Yu. P. Gangrskii

Resonance conversion of gamma radiation in the radiative transitions between neutron resonances

The influence of the resonance conversion on the α-particle spectra in the reaction (n, α) in low-energy transitions between neutron resonances is discussed. Unusual α spectra from neutron resonances in the reaction 147Sm(n, α)144Nd are considered as an example of such influence. The calculation of resonance conversion coefficients was performed for the transitions from K shell in the free levels of P shell of Sm atom. The large effect of resonance in the radiative transitions for the nuclei and atomic electron shells is observed.

Transport of Fission Fragments by a Gas Flow with Aerosols

An experimental setup for transporting fission fragments by a gas flow with aerosols is described. The results of tests of the setup on fragments of 238U photofission by bremsstrahlung from a microtron are presented. The parameters of the setup obtained experimentally (the transport efficiency reaches 70%, and the transport time reaches 0.1 s to a distance of 1 m) make it possible to successfully use it in experiments on the fission of heavy nuclei and study of properties of fission fragments

Production of heavy atomic clusters upon interaction of laser radiation with matter

The results of an investigation of the formation of Pb, Th, and U clusters over a broad range of numbers of atoms (from a few atoms to macroparticles) upon interaction of high-power pulsed laser radiation with matter are presented. Clusters of fissionable elements are studied for the first time. A setup for determining the yield of clusters and the number of atoms in them, which is based on the use of several different methods (laser resonance fluorescence, time-of-flight measurements, and counting the number of tracks of fission fragments from the cluster nuclei), is described. The dependence of the yield of clusters with various numbers of atoms on the conditions for their formation is discussed.

Yield of fission fragments from the photofission of actinide nuclei

Yields of the 101Mo, 135I, and 135mCs isotopes from the photofission of the actinide nuclei 232Th 238U, and 237Np are measured. These fission fragments have specific nuclear structure features or are of practical use. The measurements are performed in the bremsstrahlung from the microtron of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (JINR) at an electron energy of 22 MeV. The yields of the fragments are measured by the activation method using a γ radiation HPGe detector.

A technique for measuring the quadrupole deformation parameter of transuranium nuclei

A method for determining the quadrupole deformation parameter of transuranium nuclei is presented. This method is based on giant dipole resonance splitting in the photofission cross section. The experimental setup containing an avalanche counter of fission fragments, as well as a method for reconstructing the cross section from the measured dependence of the photofission reaction yield on the endpoint energy of the bremsstrahlung spectrum, are described. The setup was tested on the bremsstrahlung beam of the MT-25 microtron at the Flerov Laboratory for Nuclear Reactions of the Joint Institute for Nuclear Research. The test results—in particular, the measured excitation function of the uranium photofission reaction—are presented.

Rare Decay Modes of Fission Fragments

The experimental data on rare modes of radioactive decay of fission fragments is reviewed. These decay modes are due to a large excess of neutrons and a high energy of β decay fragments. They appear in delayed emission of various particles after the β decay (several neutrons, α particles, or heavy clusters) and excitation of unusual states (giant multipole resonances and shape isomers). The β decay and internal conversion of γ radiation into bound states of the atomic electron shell and their influence on the probability of secondary particle emission are considered. The possibility is discussed of observing decays that have not yet been experimentally detected, but theoretically predicted, as well as information on the nuclear structure obtained by studying such decay modes.

Resonance internal conversion in hydrogen-like ions

The resonance internal conversion effect in hydrogen-like ions is considered. For the M1 transition with an energy of 70.6 keV in 171Yb, the lifetime of this nucleus in the excited state decreases by five orders of magnitude as a result of deexcitation via a new channel—the resonance conversion—provided that the nuclear transition energy is equal to the energy of transition of a single 1s electron to a higher ns state. Observation of the resonance conversion in hydrogen-like ions is a powerful method for investigating their nuclear structure.