DieK-ElektroneneinfangwahrscheinlichkeitP K beim Zerfall von139Ce

TheK-Shell Electron-Capture ProbabilityP _K for the Electron Capture of¹³⁹Ce has been measured using the coincidence method. The detectors used have been a NaJ(Tl)-detector with Be-window for the Lanthan-X-ray, a Ge(Li)- and a 76.2 mm Ø×76.2 mm-NaJ(Tl)-detector for the 166 keV-γ-ray. The escape-effect of the Lanthan-X-ray in the NaJ(Tl)-detector was investigated. The experimental results areP _K Ω_K= 0.726±0.010 andP _K =0.801±0.034 using Ω_K=0.906±0.026.     

The electron capture decay of125I and145Pm

The productP _K ω _K of theK-capture probability and theK-fluorescence yieldω _K was measured in the EC decay of 17.7 y¹⁴⁵Pm and 60.14d¹²⁵I by means ofK x-ray-γ-ray coincidences with semiconductor detectors. Accepting a best value ofω _K =0.920 forZ=60 from the literature, values ofP _K =0.606±0.025 and 0.554±0.025 for decay of¹⁴⁵Pm to the 67.2 and 72.4 keV levels in¹⁴⁵Nd, respectively, were determined, from which the application of EC theory givesQ _EC=153±4 keV to the ground state. TheP _K ω _K ratio to the 67.2 and 72.4 keV levels also was determined independently to be 1.11±0.01, which serves as a good check on theγ-ray-gatedP _K values. Theγ-ray energies were determined more accurately to be 72.4±0.1 and 67.2±0.1 keV, together with a ratio of their relative intensities,I _72.4/I _67.2=3.35±0.09. In the decay of¹²⁵I, a value ofP _K ω _K =0.699±0.030 was measured, and by using an independent determination ofQ _EC=178±2 keV to the ground-state from the literature, a value ofP _K=0.801 is calculated from allowed EC theory, from whichω _K =0.873±0.017 atZ=52 is obtained. This value is in good agreement with theoretical values and with a value of 0.875±0.028 predicted by the best fit curve of Bambyneket al.     

Experimentelle Untersuchungen am Elektroneneinfang des Mangan 54 und Zink 65

The electron capture decay of Mn 54 and Zn 65 was investigated using Na I(Tl)-detectors. Spectroscopic-coincidence techniques were employed to examine theK-electron capture rates of Mn 54 and Zn 65, the branching ratio and positron rate of Zn 65. The experimental results are:P _k ω _k (Mn)=0.2492±0.0017,P _k ω _k (Zn)=0.3927±0.0026,EC ^* /EC ⁰(Zn)=53.2±1.0/46.8±1.0,γ/β ⁺=35.1±1.7,K ⁰/β ⁺=27.7±1.5. Thus electron capture to the excited state of Cu 65 occurs to the extent of 52.4±1.0% while electron capture and positron decay to the ground state were found to be associated with 46.1±1.0% and 1.49±0.05% of the disintegrations. These data partly disagree significantly from measurements of other authors. Using the fluorescence yieldsω _k (Cr)=0.279 andω _k (Cu)=0.4425, deduced from other measurements, values ofL+M/K of electron capture to the excited state could be derived:L+M/K(Mn 54)=0.120±0.015 andL+M/K(Zn 65)=0.127±0.015. These ratios agree with the calculations ofBahcall. The half-lives of Mn 54 and Zn 65 have been determined to beT _1/2(Mn 54)=312±5d,T _1/2(Zn 65)=243±4d The energy of the Zn 65-γ-rays was measured with a Ge(Li)-counter:E ^γ=1115.5±0.5 keV.     

TheEC-decay of170Tm

The spectrum ofK X-rays andγ-rays following the decay of¹⁷⁰Tm has been reinvestigated using a high resolution Si(Li) detector. The intensities of theEC-branches from the ground state of¹⁷⁰Tm to the ground state as well as to the first excited level in¹⁷⁰Er have been measured. The total intensity of theEC-decay is (0.25 ± 0.05)% of all¹⁷⁰Tm disintegrations with (0.18 ± 0.05)% leading to the ground state and (0.07±0.02)% leading to the first excited level of¹⁷⁰Er. The energy of the de-excitingγ-ray has been determined to (78.7±0.5) keV. Its intensity is (0.28 ± 0.06)% of that of the 84.3 keVγ-ray in¹⁷⁰Yb.     

Revision of the109Cd decay data

Combining measurement with the use of a Si(Li) detector and a windowless 4π NaI(T1) detector a new value ofω _K(Ag) equal to 0.84±0.02 has been determined. From the measured ratio of the KX-ray and conversion electron emission rates the relative K-capture probabilityP _K=0.77±0.015 was calculated. Through analysis of data reported in literature and taking into account the new value ofP _K andω _K and the results of the international comparison of absolute activity measurements of¹⁰⁹Cd, the following decay data were chosen for the calculation of yields:ω _K=0.836±0.007;α _T=26.4±0.3; α_K=11.4±0.3; P_K=0.78±0.015. The number of gamma photons per disintegration (gamma-yield) was then determined equal to 0.0365±0.0004; the KX-yield equal to 0.997±0.008; the conversion electrons yield equal to 0.9635±0.0005 and the KX/γ ratio equal to 27.3±0.6.     

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.     

Precise atomic masses of147Eu,147Gd,and151Tb derived from their decay properties

Theβ-decay energies of¹⁴⁷Eu,¹⁴⁷Gd, and¹⁵¹Tb were determined by usingγ-spectroscopical methods. The comparison of experimental with calculatedK-capture probabilities yielded theQ _EC values 1.690( _?16 ⁺²¹ )MeV and 2.203( _?13 ⁺¹⁹ )MeV for¹⁴⁷Eu and¹⁴⁷Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in¹⁴⁷Eu decay, the decay energiesQ _EC=1.702(13) MeV andQ _EC=1.709(18)MeV were derived. Also fromEC/β ⁺ ratios the valuesQ _EC=2.225(75) MeV for¹⁴⁷Gd, andQ _EC=2.566(12)MeV for¹⁵¹Tb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studiesγ-decay properties of¹⁴⁷Eu and¹⁴⁷Gd were reinvestigated.     

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.     

Konversionskoeffizient von69m Zn und Fluoreszenzausbeute von Zink

The decay of^69m Zn and⁶⁹Zn has been investigated using a radioactive source obtained by irradiating a sample of 99%⁶⁸ZnO with neutrons. Theβ-spectrum of⁶⁹Zn and the conversion electrons of the^69m Zn decay have been studied with an anthracene scintillation spectrometer of the split crystal type. The measured value of the conversion coefficient of^69m Zn is α=0.054±0.003. With this result and those obtained by measurement of theγ-ray spectra of^69m Zn with NaI(Tl) scintillation crystals, theK-fluorescent yield of Zn has been determined to be ω_K=0.45±0.04.     

TheK-Fluorescence Yield of Germanium

TheK-Fluorescence Yield _k of Germanium has been measured using the coincidence method and investigating the decay of⁷⁴As. The branching ratios of this decay had to be measured and all relevant determining values, as detection efficiencies, absorption coefficients etc. The experimental results areP _{K K} = 0.494±0.012 and _K= 0.561±0.015 usingP _K= 0.881±0.003. For the branching ratios of the decay of⁷⁴As we obtainedEC ₂ (1.204) 0.88±0.06%EC ₁ (0.596) 32.8±0.8 % ₁ ⁺ (0.596) 24.7±0.8 %EC _{1 1} ⁺ =1.332±0.046.Additionally the half-lifeT _1/2=(17.76±0.03) d has been measured.     

L 1 subshell yields atZ=73 from the electron capture decay of181W

The TaL x ray spectrum from the electron capture decay of¹⁸¹W is analyzed into components characteristic of the threeL-subshells and theL ₁ subshell yields atZ=73 are determined to beΩ ₁=0.15±0.02,f ₁₂=0.23±0.05 andf ₁₃=0.32±0.02. A revised decay scheme for the decay of¹⁸¹W is proposed from measurements of x-ray and gamma intensities. A value of 0.97±0.08 for theK-conversion coefficient of the 153 keV transition is obtained and itsE ₂/M ₁ multipolarity mixing ratio,δ ²(0.25) is deduced.     

Zum Elektroneneinfang des185Os

The relative probabilities forK-capturePK ₉₃₁/PK ₆₄₆=0.109±0.005 andPK ₈₈₀/PK ₆₄₆=0.708±0.010 were measured yielding a total transition energyQ _EC =(1015.0 ±0.7)keV andQ _EC =(1016±3)keV, rsp. The reported 5 keV-transition in the decay of¹⁸⁵Os between the 880 keV- and 875 keV-level was not confirmed by comparing the measured relativeK-capture probabilityPK ₈₇₅/PK ₆₄₆=0.732±0.007 with the calculated value. This is in accord with the measured upper limit for the lifetime of the 880 keV-level,τ<3 nsec.     

States inN=80140Nd populated in the decay of140Pm

The level structure of theN=80,¹⁴⁰Nd has been investigated through the beta decay of^140m Pm and^140g Pm, whose decay half-lives were measured to be 5.95±0.05 min and 9.1±0.5 sec, respectively. Decay schemes for the two isomers have been constructed fromγ-ray measurements. With the help of the beta decayft values and internal conversion electron measurements, spins and parities were deduced for levels in¹⁴⁰Nd. Among the levels a 7^? state at 2222.0 keV and a 5^? state at 2273.3 keV are identified as two-neutron quasiparticle states. The (ie233-01) for^140m Pm and^140g Pm have been deduced as 7^? and 1⁺, respectively. From beta end-point measurements, the decay energies of the two isomers have been determined asQ _EC=6.48±0.07 MeV^140m (Pm) andQ _EC=6.08±0.10 MeV (^140gPm). The results are discussed in the light of nuclear systematics of theN=79 and 80 isotones.     

Innere Konversion der 161 keV- und 223 keV-Übergänge in133Cs

Using a Ge(Li)-Si (Li)-spectrometer the 161 keV and 223 keV transitions of¹³³Cs were investigated. TheK-conversion coefficients were deduced to beα _K =0.205±0.007 andK-conversion coefficients were deduced to beα _K =0.0743±0.0043, respectively. TheK/L ratio for the 161 keV transition is 4.72±0.37. From theK-conversion coefficients were deduced to beα _K -values,M1 penetration factors ofλ=8.6±3.4 andλ=7.8 _?2.8 ^3.0 were deduced which are inconsistent with known data from angular correlation experiments (λ=40±10 andλ=90±13). The penetration factor fromK/L-measurement for the 161 keV-transition isλ=52±19. A theoretical reinvestigation of the formulas used in the literature appears recommendable. Furthermore, theK/L ratio of the 1770 keV transition of²⁰⁷Pb was determined experimentally to be 5.52±0.54.     

Multipole mixing ratios of transitions in168Er

Time-integral and time-differentialγ-γ directional correlation measurements were performed for cascades in¹⁶⁸Er populated from the electron-capture decay of¹⁶⁸Tm(87d). The¹⁶⁸Tm source was dissolved in HF acid to minimize extranuclear perturbations. The results of the time-differential experiment for the 448-99.3 keV and 448-198 keV cascades showed agreement with time dependent interaction and gaveλ ₂(1094)=(0.79±0.09) ×10⁷ sec^?1. The attenuation factors for the 80 keV level were determined asG ₂₂ (80)=0.90±0.01 and G₄₄(80)=0.94±0.01. OnlyI=4 spin value for the 1094 keV level is consistent with our measurements. The 632, 731, 741, and 816 keV transitions connecting theK=2⁺ andK = 0⁺ rotational bands were found to be of almost pureE2 character. The 99.3, 198, 547, 720, 830, and 1277 keV transitions are of practically pureE1 multipolarity. The 448 keVMl transition has (0.8 _?0.4 ^+2.0 )%E2 admixture. The results for the 1014?80keV cascade give (23±4)%E3 component in the 1014 keV transition.     

Decay of194Os andL 1 subshell yields atZ=77

The relative intensities of x rays and gammas emitted in the beta decay of¹⁹⁴Os are measured. No evidence for the feeding of a level at 83 keV in¹⁹⁴Ir is found. An upper limit of 1.7×10^?4 was set for theK shell internal ionization probability in the beta decay to the ground state of¹⁹⁴Ir. TheL-conversion coefficient of 43 keV transition is found to be 12.1 and the transition is mainly ofM1 type with an admixture of 1.3%E2 type. TheL ₁ subshell yields atZ=77 are determined to beω ₁=0.16±0.04,f ₁₂=0.11±0.04 andf ₁₃=0.37±0.03.     

Experimentelle Untersuchungen am Elektroneneinfang des85Strontium und88Yttrium

The electron capture decay of⁸⁵Sr and⁵⁵Y has been investigated using NaI(Tl)-detectors. Spectroscopic-coincidence techniques have been employed to examine theK-electron capture rates. The experimental results areP _K ω _K (Sr)=.5959 ± 0.0035 andP _K ω _K (Y)=0.6340± 0.0032. Using theK-capture probabilities, derived from the capture ratios ofBrysk andRose with the exchange correction ofBahcall:P _K (Sr)=0.880± 0.008 andP _K (Y)=0.883 ± 0.008, one can derive from these results the fluorescence yieldsω _K (Rb)=0.677± 0.009 andω _K (Sr)=0.712± 0.010. Functions ofω _K (Z) were fitted to recent experimental data and tabulated forZ=5–90. In addition to these results the half life of the 514 keV state of⁸⁵Rb and the branching ratios and the positron rate of the⁸⁸Y-decay have been measured with the same techniques. The data obtained partly disagree from measurements of other authors.     

The decay of141Ce

The decay of¹⁴¹Ce has been reinvestigated using different experimental methods. The efficiency extrapolation technique applied to 4πβ —γ coincidence measurements has been employed for the determination of the disintegration rate of the sources and of the total internal conversion coefficient. TheK X-ray andγ-ray emisssion rates have been measured with a calibrated Si(Li) and an intrinsic germanium detector. Additionally the photon intensities have been determined from the internal conversion coefficients. Electron experiments with a magneticβ-spectrometer yielded the relative intensities, the shape factors and the maximum energies of the two β^?-transitions and the internal conversion ratiosK/L andK/(L + M+...). TheK-shell internal conversion probability has been determined with an electronK X-ray coincidence technique using the magneticβ-spectrometer together with a high energy resolution Si(Li) detector. New values for the following decay properties have been deduced:β ^?-intensities (p ₁ =0.306 + 0.006,p ₂= 0.694±0.006), shape factorsC = const (1+Aε) (A ₁ = ?(0.24±0.03),A ₂=?(0.22±0.04)), maximumβ ^?-energies (E ₀₁ = (582.2±2.6) keV,E ₀₂= (436.7±4.6) keV),K- shell internal conversion coefficient (α _K = 0.376±0.008), total internal conversion coefficient (α = 0.438±0.010), internal conversion ratios (K/L = 7.29±0.24, K/(L + M + ...) = 5.78±0.18),γ-ray intensity (I _γ = 0.482±0.003),K X-ray intensity (I_{K X} = 0.168±0.002) and the photon intensity ratio (I _{K X} /I _γ = 0.349±0.005). The procedure of uncertainty quotation is presented in some detail. The results are discussed with respect to existing experimental data.     

K-capture probabilities in the electron capture decay of159Dy

TheK-electron capture probabilities (P _k) for the 58 keV state and the ground state of¹⁵⁹Tb in the decay of¹⁵⁹Dy have been determined. The measured values,P _k ⁵⁸ =0.81±0.05 andP _k ⁰ =0.79±0.06 are found to be in excellent agreement with theoretical results.     

Determination of theK-shell electron capture probabilityP K in the decay of139Ce

A new coincidence procedure for the determination of theK-shell electron capture probability in simpleEC decays is described. By measuringγ-rays andK-shell conversion electrons separately and in coincidence with theK X-rays theK capture probability can be deduced only from counting rates. The method has been applied to¹³⁹Ce. The result ofP _K = 0.726±0.010 is in fairly good agreement with other experimental values reported previously.