Energy levels of A = 21−44 nuclei (V)

The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases.

Orbital electron capture by the nucleus

Electric monopole transitions between 0+ states for nuclei throughout the periodic table

Quasi-ground, quasi-beta, and quasi-gamma bands

Measurements of E2/M1 and E0/E2 multipole mixing ratios of transitions in even-even nuclei have long provided important tests of nuclear models. The experimental data for transitions in even-even nuclei have been critically surveyed to provide the most accurate results for comparisons with theoretical calculations. The theoretical approaches to the calculations of these mixing ratios on the bases of different nuclear models are considered and compared with experimental data. The variations in signs and magnitudes of the E2/M1 mixing ratios from nucleus to nucleus for the same class transitions and within a given nucleus for transitions from different spin states suggest that a microscopic approach is needed to explain the data theoretically. The pairing-plus quadrupole model has achieved the first successes in predicting these variations, primarily in the osmium to platinum region.

E0-E2-M1 multipole admixtures of transitions in even-even nuclei

Excited states of 156Gd studied by the conversion electron spectra of 5.4 d 156Tb

The decay of 2.2 h 138Pr and excited states in 138Ce

The gamma-ray spectrum and the conversion-electron spectrum are measured in the decay of the Tb 152 activity. The L -subshell electron lines of the 586.7 keV 2 2 + →2 1 + transition are separated by the ion-free beta-ray spectrometer. The M1-E2 mixing ratio, δ 2 , and the dimensionless ratio X of E0-E2 mixing of the 586.7 keV transition are obtained to be δ 2 ≦0.16 and 0.034≦ X ≦0.038, respectively. The E2 branching ratio B (E2; 2 2 + →0 g + ): B (E2; 2 2 + →2 1 + ): B (E2; 2 2 + →0 1 + ) is determined to be 0.023 : 1.0 : 5.6.

Manabu Fujioka

Papers

Excited states of 156Gd studied by the conversion electron spectra of 5.4 d 156Tb

The decay of 2.2 h 138Pr and excited states in 138Ce

Deexcitation of the 931.1 keV 2 2 + -State of Cd 152

Level structure of 206Pb studied from the decay of 206Bi

The half-life of the 2211 keV state in 136Ba