Photodisintegration of Hg isotopes

Yields of photonuclear reactions of several Hg isotopes are measured on a bremsstrahlung photon beam with a maximal energy of 19.5 MeV using a gamma-activation analysis. Cross sections of photonuclear reactions on stable Hg isotopes are calculated within bonds of the collective model taking isospin splitting of giant dipole resonance into account. The experimental results are compared with the results of theoretical calculations and earlier experimental studies.     

Photonuclear reactions on mercury isotopes in the region of the giant-dipole-resonance energy

The induced-activity method is used to measure yields of photonuclear reactions induced in stable mercury isotopes by beams of bremsstrahlung photons whose spectra have the endpoint energies of 19.5 and 29.1 MeV. On the basis of a collective model, the partial cross sections and yields are calculated for photoproton and photoneutron reactions on these isotopes. The yields calculated theoretically are compared with their measured counterparts. The possibility for the production in photonuclear reactions of the bypassed nucleus ¹⁹⁶Hg, which cannot be formed in astrophysical r and s processes, is analyzed.     

Cross sections of multiparticle photonuclear reactions with <Superscript>203, 205</Superscript>Tl isotopes

An experiment on the irradiation of the natural mixture of ^203,205Tl isotopes by the bremsstrahlung beam of pulsed racetrack microtron RTM-70 (Skobeltsyn Institute of Nuclear Physics, Moscow State University) at an electron energy of 67.7 MeV was performed. The yields and integral cross sections of multiparticle photonuclear reactions with ^203,205Tl isotopes were measured.     

Yields of photonuclear reactions on Hg isotopes under a bremsstrahlung beam with a maximum energy of 29.1 MeV

Yields of photonuclear reactions on stable Hg isotopes under a bremsstrahlung photon beam with a maximum energy of 29.1 MeV were measured using the induced activity method. Single-neutron and single-proton reactions and the ¹⁹⁸Hg(γ,1p1n) reaction were observed. Photoneutron reaction yields with the production of metastable states were measured.     

Electromagnetic processes in silver isotopes

Peculiarities of electromagnetic interactions in silver isotopes are considered. Excited states of Ag isotopes are studied as a function of the mass number A = 95–117. Low-lying excited states reveal clear features that are specific for rotational spectra for the energies E < 4–5 MeV. In the energy domain above the nucleon separation threshold of 5–10 MeV, single-particle excited states overlap and produce a continuous spectrum. For energies E = 10–35 MeV, excitation of giant dipole resonance plays the most important role in Ag isotopes. Experimental data on the cross sections of photonuclear reactions in Ag isotopes are analyzed.     

Photonuclear reactions on the cadmium isotopes <Superscript>106,108</Superscript>Cd at the bremsstrahlung endpoint energy of 55.5 MeV

The gamma-activation technique was used to measure the absolute yields of photonuclear reactions on the cadmium isotopes ^106,108Cd. The results obtained in this way were compared with the results of the calculations based on the statistical model. For reactions on the isotope ¹⁰⁸Cd, agreement between these theoretical and experimental results is good, but the experimental ratio of the yields of photoproton and photoneutron reactions on the isotope ¹⁰⁶Cd differs substantially from its theoretical counterpart. The results of our present study are discussed from the point of view of the production of bypassed nuclei in the p-process of nucleosynthesis.     

Yields of photonuclear reactions on Sn isotopes at an energy of 29.1 MeV

Yields of photonuclear reaction on natural mixture of Sn isotopes irradiated by bremsstrahlung beam with maximum energy of 29.1 MeV are studied via the residual activity method. Using the TALYS code and a combined model, the cross sections of the photonucleon reaction in stable isotopes of Sn are calculated. Measured yields are compared with the yields calculated using theoretical, experimental, and estimated cross sections.     

A model taking into account the contribution of secondary particles to the relative biological efficiency of primary radiation

A model describing the biological efficiency of different types of ionizing radiation as a function of radiation energy has been developed. A method for estimating the relative biological efficiency by taking into account the contribution of photonuclear reactions in the energy range from the threshold of photonuclear reactions on light elements to 50 MeV is proposed. The results obtained are compared with the experimental and calculated data of other researchers.     

Photonuclear physics when a multiterawatt laser pulse interacts with solid targets

When a laser pulse of intensity 10(19) W cm(-2) interacts with solid targets, electrons of energies of some tens of MeV are produced. In a tantalum target, the electrons generate an intense highly directional gamma-ray beam that can be used to carry out photonuclear reactions. The isotopes 11C, 38K, (62,64)Cu, 63Zn, 106Ag, 140Pr, and 180Ta have been produced by (gamma,n) reactions using the VULCAN laser beam. In addition, laser-induced nuclear fission in 238U has been demonstrated, a process which was theoretically predicted at such laser intensities more than ten years ago. The ratio of the 11C and the 62Cu beta(+) activities yields shot-by-shot temperatures of the suprathermal electrons at laser intensities of approximately 10(19) W cm(-2).     

Chiral invariant phase space event generator

Nuclear fragment production in photonuclear reactions below pion production threshold is implemented in the developed version of the new event generator, based on the CHIPS model, within the GEANT4 simulation toolkit. The spectra of secondary nucleons in the photonuclear process are compared with experimental data.     

Analysis of isomeric ratios in (γ, n) and (γ, p) reactions around giant-resonance energies

Isomeric ratios are investigated in simple photonuclear reactions occurring on targets in the mass range 90–180 amu that are irradiated with 20-to 40-MeV photons. The results of measurements are compared with estimates based on the statistical model of deexcitation of compound nuclei. The isomeric ratios in question are calculated with allowance for special features of photonuclear reactions induced by bremsstrahlung photons and for the properties of nuclear transitions in residual products. The results of these calculations, involving no free parameters, agree satisfactorily with experimental data.     

Neutron generation in (γ, <Emphasis Type="Italic">n</Emphasis>) process assisted by inversely populated medium

Neutron production upon interaction of a γ-ray beam (generated using an inversely populated medium) with a target (which contains isotopes with a pronounced first photoneutron resonance) has been investigated. The research is mainly focused on the influence of the inversely populated medium on the prodaction and parameters of the γ radiation that causes the photonuclear reaction.     

Total photoabsorption cross sections for high-Z ELEMENTS in the energy range 7–20 MeV

Total photoabsorption cross sections for 13 isotopes between Sm and Bi were measured in the energy range 7–20 MeV with uncertainties generally better than 0.3 % using the narrow beam attenuation method. The measured cross sections after subtracting the photonuclear contribution are generally in good agreement with the latest NBS calculations of atomic cross sections.     

Study on the isomeric ratios of (γ,p) photonuclear reactions with isotopes 40 92 Zr and 74 183 W in the giant dipole resonance region

We have carried out the study on the isomeric ratios in (γ,p) photonuclear reactions with isotopes ₄₀ ⁹² Zr and ₇₄ ¹⁸³ W in the giant dipole resonance (GDR) region. The targets were irradiated with bremsstrahlungs produced by electron accelerator Microtron MT-25 of the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Dubna, Russia. Spectra of the irradiated samples were measured with a spectroscopic system consisting of 8192-channel analyzer CANBERRA and high-energy resolution semiconductor detector CANBERRA. The results were discussed and compared with those of other authors. The text was submitted by the authors in English.     

Refinement of the giant dipole resonance parameters with allowance for all exit channels of photonuclear reactions

The contribution from various channels of photonuclear reactions is considered to obtain parameters of the giant dipole resonance (GDR). It is pointed out that the channel with emission of charged particles is very important for some nuclei. GDR parameters for the ⁶⁰Ni, ⁶³Cu, and ⁶⁴Zn nuclei are evaluated with allowance for all exit channels of photonuclear reactions. The EMPIRE-II code is used for theoretical calculations.     

Photonuclear Reactions on Bypassed Nuclei <Superscript>84</Superscript>Sr and <Superscript>92</Superscript>Mo

The yields of photonuclear reactions on mixtures of natural isotopes of strontium and molybdenum that result in the formation and decay of bypassed nuclei ⁸⁴Sr and ⁹²Mo are measured and compared to theoretical results obtained using the TALYS code and calculations in the combined model of photonucleon reaction (CMPR). The need is demonstrated to consider isospin splitting in cases of photoproton reactions. The yields of the ⁹²Mo(γ,p)⁹¹mNb, ⁸⁴Sr(γ,p)⁸³Rb reactions that make the main contribution to the formation and decay of ⁸⁴Sr and ⁹²Mo in the p-process of nucleosynthesis differ from the TALYS and CMPR results by several hundred percent.     

Nuclear physics with synchrotron radiation

The characteristics of synchrotron radiation originating from a very high energy electron-positron storage ring are presented. Emphasis is put on the high energy part of the spectrum which is relevant to nuclear physics research. The physics potential of such intense photon beams is reviewed with discussions of photonuclear reactions and of neutron-induced reactions with photoproduced neutrons.     

Main channels of the decay of the giant dipole resonance in the 20,22Ne nuclei and isospin splitting of the giant dipole resonance in the 22Ne nucleus

Data published in the literature on various photonuclear reactions for the ^20,22Ne isotopes and for their natural mixture are analyzed with the aim of exploring special features of the decay of giant-dipole-resonance states in these two isotopes. With the aid of data on the abundances of the isotopes and on the energy reaction thresholds, the cross sections for the reactions ^20,22Ne[(γ, n)+(γ, np)] and ^20,22Ne[(γ, p)+(γ, np)] are broken down into the contributions from the one-nucleon reactions (γ, n) and (γ, p) and the contributions from the reactions (γ, np). The cross sections for the reactions ^20,22Ne(γ, n)^19,21Ne and ^20,22Ne(γ, p)^19,21F in the energy range E _γ=16.0–28.0 MeV and the cross sections for the reactions ^20,22Ne(γ, np)^18,20F in the energy range E _γ=23.3–28.0 MeV are estimated. The behavior of the cross-section ratio r=σ(γ, p)/σ(γ, n) for the ²²Ne nucleus as a function of energy is analyzed, and the isospin components of the giant dipole resonance in the ²²Ne nucleus are identified. The contributions of the isospin components of the giant dipole resonance in the ²²Ne nucleus to the cross sections for various photonuclear reactions are determined on the basis of an analysis of the diagram of the excitation and decay of pure isospin states in the ²²Ne nucleus and in nuclei neighboring it, which are members of the corresponding isospin multiplets. The isospin splitting of the giant dipole resonance and the ratio of the intensities of the isospin components are determined to be ΔE=4.57±0.69 MeV and R=0.24±0.04, respectively.