Relation of contact densities with Mössbauer isomer shifts for 35.46 keV M1 transition of125Te

The internal conversion electron and Mössbauer isomer shifts associated with the 35.46 keV M1 transition of¹²⁵Te were observed for different metal samples into which radioactive¹²⁵I as probe atoms were introduced by means of ion-implantation. From the correlation between the Mössbauer isomer shifts and intensity ratios of O shell to N_I shell conversion electrons, a relation between 5s-electron contact densityp _5s(0) in a.u. and isomer shift δ in mm/s was deduced to bep _5s(0)=106+30.3 δ±4.3[(δ?0.30)²+0.069]^1/2, where δ was measured relative to ZnTe in mm/s. The change of the nuclear charge radius in the 35.46 keV M1 transition of¹²⁵Te was found to be ΔR/R=(0.85±0.12)×10^?4 (corresponding to Δ<r ²>=(3.7±0.5)×10^?3 fm²) when a theoretical 4s-electron contact density of 928 a.u. was used.     

Der Zerfall des125m Xe,des127m Xe und des127g Xe

The decay of^125m Xe produced by the reaction¹²²Te(α, n)^125m Xe using a target enriched in¹²²Te (95.4%) and the decay of^127m Xe produced by the reaction¹²⁷J(d, 2n)^127m Xe have been investigated: ^125m Xe decays with a half-life ofT _1/2=(56±3) sec by ayy- cascade withE _γ1=(140.4 ±0.5) keV andE _γ2=(110.5 ±0.5) keV. The experimental conversion coefficients yield multipolarities ofE3 for the 140.4 keV isomeric transition and predominantlyM1 for the 110.5 keV-transition. ^127m Xe decays with a half-life ofT _1/2=(71±2) sec. The decay also proceeds by aγγ-cascade with an isomeric E3 transition ofE _γ1=(172.5±0.3) keV and a predominantlyM1 transition ofE _γ2=(124.6±0.3) keV. In the decay of^127g Xe an additional branching of the electron capture to a level at (618.1±0.3) keV was observed. The relative probability forK-captureP _K618/P_K375=0.40 ±0.07 yields a total transition energyQ _EC=(664 ±4)keV. A spin of 1/2⁺ was assigned to the ground state.     

The supertransferred magnetic hyperfine field in chromium-iron tellurates

The broadening of the¹²⁵Te Mössbauer spectral absorption with decreasing temperature in compounds of the type Cr_2?x Fe _x Te _x TeO₆ (x=0.4, 0.8, 1.0, 1.5) is attributed to the presence of a supertransferred magnetic hyperfine field. The origin of the supertransferred magnetic hyperfine field, which is not observed in antiferromagnetically ordered Cr₂TeO₆ or Fe₂TeO₆, is associated with an imbalance in the magnetic exchange interaction at tellurium which results from the replacement of chromium by iron.     

An investigation of iron chromium tellurates by iron-57, tellurium-125 and iodine-129 Mössbauer spectroscopy

The⁵⁷Fe Mössbauer spectra recorded at 4.2K from the trirutile-type iron chromium tellurates of composition Fe_2?xCr_xTeO₆, where x=0–2, show that the angle θ, which describes the perpendicular orientation of the magnetic moment to the basal plane of the Fe₂TeO₆ unit cell, is not changed by the incorporation of chromium until x exceeds 1.2 At this critical limit θ begins to rapidly cant to smaller values until, at compositions approaching Cr₂TeO₆, it approaches a parallel orientation to the basal plane. The¹²⁵Te and¹²⁹I Mössbauer spectra recorded from the compound FeCrTeO₆ at 77 and 4.2K are consistent with the presence of a supertransferred magnetic hyperfine field at the tellurium nucleus ofca. 76 kG.     

Magnetic moment measurement in125Te by IPAC

The magnetic moment of the 35.5 keV (3/2⁺) excited state in¹²⁵Te was measured in an external magnetic field. The value obtained μ=0.57 ± 0.07μ _N agrees with Mössbauer determinations and Kisslinger-Sorensen calculations.     

Internal conversion coefficients ofM4 transitions in125m, 127m, 129mTe decay

The internal conversion coefficients have been measured using a high resolution low energy Ge(Li) detector for the followingM4 transitions:¹²⁵Te: 109.27keV transitionα _T =357±11; RG method,¹²⁷Te: 88.26 keV transitionα _T =484±23; XPG method,¹²⁹Te: 105.50keV transitionα _T =213±10; XPG method. It is observed that these values are lower by 2.5–3.6% as compared with Hager and Seltzer's calculations. A comparison between experimental and theoreticalα _T andα _T values for elevenM4 transitions shows that the experimental values are systematically lower.     

Radioactive decay of Os191 and Os191m

Beta and gamma spectra of Os¹⁹¹ were studied using a magnetic double-focusing beta-spectrometer and a scintillation spectrometer. The isomeric state Os^191m decays through the 74·4 ± 0·1 keV (E3/M4=50) transition with a half-lifeT _1/2=13·0 ± 0·5 hours. A continuous beta spectrum withE _max=147 ± 3 keV and the gamma transitions 41·83 ± 0·05 keV (E3), 82·5 ± 0·3 keV and 129·4 ± 0·1 keV (70%M1 + 30%E2) were observed in the decay of the ground state of Os¹⁹¹. The conversion coefficient of the last transition was determined as 1·94 ±± — 0·10. Gamma transitions with energies of 47 keV and 185·8 keV were not observed.     

Mössbauer spectroscopy study of iodine and tellurium atoms in solid argon

Mössbauer effect studies were performed on the nucleogenic ¹²⁵Te and ¹²⁹I monomers formed by the decay of their respective parents ^125mTe and ^129mTe embedded in solid argon at 4.2 K. Rare-gasmatrix-isolation (RGMI) and ion implantation techniques were combined to produce those extremely diluted Mössbauer emitters. The ¹²⁵Te spectrum is composed of a quadrupole split component with splitting $\text{e}{}^2\text{qQ}\text{2}\text{= 9.2(4)}\text{mm}\text{s}$ and isomer shift $\text{IS = + 0.35(5)}\text{mm}\text{s}$, and a single line component with $\text{IS = +0.15(5)}\text{mm}\text{s}$ with respect to a ZnTe absorber. They are attributed to Te⁰ and Te^?1 species, respectively. The ¹²⁹I spectrum is composed of a single quadrupole split component with $\text{e}{}^2\text{qQ = ?685(20) MHz and IS = +0.75(4)}\text{mm}\text{s}$ with respect to a ZnTe source. This species is attributed to I⁰. Two novel single-line absorbers with high f values at RT were developed for the Te and I experiments, e.g. Mg₃TeO₆ and Na₅IO₆. Based on our results for Te⁰ and Te^?1 and on relativistic Dirac-Slater atomic calculations, a new IS calibration curve under the form of a nonlinear relationship of IS versus the number of p holes (h_p) in the closed shell configuration of 5s²5p⁶ is established for ¹²⁵Te. The IS data of the I⁰ monomer are used to refine the IS(h_p) relationship for ¹²⁹I. From these new calibration curves values are deduced for the change in mean-squared charge radius Δ〈r²〉 = 3.4(3) 10^?3fm² for ${}^{125}\text{Te and Δ〈r}{}^2\text{〉 = 19.9(7) 10}{}^{\mathrm{?3}}\text{fm}{}^2$ for ¹²⁹I, respectively. The origin of the quadrupole interaction and the experimental features of this RGMI-implantation-Mössbauer emission spectroscopy are fully discussed.     

TheK-conversion coefficient near threshold of the 30 keV isomeric transition in108mAg decay

With calibrated Ge(Li) x-ray detectorsK x rays in the conversion of the 30 keV isomeric transition in the decay of^108mAg were observed in coincidence with 79 keV γ-rays. Thus, the fraction of 30 keV transitions which take place byK conversion was measured to be (2.44±0.23) × 10^?2. Making use of a theoretical total conversion coefficient (K conversion contributes only a minor part of the total conversion coefficient), an experimental value of theK-conversion coefficient was obtained, α_K=(1.07 ± 0.10) × 10⁴ (where the error represents twice the standard deviation to which the error in the detector efficiency has been added linearly). This value agrees with the theory of Hager and Seltzer forM4 conversion. The energy of the cascading γ-ray was remeasured to be 79.20 ± 0.05 keV.     

Die isomeren Atomkerne: Yb169m,Yb175m,Yb177m

Short lived isomers of Yb were produced by neutron irradiation of enriched isotopes and have been investigated with the aid of scintillation spectrometers. Yb^169m decays with a half-life ofT _1/2=(46±2) sec emitting only L-radiation. This decay is assumed to be the same as the E 3-transition of 24 keV following the electron capture of Lu¹⁶⁹. Yb^175m [T _1/2=(0,072±0,005) sec] emitsγ-rays of (495±15) keV. The measured K-conversion coefficientα _{K 495}=0,24±0,04 and the total conversion coefficientα _{4 5}=0,6±0,3 indicate the transition to be M3. Yb^177m [T _1/2=(6,4±0,1) sec] decays by a cascade of twoγ-rays. The isomeric (228±3) keV-transition is followed by a (104±1,5) keV-radiation. The measured conversion coefficients areα _{K 228}=4,1±0,4 andα _{K 228}=6,5±0,5 for the first transition andα _{K 104}=0,39±0,05 andα ₁₀₄=0,51±0,05 for the second, indicating a M3-E1-cascade. For the M 3-transition the measured coefficients agree well with those calculated for a nucleus of finite size, but they differ by a factor of 1,5 for the E1-transition.     

Decay of126m Sb and the energy levels of126Te

The decay characteristics of 19 min^126m Sb have been studied using Ge(Li) and scintillation spectrometers. The sources of^126m Sb were obtained by the (n, p) reaction on enriched¹²⁶Te. The gamma rays of energies 414.4±0.3, 666.7±0.5 and 696.1±0.5 keV were found decaying with a half-life of 19 min. The study of beta spectra employing an anthracene crystal yielded two beta groups with end-point energies of 1.9±0.15 and 2.5±0.15 MeV. The results of singles and coincidence measurements have been incorporated into a decay scheme with excited states of¹²⁶Te at 666.7, 1,362.8 and 1,777.2 keV.     

Location of 125I implanted in silicon and germanium

A Mössbauer study of ¹²⁵I implanted into silicon and germanium lattices with various dose values was performed. The spectra measured after thermal annealing suggested an off-substitutional site population for I in the silicon lattice. The Mössbauer spectra showed no difference in the hyperfine splitting of ¹²⁵Te after electron capture of ¹²⁵I in comparison with that obtained after the isomeric transition of implanted ^125mTe. The site populations of Te and I atoms after implantation and thermal annealings were concluded as being the same.     

The decay of115 mIn

The decay of^115m In has been investigated using accurate counting methods. The emission rate of conversion electrons plusβ ^?-particles was determined with a 4π proportional flow counter. The total andK-shell internal conversion coefficients of the 336 keVγ-ray in¹¹⁵In were measured by the electron X-ray coincidence method using combinations of a Si surface barrier with a NaI(Tl) detector and of a magneticβ-spectrometer with a high energy resolution Si(Li) detector, respectively. The conversion ratioR=K/(L+M+...) was deduced from electron spectra recorded with the magneticβ-spectrometer. The 336 keVγ-ray emission rate of all used sources was determined with a calibrated NaI(Tl)γ-ray spectrometer. A Ge(Li) detector has been used to determine the relative intensity of the 497 keVγ-ray in¹¹⁵Sn. As results have been deduced the 336 keVγ-ray emission per decay (N _γ1/N ₀=(45.9 ± 0.1)%), the total internal conversion coefficient (α=1.073 ± 0.014), theK-shell internal conversion coefficient (α _K=0.843±0.012), the conversion ratioR=3.63±0.07, theβ ^?-transition per decay going to the ground state (N _β1/N ₀=(5.0 ± 0.7)%) and to the first excited level in¹¹⁵Sn¹¹⁵Sn(N _β2/N ₀=(0.047 ± 0.002)%), and the 497 keVγ-ray emission (N _γ2/N _γ1=(0.103 ± 0.004)%). From the obtained internal conversion data it follows that the 336 keVγ-ray transition is ofM4 character with anE5 admixture of less than (3.5±1.5)%. The half-life of the isomeric state¹¹⁵ mIn has been determined with four different methods. The result isT _1/2=(4.486±0.004) h.     

Reorientation effect measurements in 124Te, 126Te and 128Te

Coulomb excitation probabilities of the first 2⁺ states of ¹²⁴Te, ¹²⁶Te and ¹²⁸Te have been determined. The measurement was performed by resolving the inelastically and elastically backward scattered ⁴He and ¹⁶O projectiles using an annular surface barrier detector. Quadrupole moments (Q₂₊) as well as the B(E2, 0⁺ → 2⁺) values were extracted by analyzing the excitation probabilities with the Winther-de Boer multiple Coulomb excitation program. The Q₂ deduced for the positive sign of the 2⁺ interference term are ?0.41 ± 0.08 e · b, ?0.144 ± 0.11 e · b and ?0.12 ± 0.09 e · b for ¹²⁴Te, ¹²⁶Te and ¹²⁸Te, respectively.     

Die Konversion des86mRb

^86mRb was produced by irradiation of natural Rb and Rb enriched in⁸⁷Rb (99.2%) with fast neutrons. The half-life ofT _1/2=(61.2±1.0) sec and the energy ofE _ρ=(556.03±0.25) keV were remeasured. The experimental conversion coefficients α_tot=0.0184±0.0015 andα _K =0.0158±0.0015 yield the multipolarity of E4 for the isomeric transition. The spin of 6^? was assigned to the isomeric state. It is proposed that the spin 6^? is formed by coupling ap _3/2-proton and ag _9/2-neutron according to Nordheim's “weak” rule.     

Measurement of Ar(I) and Ar(II) transition probabilities in LTE ARC plasmas

The transition probabilities of two Ar(I) lines and one Ar(II) line have been measured in emission on wall-stabilized argon arc plasmas (0·5×10⁵?p, Nm^-2?3×10⁵; 10,000?T, K?20,000; 10²²?N_e, m^-3?5×10²³) using the “method of best fit (MBF)”. The results (without line-wing correction) are for Ar(I) at 714·7 nm, A_nm=5·66×10⁵ s^-1±5%; for Ar(I) at 430·0 nm, A_nm=3·40×10⁵ s^-1±5%; for Ar(II) at 480·6 nm, A_nm=8·82×10⁷ s^-1±7%. These values were not influenced by deviations from LTE, which have been observed at electron number densities n_e?10²³ m^-3. The small uncertainties were achieved after careful corrections of different sources of error.     

Determination of absoluteK-internal conversion coefficients of some transitions in Ce140 by the internal-external conversion method

The internalK-conversion coefficients of the 331, 431, 815 and 933 keV transitions following the decay of La¹⁴⁰ have been determined absolutely by the method of comparing internal and external conversion lines measured in a double — focusing beta — ray spectrometers. TheK-internal conversion coefficients of the 4+→2+ 487 keV transition in Ce¹⁴⁰ was used to normalize relativeK-electron and gamma-ray intensities for these transitions. The results obtained are:α _K (331)=0.04432±0.00471,α _K (431)=0.28110±0.02913,α _K (815)=0.00396±0.00043,α _K (933)=0.00282±0.00031. Multipolarity assignments based on these values are suggested. The 815 keV transition is found to be pure magnetic dipole character in good agreement with the theoretical values calculated bySliv andBand. The 331 and 933 keV transitions are proved to have magnetic dipole character withE2/M1 equal 0.2852±0.0143 and 0.1750±0.0088 respectively. The 431 keV transition was found to have magnetic octupole character. The results obtained are most consistent with the assignment 2+, 4+, 2+, 3+ and 1+ for the 1597, 2084, 2184, 2410 and 2515 keV levels respectively.     

Zur Isomerie des Tl197

Tl^197m was produced by the (α, 4n) reaction on Au¹⁹⁷ using 49 MeVα particles. The following results were obtained: Half-lifeT _1/2=(0.55±0.02) sec; energy of the isomeric level (607±4) keV, determined directly by summing up the cascade transitions in a well-type scintillator; energy of the isomeric transition (222±2) keV; conversion coefficients of this transitionα _K222=0.41±0.05 andα _tot222=2.1±0.2, indicating anE3 multipolarity; energy of the second transition (385±3)keV; conversion coefficientsα _K385=0.09±0.03 andα _tot385<0.1. This transition was identified asE2 with aM1 admixture of 20 to 30%. Spins and parities are 1/2⁺, 3/2⁺ and 9/2^? for the ground state, the 385 keV state and the 607 keV isomeric state, respectively, in disagreement with the extreme single-particle model. If this model were correct, anotherM1 transition should appear. No furtherM1 transition having an energy greater than theL-shell binding energy of T1 was observed.     

Die Konversion des Hg199m

Hg^199m was produced from natural HgO by fastn irradiation. The cascade decay was investigated with scintillation spectrometers by application of the summing technique. The following results were obtained: half-lifeT _1/2=(43±0,5) min; energy of the isomeric transitionE _γ1=(375±3)keV; conversion coefficients α _K375=3,05±0,25; α_total=5,45±0,25; yielding the multipole order of the isomeric transition to beM4+(25±15)%E5; energy of the second transitionE _γ2=(159±2)keV; conversion coefficients α _K159=0,30±0,03; α_total=0,9±0,1, confirming the multipolarityE2 of this transition.