[en] A review of α-decay experiments is given with emphasis being put on nuclear structure studies performed by means of online mass separators or recoil spectrometers. (orig.)

[en] A review of alpha-decay experiments is given with emphasis being put on nuclear structure studies performed by means of online mass separators or recoil spectrometers. (author)

[en] Alpha-decay data from doubly-even nuclei throughout the periodic table are reviewed and evaluated. From these data, nuclear radius parameters are calculated by using the Preston formula for α-decay probabilities. The radius parameters for each element behave rather regularly as a function of neutron number. They show minima at the major closed shells, increase sharply for parents just above the closed shells, and decrease smoothly toward the next shell closure. The same trend is observed for α reduced widths calculated using the Rasmussen formalism. Any irregularity or large departure from this behavior indicates probable incorrect input data. This systematic behavior can also be utilized to estimate partial half-lives. (author)

[en] An empirical finding that the life-time of a natural even-even emitter against α-decay and possible Be-activity is the same has no explantion in the barrier-penetrability concept of Gamow theory. An explanation is provided by the theory of α-decay due to Basu. (author)

[en] The excited levels in 233^Pa following the 237^Np alpha decay have been studied, by performing different experiences to complete available data and supply new information. Thus, two direct alpha spectrum measurement, one alpha-gamma bidimensional coincidence experiment, three gamma-gamma and gamma-X ray coincidences and some other measurements of the gamma spectrum, direct and coincident with alpha-particles have been made. These last experiences have allowed to obviate usual radiochemical separation methods, the 233^Pa radioactive descendent interferences being eliminated by means of the coincidence technic. As a result, a primary decay scheme has been elaborated, including 15 new gamma transitions and two new levels, not observed in the most recent works. (Author) 60 refs

[en] α-activity of even-Z odd-N g.s. α-emitters like even-even ones is also found to be a case of spontaneous fission on the basis of Bohr-Wheeler theory. But contrary to true import of fissility parameter Z₂/A, some features like higher Z₂/A corresponding to higher Tsub(1/2) for N < 126 and lower Z₂/A corresponding to lower Tsub(1/2) for N > 126 for both Po and Em series are observed. These anomalous features, however, are well explained by α-decay without tunneling (ADWT) parameter Esub(coul(max))/Esub(core) obviously because this parameter contains right proportion of coulomb repulsive energy Esub(coul(max)) and attractive core-interaction Esub(core) operative specifically in α-decay mode of each nucleus as reported elsewhere. Calculated α-preformation probability 'Psub(α)' is usually approximately 10^-₂ -10^-₃, one and, at times, two order of magnitude smaller than that for even-even cases, expectedly in view of participation of the unpaired odd neutron in the assembly of last four nucleons into an α-cluster. Calculated α-decay radius R=Ro(1+Psub(α)), daughter radius and daughter radius constant lie roughly in the regions 8.2-10.5 fm, 6.2-8.5 fm and 1.05-1.35 fm, respectively. (author)

[en] Neutron-deficient α-decaying nuclei have been produced using fusion-evaporation reactions. A gas-filled recoil separator was used to separate the fusion products from the scattered beam. The activities were implanted in a position sensitive silicon detector. The isotopes were identified using spatial and time correlations between implants and decays. During ten years of operation time about twenty new α-decaying isotopes have been identified in the translead region. In addition numerous α-decay studies have been performed on already known isotopes yielding much improved precision for the measured decay properties. An overview of the α-decay studies performed for the translead nuclei employing the gas-filled recoil separator will be given. (orig.)

[en] A model of the α-decay is constructed under assumptions that the α-particle is generated only near the surface region of the nucleus. The α-particle is supposed to move in the potential well of the form: V(r)=V₁ if c-t(<=) r (<=)c and V(r)=V₂ if c(<=)r(<=)c+t; VsubB=(2(z-2)/c+t) e². The parameters c and t are linked with the parameters of the distribution density of the daughter nucleus and the α-particle. The experimental data for the energies Esub(α) and the half-lives for a number of isotops of U₉₂ and Th₉₀ permit one to calculate the radii of the daughter nuclei in the framework of this model. For the equivalent radius the dependence rsubo(A-4)sup(1/3) is found with parameter r₀=1,17+1,22f. This dependence is well correlated with the electron-nucleus scattering experiments. (S.P.)

[en] A revised compilation of experimental values of α-particle energies and intensities is presented. It includes all α-emitters for which the stated uncertainty of energy measurements is not larger than 5 keV. All α-lines with at least 5% of the total α-intensity are registered. The energy values have been adjusted with recent absolute determinations of standard energies. The weighted means form a consistent set of recommended energy values

[en] Published in summary form only