R.W. Fink

L2,3 subshell X-ray fluorescence yields and Coster-Kronig transition probabilities of Nd and Yb

X-ray spectra emitted in the radioactive decay of 17.7y 145Pm and 1.9y 171Tm were studied using a three-parameter technique for XX · t coincidence measurements. The following L2 and L3 subshell X-ray fluorescence yields, ω2, ω3, Coster-Kronig transition probabilities, f23, and radiative decay branching ratios, s2, s3, were determined for Nd (Z = 60) and Yb (Z = 70); At Z = 60, ω3 = 0.108 ± 0.010, ω2 = 0.128 ± 0.018, f23 = 0.123 ± 0.013, s3 = 0.178 ± 0.006, and s2 = 0.205 ± 0.010. At Z = 70, ω3 = 0.227 ± 0.022, ω2 = 0.217 ± 0.030, f23 = 0.141 ± 0.007, s3 = 0.175 ± 0.003, and s2 = 0.197 ± 0.004. These results are compared with available theoretical calculations.

X-Ray Fluorescence Yields and Coster-Kronig Transition Probabilities of the L1, L2 and L3 Subshells of Pb

A three-parameter technique for XX · t and Xe · t coincidence measurements was employed to acquire coincident energy spectra, singles spectra from two semiconductor detectors, and a TAC spectrum simultaneously. From analysis of the singles spectra in each detectror, the total coincidence spectra in each detector, and gated coincidence spectra in each detector, the L1, L2, and L3 subshell X-ray branching ratios (sj) and fluorescence yields (ωi), together with the Coster-Kronig transition probabilities (fij) were determined at Z = 82 from the radioactive decay of 33.4 y207 Bi. The L3 subshell values are: s3 = 0.241 ± 0.024 and ω3 = 0.302 ± 0.021; for the L2 subshell, s2 = 0.235 ± 0.024, ω2 = 0.366 ± 0.026, and f23 = 0.130 ± 0.002. Using these values of ω2 ω3, and f23 as input, the L1 subshell quantities were then determined by a direct measurement of the number of characteristic L1 subshell X-rays per initial vacancy from L X-ray spectra gated by L conversion electrons. This gives s1 = 0.346 ± 0.084, ω1 = 0.104 ± 0.019, f12 = 0.105 ± 0.026, and f13 = 0.658 ± 0.086. Uncertainties are all to 95% confidence. The experimental L-subshell values are compared with theoretical calculations reported in the literature. The f12 value confirms the predicted decrease above Z = 74 due to the absence of some of the L1-L2N Coster-Kronig transitions. The value of ω3 is smaller than the theoretical estimates, while s3 is in good agreement. The value of ω2 also is lower than theory predicts, but s2 agrees well. The measured value of f23 is somewhat larger than theory predicts, but agrees better with the more recent relativistic calculations than with older non-relativistic ones. The values of f12 and f13 are in better agreement with the relativistic calculations than with the older non-relativistic theory.

Decay of mass-separated 3.0 min 195gBi to levels in 195Pb and shape coexistence in the neutron-deficient odd-mass Pb isotopes

Abstract The radioactive decay of mass-separated 3.0 m 195g Bi to 195 Pb has been studied with the UNISOR and LISOL facilities. Time-sequenced spectra of γ-rays, X-rays, and conversion electrons have been obtained, together with γγt, γXt, eγt, and eXt coincidence data. From this information, a decay scheme has been constructed consisting of 23 excited states and 34 transitions in 195 Pb. Transitions with E0 multipole admixtures, indicative of shape coexistence, have been found to de-excite positive-parity levels at 1093, 1329, and 1380 keV. The beta-decay energy of the 195 Bi ground state is deduced to be Q EC = 4800 −550 +600 keV based on the measurement of γ-ray-gated K / β + ratios. The excitation energy of the i 13 2 isomer in 195 Pb has been determined to be 203±4 keV from the α-decays of 199m,g Po.

Half-life of the h92 shell-model intruder-state isomer 187mAu

The half-life of the 92− shell-model intruder-state isomer in 187Au has been measured by employing a technique in which each incoming event is tagged with a digital representation of time by means of a real-time clock. With this method we obtain a 2.3 ± 0.1 sec half-life for the h92 → d32 E3 isomeric transition resulting in a retardation of 50 relative to the Weisskopf single-particle estimate.

Decay of mass-separated 201mPo and 201gPo

Abstract The decays of 201Po (9.0 min) and 201gPo (15.3 min) have been studied with mass-separated sources from the UNISOR facility. Time-sequenced spectra of γ-rays, X-rays, and conversion electrons, as well as γγt and Xγt (coincidences were obtained. A decay scheme has been constructed incorporating 93% of the decay intensity assigned to 201Bi. Levels resulting from h 9 2 , f 7 2 and i 13 2 particle states have been observed.

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

Abstract The L 1 subshell orbital electron capture probability P L1 in the decay of 33.4 y 207 Bi to the 2339.89 keV level in 207 Pb is measured to be 0.518 ± 0.081 (95% confidence) by a new method in which L 1 subshell characteristic X-rays in the L γ X-ray peak are observed in an X γt coincidence mode with 1770.23 keV γ-rays. The value of P L2 is 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.

Decay of mass-separated 7.4 min 203At

Abstract The radioactive decay of 7.4 min 203 At to 203 Po has been studied with mass separated sources from the UNISOR facility. Time-sequenced spectra of γ-rays. X-rays, and conversion electrons were obtained, together with γγt, γXt, e − γt, and e − Xt coincidence data. A decay scheme has been constructed that incorporates approximately 90% of the decay intensity assigned to 203 At. All excited states below 1 MeV have been assigned unique spin-parity values, and the observed level scheme can be qualitatively understood in terms of a particle-core weak coupling description. The ground-state decay energy has been deduced to be Q EC = 5.06 ± 0.20 MeV from γ-ray-gated EC/β + ratios.

Non-yrast level structure of35Nd via beta decay of135Pm

The isotope135Nd has been studied through the β-decay of mass-separated135pm. He-jet transported samples without mass-separation were also studied. The parent135Pm has isomers with β-decay half-lives of 40±3 s and 49±3 s. The low-lying non-yrast structure of135Nd is shown to consist of a group of levels which decay to a 65.1-keV isomeric level which is not reached in the yrast cascades.

Energy levels and structure of light rare‐earth nuclei 136,138,140Sm and 132,134,136Nd, via beta decay

Levels in 136,138,140Sm were populated by the beta decay of Eu, following (HI,pxn) reactions and on‐line mass separation, Members of the γ band were observed in all three daughter nuclei. Spectroscopic calculations were made using the triaxial rotor model, with all parameters derived microscopically from Woods–Saxon deformed shell model. Comparison with the data supports the characterization of these nuclei in terms of a triaxial intrinsic shape. Improved decay schemes for 132,134,136Nd are given.