Search results for "Excitation function"
showing 10 items of 21 documents
A new resonance in thee-H2-scattering
1969
A short-lived compound state of the systeme-H2 in the energy region from 13.5 to 15 eV has been investigated. It desintegrates preferably into theC 1 π u v=0, 1, 2, 3,... vibrational states of H2. Excitation functions and angular dependences of these states have been measured. The H2 vibrational levels are situated at 13.63, 13.93, 14.20, 14.70, 14.92,... eV. The shape of the potential energy curve and the internuclear distance of the compound state should be very similar to that of theC 1 π u resp.D 1 π u state ofH 2.
Crossing the dripline to11Nusing elastic resonance scattering
2000
The level structure of the unbound nucleus N-11 has been studied by C-10+p elastic resonance scattering in inverse geometry with the LISE3 spectrometer at GANIL, using a C-10 beam with an energy of 9.0 MeV/ nucleon. An additional measurement was done at the A1200 spectrometer at MSU. The excitation function above the C-10+p threshold has been determined up to 5 MeV. A potential-model analysis revealed three resonance states at energies 1.27(-0.05)(+0.18) MeV (Gamma = 1.44 +/- 0.2 MeV), 2.01(-0.05)(+0.15) MeV (Gamma = 0.84 +/- 0.2 MeV), and 3.75 +/- 0.05 MeV (Gamma = 0.60 +/- 0.05 MeV) with the spin-parity assignments I-pi=1/2+,1/2,-,5/2+, respectively. Hence, N-11 is shown to have a ground …
Determination of theη′-Proton Scattering Length in Free Space
2014
Taking advantage of both the high mass resolution of the COSY-11 detector and the high energy resolution of the low-emittance proton beam of the cooler synchrotron COSY, we determine the excitation function for the $pp\ensuremath{\rightarrow}pp{\ensuremath{\eta}}^{\ensuremath{'}}$ reaction close to threshold. Combining these data with previous results, we extract the scattering length for the ${\ensuremath{\eta}}^{\ensuremath{'}}$-proton potential in free space to be $\mathrm{Re}({a}_{p{\ensuremath{\eta}}^{\ensuremath{'}}})=0\ifmmode\pm\else\textpm\fi{}0.43\text{ }\text{ }\mathrm{fm}$ and $\mathrm{Im}({a}_{p{\ensuremath{\eta}}^{\ensuremath{'}}})={0.37}_{\ensuremath{-}0.16}^{+0.40}\text{ }\t…
Multinucleon transfer reactions and proton transfer channels
2019
Transfer reactions have always been of great importance for nuclear structure and reaction mechanism studies. So far, in multinucleon transfer studies, proton pickup channels have been completely identified in atomic and mass numbers at energies close to the Coulomb barrier only in few cases. We measured the multinucleon transfer reactions in the 40Ar+208Pb system near the Coulomb barrier, by employing the PRISMA magnetic spectrometer. By using the most neutron-rich stable 40Ar beam we could populate, besidesneutron pickup and proton stripping channels, also neutron stripping and proton pickup channels. Comparison ofcross sections between different systems with the 208Pb target and with pro…
N22e(α,n)M25g: The Key Neutron Source in Massive Stars
2001
The excitation function of the reaction (22)Ne(alpha,n)(25)Mg, the key neutron source in the astrophysical s process in massive stars, has been determined from threshold at E(alpha) = 570 up to 1450 keV with an experimental sensitivity of 10(-11) b. For all resonances in this energy range new resonance parameters have been measured. For a possible resonance at about 635 keV a new upper limit omega gamma < 60 neV for the strength was obtained. Based on the new data, improved reaction rates were calculated as a function of temperature. The new uncertainty limits are considerably smaller than in previous determinations, ruling out the large enhancement factors, up to 500, assumed in some stell…
Cross sections for nuclear reactions in collisions of238U+238U and238U +197Au near and below the coulomb barrier
1991
Cross sections for nuclear reactions at beam energies near and below the spherical Coulomb barrier V c were measured in the very heavy collision systems238U +238U and238U +197Au. The most probable reaction channel with mass transfer is the one-neutron transfer. Its excitation function is understood in terms of Rutherford trajectories together with the quantal process of neutron tunnelling over large distances. In addition, the exchange of up to 15 nucleons is observed down to 0.90 V c . The excitation functions for the multi-nucleon transfer products have much steeper slopes than that for one-neutron transfer, and are steeper for238U +197Au than for238U +238U, suggesting that nuclear contac…
New microsecond isomers in 189, 190Bi
2001
New microsecond isomers in the neutron-deficient isotopes 189g, 190Bi have been identified after in-flight separation by the velocity filter SHIP. The evaporation residues were identified on the basis of delayed recoil-γ/X-ray, recoil-γ/X-ray-α and excitation function measurements. The systematics of the [ π1i 13/2]13/2+ excited states in the odd-mass Bi nuclei is discussed.
Coherent photoproduction of η-mesons off 3He – search for η-mesic nuclei
2012
Coherent photoproduction of $\eta$-mesons off $^3$He, i.e. the reaction $\gamma ^3{He}\rightarrow \eta ^3{He}$, has been investigated in the near-threshold region. The experiment was performed at the Glasgow tagged photon facility of the Mainz MAMI accelerator with the combined Crystal Ball - TAPS detector. Angular distributions and the total cross section were measured using the $\eta\rightarrow \gamma\gamma$ and $\eta\rightarrow 3\pi^0\rightarrow 6\gamma$ decay channels. The observed extremely sharp rise of the cross section at threshold and the behavior of the angular distributions are evidence for a strong $\eta {^3{He}}$ final state interaction, pointing to the existence of a resonant …
Radiative capture of protons by the deformed nuclide232Th
1986
The excitation function for the radiative capture232Th(p, γ)233Pa has been determined in the proton energy range 7 to 20 MeV by an activation method. The results are compared with a compound nucleus model prediction and earlier experimental data for another deformed nuclide176Yb. As in previous cases an enhancement over the CN-model prediction is observed and the excitation of the giant dipole resonance via the direct-semidirect reaction process is a likely explanation. Supplementary measurements of the232Th (p, f) excitation function in the proton energy range 11–20 MeV have been performed.
The key reactions in Stellar helium burning: 12C(α,γ)16O and 22Ne(α,n)25Mg
2003
Abstract The excitation functions of 12C(α,γ)16O and 22Ne(α,n)25Mg have been determined with a yet unequaled experimental sensitivity of 10−11 b. From γ-angular distributions the SE1-and SE2-factors for 12C(α,γ)16O have been deduced and extrapolated into the range of helium burning temperatures using the R-matrix method. An improved reaction rate has been calculated: NA〈σν〉=(7.9±2.5)x10−15cm3(mols)−1 at T9 = 0.2. For a more precise extrapolation the excitation function has to be measured with better statistics. Therefore a new experiment on 12C(α,γ)16O with a better suited setup has been started recently. The accuracy of the 22Ne(α,n)25Mg reaction rate could be improved considerably compare…