R. W. Fink

The determination by an independent method of P k electron capture probabilities in 133 Ba and 139 Ce decays gamma decay of 133 Ba

The electron capture decays of133Ba (10.4 y) and139Ce (140 d) were investigated with high resolution Ge(Li) detectors. By x-ray — γ-ray coincidences values of the quantityPkωkɛk for various transitions in the decay of133Ba and139Ce are obtained. The factor ωkɛk was measured independently by means ofK-conversion electron-K x-ray coincidences and was then used to determinePk, theK-capture probability. The independent measurement of the product ωkɛk, together with recent accurate values of ωk, provides a new method for the accurate calibration of semiconductor x-ray detectors. In the decay of139Ce, a value ofPk=0.78±0.03 is found (where the error represents twice the standard deviation) from whichQec=326−30+70 keV to the139La ground-state is found by use of theory. In133Ba decay, values are found ofPk1=0.72±0.04 for theEC transition to the 437 keV level in133Cs,Pk2=0.80±0.07 to the 384 keV level, and from an independent measurement, the ratioPk1/Pk2=0.87±0.07. From these results the ground-state value ofQec=522−10+20 keV is derived from theory for133Ba decay. The gamma spectrum of133Ba also was remeasured. From the present gamma intensities and previous conversion electron intensities, new values forK-shell conversion coefficients are obtained. Previously reported γ-rays at 35 and 391 keV are not confirmed.

Multipolarity determination fromL x-ray spectra in the decays of227Th,243Am, and249Cf

A new method to determine the multipolarity of a converted γ-transition from itsL x-ray spectrum has been extended by a coincidence technique and applied in the complex decays of227Th,243Am, and249Cf. TheL x-ray spectra of four low energy transitions have been measured in coincidence with cascading high energy γ-rays and theirM1-E2 mixing ratios obtained by comparison with calculatedL x-ray line intensities. The following results were obtained: for the 3/2+→l/2+ ground-state transition in223Ra, an admixture of (74±12)%E2, for the 7/2+→5/2+ ground-state transition in239Np, less than 30%E2, for the 9/2+→7/2+ ground-state transition in245Cm, (63±10)%E2, and for the 11/2−→ 9/2− transition in the third rotational band in245Cm, (32±10)%E2.

A γγ coincidence study of transitions in239Np and239Pu from decay of243Am

Gamma-gamma coincidences and singles measurements with Ge detectors have been made on transitions in239Np and239Pu. Eighteen transitions in239Pu and three in239Np have been verified by coincidence data. High resolution singles measurements were made and new values for the energy and intensities ofγ-rays below 350 keV were obtained.

L-subshell fluorescence and coster-kronig yields atZ=92 and the decay of235Np

TheK andL x-rays emitted in the decay of235Np have been studied with high resolution Ge(HP) and Si(Li) detectors in coincidence, in order to obtain theL2 andL3 subshell fluorescence and Coster-Kronig yields atZ=92. The results are:v2=0.630±0.036, ω2=0.560±0.033,f23=0.147±0.010, and ω3=0.481±0.029. Results for theL1 subshell were derived from singles spectra, by assuming a value off13 of 0.67, and are:v1=0.54±0.04, ω1=0.21±0.04, andf12<0.07. With the same assumption, theL1/K electron capture ratio and decay energyQec for235Np were found to be 29.0±3.6 and 123.6±0.7 keV, respectively. RelativeL x-ray intensities forZ=92 also were measured and are compared with the theory of Scofield and with recent diffraction experiments. Electron ejection from theL shell during235Np decay has been studied byL x-ray-L x-ray coincidences and found to occur with a probability of (1.3±1.0) × 10−4 per disintegration.

Gamma branching and total conversion coefficients of intraband transitions in the groundstate rotational band of245Cm

With calibrated Ge(Li) detectors, γ-γ coincidences have been observed in the decay of249Cf. The total conversion coefficient of the 54.7 and 66.7 keV transitions in the first rotational band have been determined to be 237±30 and 69±15, respectively. The branching ratio of the 121.5keV crossover transition is (22±7)%. The errors are the 2σ statistical uncertainties, linearily added to the errors in the detector efficiencies.

X-ray intensity ratio ILαILℓ in the region 55 ⩽ Z ⩽ 94

Abstract The X-ray intensity ratio I L α I L l has been measured, using radioactive sources and high resolution Si(Li) X-ray detectors over a range of 55 ⩽ Z ⩽ 94. The theoretical ratios are found to be underestimated at low Z in the calculations of Scofield and of Rosner and Bhalla.

Mean L-shell x-ray fluorescence yields at Z =47, 60, and 63

AbstractMeanL-shell x-ray fluorescence yields

TheK-shell conversion coefficient of the 135.5 keVM4 transition in193mPt decay

(\bar \omega _L )