Nobutsugu Imanishi

Coulomb excitation of 45Sc, 75As, 127I and 133Cs

Abstract The Coulomb excitation of 45 Sc, 75 As, 127 I and 133 Cs has been studied using 11.5 MeV nitrogen ions as bombarding particles. From the thick target yields of de-excitation gamma rays, the B (E2)↑ values are obtained as 45 Sc: 378 keV, 0.0086±0.0017; 75 As: 280 and 199 keV, 0.051±0.012 and 0.015±0.003; 127 I: 203 and 59 keV, 0.072±0.014 and 0.054±0.011; 133 Cs: 160 and 81 keV, 0.13±0.03 and 0.022±0.004, respectively, in units of e 2 b 2 . The results for 127 I and 133 Cs are compared with theoretical predictions.

Independent isomer yields of Sb and Te isotopes in thermal-neutron fission of 233U, 235U and 239Pu

Independent isomer yields of 130Sb(5+, 8−), 132Sb(4+, 8−), 131Te(32+,112−) and 133Te (32+, 112−) in the thermal-neutron fission of 233U(52+), 235U(72−) and 239Pu(12+), and those of 128Sb(5+ , 8−) for 233U and 239Pu were measured by the conventional radiochemical method. The mean angular momentum −J z.xl;h of the primary fragments has been deduced from the isomer-yield ratios. The result may indicate that the value of −J tends to decrease as the number of neutrons in the Sb and Te isotopes approaches the neutron magic number, and is independent of the angular momentum of the fissioning nucleus.

Coriolis-coupling calculation of low-lying states in Ru, Pd and Cd isotopes

Abstract The theoretical potential energies and level spectra are reported for odd-mass Ru, Pd and Cd nuclei. The potential energy is calculated by taking into account the blocking effect. The level spectra are obtained by considering a collective and an intrinsic degree of freedom, where the motion of an unpaired quasiparticle in Nilssons deformed orbital is coupled by a Coriolis force with the rotational motion. For all the nuclei investigated here, the ground state spin-parity and the presence of many even-parity states and of the ccase11 2 − isomeric state are well reproduced by the model. The possible existence of shape isomeric states is suggested.

Ionization cross sections of C60 by fast electron impact

By means of a time-of-flight technique, we have measured cross sections for production of and ions from a gas-phase C60 target bombarded by 0.4-5.0 keV electrons. The results were in fairly good agreement with other data at overlapping energies below 1 keV. Semiclassical calculations of the single-ionization cross sections were also performed up to 10 keV using the Deutsch-Mark formula proposed for the molecule. A fairly good agreement between the experimental and theoretical cross sections was obtained both in magnitude and in energy dependence. It was found that the double and triple ionization cross sections both decrease monotonically and exhibit no hump structure, indicating that the inner-shell ionization does not play an important role in electron-impact multiple ionization of C60 .

Isomer-Yield Rations and Primary Angular Momenta of I, Xe and Cs Isotopes Produced in Thermal-Neutron Fission of 233U, 235U and 239Pu

The independent isomer-yields of 132 I(4 + , 8 - ), 134 I(4 + , 8 - ), 135 Xe(3/2 + , 11/2 - ) and 138 Cs(3 - , 6 - ) have been measured in the thermal-neutron induced fission of 233 U, 235 U and 239 Pu. From the isomer-yield ratios, the mean angular momenta of the primary fragements have been deduced on the basis of thc statistical analysis. Obtained results indicate that the primary angular momentum \({\langle}J{\rangle}\hbar\) is higher in odd- Z products than in even- Z ones, and increases up to a certain value at an approximate rate of \({-\varDelta}{\langle}J{\rangle}/\varDelta(\delta N){\sim}0.8\hbar\) with decreasing neutron displacements δ N , which is defined as the difference between the number of neutron N in the products and the most probable neutron number N p in the isotopic yield distribution.

Strong projectile dependence of C60 fragmentation by MeV-energy heavy ions

Experimental results are presented for ionization and fragmentation of C60 bombarded by various projectile ions of H+, Li1,2+, B1,2+, O2+, Si1,2+, Ag2+ and Au3+ with velocities 0.9v0-3v0 (v0: Bohr velocity). Mass distributions of light fragment ions Cn+ (n = 1-12) are found to change drastically depending on the projectile species or atomic number Zp. The result indicates that multifragmentation of C60 takes place at small impact parameters where the projectile nuclear charge is less screened. It is found that for heavy projectiles multiple ionization is apt to occur and lighter fragment ions are produced predominantly. Assuming the multifragmentation caused by penetration of the projectile through C60, energy deposition to C60 is calculated, and internal energy and ionization degree of C60 after collisions are estimated. It is concluded that the final fragment pattern is governed by the internal energy.

Cross sections for ionization and fragmentation of by fast impact

Absolute cross sections have been measured for the first time for -impact ionization and fragmentation of at proton energies ranging from 0.2 to 2.0 MeV. The cross sections were in fairly good agreement with other electron-impact data in the high-velocity region, indicating that the charge transfer is negligible in the present energy range. Theoretical cross sections for plasmon excitations were also calculated and compared with the experimental ionization cross sections. Agreement between them was within a factor of two, indicating that the plasmon excitation contributes to the total ionization by about 50%. A careful analysis of the energy dependence of the cross sections for and ions indicates that these ions are produced from the same initial excited states created in collisions with ions.

Dynamical diffraction effects in the transition radiation of a relativistic electron crossing a thin crystal

Abstract Transition radiation (TR) of a relativistic electron crossing the in surface of a crystal may be scattered by a system of atomic planes. This effect may change essentially the interference between TR waves emitted from in and out surfaces of a crystalline target. The influence of the mentioned effect on total emission properties is studied in this work within the frame of the dynamical diffraction approach.

Mass yields of 241Am thermal-neutron fission

Mass yields of sub-threshold fission induced by thermal neutrons were investigated, namely, mass yields of 23 mass chains were determined for 241Am thermal-neutron fission by the conventional radiochemical method and by the direct γ-ray spectrometry method. The peak-to-trough ratio in terms of 99Mo/117Cd was found to be as large as 800±200. Three fission systems of spontaneous fission, sub-threshold fission and above-threshold fission with the compound mass AF = 242 were compared and discussed. The average number of neutrons released per fission was evaluated to be 4·0±0·2 from the mass yield curve.

Resonance effects of transition radiation emitted from thin-foil stacks

Abstract Transmission of charged particles through a regular dielectric foil-stack intensifies transition radiation (TR) X rays owing to the intrafoil and the interfoil resonances. In order to study the effects of both resonances on energy spectra of TR, we measured the spectra for different sets of foil-stacks at several emission angles and compared them with the calculated ones. It was found that interfoil resonance modifies the energy of the peaks observed in the spectra depending on the emission angle but intrafoil resonance has little effect.