Nuclear reactions of medium and heavy target nuclei with high-energy projectiles II. Fragmentation ofnatAg and197Au by 3.65 AGeV12C-ions and 3.65 GeV protons

The cross sections of a number of target fragmentation products formed in nuclear reactions of 3·65 A GeV¹²C-ions and 3·65 GeV protons with^natAg and¹⁹⁷Au have been measured. The measurements have been done by direct counting of irradiated targets with Ge(Li) gamma-ray spectrometers. Comparisons between these and other data have been used to test the hypotheses of factorization and limiting fragmentation. The total cross section for residue production in both reactions indicates that target residues are formed mainly in central collisions.     

Nuclear reactions of medium and heavy target nuclei with high-energy projectiles III. Emission of24Na and28Mg fragments

The emission of²⁴Na and²⁸Mg fragments in the reaction induced by 3·65 A GeV¹²C-ions and 3·65 GeV protons on Mn, Co, Cu, Ag, Au, and Pb targets has been studied. The experimental ratios of forward-to-backward emission and the mean ranges of these fragments were used to obtain the corresponding kinematic parameters. The results are analyzed by means of the two-step vector velocity model.     

Fission cross sections of medium-weight and heavy nuclei induced by 1 GeV protons

Coincidence studies performed in 4π geometry with silicon detectors and parallel plate avalanche counters have been used to measure total fission cross sections of²³⁸U,²³²Th,²⁰⁹Bi,²⁰⁸Pb,¹⁹⁷Au,^natYb,^natHo,^natTb,^natSm,^natTe,^natAg and^natNi nuclei induced by 1 GeV protons. The experimental results agree qualitatively with cascade-evaporation calculations.     

Transient creep during transformation in Cd-Zn alloys

Transient creep of Cd-2 wt. % Zn and Cd-17·4 wt. % Zn alloys has been studied under different constant stresses ranging from 6·4 MPa to 12·7 MPa near the transformation temperature. The results of both compositions showed two transient deformation regions, the low temperature region (below 483 K) and the high temperature region (above 483 K). From the transient creep described by the equation _tr=Bt ⁿ, where _tr andt are the transient creep strain and time. The parametersB andn were calculated. The parameterB was found to change with the applied stress from 0·3×10^–4 to 3×10^–4 and from 0·6×10^–4 to 18×10^–4 for Cd-2 wt. % Zn and Cd-17·4 wt. % Zn, respectively. The exponentn was found to change from 0·8 to 0·95 for both alloys. The parameterB was related to the steady state creep rate through the equation , the exponent was found to be 0·5 for Cd-2 wt. % Zn and 0·6 for the eutectic composition. The activation energies of transient creep in the vicinity of the transformation regions (above 483 K) were found to be 50·2 kJ/mole for Cd-2 wt. % Zn and 104·7 kJ/mole for the eutectic composition characterizing the mechanisms of grain boundary diffusion and volume diffusion in Cd, respectively.     

Nuclear reactions of medium and heavy target nuclei with high-energy particles IV. Interpretation of mass fragment yields

Target residue mass distributions in 3·65 A GeV¹²C-ion- and 3·65 GeV proton-induced reactions on medium and heavy target nuclei have been interpreted in the theoretical framework of the intranuclear cascade and abrasion-ablation models. While the intranuclear cascade model gives a good approximation to experimental yields of residues produced in both types of interaction, the abrasion-ablation model was found to overestimate mass-yield distributions in the vicinity of the target mass numbers.     

Multiplicities for evaporative4He emission in heavy ion reactions: Relationships to spin and lifetime expectancy of the composite nucleus

Multiplicities are compared for⁴He evaporation in reactions of⁴⁰Ar and⁵⁶Fe projectiles (8.5 MeV/u) with with^natAg and²³⁸U targets. Coincidence requirements involving fusion-fission and projectile-like fragments have been used to select separate entrance-channel spin zones. Evaporation-like⁴He emission from the composite nuclei is shown to be large for mean spins ≦100?, and to decrease dramatically with increasing spin. Coincidence measurements between two⁴He particles have also been studied for⁴⁰Ar+^natAg. This requirement is shown to select reactions that lead to evaporation residues and therefore to a zone of relatively low spin. The shapes of the⁴He spectra provide an interesting probe of the mechanism and also of the thermodynamic properties of hot nuclei.     

Multi-nucleon transfer reactions and the formation of light charged particles in the systemnatAg+40Ar (285 MeV)

In the reaction^natAg+⁴⁰Ar (285 MeV) there have been measured the energy spectra of the isotopes of elements from H to Cl at an emission angle of 40°, the energy spectra and angular distributions of¹H,²H,³H, and⁴He, and the angular distributions of Li, Be, B, and C. The contribution from multinucleon transfer reactions to the formation of light charged particles is discussed.     

Search for proton radioactivity in65As,69Br and77Y

A search for proton radioactivity in⁶⁵As,⁶⁹Br and⁷⁷Y, produced as residues of fusion reactions, was carried out at the Orsay Tandem accelerator. The residues were collected at the image point of the spectrometer Soleno and implanted into the gaseous medium of an ionization chamber which was also used to detect the radioactivity protons. No such protons have been observed in the energy range of 250–600 keV and in the half-life interval of 10 μs-100 ms, within a production cross section sensitivity of 1 μb.     

Search for cold nuclear fusion in palladium-deuteride

We searched for protons generated in cold D fusion reactions in Pd cathodes doped electrolytically with D. The applied experimental technique allowed the detection of proton production rates exceeding 0.074 s^–1 per cm³ cathode material (or 3.1·10^–24 s^–1 per D pair). Our results do not confirm fusion rates such like those recently reported.     

Spatial distribution of albedo particles on altitudes ∼500 km

Spatial distributions of energetic charged particles, neutrons and gamma rays at altitude 500 km (below the radiation belts of the Earth), obtained by the measurements of two apparatuses on board the Intercosmos-17 satellite, are presented. The latitudinal dependences, [i.e. the variation of flux with vertical cut-off rigidity of the measurement point], for neutrons (E _n = 1 –30 MeV), gamma rays (E =0·15–6 MeV), secondary electrons (E _e > 100 MeV) and for primary protons coming from the west and the east, respectively, are given. The main characteristic, the ratioN _p/N _e of the counting rate of the particles in the polar regionN _p(R_vert< <0·1 GeV/c) and on the equatorN _e(R_vert > 16 GeV/c), is obtained for the various types of particles. This value is 10 for neutrons, 3.7 for gamma rays, 1·8 for electrons, 11 for protons in westward direction, 10 for protons in eastward direction. The latitude profile of neutrons and gamma rays is in a good agreement with calculations assuming their production by nuclear reactions of primary cosmic rays with nuclei of the atmosphere. The weakening of rigidity dependence of protons coming from east in comparison with those coming from the west, is interpreted as the cause of additional proton albedo flux. The equality of albedo electron fluxes (E_e = 100–3500 MeV) from these directions is observed. With the use of the shadowing effect the obtained data on electron-positron component are consistent with the flux of albedo positrons (E_e + > 3·5 GeV) of the value (0·5±0·2) m^–2. s^–1. ster^–1. The possibility of abundance of albedo positrons above electrons at these altitudes for the energy intervalE=0·2÷0·3 GeV is indicated.     

On the evolution of the mass asymmetry in damped heavy-ion collisions

TotaT kinetic energy vs. fragment mass distributions have been measured in the reactions of⁶⁴Zn projectiles with¹¹⁴Sn,^natAg and¹³⁹La nuclei at incidence energies of 20–50% above the Coulomb barrier. Conclusions are drawn on the possible influence of nuclear structure effects on the energy dissipation and the mass drift behaviour of the present collision systems.     

Mechanism of formation of delta FeOOH in a basic aqueous medium

The mechanism of oxidation of ferrous hydroxide precipitated by mixing FeSO₄ · 7H₂O and NaOH solutions depends on the ratioR=[FeSO₄]/[NaOH]. The study presented here concerns values ofR ranging from 0.38 to 0.43, i.e. Fe(OH)₂ is precipitated in the presence of an excess of caustic soda. The analysis made by Mössbauer spectroscopy of the final compounds of oxidation shows that the valueR=5/12 is particular. At this value, 8FeOOH is the main product of oxidation. Its formation is assumed to take place through an intermediate compound, which formula is deduced from the value R=5/12 to be: 3Fe(OH)₂ · 2Fe(OH)₃ ·nH₂O. This compound could be considered as a green rust one compound including excess OH^– ions in theAcB i BaC j CbA k stacking, whereA, B andC are the OH^– planes,a, b andc the iron planes, andi, j andk layers made of the excess OH^– ions and water molecules.     

Evidence for a K<Superscript>π</Superscript> = 1/2<Superscript>+</Superscript> isomer in neutron-rich <Superscript>185</Superscript>Ta

In this paper we present for the first time the measured delayed neutron (DN) yields and time spectra from high-energy protons interacting with thick ^natPb targets. The 1GeV protons from the accelerator impinged on targets of different thicknesses producing a huge number of spallation-fission products, some of which can be DN precursors. After the beam is switched off, the DNs were detected with optimized ³He counter. The production yields of light DN precursors as ¹⁷N and “usual” fission products as ⁸⁷Br and ⁸⁸Br, which dominate the total DN activity, are obtained both for thin and thick targets. These new data are of great interest for the new generation high-power spallation targets based on liquid-metal technologies. Our findings also should help to constrain the physics models within the simulations codes.     

Streuwirkungsquerschnitte12C(p,p)12C undl2C(d,d)12C im EnergiebereichE p=350...550 keV,bzw.E d=600...1100 keV

Scattering Cross Sections¹²C(p, p)¹²C and^l2C(d, d)¹²C in the Energy Range E_p=350...550 keV resp. E_d=600...1,100 keV For an application in a work in nuclear solid state physics (elastic recoil detection with fast¹²C-ions) the scattering cross sections were measured. When adapting excitation functions with a Breit-Wigner formalism it was found that a satisfactory adaptation needed the reduction of one hard-sphere phase by the factor 0.4, and smaller, in order to maintain a reasonable value of the interaction radius.     

Optical,photoelectric and electric properties of single-crystalline Sb2Se3

Measurements of absorption coefficient in the region of the absorption edge, of spectral distribution of photoconductivity and dependence of electrical conductivity upon temperature on Sb₂Se₃ single crystals are given. The absorption of light was proved to correspond to indirect forbidden transitions. The value of optical gapE _g ^opt =(1·11±0·02) eV forE a andE c was determined. From photoconductivity and conductivity measurements the values of the gaps areE _g ^opt =1·11 eV andE _g ^el =1·04 eV. The anisotropy of the electrical conductivity parallel and perpendicular to the cleavage plane is 2·2.     

Anomalous internal conversion ofE1 transitions in outer atomic shells

The experimentalN andO shell conversion coefficients of highly hinderedE1 transitions were found to be anomalous. The discrepancies as well as those for theL andM shells were removed by using the following values of the nuclear current parameter: 9·2±0·1 for the 6·21 keV transition in¹⁸¹Ta, 8·5±0·5 or –7·5±0·5 for the 84·20 keV transition in²³¹Pa and 1·9±0·2 for the 26·38 keV one in²³⁷Np.     

Hadron production near threshold

Final state interaction effects inpp→ pΛK ⁺ andpd →³Heη reactions are explored near threshold to study the sensitivity of the cross-sections to thepΛ potential and theηN scattering matrix. The final state scattering wave functions between Λ andp andη and³He are described rigorously. The Λ production is described by the exchange of one pion and aK-meson between two protons in the incident channel. Theη production is described by a two-step model, where in the first step a pion is produced. This pion then produces anη by interacting with another nucleon     

Inelastic interactions of protons with photoemulsion nuclei at 4·5 GeV/c

In inelastic collisions of protons with photoemulsion nuclei at 4·5 GeV/c, data have been obtained on multiplicity of shower particles, energy spectrum of fast secondary protons with (2·5±0·1) GeV average energy, and energy spectrum of produced charged pions with (640±±50) MeV average energy. The multiplicity, angular distributions, and energy of particles arising from splitting target-nuclei are also determined: the proton spectrum is approximated by the power dependenceE ^- with=1·4±0·1. The distribution of protons and-mesons over rapiditiesy=0·5 In[(E+p)/(E–p)] have been obtained. The average multiplicity for secondary particles coincide with the predicted values given by the cascade-evaporation model.Dedicated to the 25th anniversary of the Joint Institute for Nuclear Research.The authors would like to express their gratitude to the synchrophasotron group of JINR and to the group of S. J. Ljubomilov for the assistance in the experiment, to V. S. Barashenkov and V. V. Ivanov for the assistance in the cascade-evaporation model calculations, and also to the laboratories which took part in the scanning and measurement.     

Excitation functions of <Superscript>6</Superscript>Li incomplete fusion reactions with Pt nuclei

Experimentally determined excitation functions of the transfer reactions producing ^194–199Au and ^197m Hg isotopes during the interaction of ⁶Li with Pt nuclei are presented. An analysis of the experimental data as compared to EMPIRE-2.18 model calculations and experimental results on the d + ^natPt and α + ^natPt reactions allow determination of the interaction channels of d- and α-clusters in ⁶Li with the target nucleus. The results from model calculations of the reaction cross sections appear considerably lower than the experimental data. This discrepancy in describing the reactions with weakly bound nuclei is probably associated with the incomplete consideration of various interaction channels in the EMPERE-2.18 software. It is clear that a complete understanding of the interaction pattern in these processes requires consideration of the direct channels of ⁶Li nucleus cluster transfer during ⁶Li breakup near the Coulomb barrier.     

Measurements of natCd(γ, x) reaction cross sections and isomer ratio of 115m,gCd with the bremsstrahlung end-point energies of 50 and 60 MeV

The flux-weighted average cross sections of ^natCd(γ, xn)^{115g,m,111m,109,107,105,104}Cd and ^natCd(γ, x)^{113g,112,111g,110m}Ag reactions were measured at the bremsstrahlung end-point energies of 50 and 60 MeV. The activation and off-line γ-ray spectrometric technique was carried out using the 100 MeV electron linear accelerator at the Pohang Accelerator Laboratory, Korea. The ^natCd(γ, xn) reaction cross sections as a function of photon energy were theoretically calculated using the TALYS-1.95 and the EMPIRE-3.2 Malta codes. Then, the flux-weighted average cross sections were obtained from the theoretical values of mono-energetic photons. These values were compared with the flux-weighted values from the present study and were found to be in general agreement. The measured experimental reaction cross-sections and integral yields were described for cadmium and silver isotopes in the ^natCd(γ, xn)^{115g,m,111m,109,107,105,104}Cd and ^natCd(γ, x)^{113g,112,111g,110m}Ag reactions. The isomeric yield ratio (IR) of ^115g,mCd in the ^natCd(γ, xn) reaction was determined for the two bremsstrahlung end-point energies. The measured isomeric yield ratios of ^115g,mCd in the ^natCd(γ, xn) reaction were also compared with the theoretical values of the nuclear model codes and previously published literature data of the ¹¹⁶Cd(γ, n) and ¹¹⁶Cd(n, 2n) reactions. It was found that the IR value increases with increasing projectile energy, which demonstrates the characteristic of excitation energy. However, the higher IR value of ^115g,mCd in the ¹¹⁶Cd(n, 2n) reaction compared to that in the ¹¹⁶Cd(γ, n) reaction indicates the role of compound nuclear spin alongside excitation energy.