Bestimmung des elektrischen Kernquadrupolmomentes des ungeraden stabilen Strontium-87-Kerns

In order to determine the electric quadrupole moment of Sr⁸⁷ (I= 9/2) the hyperfine structure-splitting of the 5s5p ³ P ₁-state of the SrI-spectra was investigated by optical double resonance. By detection of high frequency transitions (ΔF=±1,Δm _F=0,±1) in an external magnetic fieldH ₀≈0 one obtains the hyperfine structure separations asv _F=11/2?F=9/2=1463·149 (6) Mc/sec andv _F=9/2?F=7/2=1130·264 (6) Mc/sec. From these frequencies one calculates the magnetic hyperfine structure-splitting constantA=?260·084 (2) Mc/sec and the electric quadrupole interaction constantB=?35·658 (6) Mc/sec. B leads to an electric quadrupole moment ofQ(Sr⁸⁷)=+0·36 (3)·10^?24 cm².     

Messung der Hyperfeinstrukturaufspaltung des4F9/2-Grundzustandes im Co59-I-Spektrum und Bestimmung des Quadrupolmomentes des Co59-Kernes

The hyperfine structure splittings of the electronic ground statea ⁴ F _9/2 in the Co⁵⁹-I-spectrum have been measured with a magnetic atomic-beam resonance-apparatus. From these splittings the magnetic dipole and electric quadrupole interaction constants are found to beA (a ⁴ F _/2)=(450,284±0,01) Mc/sec,B (a ⁴ F _9/2)= (139,63±0,5) Mc/sec. Taking into account the mixture of thea ⁴ F _9/2 state with states of the same 3d ⁷ 4s ²-electron-configuration, an electric quadrupole moment of Co⁵⁹ ofQ=(0,404±0,04) 10^?24 cm² was obtained. No Sternheimer-correction has been included.     

Bestimmung der Hyperfeinstrukturaufspaltungen der Scandium-Grundzustände2 D 3/2 und2 D 5/2 und des Quadrupolmomentes des Sc45-Kernes

The hyperfine structure splittings of the electronic ground states² D _3/2 and² D _3/2 of the stable isotope Sc⁴⁵ have been measured by the atomic beam magnetic resonance method. From these splittings the magnetic dipole and electric quadrupole interaction constants are found to bea _3/2=(269,560±0,02) Mc/sb _3/2=?(26,37±0,1) Mc/sa _5/2=(109,034±0,01) Mc/sb _5/2=?(37,31±0,1) Mc/s. The values of the electric quadrupole moment calculated fromb _3/2 andb _5/2 differ by about 5% indicating that the configuration 3d 4s ² of the ground states is perturbed by higher configurations. Averaging these two values we obtain for the quadrupole moment of Sc⁴⁵ Q(Sc⁴⁵)=?(0,22±0,01) · 10^?24 cm².     

Die Hyperfeinstruktur des 32P3/2-Zustands von Natrium im starken Magnetfeld

The hyperfine structure of the 3²P_3/2 State of Na²³has been measured by the optical double resonance technique in a magnetic field of 3.1 kG sufficiently strong to decouple completelyI andJ. In the case of π or (σ⁺+σ^?) excitation the double resonance signal represents the superposition curve of eight unresolved radio-frequency transitions. The dependence of the signal on the pressure of sodium vapour and the radio-frequency field strength has been studied. The analysis of the experimental curves yields for the hyperfine coupling constants the valuesa=(18.7±0.4) Mc/s andb=(3.4±0.4) Mc/s. The nuclear electric quadrupole moment derived from the ratio ofb/a isQ=(0.146±0.02) · 10^?24cm². The Lande factor and the lifetime for the 3²P_3/2state are g_J=1.3344±0.0004 and τ=(1.61±0.07) · 10^?8 sec.     

Level-crossing-Untersuchung der Hyperfeinstruktur des 3d 10 4p 2 P 3/2-Terms von Cu63 und Cu65

The level-crossing technic has been used to investigate the hyperfinestructur of the 3d ¹⁰ 4p ² P _3/2-term in Copper I by scattering the resonance line λ=3248 Å on an atomic beam of separated isotop Cu⁶³ respectively Cu⁶⁵ in an external magnetic field. From the level-crossing signals values for the magnetic dipol interaction constantsA and for the electric quadrupol interaction constantsB are deduced to beeA(Cu⁶³)=(194,72±0,15) Mc/secB(Cu⁶³)=?(28,8±0,6) Mc/secA(Cu⁶⁵)=(208,57±0,15) Mc/secB(Cu⁶⁵)=?(25,9±0,6) Mc/sec. With theA-value of the 3d ¹⁰ 4p²P_1/2-term from optical measurements the ratioA(² P _3/2)∶A(² P _1/2)≈0,4 is about twice greater than for an unperturbetalkali-like²P-term. From the width of the level-crossing signals a mean lifetime of the 3d¹⁰ 4p²P_3/2-term τ=(7,0±0,2) · 10^?9 sec is deduced.     

Hyperfine-structure measurements on Dy161 and Dy163

In an atomic beam magnetic resonance experiment the hyperfine interaction constantsA andB of the⁵ I ₈ groundstate of Dy¹⁶¹ and Dy¹⁶³ were found to be Dy¹⁶¹:A=?(115.8±1)MHz, Dy¹⁶³:A=(162.9±0.6)MHz,B=(1102±15)MHz,B=(1150±20)MHz. Using an effective value for 〈r^?3〉, the magnetic moments and electric quadrupole moments of the Dy¹⁶¹ and Dy¹⁶³ nuclei were calculated to be Dy¹⁶¹:μ _I=?(0.47±0.09) n.m., Dy¹⁶³:μ _I=(0.66±0.13)n.m.,Q=(2.36±0.4)barns,Q=(2.46±0.4)barns.     

Präzisionsmessung der Hyperfeinstruktur des 52P3/2-Terms und des 62P3/2-Terms von Rb85 und Rb87

To study the modification of the value of the nuclear quadrupole moment obtained without Sternheimer correction from measurements in states with different principal quantum numbers, the hyperfine structure splitting of the 5² P _3/2 and the 6² P _3/2 excited states of Rb I has been investigated with the optical double resonance method. The experiments, in which isotopic enriched samples of Rb⁸⁵ and Rb⁸⁷ were used, have been carried out in the 5² P _3/2 state without a static magnetic field. In the 6² P _3/2 state, a static magnetic field was applied. For the 5² P _3/2 state, the hyperfine structure constants areA(Rb⁸⁵)=25.029(16) Mc/s,B(Rb⁸⁵)=26.032(70) Mc/s,A(Rb⁸⁷)=84.852(30) Mc/s,B(Rb⁸⁷)=12.611(70) Mc/s. The corresponding constants for the 6² P _3/2 state areA(Rb⁸⁵)=8.25(10) Mc/s,B(Rb⁸⁵)=8.16(20) Mc/s,A(Rb⁸⁷)=27.96(35) Mc/s,B(Rb⁸⁷)=3.95(10) Mc/s. The values of the nuclear quadrupole moments, derived from both finestructure states, can be brought into agreement when the Sternheimer core correction is applied. The Landé factor for the 6² P _3/2 state isg _j=1.334(1).     

Magnetisches Moment und Quadrupolmoment des 8,42 keV-Zustandes von Tm169 aus der Hyperfeinstrukturaufspaltung in Tm-Metall

The hyperfine transition from the 8·42 kev level to the groundstate of Tm¹⁶⁹ was investigated using the Mössbauer-Effect in Tm-metal in the temperature range between 5° K and 60° K. Well resolved hyperfine spectra were found between 5° K and 25° K indicating an internal magnetic field of about 7×10⁶ Oe and a large electric fieldgradient. The ratio of the magnetic moments of the 8·42 keV rotational state to the groundstateμ _a /μ _g =?2·33±0·04 was deduced from these measurements. The magnetic moment of the groundstate and the quadrupole moment of the 8·42 kev level were deduced from calculated internal fields. These data were analyzed in terms of the “Unified Nuclear Model” and the results compared with other known magnetic moments andM-1-transition probabilities in theK=1/2 rotational band of Tm¹⁶⁹. The complicated hyperfine spectra obtained above 25° K reveal the influence of complex magnetic ordering on the internal fields in Tm-metal.     

Die Hyperfeinstrukturaufspaltung des Grundzustandes2 S 1/2 und das magnetische Kerndipolmoment von Au197

The hyperfine structure of the groundstate 6s ² S _1/2 and the nuclear magnetic dipole moment of gold 197 have been studied by the atomic beam magnetic resonance technique. A special high frequency arrangement is described. The hyperfine structure separationΔ v was determined fromΔF=1 transitions. The magnetic dipole momentμ _I was measured by a direct method. The experiments yield the following results:Δv (²S_1/2)=(6099,309±0,010) Mc/secμ _I (Au¹⁹⁷)=+(0,1445±0,0014)μ _K.     

Mössbauer effect and nuclear moments of the 75 keV state of Dy161 and the 81 keV state of Dy162

The Mössbauer effect of theγ rays from the 74.5 keV state of Dy¹⁶¹ and the 80.7 keV state of Dy¹⁶² has been investigated. From hyperfine splitting patterns the magnetic moments μ(75 keV)=?(0.39±0.04) nm, μ(81 keV)=+(0.74±0.08) nm and the quadrupole momentQ(75 keV)=+(1.4±0.2)b have been determined. For the odd neutron nucleus Dy¹⁶¹ an effective spin g factorg _{s, eff}=0.76 g_{s, free} is deduced for the 75 keV level.     

Zur Hyperfeinstruktur des 62P3/2-Terms von Rb87

The hyperfine structure of the 6² P _3/2 state of Rb⁸⁷ has been reinvestigated with optical double resonance in zero magnetic field. The results for the hfs-splitting constants areA(6² P _3/2, Rb⁸⁷)=27.70 (2) Mc/s andB(6² P _3/2, Rb⁸⁷)=3.94 (4) Mc/s. From these constants one obtains a value for the nuclear quadrupole moment uncorrected for shielding effects ofQ=+0.138 (1)·10^?24 cm².     

Relativistic theory of the electric quadrupole moment of a hydrogen-like atom in the <Emphasis Type="Italic">s</Emphasis>1/2 and <Emphasis Type="Italic">p</Emphasis>1/2 states

Relativistic analytical expressions are derived for the electric quadrupole moment induced by the hyperfine interaction of the electron with the nucleus of a hydrogen-like atom in the ns_1/2 and np_1/2 states. The magnetic dipole and electric quadrupole hyperfine interactions are taken into account. The calculations are performed using the generalized virial relationships for the Dirac equation in a central field. The dependences of the electric quadrupole moment on the nuclear charge Z and the principal quantum number n are analyzed. The induced quadrupole moments are compared with the nuclear quadrupole moments.     

Studies of characteristic flash X-ray lines

Level crossings obeying the selection ruleΔm=2 have been detected in the 6² P _3/2-state of both Rb⁸⁵ and Rb⁸⁷. Using the measured crossing points, the ratios of the hyperfinestructure constants to theg _J -factor are determined from a calculation for intermediate magnetic fields. The ratios areA ₈₅/g _J =6.119 (3) Mc/s,B ₈₅/g _J =6.14 (2) Mc/s,A ₈₇/g _J =20.70 (3) Mc/s,B ₈₇/g _J =2.93 (5) Mc/s. From the zero field level crossing of Rb⁸⁷ the lifetimeτ=1.14 (6) · 10^?7sec of the 6²P_3/2-state is obtained. Level crossing signals have also been observed in the presence of noble gas admixtures.     

Verzweigungsverhältnisse undβ +-Maximalenergie beim Zerfall von Ag108

The branching ratios of Ag¹⁰⁸ have been remeasured with scintillation spectrometers. There is evidence for a weak 177 keV-β ^?-branch going to the 1473 keV level of Cd¹⁰⁸, followed by aγ-γ-cascade of (841+632)keV. Spin and parity 2+ of this level are supported by logft=4.7 of theβ ^?-branch. Theβ ⁺-spectrum has been measured for the first time yielding an end point energy of (880±25)keV, in agreement with the value derived from theK/β ⁺ratio.     

Die relativen Quadrupolmomente der ersten angeregten 2+-Zustände von Os188, Os190 und Os192

The angular distributions of the deexitationγ-rays following Coulomb-excitation of the first excited 2⁺-states in Os¹⁸⁸, Os¹⁹⁰ and Os¹⁹² were measured using a metallic Target of natural Osmium. The measured attenuation coefficients areG ₂(Os¹⁸⁸)=0.798±0.013,G ₂(Os¹⁹⁰)=0.917±0.030 andG ₂(Os¹⁹²)=0.940±0.030. As a general test the angular distribution of the 330 keV-γ-rays of Pt¹⁹⁴ was also measured. This distribution was found to be completely undisturbed. Assuming pure electric quadrupole interaction with the internal crystalline fields one obtains an interaction frequency ofΔv _Q =eQ V _zz /h=278±32 MHz for the 155 keV-state of Os¹⁸⁸. Because the electric field gradients acting on the decaying nucleus are the same for all isotopes, one can deduce the ratio of the quadrupole moments of the excited states. The result isQ(Os¹⁸⁸)∶Q(Os¹⁹⁰)=1.11 _?0.19 ^+0.28 andQ(Os¹⁹⁰)∶Q(Os¹⁹²)=1.03±0.30. The effects of the uncertainties in the effective field gradients and their possible asymmetries on the integral attenuation factors are discussed. For 1≧G ₂?0.75 these effects are found to be small.     

Suche nach Zweiquantenprozessen beim Zerfall von Xe131m

The decay of Xe^131m was investigated in order to detect nuclear double decay processes, in which the transition energy is distributed either between twoγ-quanta or between oneγ-quantum and oneK-conversion electron or between twoK-conversion electrons. By analyzing the emittedγ-radiation in a two-dimensional way an upper limit of 2.2 · 10^?5 was derived for the ratio of theγγ- toγ-transition probability. An investigation of theγ-spectrum in coincidence withK-quanta yielded an upper limit of 3 · 10^?2 for the rate ofe _Kγ-transitions relative toγ-transitions. The simultaneous emission of twoK-quanta was actually observed. These doubleK-quanta result either from the doubleK-conversion that was sought or from the internal conversion of the internal Compton-effect. For the doubleK-electron emission toγ-emission probability a value of (3.6±0.7) · 10^?3 was obtained. TheK-conversion coefficient and the half-life of Xe^131m were measured to be 32.1±0.4 and 11.94±0.04 d, respectively.     

Mössbauer study of the magnetocaloric compound AlFe<Subscript>2</Subscript><Emphasis Type="Bold">B</Emphasis><Subscript>2</Subscript>

Mössbauer spectroscopy in the ferromagnetic AlFe₂ B ₂ reveals T_c=299 K and shows good agreement with magnetic measurements. The crystals are plate-shaped. The flakes are found from X-ray diffraction to be in the crystallographic ac-plane in the orthorhombic system. The axes of the principle electric field gradient tensor are, by symmetry, colinear with the crystal a-, b- and c-axes. By using information about the quadrupole splitting and line asymmetry in the paramagnetic regime together with the quadrupole shift of the resonance lines in the ferromagnetic regime the magnetic hyperfine field direction is found to be in the ab-plane having an angle =40^° to the b-axis.     

Derg R -Faktor des 2+-Rotationsniveaus von Er168

The rotation of the angular correlation between theγ-group at about 820 keV and the 80 keV radiation in the decay of Tm¹⁶⁸ has been observed in an external magnetic field of 20300 gauss. The result:ω _R·τ=0,485±0,051 yields for theg _R -factor of the 80 keV state of Er¹⁶⁸:g _R =+0,25±0,03. The evaluation includes a paramagnetic correction factor of:β=7,26, (B _eff=β·B _ext). The angular correlation is slightly attenuated by internal fields. For a liquid source of Tm (NO₃)₃ solved in 3 n HNO₃, a measurement of the differential angular correlation as a function of the delay time gave:λ ₂=(5,8±2,9)·10⁷sec^?1, assumingA ₂(t)=A ₂(0)·e ^?λ ₂·t. The half life of the 80 keV state was found to be:T _1/2=(1,92±0,04)·10^?9sec in agreement with earlier measurements.     

Das Kernquadrupolmoment des Mn55

With a recording photoelectric Fabry-Perot spectrometer and an atomic-beam light source the hyperfine structure of the Mn I-resonance linesλ=4031 Å,λ=4033 Å,λ=4034 Å (3d ⁵4s ² a ⁶ S _5/2?3d ⁵4s4p z ⁶ P _7/2,5/2,3/2 ⁰)and of the inter-combination linesλ=5395 Å andλ=5433 Å (3d ⁵4s ² a ⁶ S _5/2?3d ⁵4s4p z ⁸ P _7/2,5/2 ⁰) was measured. Furthermore the resonance lines have been measured with a pulsed atomic-beam in absorption. In this case the quotient (I ₀(ν)?I(ν))/I ₀(ν) was recorded, whereI(ν)=I ₀(ν) exp(?α(ν)d) is the observed intensity with absorption andI ₀(ν) the intensity of the light source. From the hyperfine structure splitting the value of the electric quadrupole moment of Mn⁵⁵ was derived to be:Q(Mn⁵⁵)=+(0.35±0.05)·10^?24 cm².     

Kern-Isomerie bei In116

The short lived indium isomer produced by thermal neutron capture is confirmed to be In¹¹⁶. A new determination of half-live andγ energy yieldsT _1/2=(2.17α0.07) sec andE _γ=(164±1) keV. From measurement of theK shell conversion coefficient follows that the multipolarity of the transition isE 3, leading to a spin and parity assignment of 8^? for the isomeric level.