Improved characteristics of the 22.5 keV (M1 + E2) nuclear transition in

The gamma ray and conversion electron spectra of the 22.5keV M1 + E2 nuclear transition depopulating the first excited level 5/2− in 149Sm were investigated in detail. A substantially improved value of 22500.2 ± 0.8 eV for the transition energy was determined that opens a possibility to establish an electron energy standard for the keV region based on the conversion electron lines of this transition. The E2 admixture parameter |δ(E2/M1)| = 0.0784 ± 0.0009 and the nuclear structure parameter λ = − 2 ± 10 were derived. The |δ(E2/M1)| and λ parameters were also obtained for all available experimental data and their mutual combination

Alpha decay sup 2 sup 2 sup 5 Ac-> sup 2 sup 2 sup 1 Fr

In-depth investigation of (alpha-gamma)-coincidences at the sup 2 sup 2 sup 5 Ac decay is carried out. Twenty-one new weak gamma-rays are found; 18 gamma-rays earlier ascribed to the sup 2 sup 2 sup 5 Ac decay are not confirmed. The quantitative analysis of the (alpha-gamma)-coincidences makes it possible to find the intensity of population of sup 2 sup 2 sup 1 Fr levels by the alpha decay and multipolarities of five weak gamma-transitions. The conversion electron spectrum is investigated in the range of 5-24 keV with a high (some 20 eV) energy resolution. A new M1 type 10.6-keV gamma-transition is found. The proposed sup 2 sup 2 sup 5 Ac decay scheme includes 31 excited sup 2 sup 2 sup 1 Fr states. Parities are established for 16 of them. Possible spin values are proposed for sup 2 sup 2 sup 1 Fr levels. Properties of excited sup 2 sup 2 sup 1 Fr states are satisfactorily described by the quasiparticle-phonon nuclear model without the assumption of static octupole deformatio

Beta-neutrino angular correlation in the decay of Ne-18

The presence of a scalar interaction in nuclear beta-decay was studied by measuring the beta-neutrino correlation coefficient alpha in the superallowed pure Fermi beta-transition Ne-18(O+) --> F-18(O+, 1040 keV) (T-1/2 = 1.67 s). The resulting value, i.e. alpha = + 1.06 +/- 0.19 (error quoted at 2 sigma), corresponds to the limit root/C-s/(2) + C-s'(2) less than or equal to 0.29C-v (95%) CL for the scalar coupling constant. (C) 1997 Elsevier Science B.V