Showing papers on "Proton published in 1985"
299 citations
01 May 1985-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, the gamma ray yield function of (p, αγ) and resonance reactions on semi-thick 19F, 23Na, 24,26Mg and 27Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Gottingen.
Abstract: Gamma ray yield functions of (p, αγ) and (p, γ) resonance reactions on semi-thick 19F, 23Na, 24,26Mg and 27Al targets were measured and used to calibrate the accelerating voltage and energy resolution of the new 500 kV heavy ion implanter at Gottingen. The energy spread of the proton beam was found to vary linearly with the accelerating voltage from ΔE(200 keV) = 55 eV fwhm to ΔE(500 keV) = 105 eV; it is made up by a 0.012% high voltage ripple and the Doppler broadening of the resonances due to the thermal motion of the target nuclei. A long term stability of the proton energy of Applications of the accelerator for the remeasurement of some resonance energies and widths and for depth profiling of light implanted ions in metals by the resonance broadening method will be briefly discussed.
293 citations
TL;DR: A search for axion-like particles was performed at the 400 GeV proton beam-dump experiment at CERN as mentioned in this paper, but no evidence for the existence for such particles was found in this experiment.
275 citations
209 citations
203 citations
TL;DR: In this paper, complete sequence-specific 1H nuclear magnetic resonance assignments for the backbone hydrogen atoms in Tendamistat, a protein with 74 residues, were obtained from NOESY observation of 1H-1H short distance constraints, measurements of the spin-spin couplings 3JHNα and a qualitative identification of slowly exchanging amide protons.
196 citations
TL;DR: Ionization cross sections for K and L subshells are tabulated according to target atomic number and incident ion energy in this article, where cross sections have been calculated in the plane-wave Born approximation (PWBA) with corrections for energy loss (E), Coulomb deflection (C), perturbed stationary state (PSS), and relativistic (R) effects (ECPSSR).
196 citations
TL;DR: In this paper, the properties of the heavy fragment nuclei (A ≥ 10.5 GeV/u) are analyzed in the framework of models for spallation, fission and multifragmentation.
195 citations
CERN1
TL;DR: In this paper, the x and Q 2 dependence of the single photon exchange cross section d 2 σ /d Q 2 d x and the proton structure functions F 2 ( x, Q 2 ) and R ( x, Q 2 ), have been measured in deep inelastic muon proton scattering in the region 0.02 x Q 2 2.
149 citations
TL;DR: The magnitude and the rise kinetics of proton release into the interior of thylakoids by flash spectrophotometty with neutral red as pH indicator are studied.
Abstract: — We studied the magnitude and the rise kinetics of proton release into the interior of thylakoids by flash spectrophotometty with neutral red as pH indicator. Excitation of dark-adapted thylakoids by a series of between 4 and 11 flashes produced a complex pattern of proton release into the thylakoid lumen. Proton release upon each flash was time resolved.
A slow component of proton release oscillated weakly in magnitude with period of two as function of flash number. It exhibited a half-rise time of approximately 20 ms from the very first flash on, and it was abolished by inhibitors of plastohydroquinone oxidation. This component was attributed to the oxidation of plastohydroquinone by PS I via the Cytb6/f complex.
Additionally, rapid and multiphasic proton release was observed with half-rise times of less than 2 ms which exhibited a pronounced and damped oscillation with period of four as function of flash number. This rapid proton release was attributed to water oxidation. A detailed kinetic analysis suggested that proton release occurred with the following stoichiometry and with the following half-rise times during the transitions S1 Si+1 of water oxidation: 1 H+(250 μs, S01): 0 H+(S1 S2):1 H+(200 μs, S2S3):2 H+(1.2 ms, S3 S4 S0). Proton release and proton rebinding upon oxidation and reduction of the intermediate electron carrier Z, respectively, may have influenced the kinetics of the respective proton yields but not the stoichiometric pattern.
124 citations
TL;DR: In this article, the cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7\char21{}4000 keV by the transverse-field method.
Abstract: Cross sections for production of electrons and positive ions by proton impact on water vapor have been measured from 7\char21{}4000 keV by the transverse-field method.
TL;DR: The role of nonequilibrium and quantal effects in fast nucleus-nucleus collisions is studied via the Vlasov-Uehling-Uhlenbeck theory which includes the nuclear mean field dynamics, two-body collisions, and Pauli blocking, supplemented with a phase space coalescence model of fragment formation.
Abstract: The role of nonequilibrium and quantal effects in fast nucleus-nucleus collisions is studied via the Vlasov-Uehling-Uhlenbeck theory which includes the nuclear mean field dynamics, two-body collisions, and Pauli blocking. The intranuclear cascade model, where the dynamics is governed by independent NN collisions, and the Vlasov equation, where the nuclear mean field determines the collision dynamics, are also studied as reference cases. The Vlasov equation (no collision term) yields single particle distribution functions which--after the reaction--are only slightly modified in momentum space; even in central collisions, transparency is predicted. This is in agreement with the predictions of the quantal time-dependent Hartree-Fock method. In contrast, large momentum transfer is obtained when the Uehling-Uhlenbeck collision term is incorporated; then the final momentum distribution is nearly spherically symmetric in the center of mass and a well-equilibrated nuclear system is formed: the nuclei stop each other; the translational kinetic energy is transformed into randomized microscopic motion. The Vlasov-Uehling-Uhlenbeck theory is supplemented with a phase space coalescence model of fragment formation. Calculated proton spectra compare well with recent data for Ar(42, 92, and 137 MeV/nucleon) + Ca. Also the total yields of medium mass fragments are well reproduced in the present approach. The mean field dynamicsmore » without two-body collisions, on the other hand, exhibits forward peaked proton distributions, in contrast to the data. The cascade approach underpredicts the yields of low energy protons by more than an order of magnitude.« less
01 Dec 1985-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: Differential elastic scattering cross sections of 0.7-2.5 MeV protons for carbon, nitrogen and silicon have been determined at a scattering angle θ = 170°.
Abstract: Differential elastic scattering cross sections of 0.7—2.5 MeV protons for carbon, nitrogen and silicon have been determined at a scattering angle θ = 170°. Results from previous measurements near θ = 170° show large variations, of the order of 10–30% in the nonresonant regions. The purpose of the present investigations is to tabulate cross section data for backscattering analysis at a single scattering angle for many elements. Proton backscattering in the non-Rutherford energy region is more sensitive in the detection of C, N and many other light elements than other ion beam methods when a high background from the matrix is absent. Proton backscattering by using the present scattering cross sections and computer data analysis are outlined. The possible interference from other nuclear reactions is considered.
TL;DR: In this article, a comparison of theoretical and experimental rate coefficients for the reactions of H 3 +, HCO +, H −, C + and O + with HCN, and H 3+ with HCl, over the temperature range 205-540 K was presented.
TL;DR: In this article, the NH3 monomer symmetry axis was found to have a vibrationally averaged displacement of 23.1° from the N...O axis, and no evidence for transfer of a proton from water to the ammonia was observed.
Abstract: Microwave and radio frequency spectra for NH3⋅H2O and deuterated analogs have been observed by molecular beam electric resonance spectroscopy. Rotational constant, Stark effect, and nitrogen quadrupole coupling interaction data were obtained. This complex is found to have a linear, hydrogen bonded structure with water as the proton donor. The NH3 monomer symmetry axis was found to have a vibrationally averaged displacement of 23.1° from the N...O axis. No evidence for transfer of a proton from water to the ammonia was observed.
TL;DR: It is found that the exchange of the imino proton is strongly buffer sensitive, and this property is used to derive the base-pair lifetime, which is in the range of milliseconds at 27 degrees C, 100 times smaller than published values.
TL;DR: The relatively large spin--spin coupling (87 +/- 3 Hz) between the 15N nucleus and the phenylalanine amide protons may be exploited in a variety of ways to selectively observe the five phenylaline amide proton resonances.
Abstract: We have produced T4 lysozyme using a bacterial expression system which allows efficient incorporation of isotopically labeled amino acids in lysozyme. By using conditions that repress the expression of various transaminases, we have incorporated 15N-labeled amino acid into the five phenylalanine residues of the protein. The relatively large spin--spin coupling (87 +/- 3 Hz) between the 15N nucleus and the phenylalanine amide protons may then be exploited in a variety of ways to selectively observe the five phenylalanine amide proton resonances. These include a simple "echo difference" technique which displays the amide proton resonances in one dimension and a "forbidden echo" technique [Bax, A., Griffey, R. H., & Hawkins, B.L. (1983) J. Magn. Reson. 55, 301-335] which gives two-dimensional information allowing the proton and 15N chemical shifts of each amide to be determined. With these approaches, all five phenylalanine amide protons give resolved resonances. Deuterium exchange experiments demonstrate that three of the five resonances are slow to exchange (half-times of about 1 week at pH 5.5 and 4 degrees C) while the other two are rapid with complete exchange in hours or less. These observations correlate well with the secondary structure of the protein which shows three residues in alpha-helical regions and two residues in surface-exposed environments. This approach of isotopic substitution on nitrogen or carbon atoms is of general utility and should allow virtually any proton on a protein of molecular weight 20 000 or thereabout to be selectively observed.
TL;DR: The total absorption cross sections for real photons by nuclei are discussed in this paper, where the authors compare the absorption of photons by real nuclei with that by the free proton.
TL;DR: In this article, the excitation functions for the Cu(p, x) 58Co, 63Cu(p 2n) 62Zn and 65cu(p n) 65Zn reactions were determined and compared with the published data.
TL;DR: In this paper, the authors studied the heating of heavy ions by the electromagnetic ion cyclotron (EMIC) waves, which are driven by proton temperature anisotropies.
Abstract: Heating of heavy ions by the electromagnetic ion cyclotron (EMIC) waves, which are driven by proton temperature anisotropies, is studied by means of hybrid particle simulations. Initially, relaxation of the temperature anisotropies in the proton distribution and isotropic heating of the heavy ions are observed (phase I), followed by substantial perpendicular heating of the heavy ions (phase II). The heavy ions are distinctly gyrophase modulated by the EMIC waves. The isotropic heating in phase I is due to magnetic trapping by the excited proton cyclotron waves. The perpendicular heating in phase II is attributed to cyclotron resonance with the EMIC waves, which becomes possible by means of the preceding heating in phase I. Saturation of the EMIC instability is instead attributed to magnetic trapping of the majority ions: protons. When the proton anisotropy is very large, frequency shift (decrease) of the proton cyclotron waves to less than 1/2 Ohm(p) is observed. The present mechanism is not only relevant to He(+) heating in the dayside equator of the magnetosphere, but it also predicts hot He2(+) ions behind the earth's bow shock.
TL;DR: In this article, the proton transfer process of 2naphthol in its first excited singlet state was investigated in water/methanol mixtures at different temperatures.
Abstract: Using picosecond spectroscopic techniques, the proton transfer process of 2‐naphthol in its first excited singlet state is investigated in water/methanol mixtures at different temperatures. The proton transfer rate is found to increase as the temperature increases, and to decrease as the methanol concentration increases. A Markov random walk theory previously used to electron transfer kinetics is employed to analyze the data. By this method, a water cluster containing 4±1 members is shown to be the proton acceptor. Suggestively, a ‘‘four‐cluster’’ structure (H9O4)+ has been hypothesized as the most probable hydrating unit for the proton in acid–base equilibria, charge transfer, and other chemical systems. The observed activation energy of 3.45 kcal/mol in pure water is attributed to the energy required for rearrangement of the hydrogen bonding in the normal water structure to form the proton accepting cluster. Proton transfer kinetics thus exactly parallels electron transfer kinetics in aqueous media. The...
TL;DR: The results of recent experimental and theoretical investigations are presented and the new insights being gained are discussed in this article, where some of the highlights described include ground-state proton radioactivity, beta-delayed 2n, 3n and 2p decays, the coexistence of states built on quite different nuclear shapes in the same nucleus, new regions of strongly deformed nuclei, and the importance of the reinforcement of proton and neutron shell gaps on the shape of a nucleus.
Abstract: Studies of the structure and decay modes of nuclei far from stability have yielded many new insights which were not seen in nuclei near the line of beta stability. The results of recent experimental and theoretical investigations are presented and the new insights being gained are discussed. Some of the highlights described include ground-state proton radioactivity, beta -delayed 2n, 3n and 2p decays, the coexistence of states built on quite different nuclear shapes in the same nucleus, new regions of strongly deformed nuclei, and the importance of the reinforcement of proton and neutron shell gaps on the shape of a nucleus.
TL;DR: Negative hydrogen ion formation is studied by scattering protons from a cesiated tungsten (110) surface as discussed by the authors, where the primary energy ranges from 50 to 400 eV.
TL;DR: In this article, relativistic direct ionization cross sections for proton impact have been computed for atomic K and L shells, with Dirac-Hartree-Slater wave functions.
TL;DR: In this article, an explanation for the H Ly-alpha bulge phenomenon is presented, which conforms to the observations and does not require a strong asymmetry in atomic hydrogen abundance, and is caused by a combination of proton collisional transfer of H 2s atoms in the H 2p state, and production through recombination of H2(+) and H3(+), in an asymmetric ionosphere.
Abstract: An analysis of the Voyager EUV spectra of the Jupiter sunlit equatorial emissions shows no evidence for a substantial dependence of atomic hydrogen abundance on magnetic longitude, required by earlier theories of the H Ly-alpha longitudinal asymmetry. An explanation for the H Ly-alpha bulge phenomenon is advanced in this work that conforms to the observations and does not require a strong asymmetry in atomic hydrogen abundance. It is proposed that the H Ly-alpha bulge is caused by a combination of proton collisional transfer of H(2s) atoms in the H(2p) state, and production through recombination of H2(+) and H3(+), in an asymmetric ionosphere. According to the present model a large fraction of the observed H Ly-alpha emission from the equatorial region is electron excited, at least at times of solar maximum.
TL;DR: In this article, the isotropic motional model was shown to be adequate for H 2 O on the picosecond timescale, and the nuclear relaxation rates of H, D and 17 O were compared.
TL;DR: In this paper, the roles of spin and convection currents are studied by inelastic proton and electron scattering to the low-lying 1+ state at 4319 MeV in the f 7 2 -shell nucleus 46Ti.
TL;DR: In this article, the quantum nature of hydrogen chemisorbed on a metal surface is explored in detail, starting from the effective medium construction of the adiabatic potential energy surfaces.