[en] An experimental search has been conducted for α-decay in the lifetime range of from 1 to 100 nsec in a variety of rare earth nuclei produced in reactions of 125 to 146 MeV ¹⁶O ions on targets of ¹³⁹La, ¹⁴¹Pr, and ¹⁴²Nd. The products of these reactions include systems in which high spin (I > 10 h-bar) isomeric states have been observed with lifetimes in the range studied. Certain of these isomers may be very high spin statistical yrast traps which have been predicted to occur at spins of from 30 to 50 h-bar in the rare earths. For such spins and lifetimes, calculations suggest that α-decay could be a major mode of de-excitation. The technique employed for these experimental investigations made use of a specially designed trajectory detector to observe α-decay directly from the reaction products which recoiled from a thin target. Analytical procedures developed for reduction of the decay-in-flight data are discussed which yielded information about the particle types detected, the energies of these particles, the trajectories followed, and the positions of parent nuclei at the time the detected particles were emitted. Kinematic and solid angle corrections are considered which permitted correction for Doppler broadening effects and allowed estimates to be made with regard to the lifetime and production cross section of the parent state. The experimental method and the associated analytical procedures were verified by study of α-decay following the reaction ²⁰⁸Pb(¹⁶O,p6n)²¹⁷Ac. No system studied in the search for yrast trap α-decay showed activity significantly above background in the 6 to 16 MeV energy range

[en] An experimental search has been conducted for α-decay in the lifetime range of from 1 to 100 nsec in a variety of rare earth nuclei produced in reactions of 125 to 146 MeV ¹⁶O ions on targets of ¹³⁹Pr, and ¹⁴²Nd. The products of these reactions include systems in which high spin (I > 10 h) isomeric states have been observed with lifetimes in the range studied. Certain of these isomers may be very high spin statistical yrast traps which have been predicted to occur at spins of from 30 to 50 h in the rare earths. For such spins and lifetimes, calculations suggest that α-decay could be a major mode of de-excitation. The technique employed for these experimental investigations made use of a specially designed trajectory detector to observe α-decay directly from the reaction products which recoiled from a thin target. Studies have been performed to optimize this decay-in-flight method for the observation of charged particle decay of short lived systems having small production cross sections. The results of these studies are reported. The experimental method and the associated analytical procedures were verified by study of α-decay following the reaction ²⁰⁸Pb(¹⁶O,p6n)²¹⁷Ac. The results obtained were in agreement with those reported by others. No system studied in the search for yrast trap α-decay showed activity significantly above background in the 6 to 16 MeV energy range. Alpha-decay cross sections limits were placed for 14 of the predicted reaction products in which high spin isomers are known with lifetimes in the range studied. These upper limits ranged from approx. 3 to 200 μb. Comparison to theoretical total cross sections allowed α-branching ratio estimates to be made

[en] γ--γ coincidence spectra were obtained for approximately 30 transitions in ²⁰⁰Bi from electron-capture decay of ²⁰⁰Po. A preliminary decay scheme is presented. The half-life of the ²⁰⁰Bi ground state is estimated to be 35 min. 1 figure

[en] Angular distribution data for the mutual excitation of the ¹²⁶Te and ²²Ne 2⁺ states have been measured for the inelastic scattering of 93.5 MeV ²²Ne on ¹²⁶Te. Data for transitions to the ground states, the ¹²⁶Te 2⁺ state and the ²²Ne 2⁺ state were also obtained. A coupled-channels analysis of the reaction is found to provide a good description of the general features of the data. (Auth.)

[en] Using a decay-in-flight technique, a search for 1--100 nsec α decay has been conducted in a variety of rare earth nuclei made in energetic heavy ion reaction. Assuming spherical rigid rotation and α particle formation factors similar to those of the ground state, this lifetime range corresponds to nuclear spins of 30 --50 h-bar where very high spin isomerism has been predicted theoretically. No evidence for α decay was observed. α decay cross section limits are set for 14 systems in which high spin isomers (I>10 h-bar) are known with lifetimes in the range studied. Comparison to theoretical total cross sections allows α-branching ratio estimates to be made

[en] Elastic and inelastic cross section data for exciting the ²²Ne 2₁⁺ (1.27 MeV) state by 132 MeV ²²Ne scattering from a ²⁰⁸Pb target are presented. The data are analyzed by a rotational model coupled-channels calculation including the 0⁺ ground state and the 2₁⁺, and 4₁⁺ states of ²²Ne. We extract β₂ and β₄ deformation parameters, as well as M(E2;0⁺-2₁⁺), M(E2;2₁⁺-2₁⁺), M(E4;0⁺-4₁⁺), and M(E2;2₁⁺- 4₁⁺) matrix elements for ²²Ne and compare these quantities to those obtained for ²⁰Ne. The extracted 2₁⁺ reorientation matrix element is considerably larger than shell-model predictions. Addition of a negative spin-orbit potential improves the fit to the 2₁⁺ differential cross section

[en] A trajectory detector especially suited to the measurement of charged particle decay energies and half lives by a decay in flight technique is described. With recoil velocities presently available at heavy-ion accelerators, the apparatus provides a low background method for in-beam investigation of α-decay in the 1-100 ns half life range. The method is demonstrated for the α-decay of ²¹⁷Ac made in the reaction ²⁰⁸Pb(¹⁴N,5n)²¹⁷Ac. (orig.)

[en] We report the experimental evidence for Coulomb-nuclear interference in the excitation of high-spin states by very heavy projectiles. The data are intepreted with use of a model described previously, and the feasibility of using this method to study the deformed nuclear surface is demonstrated

[en] Theoretical and experimental methods for studying heavy-ion inelastic scattering from deformed nuclei are described. The theoretical methods involve classical-limit approximations, while particle-γ-spectroscopy techniques are employed experimentally. With these approaches, heavy-ion excitation in the Coulomb-nuclear interference region acquires a transparent interpretation, despite the apparent complexity of the multistep excitation processes involved. The examples discussed provide a good illustration of the relationship between classical and quantum physics. The sensitivity of the inelastic scattering to details of the surface ion-ion potential due to radial and angular localization is exploited to provide a method of determining the equipotential contours in a direct manner which bypasses particular model-dependent parametrizations. The method is used to construct ion-ion potentials from inelastic scattering data for the systems ⁴⁰Ar+¹⁶⁰Gd, ¹⁵⁶Gd, ¹⁶²Dy, ¹⁶⁴Dy, and ¹⁸⁰Hf. The contribution of adiabatic giant resonance polarization to this potential is discussed. The relation between the deformed ion-ion potential and nuclear shapes is illustrated by comparing the experimental potentials to deformed double-folding and deformed proximity-potential calculations. (orig.)