\left( {26} \right) \cdot 10^{ - 6} \mu _B \hfill \\ \left( {\sigma _ \bot - \sigma _\parallel } \right)_{Cs} = - 1.71\left( {21} \right) \cdot 10^{ - 4} \hfill \\ \left( {\sigma _ \bot - \sigma _\parallel } \right)_F = - 5.016\left( {15} \right) \cdot 10^{ - 4} \hfill \\ \left( {\xi _ \bot - \xi _\parallel } \right) = 14.7\left( {60} \right) \cdot 10^{ - 30} erg/Gau\beta ^2 \hfill \\ c_{cs} /h = 0.638\left( {20} \right)kHz \hfill \\ c_F /h = 14.94\left( 6 \right)kHz \hfill \\ d_T /h = 0.94\left( 4 \right)kHz \hfill \\ \left| {d_s /h} \right|< 5kHz \hfill \\ eqQ/h\left( {\upsilon = 0} \right) = 1238.3\left( 6 \right) kHz \hfill \\ eqQ/h\left( {\upsilon = 1} \right) = 1224\left( 5 \right) kHz \hfill \\ \end{gathered} $$     

Measurement of the ∑± lifetimes

From about 2 × 10⁶ measured ∑^± decay's produced by stoppingK ^? mesons in the 81 cm Saclay hydrogen bubble chamber about 140,000 ∑^? →n π^? and 20,000 ∑⁺ →nπ⁺ decays were selected for a lifetime measurement. We obtained: $$\begin{gathered} \tau _{\Sigma ^ + } = (0.795 \pm 0.010) \times 10^{ - 10} \sec \hfill \\ \tau _{\Sigma ^ - } = (1.485 \pm 0.022) \times 10^{ - 10} \sec . \hfill \\ \end{gathered} $$      

Gleichzeitige Messung von Hyperfeinstruktur,Starkeffekt und Zeemaneffekt des23Na19F mit einer Molekülstrahl-Resonanzapparatur

An electric molecular beam resonance spectrometer has been used to measure simultaneously the Zeeman- and Stark-effect splitting of the hyperfine structure of²³Na¹⁹F. Electric four pole lenses served as focusing and refocusing fields of the spectrometer. A homogenous magnetic field (Zeeman field) was superimposed to the electric field (Stark field) in the transition region of the apparatus. The observed (Δm _J=±1)-transitions were induced electrically. Completely resolved spectra of NaF in theJ=1 rotational state have been measured in several vibrational states. The obtained quantities are: The electric dipolmomentμ _el of the molecule forv=0, 1 and 2, the rotational magnetic dipolmomentμ _J forv=0, 1, the difference of the magnetic shielding (σ _⊥-σ _‖) by the electrons of both nuclei as well as the difference of the molecular susceptibility (ξ _⊥-ξ _‖), the spin rotational constantsc _F andc _Na, the scalar and the tensor part of the molecular spin-spin interaction, the quadrupol interactione q Q forv=0, 1 and 2. The numerical values are

$$\begin{gathered} \mu _{\mathfrak{e}1} = 8,152(6) deb \hfill \\ \frac{{\mu _{\mathfrak{e}1} (v = 1)}}{{\mu _{\mathfrak{e}1} (v = 0)}} = 1,007985 (7) \hfill \\ \frac{{\mu _{\mathfrak{e}1} (v = 2)}}{{\mu _{\mathfrak{e}1} (v = 1)}} = 1,00798 (5) \hfill \\ \mu _J = - 2,89(3)10^{ - 6} \mu _B \hfill \\ \frac{{\mu _J (v = 0)}}{{\mu _J (v = 1)}} = 1,020 (13) \hfill \\ (\sigma _ \bot - \sigma _\parallel )_{Na} = - 51(12) \cdot 10^{ - 5} \hfill \\ (\sigma _ \bot - \sigma _\parallel )_F = - 51(12) \cdot 10^{ - 6} \hfill \\ (\xi _ \bot - \xi _\parallel ) = - 1,59(120)10^{ - 30} erg/Gau\beta ^2 \hfill \\ {}^CNa/^h = 1,7 (2)kHz \hfill \\ {}^CF/^h = 2,2 (2)kHz \hfill \\ {}^dT/^h = 3,7 (2)kHz \hfill \\ {}^dS/^h = 0,2 (2)kHz \hfill \\ eq Q/h = - 8,4393 (19)MHz \hfill \\ \frac{{eq Q(v = 0)}}{{eq Q(v = 1)}} = 1,0134 (2) \hfill \\ \frac{{eq Q(v = 1)}}{{eq Q(v = 2)}} = 1,0135 (2) \hfill \\ \end{gathered} $$     

Hyperfeinstruktur- und Stark-Effekt-Untersuchungen der Terme 4d5s5p z 2 F 5/2 undz 2 F 7/2 im Yttrium I Spektrum

The hyperfine structure and the Stark effect shift of the 4d5s5p z ² F _5/2 states in the Y I spectrum were investigated by level-crossing technique. Between the Zeeman effect region and the Paschen-Back region of hyperfine structure states some of the levels cross. The resonance radiation of these coherently excited levels show an interference effect of the scattering amplitudes in the crossing region. The level-crossing signals give information about hfs splitting and lifetime of the excited states under investigation. The magnetic hfs splitting factorsA of the 4d5s5p z ² F _{5/2, 7/2} states and their lifetimes were deduced. $$\begin{gathered} |A (z^2 F_{5/2} )| = (23.8 \pm 0.04) MHz \frac{{g_J }}{{0.854}} \hfill \\ |A (z^2 F_{7/2} )| = (84.08 \pm 0.01) MHz \frac{{g_J }}{{1.148}} \hfill \\ \tau (z^2 F_{5/2} ) = (46 \pm 3) 10^{ - 9} s \frac{{0.854}}{{g_J }} \hfill \\ \tau (z^2 F_{7/2} ) = (44 \pm 4) 10^{ - 9} s \frac{{1.148}}{{g_J }}. \hfill \\ \end{gathered} $$ With an electric field parallel to the magnetic field a shift of the level-crossing signals of the 4d5s5p z ² F _{5/2, 7/2} states was observed, and the Stark constants β were deduced. $$\begin{gathered} |\beta (z^2 F_{5/2} )| = (0.0020 \pm 0.0002) MHz/(kV/cm)^2 \hfill \\ |\beta (z^2 F_{7/2} )| = (0.0025 \pm 0.0015) MHz/(kV/cm)^2 . \hfill \\ \end{gathered} $$      

Search for rare radiative decays ofΦ-meson at VEPP-2M

Results of the search for rare radiative decay modes of the ?-meson performed with the Neutral Detector at the VEPP-2M collider are presented. For the first time upper limits for the branching ratios of the following decay modes have been placed at 90% confidence level: $$\begin{gathered} B(\phi \to \eta '\gamma )< 4 \cdot 10^{ - 4} , \hfill \\ B(\phi \to \pi ^0 \pi ^0 \gamma )< 10^{ - 3} , \hfill \\ B(\phi \to f_0 (975)\gamma )< 2 \cdot 10^{ - 3} , \hfill \\ B(\phi \to H\gamma )< 3 \cdot 10^{ - 4} , \hfill \\ \end{gathered} $$ whereH is a scalar (Higgs) boson with a mass 600 MeV<m _H <1000 MeV, the real measurement isB(φ→H γ)·B(H→2π⁰)<0.8·10^-4, the quoted result is model dependent, as explained in the text, $$\begin{gathered} B(\phi \to a\gamma ) \cdot B(a \to e^ + e^ - )< 5 \cdot 10^{ - 5} , \hfill \\ B(\phi \to a\gamma ) \cdot B(a \to \gamma \gamma )< 2 \cdot 10^{ - 3} , \hfill \\ \end{gathered} $$ wherea is a particle with a low mass and a short lifetime, $$B(\phi \to a\gamma )< 0.7 \cdot 10^{ - 5} ,$$ wherea is a particle with a low mass not observed in the detector.     

Radiative decays of ρ and ω mesons

The results of the measurements of radiative decays of ρ and ω mesons with the Neutral Detector at thee ⁺ e ^? collider VEPP-2M are presented. The branching ratio of the decay ω→π ⁰γ was measured with higher than in previous experiments accuracy: $${\rm B}(\omega \to \pi ^0 \gamma ) = 0.0888 \pm 0.0062$$ . The ρ⁰→π ⁰ γ branching ratio was measured for the first time: $$B(\rho ^0 \to \pi ^0 \gamma ) = (7.9 \pm 2.0) \cdot 10^{ - 4} $$ . The decays ρ, ω→ηγ were studied. Their branching ratios with the assumption of constructive ρ?ω interference are: $$\begin{gathered} B(\omega \to \eta \gamma ) = (7.3 \pm 2.9) \cdot 10^{ - 4} , \hfill \\ B(\rho \to \eta \gamma ) = (4.0 \pm 1.1) \cdot 10^{ - 4} \hfill \\ \end{gathered} $$ . The branching ratios of ρ, ω→ηγ and ω→e ⁺ e ^? decays were also measured: $$\begin{gathered} B(\omega \to \pi ^ + \pi ^ - \pi ^0 ) = 0.8942 \pm 0.0062, \hfill \\ B(\omega \to e^ + e^ - ) = (7.14 \pm 0.36) \cdot 10^{ - 5} \hfill \\ \end{gathered} $$ . The upper limit for the ω→π ⁰ π ⁰ γ branching ratio was placed: B(ω→π ⁰ π ⁰ γ)<4·10^?4 at 90% confidence level.     

Total cross sections of charged-current neutrino and antineutrino interactions on isoscalar nuclei

New measurements of the total crosssections of charged-current interactions of muonneutrinos and antineutrinos on isoscalar nuclei have been performed. Data were recorded in an exposure of the CHARM detector in an 160 GeV narrow-band beam. The antineutrino flux was determined from the measurements of the pion and kaon flux, and independently from the muon flux measured in the shield; the two methods are found to agree. The neutrino flux was determined from the muon flux ratio forv _μ and \(\bar v_\mu \) runs which was normalized to the antineutrino flux. The cross-section slopes thus determined are $$\begin{gathered} \sigma _T^{\bar v} /E = (0.335 \pm 0.004(stat) \hfill \\ \pm 0.010(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \sigma _T^v /E = (0.686 \pm 0.002(stat) \hfill \\ \pm 0.020(syst)).10^{ - 38} cm^2 /(GeV \cdot nucleon) \hfill \\ \end{gathered} $$ The momentum sum of the quarks in the nucleon and the ratio of sea quark to total quark momentum are derived from the measurements.     

Antiproton-proton annihilation at rest intoπ + π − η ′ andπ + π − η from atomicS andP states

We have measured the branching ratios for \(\bar pp\) annihilation at rest intoπ ⁺ π ^? η andπ ⁺ π ^? η′ in hydrogen gas in two data samples that have different fractions ofS-wave andP-wave initial states. The branching ratios are derived from a comparison with the topological branching ratio for \(\bar pp\) annihilations into four charged pions of (49±4)% and the branching ratio intoπ ⁺ π ^? π ⁺ π ^? π ⁰ of (18.7±1.6)%. We find a significant reduction of the branching ratios fromP-states for \(\bar pp \to \pi ^ + \pi ^ - \eta \) andπ ⁺ π ^? η′ in comparison toS-state annihilation. $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta ) = (13.7 \pm 1.46) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ) = (3.35 \pm 0.84) \cdot 10^{ - 3} \hfill \\ BR(S - wave \to \pi ^ + \pi ^ - \eta ') = (3.46 \pm 0.67) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta ') = (0.61 \pm 0.33) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ In a partial wave analysis of theπ ⁺ π ^? η Dalitz plot we find the following contributions: Phase space, \(a_2^ + (1320)\pi ^ \mp \) ,ηρ⁰ andf ₂(1270)η: $$\begin{gathered} BR(S - wave \to \pi ^ + \pi ^ - \eta PS) = (6.31 \pm 1.22) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to \pi ^ + \pi ^ - \eta PS) = (0.47 \pm 0.26) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to a_2^ \pm (1320)\pi ^ \mp ) = (2.59 \pm 0.73) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.48) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to a_2^ \pm (1320)\pi ^ \mp ) = (1.31 \pm 0.69) \cdot 10^{ - 3} \hfill \\ BR(^3 S_1 \to \rho \eta ) = (3.29 \pm 0.90) \cdot 10^{ - 3} \hfill \\ BR(^1 P_1 \to \rho \eta ) = (0.94 \pm 0.53) \cdot 10^{ - 3} \hfill \\ BR(^1 S_0 \to f_2 (1270)\eta ) = (0.083 \pm 0.086) \cdot 10^{ - 3} \hfill \\ BR(P - wave \to f_2 (1270)\eta ) = (0.64 \pm 0.26) \cdot 10^{ - 3} . \hfill \\ \end{gathered} $$ We find a 2 σ effect for the reaction \(\bar pp \to a_0^ \pm (980)\pi ^ \mp \) , \(a_0^ \pm \to \eta \pi ^ \pm \) , with a branching ratio of (0.13±0.07)·10^?3. For η' production we give a branching ratio of \(\bar pp \to \rho \eta '\) of (1.81±0.44)·10^?3 from³ S ₁. We estmate a contribution of about 0.3·10^?3 for ρη' fromP-states. The ratio of ρη and ρη' rpoduction is used to test the validity of the quark line rule. In theπ ⁺ π ^? π ⁺ π ^? γ final state we do not observe the reaction \(\bar pp \to \pi ^ + \pi ^ - \omega \) , ω→π ⁺ π ^? λ and derive an upper limit of 3·10^?3 for decay modeω→π ⁺ π ^? λ.     

Gyromagnetic ratios of collective states of166Er

The static hyperfine field ofB _hf ^4.2k (ErHo) = 739(18)T of a ferromagnetic holmium single crystal polarized in an external magnetic field of ± 0.48T at ～4.2K was used for integral perturbed γ-γ angular correlation (IPAQ measurements of the g-factors of collective states of¹⁶⁶Er. The 1,200y ^166m Ho activity was used which populates the ground state band and the γ vibrational band up to high spins. The results: $$\begin{gathered} g(4_g^ + ) = + 0.315(16) \hfill \\ g(6_g^ + ) = + 0.258(11) \hfill \\ g(8_g^ + ) = + 0.262(47)and \hfill \\ g(6_\gamma ^ + ) = + 0.254(32) \hfill \\ \end{gathered}$$ exhibit a significant reduction of the g-factors with increasing rotational angular momentum. The followingE2/M1 mixing ratios of interband transitions were derived from the angular correlation coefficients: $$\begin{gathered} 5_\gamma ^ + \Rightarrow 4_g^ + :\delta (810keV) = - (36_{ - 7}^{ + 11} ) \hfill \\ 7_\gamma ^ + \Rightarrow 6_g^ + :\delta (831keV) = - (18_{ - 2}^{ + 3} )and \hfill \\ 7_\gamma ^ + \Rightarrow 8_g^ + :\delta (465keV) = - (63_{ - 12}^{ + 19} ). \hfill \\ \end{gathered}$$ The results are discussed and compared with theoretical predictions.     

Band spectrum of manganese oxide (MnO)

New measurements of the wavelengths of the band heads of MnO spectrum have been made. In all 57 band heads, including 15 hitherto unrecorded ones, have been measured. The equation representing the wave-number of a band head has been modified as,

$$\begin{gathered} v = 17949 \cdot 19 + \{ 762 \cdot 75(v' + \tfrac{1}{2}) - 9 \cdot 60(v' + \tfrac{1}{2})^2 + 0 \cdot 06(v' + \tfrac{1}{2})^3 \} \hfill \\ - \{ 839 \cdot 55(v'' + \tfrac{1}{2}) - 4 \cdot 79(v'' + \tfrac{1}{2})^2 \} \hfill \\ \end{gathered} $$     

Hyperfine structure measurements in the ground states4 F 3/2,4 F 5/2 and4 F 7/2 of Ta181 with the atomic beam magnetic resonance method

Applying a recently developed evaporation technique for refractory elements the following results have been obtained for Ta¹⁸¹ in an atomic beam magnetic resonance experiment studying the hyperfine structure of 3 levels of the ground state multiplet⁴ F: $$\begin{gathered} g_J (^4 F_{3/2} ) = 0.45024 (4) \hfill \\ \Delta v (^4 F_{3/2} ;F = 5 \leftrightarrow F = 4) = 1822.389 (6) MHz \hfill \\ \Delta v (^4 F_{3/2} ;F = 4 \leftrightarrow F = 3) = 2325.537 (2) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 6 \leftrightarrow F = 5) = 1451.476 (7) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 5 \leftrightarrow F = 4) = 1537.530 (8) MHz \hfill \\ \Delta v (^4 F_{5/2} ;F = 4 \leftrightarrow F = 3) = 1444.685 (2) MHz \hfill \\ \Delta v (^4 F_{7/2} ;F = 4 \leftrightarrow F = 3) = 1218.372 (2) MHz. \hfill \\ \end{gathered}$$ From these measurements the following constants of the magnetic dipole interaction (A) and the electric quadrupole interaction (B) have been derived: $$\begin{gathered} A (^4 F_{3/2} ) = 509.0801 (8) MHz \hfill \\ B (^4 F_{3/2} ) = - 1012.251 (8) MHz \hfill \\ A (^4 F_{5/2} ) = 313.4681 (8) MHz \hfill \\ B (^4 F_{5/2} ) = - 834.820 (12) MHz. \hfill \\ \end{gathered}$$      

QCD perturbation theory in the temporal gauge

In this paper we present a non-trivial check of the consistency of the quantization of a gauge theory with fermions (QCD) in the temporal gauge. We use the approach based on the finite time Feynman propagation kernel, in which the Gauss law is imposed as a constraint on the states by means of a functional integration over all the time independent gauge transformations acting on the boundary values of the fields. We spell out in detail the “Feynman rules” when fermions are present and we compute, as an example, the gauge invariant correlation function $$\begin{gathered} G(t) = \left\langle {\bar \psi (0,t)(\gamma _5 \gamma _0 )\frac{{1 - \gamma _0 }}{2}P} \right. \hfill \\ \left. { \cdot \exp \left( {ig\int\limits_0^t {A_0 (0,t')dt'} } \right)(\gamma _5 \gamma _0 )^ + (0,0)} \right\rangle \hfill \\ \end{gathered} $$ up to orderg ², obtaining the expected result.     

The nonlocal tensor operatorS 12 N (ρ, ρ′)

The extension of the tensor potentialS ₁₂ V _T (r) to the case of a nonlocal interaction is shown to be $$\begin{gathered} V_T (r{\text{,}}r'{\text{) = }}S_{12}^N F(r,r') \hfill \\ {\text{ = }}\tfrac{{\text{1}}}{{\text{2}}}[9(\rho \cdot \rho '{\text{)(}}\sigma _1 \cdot \rho \sigma _2 \cdot \rho '{\text{ + }}\sigma _1 \cdot \rho '\sigma _2 \cdot \rho {\text{)}} - 2(\sigma _1 \cdot \sigma _2 )]F(r,r'), \hfill \\ \end{gathered}$$ where ρ=r/r. This potential has the necessary invariance properties provided thatF(r, r′)=F(r′, r). With this potential andF(r, r′) taken to have a rank-one separable form, the behaviour of the model-deuteron radius with respect to the strength of the tensor nonlocality is investigated. It is found that the model radius decreases as the tensor nonlocality becomes more attractive. This is consistent with recent work which considers only central nonlocality.     

Hyperfine structure,g j factors and lifetimes of excited2 P 1/2 states of Rb

The hyperfine structure of the 6² P _1/2 and 7² P _1/2 state of⁸⁵Rb and⁸⁷Rb and of the 6² P _3/2 state of⁸⁷Rb has been investigated with optical double resonance at intermediate magnetic fields. The magnetic interaction constants,g _j factors and lifetimes are: $$\begin{gathered} 6^2 P_{1/2} state: A\left( {^{85} Rb} \right) = 39.11\left( 3 \right) MHz,A\left( {^{87} Rb} \right) = 132.56 \left( 3 \right)MHz, \hfill \\ g_j = 0.6659\left( 3 \right), \tau = 1.14\left( {13} \right) \cdot 10^{ - 7} \sec , \hfill \\ 7^2 P_{1/2} state: A\left( {^{85} Rb} \right) = 17.68\left( 8 \right)MHz,A\left( {^{87} Rb} \right) = 59.92\left( 9 \right)MHz, \hfill \\ g_j = 0.6655\left( 5 \right), \hfill \\ 6^2 P_{3/2} state: g_j = 1.3337\left( {10} \right), \tau = 1.12\left( 8 \right) \cdot 10^{ - 7} \sec for ^{87} Rb. \hfill \\ \end{gathered} $$ From the hfs coupling constants of then ² P multiplets a 11.5% core polarization contribution to the magnetic hfs of then ² P _3/2 states is obtained, which is found to be independent from the main quantum numbern. The expectation values <r ^?3> _j for thenp valence electrons corrected for core polarization are compared with those derived from the² P fine structure separation. Good agreement is achieved for allnp levels with the choice ofZ _i =Z?3=34 for the effective nuclear charge number. The nuclear quadrupole moments of⁸⁵Rb and⁸⁷Rb are rederived on the basis of this more improved treatment for thep-electron-nucleus interaction yielding $$\begin{gathered} Q_N \left( {^{85} Rb} \right) = + 0.274\left( 2 \right) \cdot 10^{ - 24} cm^2 \hfill \\ Q_N \left( {^{85} Rb} \right) = + 0.132\left( 1 \right) \cdot 10^{ - 24} cm^2 \hfill \\ \end{gathered} $$ where the error does not include the remaining theoretical uncertainty of about 10%.     

Nuclear orientation and NMR/ON of205,207Po

^205,207Po have keen implanted with an isotope separator on-line into cold host matrices of Fe, Ni, Zn and Be. Nuclear magnetic resonance of oriented²⁰⁷Po has been observed in Fe and Ni, of²⁰⁵Po in Fe. The resonance frequencies for zero external field are $$\begin{gathered} v_L (^{207} Po\underline {Fe} ) = 575.08(20)MHz \hfill \\ v_L (^{207} Po\underline {Ni} ) = 160.1(8)MHz \hfill \\ v_L (^{205} Po\underline {Fe} ) = 551.7(8)MHz. \hfill \\ \end{gathered} $$ From the dependence of the resonance frequency on external magnetic field theg-factor of²⁰⁷Po was derived as $$g(^{207} Po) = + 0.31(22).$$ Using this value the magnetic hyperfine fields of Po in Fe and Ni were obtained as $$\begin{gathered} B_{hf} (Po\underline {Fe} ) = + 238(16)T \hfill \\ B_{hf} (Po\underline {Ni} ) = 66.3(4.6)T. \hfill \\ \end{gathered}$$ Theg-factor of²⁰⁵Po follows as $$g(^{205} Po) = + 0.304(22).$$ From the temperature dependence of the anisotropies ofγ-lines in the decay of^205,207Po the multipole mixing of several transitions was derived. The electric interaction frequenciesv _Q=eQV_zz/h in the hosts Zn and Be were measured as $$\begin{gathered} v_Q (^{207} Po\underline {Zn} ) = + 42(3)MHz \hfill \\ v_Q (^{207} Po\underline {Be} ) = - 70(20)MHz \hfill \\ v_Q (^{205} Po\underline {Be} ) = - 42(17)MHz. \hfill \\ \end{gathered}$$      

Internal magnetic hyperfine fields at Hf nuclei in iron,cobalt and nickel hosts

Integral perturbed angular correlation technique has been used to measure the internal hyperfine magnetic fields at Hf nuclei in Fe, Co and Ni matrices. These represent a consistent set of measurements with diffused sources. The 9+/2 (208 keV) 9?/2 (113 keV) 7?/2 cascade in the decay of¹⁷⁷Lu→¹⁷⁷Hf was used for measurements. The results obtained are: $$\begin{gathered} H_{Fe}^{Hf} = - 266 \pm 47 kG, \hfill \\ H_{Co}^{Hf} = - 116 \pm 18 kG, \hfill \\ H_{Ni}^{Hf} = - 118 \pm 26 kG. \hfill \\ \end{gathered} $$ These measurements are compared with previous results and discussed in terms of methods of source preparation.     

A measurement of the forward-backward asymmetry of e+e?→bb by applying a jet charge algorithm to lifetime tagged events

The forward-backward asymmetry of has been measured using approximately 2.15 million hadronicZ ⁰ decays collected at the LEP e⁺e^– collider with the OPAL detector. A lifetime tag technique was used to select an enriched event sample. The measurement of the asymmetry was then performed using a jet charge algorithm to determine the direction of the primary quark. Values of:

Nuclear quadrupole moments of radioactive83Rb,84Rb and86Rb

Excited atomic² P _3/2-states of radioactive Rb isotopes have been investigated by level crossing and optical double resonance spectroscopy. The measured hyperfine structure constants yielded the nuclear moments $$\begin{gathered} \mu _I (^{84} Rb) = - 1.296(11)\mu _K Q(^{83} Rb) = + 0.27(5) \cdot 10^{ - 24} cm^2 \hfill \\ Q(^{84} Rb) = + 0.005(13) \cdot 10^{ - 24} cm^2 \hfill \\ Q(^{86} Rb) = + 0.20(3) \cdot 10^{ - 24} cm^2 \hfill \\ \end{gathered} $$ and the hyperfine anomaly₈₄Δ₈₅=+1.7(1.0) · 10^?2. The quadrupole moments of⁸³Rb to⁸⁷Rb can be explained with the unified model of vibrations.     

Editorial

The production of charmed mesons ,D ^± , andD ^*± is studied in a sample of 478,000 hadronicZ decays. The production rates are measured to be