Cross section for the subthreshold fission of 236U

The cross section for ²³⁶U fission in the neutron-energy range E _n = 0.001–20 keV was measured by using the INR RAS (Institute of Nuclear Research, Russian Academy of Sciences, Moscow) LSDS-100 neutron spectrometer of the lead slowing-down spectrometer type. The resonance fission areas of the resonances at 5.45 eV and 1.28 keV were found, and the fission widths of these resonances were evaluated. The cross section for the ²³⁸U(n, f) fission process was measured, and the threshold sensitivity of the LSDS-100 to small values of fission cross sections was estimated. The well-known intermediate structure in the cross section for the neutron-induced subbarrier fission of ²³⁶U was confirmed.     

Cross section for the subbarrier fission of <Superscript>244</Superscript>Cm

The cross section for ²⁴⁴Cm fission induced by neutrons of energy in the range between 0.07 eV and 20 keV was measured by using the lead slowing-down spectrometer (LSDS-100) of the Institute for Nuclear Research (Russian Academy of Sciences, Moscow). The parameters of the resonance areas were determined for the lowest eight s-wave neutron resonances, and the respective fission widths were evaluated. Also, the parameters of the intermediate structure in the cross section for the subbarrier fission of ²⁴⁴Cm nuclei were evaluated. The results were compared with available data and recommendations based on evaluations.     

Photoproton cross section and isospin components of the giant resonance in 64Zn

The absolute cross section for the reaction ⁶⁴Zn(γ, p)⁶³Cu using a thin target of 99.6 % isotopically pure ⁶⁴Zn has been measured at four angles using bremsstrahlung from the Los Alamos Electron Prototype Accelerator. The results are compared with the previously measured ⁶⁴Zn(γ, n)⁶³Zn cross section to clearly show the two isospin components of the giant dipole resonance. The measured photoproton cross section is combined with previously measured (γ, n), (γ, 2n) and (γ, np) results to obtain a “total” photodisintegration cross section for ⁶⁴Zn.     

Cross section for <Superscript>246</Superscript>Cm subbarrier fission

The cross section for ²⁴⁶Cm fission induced by neutrons of energy in the range 0.1 eV-20 keV was measured by the neutron lead slowing-down spectrometer (LSDS-100) of the Institute for Nuclear Research (INR, Russian Academy of Sciences, Moscow). The parameters of the resonance area and of the fission width were evaluated for several low-lying s-wave neutron resonances. The parameters of the intermediate structure in the cross section for the subbarrier fusion of ²⁴⁶Cm nuclei were found. The results obtained in this way were compared with available experimental data and with recommended evaluated data.     

Currents of the second kind in the neutrino splitting of a deuteron

Differential cross sections of the neutrino splitting of a deuteron due to both charged (1) and neutral (2) weak currents are obtained in analytical form. Within the framework of the Weinberg-Salem model for currents of the first kind (CFK) and additional assumptions regarding currents of the second kind (CSK), in the case of dipole parameterization of the nucleon form factors, the dependence of the cross sections of processes (1) and (2) on q² with E _v =1 and 2 GeV is studied by means of a computer. It is shown that the relative contribution of CSK to the cross section (with respect to CFK) is 1–3%, measurement of dependence of the cross section on q², with the aim of detecting CSK, may be expediently conducted, for process (1), in the range 0.1 GeV² < q² < 0.2 GeV², since the cross section reaches a maximum in this range. For process (2), the cross section monotonically decreases with rise in q², and it may be measured in any region where q² > 0.1 GeV², since the contribution of CSK is practically the same anywhere above this value.Work presented to a session of the Nuclear Physics Department, Academy of Sciences of the USSR, Moscow, January 27–31, 1980.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 48–52, September, 1981.     

Electron impact ionization cross sections of beryllium and beryllium hydrides

We report calculated electron impact ionization cross sections (EICSs) for beryllium (Be) and some of its hydrides from the ionization threshold to 1 keV using the Deutsch-Märk (DM) and the Binary-Encounter-Bethe (BEB) formalisms. The positions of the maxima of the DM and BEB cross sections are very close in each case while the DM cross section values at the maxima are consistently higher. Our calculations for Be are in qualitative agreement with results from earlier calculations (convergent close-coupling, R matrix, distorted-wave and plane-wave Born approximation) in the low energy region. For the various beryllium hydrides, we know of no other available data. The maximum cross section values for the various compounds range from 4.0 × 10^?16 to 9.4 × 10^?16 cm² at energies of 44 to 56 eV for the DM cross sections and 3.0 × 10^?16 to 5.4 × 10^?16 cm² at energies of 40.5 to 60 eV for the BEB cross sections.     

Total cross section measurements for charge exchange of He++ ions with He and Ar atoms

Total charge exchange cross sections were measured for He⁺⁺ in He and Ar gas in the energy range from 50 to 540 eV using a single beam apparatus. For He⁺⁺ in He the measured cross section is in agreement with calculations for symmetric resonant charge exchange. For He⁺⁺ in Ar the cross section for charge exchange decreases with decreasing energy below 300 eV. The measured cross section suggests the formation of Ar⁺ ions to be more important at lower energies and the production of Ar⁺⁺ to be dominant at higher energies.     

Proton induced fission of <Superscript>232</Superscript>Th at intermediate energies

The mass-energy distributions and cross sections of proton-induced fission of ²³²Th have been measured at the proton energies of 7, 10, 13, 20, 40, and 55 MeV. Experiments were carried out at the proton beam of the K-130 cyclotron of the JYFL Accelerator Laboratory of the University of Jyväskylä and U-150m cyclotron of the Institute of Nuclear Physics, Ministry of Energy of the Republic of Kazakhstan. The yields of fission fragments in the mass range A = 60–170 a.m.u. have been measured up to the level of 10?4%. The three humped shape of the mass distribution up has been observed at higher proton energies. The contribution of the symmetric component grows up with increasing proton incident energy; although even at 55 MeV of proton energy the shoulders in the mass energy distribution clearly indicate the asymmetric fission peaks. Evolution of shell structure was observed in the fission fragment mass distributions even at high excitation energy.     

A measurement of the photonuclear interactions of 180 GeV muons in iron

The energy spectrum and the cross section of photonuclear interactions of 180 GeV muons in iron were measured at the CERN SPS using prototype modules of the ATLAS hadron calorimeter. The differential cross section for a muon fractional energy loss was measured in the range 0.1&lt;v&lt;1. The integrated cross section is cm²g^-1 in agreement with the theoretical prediction of cm²g^-1. The best adjustment of the data to the theory is achieved for the value of of the photon-nucleon cross section for photons with energies in the range from 18 to 180 GeV. Received: 22 January 2003 / Published online: 5 May 2003     

Study of the 182W(t,p)184W reaction at 20 MeV

The ¹⁸²W(t, p)¹⁸⁴W reaction has been studied at 20 MeV. The outgoing protons were detected in an Elbek broad range magnetic spectrograph. Absolute cross sections and angular distributions were measured. Evidence for inelastic effects in the reaction mechanism was observed for the first excited 2⁺ state, the 3^? level at 1221 keV and the 5⁺ state at 1295 keV. The 0⁺ level at 1002 keV was populated with ≈ 2% the ground state cross section. A 4⁺ level at 1536 keV was observed with ≈ 50% the ground state cross section. Calculations of the absolute (t, p) cross sections to this and other states with known structure resulted in excellent agreement with the measured values.     

Investigating the nuclear fusion and nucleon transfer channels in the 197Au + 6He reaction at 6He energies up to 20 MeV/A

New data on the cross sections of reactions that proceed during the interaction of ⁶He and ¹⁹⁷Au nuclei in the ⁶He energy range of 40 to 120 MeV are reported. The experiments were performed using the secondary beam of the ACCULINNA separator at the Flerov Laboratory of Nuclear Reactions (FLNR), JINR. Reaction products are identified by means of activation method to measure the gamma activity of a thin-foil target assembly. Excitation functions for ⁶He fusion reactions with subsequent emission of up to 10 neutrons from the compound nucleus are measured. Cross sections for reactions with emission of charged particles and nucleon transfer were also measured. The experimental cross sections for the (⁶He, xn) reactions that proceed via the formation of a compound nucleus agree in general with calculations using models that involve the statistical approach. It is shown that the complete fusion reaction cross section drops slightly up to an energy of 114 MeV. The experimental excitation functions for the reactions resulting in the formation of mercury and gold isotopes indicate that the main contribution to their formation comes from direct processes, while the evaporation reactions (⁶He, pxn) and (⁶He, αxn) are of minor importance.     

Development of a Method for Measurement of Photonuclear-Reaction Cross Sections with the Aid of Simulated Quasimonoenergetic-Photon Spectra

A procedure for measuring photonuclear-reaction cross sections by employing the method of quasimonochromatization of the bremsstrahlung photon spectrum is developed. This procedure permits determining reaction cross sections via measuring the reaction yield at three fixed values of the electron energy. The procedure is equivalent to measuring the cross section in question for quasimonochromatic photons. Bremsstrahlung-photon spectra are obtained using state-of-the-art simulation means involving the GEANT4 code as applied to a specific experiment with allowance for its geometry, target thicknesses, electron-beam parameters, etc. The results obtained by simulating quasimonochromatic distributions of bremsstrahlung photons are presented for experiments at the LUE-8-5 linear electron accelerator of Institute for Nuclear Research (Moscow, Russian Academy of Sciences). These results are found to be in good agreement with the experimental energy distribution of the cross section for the reaction ¹¹¹Cd(γ, γ') in the energy range between 5 and 8 MeV.     

The polarization and differential cross section of fast neutrons scattered from 6Li and an R-function analysis of the interaction below 4 MeV

The analyzing power of ⁶Li for the elastic scattering of polarized neutrons with energies between 2 and 4 MeV, has been measured at six angles ranging from 25° to 150°. The polarized neutrons were generated from the reactions Pb(γ, n) and ¹²C(n, $\text{n}$), and their polarization was measured using the double-scattering method. The neutron energies were determined with a nanosecond timeof-flight spectrometer. In addition, the differential cross section was measured at three angles in the same energy range; the cross section was determined relative to the well-known n-¹²C cross section. The present results have been combined with existing data for the neutron total, (n, α), and differential elastic cross sections, in a reduced R-function analysis. Clear evidence of a p-wave triplet of shellmodel states emerges from the analysis.     

Electron Transitions during the Capture of an Electron by a He<Superscript>2+</Superscript> Ion at the Argon Atom

We have measured the absolute values of the total cross section of the one-electron capture by He²⁺ ions in the kinetic energy range 2–30 keV at the Ar atoms. The absolute values of the differential scattering cross sections of He⁺ ions formed during the one-electron capture and the electron capture with ionization at energies of 2.2, 5.4, and 30 keV have been determined. The electronic states of the formed ions have been determined using collision spectroscopy based on analysis of the change in the kinetic energy of He⁺ after the interaction. We have measured doubly differential (with respect to the kinetic energy and the scattering angle) cross sections of the formation of free electrons. The free electron formation channels (direct ionization and electron capture with ionization) have been analyzed by calculating the electron terms of the (HeAr)²⁺ system. The calculated cross section of capture with ionization is in conformity with the cross section measured using collision spectroscopy.     

Study of the W(t, p)W reaction at 20 MeV

The ¹⁸²W(t, p)¹⁸⁴W reaction has been studied at 20 MeV. The outgoing protons were detected in an Elbek broad range magnetic spectrograph. Absolute cross sections and angular distributions were measured. Evidence for inelastic effects in the reaction mechanism was observed for the first excited 2⁺ state, the 3⁻ level at 1221 keV and the 5⁺ state at 1295 keV. The 0⁺ level at 1002 keV was populated with ≈ 2% the ground state cross section. A 4⁺ level at 1536 keV was observed with ≈ 50% the ground state cross section. Calculations of the absolute (t, p) cross sections to this and other states with known structure resulted in excellent agreement with the measured values.     

Heavy ion induced transfer reactions on 148Nd

Transfer reactions induced by ¹⁶O and ¹⁸O beams on ¹⁴⁸Nd were measured with a time-of-flight setup at 72 MeV incident energy. The angular distributions are bell shapes having their maxima at angles somewhat below the grazing angle. The excitation in the final nuclei takes place (if possible) near the optimum Q-value and is spread over 5 MeV for the one-particle transfer reactions and up to 10 MeV for the multiparticle transfers. The cross sections for the individual channels are explained mostly by Q-window considerations. In spite of the differences in the individual channels the total transfer cross section integrated over excitation energy, angle, and all channels turns out to be the same same for both ¹⁶O and ¹⁸O beams. This cross section amounts to 20 % of the total reaction cross section and nicely fills the gap between the measured fusion cross section and the total reaction cross section obtained from optical model calculations based on elastic scattering data.     

K+ nucleon elastic scattering at 180° between 1.0 and 1.5 GeV/c incident momentum

We have measured the cross section at 180° for K⁺p and K⁺n elastic scattering in the momentum range 1.0 to 1.5 GeV/c. The K⁺n cross section was measured on deuterium and the K⁺p on hydrogen and deuterium. We were thus able to measure directly the difference between free nucleon (proton) scattering and bound nucleon (proton) scattering at large angles. This difference was found to be small and within our experimental accuracy the K⁺p(n) cross section should be equal to the K⁺p (free) cross section at 180°. We found no evidence for an s-channel resonance Z¹ in either the K⁺p or K⁺n system. A comparison of our data and those of other groups with theoretical predictions is given.     

Comparison of small-angle p and pp elastic scattering at 52.8 GeV center-of-mass energy at the CERN intersecting storage rings

Proton-antiproton and proton-proton elastic scattering have been measured in the four-momentum transfer range 0.001|t|0.06 GeV² for center-of-mass energy 52.8 GeV at the CERN Intersecting Storage Rings (ISR). Using the known pp total cross section, a simultaneous fit to the p and pp differential cross sections yields the p total cross section; in addition, we obtain the ratio of the real-to-imaginary part of the forward nuclear-scattering amplitude and the nuclear-slope parameter for both p and pp. Our results show conclusively that the p total cross section is rising at ISR energies and lend support to conventional theories in which the difference between the p and pp total cross section vanishes at very high energy.     

Measurement of the absolute Raman scattering cross section of the 1584‐cm−1 band of benzenethiol and the surface‐enhanced Raman scattering cross section enhancement factor for femtosecond laser‐nanostructured substrates

The absolute Raman scattering cross section (σ_RS) for the 1584‐cm⁻¹ band of benzenethiol at 897 nm (1.383 eV) has been measured to be 8.9 ± 1.8 × 10⁻³⁰ cm² using a 785‐nm pump laser. A temperature‐controlled, small‐cavity blackbody source was used to calibrate the signal output of the Raman spectrometer. We also measured the absolute surface‐enhanced Raman scattering cross section (σ_SERS) of benzenethiol adsorbed onto a silver‐coated, femtosecond laser‐nanostructured substrate. Using the measured values of 8.9 ± 1.8 × 10⁻³⁰ and 6.6 ± 1.3 × 10⁻²⁴ cm² for σ_RS and σ_SERS respectively, we calculate an average cross‐section enhancement factor (EF) of 0.8 ± 0.3 × 10⁶. Copyright © 2009 John Wiley & Sons, Ltd.     

Autoionization cross section of potassium atom excited by electron impact

The autoionization cross section of potassium atoms excited by electron impact is measured in the energy range from the first autoionization threshold at 18.72 eV to 202 eV. The data are obtained by deter-mining the total intensity of electron spectra resulting from the decay of the 3p ⁵ n ₁ l ₁ n ₂ l ₂ autoionizing states. The cross section has two maxima, 1.8 × 10^?16 and 2.2 × 10^?16 cm², at 21 and 32 eV, respectively. The excitation dynamics of autoionization states suggests that the first maximum is associated with the resonance character of the near-threshold excitation. The second maximum, as well as the behavior of the cross section at energies above 50 eV, reflects the dynamics of electron excitation of quartet and doublet autoionizing states. The measured autoionization cross section is compared with known data for the total single ionization cross section of potassium atom by electron impact. The relative contribution of the autoionization cross section to the total single ionization cross section is found to reach 30% at 32 eV.