K-electron capture probabilities in the decays of Gd151 and Dy159

TheK-electron capture probability,P _K, in the allowed and non-unique first-forbidden transitions is measured by observing coincidences betweenK x rays and γ rays. The following results are obtained. In Gd¹⁵¹ decayP _K to the 349.8 keV level is 0.713 ± 0.015 andP _K to the 307.4 keV level is 0.813 ± 0.020. It is also deduced that the decay energyQ _EC is 491 _?9 ⁺¹⁴ keV and the spin of the 307.4 keV level is 7/2. In Dy¹⁵⁹ decayP _K to the 58.0 keV level is found to be 0.803 ± 0.032.     

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.     

Environmental effects on the electron capture decay rate

The change of the lifetime in electron capture of ⁸⁹Zr in different chemical environments is discussed.     

The ratio of K-capture to positon emission in the decay of P

The ratio of K-capture to positon emission in the 2.5 min decay of ³⁰P has been measured by a proportional counter-flow technique. The experimental value of the K/β⁺ was found to be (1.24 ± 0.04) × 10⁻³ in agreement with the conventional theoretical ratio i.e. apparently supporting the view that exchange and overlap effects are small.     

K-capture probability in the decay of139Ce(137.5d)

The K-capture probability (P _K) in the decay of¹³⁹Ce (137.5d) has been determined from the analysis of the K x-ray gamma ray sum-peak observed with a Ge (Li) x-ray detector. Furthermore,P _K is estimated independently from the measurement of the K x-ray intensity in the decay, using the known conversion coefficients of the 165.8 keV transition. Using the weighted average ofP _K measured as above, the mass difference between¹³⁹Ce and¹³⁹La is found to be 273 _?13 ⁺²¹ keV.     

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.     

The electron capture decay of 106mAg

The electron capture decay of 8.4d ^106mAg has been investigated by means of a 4π internal source scintillation spectrometer and a Ge(Li) detector. The L/K capture ratios to the 2952 and 2757 keV excited states of ¹⁰⁶Pd have been measured: (L/K)₂₉₅₂ = 0.203 ± 0.003 and (L/K)₂₇₅₇ = 0.1457 ± 0.0010. The value of Q = 3053 ± 3 keV has been deduced from these L/K ratios.     

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.     

Orbital electron capture decay of hydrogen- and helium-like Pm ions

The β⁺${\beta }^{+}$ and orbital electron-capture decays of stored hydrogen- and helium-like ¹⁴²Pm ions have been measured. So far, such measurements have been performed with only one nucleus, namely ¹⁴⁰Pr. The electron-capture decay constant of hydrogen-like ¹⁴²Pm⁶⁰⁺ ions is about 50% larger than that of helium-like ¹⁴²Pm⁵⁹⁺ ions, which is in excellent agreement with the previous measurements in ¹⁴⁰Pr ions and with new theoretical predictions.     

The electron capture decay of 85gsr

In order to resolve the controversy concerning the existence of an 868 keV γ-transition in the decay of 65d ^85sSr and to determine the electron capture decay energy, radiochemically separated sources, Ge(Li), Ge(Li)-NaI(Tl), and NaI(Tl)-NaI(Tl) spectrometers have been used for singles and (X-ray-γ and γ-γ coincidence measurements. A γ-ray at 868.5±0.5 keV decaying with a 65±5 d half-life was conclusively identified in ^85gSr decay. From measurements of the ratio $\text{P}{}_{\mathrm{\kappa (868.5)}}\text{P}{}_{\mathrm{\kappa (514)}}$ of K-capture probabilities by (KX-ray-γ coincidences, a value of Q_EC was determined for the EC decay feeding the 868.5 keV transition. Thus, a level in ⁸⁵Rb is established at 868.5 keV, and an upper limit of 0.45 μsec is set on its lifetime.     

Comments on the use of exchange and overlap corrections to electron capture probabilities

This paper discusses whether it is advisable to use exchange and overlap corrections in calculations of the relation between the relative changes in the electron-capture probabilities δλ/λ and in the electron density at the nucleus δϱ/ϱ. It is clearly shown that such corrections are not needed for δλ/gl measurements obtained from total electron capture decay rates.     

The electron capture decay of 131Ba

The decay of ¹³¹Ba has been investigated by means of a 4π internal source scintillation spectrometer and a Ge(Li) detector. The L/K. and M/L electron capture ratios of the allowed transitions to the 373, 620 and 1048 keV levels in ¹³¹Cs have been measured. From these electron capture ratios, the ifQ_EC value and the exchange and overlap corrections X^L/K and X^M/L have been derived.     

The electron capture decay of 195Au

The decay of ¹⁹⁵Au has been investigated by means of a 4π internal source scintillation spectrometer and a Ge(Li) detector. Electron capture branching ratios and several L/K and M+…/L capture ratios have been measured. The atomic electron capture transition energy and the cross-over decay probability of the 130 keV state have been calculated.     

Internal bremsstrahlung in the electron capture decay of 145Sm

Internal bremsstrahlung (IB) emitted in the non-unique first-forbidden electron capture decay of the $\text{7}\text{2}{}^{\mathrm{?}}$ ground state of ¹⁴⁵Sm to the $\text{7}\text{2}{}^{\mathrm{+}}\text{61}\text{keV}$ first excited level of ¹⁴⁵Pm has been studied. The total IB spectrum and the IB spectrum for captures proceeding via the 1s shell were measured for photons in the energy range of 100–580 keV and the spectra were normalized to the non-radiative capture rate. The experimental data agree with theoretical predictions.     

Study of159Yb decay

Theβ ⁺-decay of 1.4 min¹⁵⁹Yb was studied at the YAS-NAPP-2 facility installed on the proton beam of the JINR Dubna phasotron. The singles γ-ray spectra and prompt and delayedγ-γ coincidences were measured on the multidetector system. The decay scheme of¹⁵⁹Yb was proposed on the basis of theγ-γ coincidence data. The low lying states of¹⁵⁹Tm were preliminary identified within the framework of the rotational model.     

The determination by an independent method ofP k electron capture probabilities in133Ba and139Ce decays gamma decay of133Ba

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 quantityP _k ω _k ? _k for various transitions in the decay of¹³³Ba and¹³⁹Ce are obtained. The factor ω _k ? _k was measured independently by means ofK-conversion electron-K x-ray coincidences and was then used to determineP _k , theK-capture probability. The independent measurement of the product ω _k ? _k , together with recent accurate values of ω _k , provides a new method for the accurate calibration of semiconductor x-ray detectors. In the decay of¹³⁹Ce, a value ofP _k =0.78±0.03 is found (where the error represents twice the standard deviation) from whichQ _ec =326 _?30 ⁺⁷⁰ keV to the¹³⁹La ground-state is found by use of theory. In¹³³Ba decay, values are found ofP _k 1=0.72±0.04 for theEC transition to the 437 keV level in¹³³Cs,P _k 2=0.80±0.07 to the 384 keV level, and from an independent measurement, the ratioP _k 1/P _k 2=0.87±0.07. From these results the ground-state value ofQ _ec =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.     

Levels in159Ho as populated from decay of159Er

The level scheme of the odd proton nucleus¹⁵⁹Ho has been investigated using Ge(Li) and Si(Li) detectors. Results ofγ-ray singles, conversion electron spectra and coincidence experiments are reported. Assignments are made for several energy levels.     

Influence of the exchange effect on the chemical changes of the internal electron capture probabilities

Calculations of the probabilities of electron capture by nuclei in atoms and ions have been performed. They show that the chemical changes of the capture probabilities for the internal electrons can be strongly affected by the changes of the exchange and overlap correction factors Bx to the partial capture probabilities. This effect is particularly strong when numbers of valence s electrons for an atom or ion differ in two chemical compounds under comparison.     

Beta decay of 157Dy

The decay of ¹⁵⁷Dy(T_1/2 = 8.14(4)h) is investigated. Spectra of γ-rays, internal conversion electrons and γ ? γ coincidences are measured. The 983.50 and 991.70 keV transitions show E0 admixtures. Our experimental results made it possible to extend substantially the decay scheme. From the coincidence relationships we established four new excited states of ¹⁵⁷Tb at 883.32, 895.06, 925.29, 970.38 keV and confirmed the 357.66 keV state. The levels at 1160.71 and 1318.62 keV are introduced from the energy balance. Tentative evidence is given for the existence of five new levels at 252.58, 327.65, 658.36, 793.52 and 922.69 keV. We assign Nilsson’s quantum characteristics to all introduced levels. The structure of the excited states of ¹⁵⁷Tb is discussed in terms of current nuclear models.