Internal conversion coefficient for the 165.8 keV transition in139La

The internal conversion process of the 165.8 keV-ray transition in the decay of¹³⁹Ce has been reinvestigated. The emission rate of the K-shell internal conversion electrons was determined by an (electron)-(X-ray)-(X-ray) triple coincidence experiment using a magnetic-spectrometer and two Si(Li) detectors. From electron spectra recorded as a function of momentum conversion electron ratios were also determined. The disintegration rate of the sources has been taken from 4- coincidence experiments. The following results were obtained: the probability for internal conversion in theK-shellk _K =0.1719±0.0020 and the conversion ratiosK/(L + M+...=5.84±0.17,K/L=7.45±0.20, andL/(M+...)=3.63±0.29. The internal conversion coefficients deduced area=(0.2520+0.0050), _K =(0.2152±0.0033), and _L =(0.0289±0.0012). The results are in good agreement with previous experimental values and with theoretical data calculated for a M1 transition of 165.8 keV in¹³⁹La.     

Reevaluation of the conversion coefficient of the 14.4 keV transition in57Fe

Existing values of the conversion coefficient of the 14.4 keV transition in⁵⁷Fe have been reevaluated using newK-shell fluorescence yields and recent decay scheme information. Previous disagreements are removed and the mean values found are α _T =8.26±0.19, α _K =7.37±0.17.     

K-shell conversion coefficient of the 102.7 keV transition in the 81Sem decay

A precision value of αK = 8.4 ± 0.4 for the 102.7 keV isomeric transition in 57 min ⁸¹Se^m decay has been measured. Since the theoretical value for a pure E3 transition is only 5.4. an M4 admixture of 4.5 ± 0.6 percent is indicated.     

Anomalous conversion of 127 keV (E3) transition in134Cs

The total conversion coefficient of the 127.49 keV E3 isomeric transition in the decay of^134mCs was measured using the gamma intensity balance method with the help of a high resolution low energy photon detector. Theα _Tvalue was found to be 5.84±0.47 as against the theoretical value of 6.96, thus showing an anomaly of (16.1±6.7)%. TheK-conversion coefficient,α _kwas also measured using the X-ray peak to gamma ray intensity method and found to be 2.24±0.04 as against the theoretical value of 2.72, which shows an anomaly of (17.6±1.4)% consistent with the experimental anomaly inα _T. TheE3 hindrance factor of the isomeric transition was estimated to be (3.44±0.23) ·10⁴.     

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.     

Internal conversion investigations for the 127·37 keV E3 transition in134Cs

Relative conversion line intensities of the 127·37 keV E3 isomeric transition in¹³⁴Cs have been measured for ten atomic subshells, using the (/2) 13 beta-ray spectrometer. The multipolarity E3 + (0·07±0·04)% M4 was determined. Internal conversion coefficients were calculated in different physical approximations. Precise calculations were performed for two atomic models (non-relativistic Hartree-Fock-Slater and relativistic Hartree-Fock-Slater). Experimental data were found in agreement with tabulations of Hager and Seltzer and mentioned calculations. An upper limit for the -branching ratio (138·6 keV M4)/(127·37 keV E3) was found to be 0·2%. The measurement of the half-life of the isomeric state has been carried out with a NaJ(Tl) crystal. The result obtained isT _1/2 = (2·95 ± 0·02) h.The authors would like to thank Prof. U.Schmidt-Rohr for the interest in this work.     

K-conversion coefficient of the 53.3 keV transition and\frac{K}{{L + M}}-ratio of the 13.34 keV transition in73Ge

TheK-conversion coefficient of the 53.3 keV transition in⁷³Ge was measured by coincidence techniques to be αk ₁=7.1 ± 0.6 indicating very good agreement with heory forM2-radiation. The \(\frac{K}{{L + M}}\) -ratio of the 13.34 keV transition to the ground state was determined using the same techniques. The resulting value \(\left( {\frac{K}{{L + M}}} \right)_2 \) =0.36 ± 0.03 supports theE2-character of this radiation and therefore a spin assignment of \(\frac{5}{2}\) for the 13.34 keV level. The measured lifetime of this transition (T _1,2=(2.95 ± 0.05) μsec) corresponds to a factor of 15 greater than the Weisskopf estimation for a pureE2-transition. A short discussion of a possible transfer of the collectivity of the⁷²Ge-nucleus to the⁷³Ge-nucleus is given.     

Determination of theL-shell conversion coefficient for the 26 keV Mössbauer transition in161Dy

TheL-shell conversion coefficient of the 26 keV Mössbauer transition in¹⁶¹Dy has been determined to be α_L=2.4 _?0.2 ^+0.3 by coincidence techniques using high resolution Ge(Li) and Si(Li) detectors. With theoretical values for theM- andN-shells the total conversion coefficient is calculated to be α_tot=2.9 _?0.2 ^+0.3 .     

124Ba Decay to the 55 124 Cs69 low-spin levels

The decay of¹²⁴Ba to the levels of odd-odd¹²⁴Cs has been studied with on-line mass-separated sources delivered at the Isocele facility. The energy level scheme has been established fromγ-ray singles,γ?γ?t coincidence ande?γ?t coincidence spectra. Spin and parity of several low-lying levels have been assigned on the basis of internal conversion coefficient measurements andβ-branchings. A completely new level pattern including approximately 50 levels and 180γ-rays is proposed for¹²⁴Cs. Several features of this level scheme are discussed and compared to those of neighbouring isotopes.     

Measurement of quadrupole moment of the 134 keV level in <Superscript>131</Superscript>Cs

The time differential as well as time integral perturbed angular correlations of the 486-134 keV cascade in ¹³¹Cs have been studied in a polycrystalline BaSO₄ powder source using a HPGe-BaF₂ detector system. The fundamental quadrupole frequency for the 134 keV level has been found to be ω₀= (4.4 ± 0.4) × 10⁷ rad/s. From a comparison of the quadrupole frequencies of this level and that of the 81 keV level in ¹³³Cs, measured earlier in the same crystalline environment of the source, the absolute value of the quadrupole moment of the 134 keV level in ¹³¹Cs has been found to be 0.022 ± 0.002 b. This value of the quadrupole moment is reported for the first time and compared with the value predicted theoretically within the unified nuclear model with intermediate coupling. Received: 21 October 1999 / Revised version: 22 December 1999     

Determination of the K-shell internal conversion coefficient for the 37.2 keV transition in the decay of121mSn

TheK-shell internal conversion coefficientα _K for the 37.2 keV transition (7/2⁺→5/2⁺) occuring in¹²¹Sb afterβ ^? decay of¹²¹ mSn has been redetermined applying theX- toγ-peak method (XPG). Measurements of photon spectra from thin sources have been performed at various source-detector distances with a high resolution, efficiency calibrated Si(Li) detector. Values ofα _K have been deduced from the number of emittedKX rays compared to that of the emittedγ rays. TheK-shell fluorescence yield for antimony has been taken from the literature. From in total 14 experimental runs a mean result ofα _K =9.52±0.27 has been obtained. The quoted uncertainty comprising statistical and systematic parts is discussed in detail. The present result is compared with the few existing earlier experimental values and with the theoretical value interpolated from the most recent tabulations.     

Search for conversion coefficient dependence of 14.4 keV Fe-57 nucleus transition on HFI magnetic field

Measurements of the X- and y- radiation energy spectrum for the temperatures above and bolow the Curie point have shown that the relative peak intensities of the X- and y- radiation do not change more than by 1% at the Curie transition. Hence, the conversion coefficient of the 14.4 keV y- transition of Fe-57 nucleus does not depend on the HFI magnetic field with the same accuracy.     

Observation of high spin levels in131Cs from131Ba decay

The γ- and conversion electron spectra following¹³¹Ba ε-decay are investigated, using HPGe detector and mini-orange electron spectrometer. Attention is particularly focussed on identifying weak transitions associated with low energy high spin levels in¹³¹Cs level scheme earlier inferred in reaction studies but not yet observed in¹³¹Ba decay. Our experiment identifies 15 new gammas and 6 new conversion lines in this decay. Internal conversion coefficients and multipolarities of several transitions are determined. Five new levels (3 with I^π = 7/2⁺ and one each with I^π 9/2⁺ and 11/2⁻) are introduced in the¹³¹Cs level scheme based on our observations taken together with the results from reaction studies. Spin-parity assignments to a few other levels are also suggested     

Isomerieverschiebungen der 81 keV γ-Linie des133Cs

Isomer shifts of the 81.0 keVγ-transition in¹³³Cs have been measured by the Mössbauer technique for eight ionic Cs compounds, and for the intermetallic compound CsBi₂. The source was¹³³Ba in CaF₂. The shifts, relative to CsCl, range from ?1.4 · 10^?8 eV for CsNO₃ to +1.6 · 10^?8 eV for CsBi₂. The difference in electron density at the Cs nucleus between CsBi₂ and CsNO₃ is discussed using chemical bonding arguments. For the Cs halides, this difference is estimated from the overlap of outer electron shells in the lattices. A relative change of the mean square charge radiusδ〈r ²〉/〈r ²〉=+2 · 10^?4 is derived.     

Internal conversion of the 6.2 keV transition in181Ta

The total conversion coefficient of the 6.2 keV Mössbauer transition in¹⁸¹Ta was measured by X- and gamma-ray spectroscopy. The result of 86 ± 20 disagrees with the literature value of 46, but agrees with theory if a nuclear penetration parameter deduced from relative conversion electron intensities is taken into account. The weak 6.2 keV gamma ray has intensity per decay that is less than the previous value by a factor of 8.5.     

Lifetime measurement of the 84 keV transition in Yb170

The halflife of the first excited state in Yb¹⁷⁰ has been measured by delayed beta-electron coincidence technique. The value of\(T_{\tfrac{1}{2}} = (1 \cdot 61 \pm 0 \cdot 06)10^{ - 9} \) sec was obtained. The transition probability was calculated and compared with the estimated value from the single particle model. An enhancement factor of 169 was found. The intrinsic quadrupole momentQ ₀ and the deformation parameterβ were determined.