High resolutionL- andM-subshell internal conversion studies of low energy transitions in149Sm and151Eu

The internal conversion subshell intensities of the (21.529±0.014) keV transition in¹⁵¹Eu and the (22.494±0.011) keV transition in¹⁴⁹Sm have been determined in a high resolution investigation using a double-focussing iron-core spectrometer. The subshell ratios yielded unambiguousM1+E2 multipole mixtures for both transitions. δ²(E2/M1) for the 21.53 keV transition was determined to be (8.8±0.7)·10^?4 and for the 22.49 keV transition to be (5.5±1.2)·10^?3.     

High resolution studies of transitions in the decay chain146Gd to146Eu to146Sm

Transitions in¹⁴⁶Eu and¹⁴⁶Sm were studied using a double-focussing beta-ray spectrometer and a Ge(Li) detector. Internal conversion and gamma-ray intensities were determined. The internal conversion spectrum of the three 155, 115 and 116 keV cascading transitions in¹⁴⁶Eu was studied for all subshells.K-,L- andM-subshell ratios were determined andE2/M1 mixing ratios were deduced for these three transitions. Intensities from theN- andO+P-shells were determined and compared to theoretical calculations. All internal conversion intensities were found to be in agreement with theoretical data for pureM1 character with smallE2 admixtures for all the three transitions. Selected parts of the internal conversion spectrum of the transitions in¹⁴⁶Sm were restudied at 0.06% momentum resolution. This study was mainly concentrated on four transition doublets feeding and deexciting the close lying levels at 1,380 and 1,381 keV. A new transition with 702.20 keV energy was detected in the 702–703 keV transition group. Internal conversion coefficients were deduced using reported gamma-ray intensities. Multipole characters of the transitions were deduced and used as a basis for a discussion of the spins and parities of the lower lying excited states of¹⁴⁶Sm.     

Gamma transitions in the decay of195mPt

The gamma transitions in the decay of^195mPt were investigated by the use of high resolution double focusing beta-ray spectrometer. Conversion electrons were observed for transition of energy 79.94±0.32 keV and ascribed for the first time to the decay of 4.2 d^195mPt. This confirmed that the 209 keV level decays either by the 208.81 keV transition (98%) or by a 79.94 keV–128.51 keV cascade (2%). The multipolarity assignment for each transition in¹⁹⁵Pt was obtained by comparing the measured conversion line intensity ratios with the theoretical line intensity ratios ofSliv andBand. Two gamma transitions of nearly equal energy 129 and 130 keV could be detected, the first found to be pureE2 transition while the latter hasM4 character. The mixing ratio of some gamma-rays have been determined and some discrepancies were found. The data were discussed on the light of Coulomb excitation results.     

An internal conversion study of the decay of193Au

The internal conversion spectrum following the decay of¹⁹³Au has been studied in the electron energy region 0.8 to 700 keV, with the use of high-resolution magnetic beta-ray spectrometers. Several not previously reported transitions have been estabblished. Multipolarities and mixing ratios have been deduced fromK/L and subshell intensity ratios, and the majority of the transitions were found to be ofM1 and/orE2 characters. A revised level scheme for¹⁹³Pt, which consistently accomodates most transitions, has been constructed. Tentative spin-parity values have been assigned to all levels.     

Determination ofL subshell ratios of pureM1 transitions

L subshell ratios have been accurately measured for two pureM1 transitions, 82.5 keV in ₆₇ ¹⁶⁶ Ho and 238.6 keV in ₈₃ ²¹² Bi. The results for all ratios are in fairly good agreement with those obtained from the theoretical calculations bySliv andBand.     

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.     

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.     

Energie- und Intensitätsmessungen an Konversionselektronen des Zerfalls75Se→75As

Energies and intensities of conversion lines of elevenγ transitions in the decay⁷⁵Se→⁷⁵As were measured with the Heidelberg (π/2)√13β-ray spectrometer. The experimental transition energies agree with the results of crystal diffraction spectrometer measurements; in some cases more precise values were obtained. The measured relativeK electron intensities for five transitions are in agreement with previous experiments. TheL group of the 97 keV transition was resolved for the first time and the multipolarity was determined to beE2 from theL subshell ratios.     

The odd-parity level at 687.59 keV in236U

The spin-parity of the 687.59 keV level in²³⁶U populated in the decay of²³⁶Np is determined to be 2^? in disagreement with recent 1^? assignments from reaction data, but in accordance with previous radioactive²³⁶Np decay studies. The 687 keV ground state transition is shown to have a pureM2 character. The 642 keV 2^?→2⁺ transition hasE1:M2:E3 mixing ratios of 64∶30∶6. The half-life of the 2^? state is 3.78 ± 0.09 ns. The hindrance factor of the E1-part fits an E1 transition withΔK=2, theM2-part has the same transition rate as the M2 transitions in the neighbouring²³⁷Np nucleus and the E3-part is enhanced by two orders of magnitude relative to the Weisskopf estimate. The data are compared to analogous transitions in the rare earth region.     

Internal conversion at the higher shells in the decay of113* In (100 min)

The ratios of the conversion coefficients at the higher shells and subshells were measured in the 391,7 keV isomeric transition of¹¹³In. On the basis of a computer analysis of theL subshell conversion lines it can be stated that the transition has anM4 character and the most probable value of theE5 admixture is zero. TheL/M andM/N conversion ratios show a good agreement with the recent calculations of Hager and Seltzer and Dragounet al.     

Relative internal conversion electron intensities of the 113 keV transition in177Hf

The intensities of the internal conversion lines of the 113 keVM1 +E2 transition in¹⁷⁷Hf have been measured. From comparison with theoretical conversion coefficients the transition has been found to be (95.2 ± 0.5)%E2 corresponding to ¦δ¦=4.5 ± 0.3. The theoreticalL _I andM _I conversion coefficients used in the comparison have been increased by 5% according to the result that for pureE2 transitions in the deformed region theL _I/L _II,L _I/L _III,M _I/M _II, andM _I/M _III theoretical ratios are too low (～5%). Moreover, the present result indicates that theL _II/L _III andM _II/M _III ratios obtained from the tabulations by Hager and Seltzer and from the computer program by Pauli are too high (1–2%).     

Spin of207mPo(2.79s); conversion measurement in207gPo decay

In^207m Po decay, the conversion of cascadingγ-rays 268 keV, 300 keV, and 814 keV was measured yielding the multipolarity to beE3.M2, andE2, respectively. Thereby, the spin of the isomeric state at 1382.95±0.14 keV was measured to be 19/2^?. In^207g Po decay, conversion electron andγ-ray intensities were remeasured in order to check earlier experimental inconsistencies.     

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.     

Measurements of γ-γ and γ-electron directional correlations in119Sb

The directional correlations ofγ-γ andγ-electron cascades in¹¹⁹Sb are measured, in the decay of^119mTe. Bothγ-γ andγ-electron directional correlation coefficients are determined for the cascades (energies in keV): 153.5-1212.7, 942.3-270.5, (976.2+979.3)-270.5, 1095.7-270.5 and 1136.8-270.5. For the cascades 912.6-1366.2, 2013.4-270.5 and 2089.9-270.5γ-γ directional correlations are measured. The mixing ratios evaluated are:δ(M2/E1, 153.5 keV)=0.0003±0.0023,δ(E2/M1, 270.5 keV)=-0.39±0.29,δ(E2/M1, 942.3 keV)= ?0.26±0.12,δ(E3/M2,1095.7 keV)=?0.01±0.07, andδ(M3/E2,1212.7 keV) =0.004±0.007. The result is compared with theoretical predictions.     

207Bi L-subshell orbital electron capture probabilities and decay energy

The L₁ subshell orbital electron capture probability P_L1 in the decay of 33.4 y ²⁰⁷Bi to the 2339.89 keV level in ²⁰⁷Pb is measured to be 0.518 ± 0.081 (95% confidence) by a new method in which L₁ subshell characteristic X-rays in the L_γ X-ray peak are observed in an Xγt coincidence mode with 1770.23 keV γ-rays. The value of P_L2is 0.047 ± 0.015 (95% confidence). From these results a value of Q_EC = 39_-8⁺²¹ keV is obtained for capture transitions to the 2339.89 keV level. The absence of K-capture to this level also is established by absence of K X-rays in coincidence with 1770.23 keV γ-rays.     

The gamma decay of analogue states in61Cu

Resonances in the reaction⁶⁰Ni(p, γ)⁶¹Cu have been studied in the proton energy rangesE _p=1840–1880 keV and 2220–2300 keV. Decay schemes and branching ratios have been determined for a number of resonances, three of which are identified as analogue fragments of the 283 keV (1/2^?) and 656 keV (3/2^?) states in⁶¹Ni. The split analogue components of the 283 keV state atE _x≈6.6 MeV are seen to decay significantly to a group of states in the region of excitation 3–4 MeV. Gamma ray angular distributions yield the following resonance spins:E _p=2248 keV,J=3/2;E _p=2263 keV,J=5/2. Also, the⁶¹Cu ground stateβ ⁺ decay to parent levels in⁶¹Ni has been compared to the respective analogue stateM1 gamma decay to the⁶¹Cu ground state.     

OnE0 transitions in the decay of152Eu m (9.3 h)

The conversion electron spectrum of the decay of¹⁵²Eu ^m (9.3 h) has been specially investigated forE0 transitions with the aid of a magnetic spectrometer and coincidence techniques. Besides the knownE0 transitions of 685 keV in¹⁵²Sm and 615 keV in¹⁵²Gd two further pureE0 transitions of 432 keV and 1048 keV have been observed. It is shown that theseE0 transitions are identical with those observed previously in the decay of¹⁵²Tb. NoE0 transitions could be found from a 0⁺ state of 1083 keV in¹⁵²Sm. The measured intensities together with the gamma spectrum measured by Barretteet al. give a consistent decay scheme of¹⁵²Eu ^m . Furthermore the half-life of the 0⁺ level at 615 keV in¹⁵²Gd was measured using the method of “delayed coincidences”. The result was (0.2≦t _1/2≦2.1)×10^?10 s. From this theE0 transition probability for the level was derived as (0.3≦W _K (E0)≦3.7)× 10⁹ s^?1 and theρ-value as 0.10≦¦ρ¦≦0.36. The results are discussed within the framework of the collective model.     

Gamma-gamma directional correlations and coincidence studies in154Gd

The intensities, placements andE2/M1 mixing ratios of transitions in the decay of¹⁵⁴Eu have been carefully studied to provide accurate data for microscopic calculations. Coincidence relationships in the decay of¹⁵⁴Eu have been studied extensively with a multiparameterγ-γ coincidence system with two large volume Ge(Li) detectors. Spectra in coincidence with twenty energy gates were analyzed. Twenty-nine new coincidence relationships were established and confirmed most, but not all, of several levels previously assigned by energy fits only. From an analysis of coincidence spectra and singles spectra with a 18% efficiency Ge(Li) detector new information on the gamma-ray intensities were obtained. Precise values of theE2/M1 mixing ratios of transitions from the gamma- and beta-vibrational bands to the g.s. band have been determined fromγ-γ directional correlation measurements with a NaI(Tl)-Ge(Li) detector coincidence system. Mixing ratios were obtained for a number of other transitions including those fromK ^π =0^? and 2⁺ bands from direct and skipped cascade correlations.     

TheL- andK- Auger spectra of tellurium

TheL- andK- Auger spectra of tellurium (Z=52) were studied from the electron capture decay of¹²⁵I. The measured relativeL- Auger transition intensities are not in agreement with the theoretical intensities of Asaad for silver (Z=47). The measured relativeKLL intensities are in agreement with those ofGraham et al. Relative intensities are given for theKL Y spectrum. TheKL Y/KLL ratio was measured to be 0.44 ± 0.02 in good agreement with the theoretical value given byWapstra.K/L andL subshell conversion ratios are given for the 35 keV nuclear transition in¹²⁵Te.     

Multipole mixing ratios of transitions in175Lu populated from the decay of175Hf

Electron capture decay of¹⁷⁵Hf(70 d) provides a possibility for unambiguous determination of the sign and magnitude of multipole mixing ratios for 89 keV and 114 keV transitions in¹⁷⁵Lu. This is because both gamma rays are in coincidence with the 230 keV transition which is of a pureE2 character. The results of theγ —γ directional correlation measurements, in terms ofE2/M1 mixing ratiosδ, areδ ₈₉ = 0.11±0.07 andδ ₁₁₄ = 0.465±0.005. In addition the directional correlation measurements of the 89γ- 343γ and 319γ-114γ cascades yieldδ ₃₄₃ = 0.08±0.07 andδ ₃₁₉ = ?0.152±0.015.Radioactivity ¹⁷⁵Hf from¹⁷⁴Hf(n, γ); measuredγ —γ(θ) deducedδ(E2/M1); Ge(Li) detectors.