Showing papers on "Proton published in 1982"

Solar wind protons: Three-dimensional velocity distributions and derived plasma parameters measured between 0.3 and 1 AU

Abstract: Such nonthermal features as temperature anisotropies, heat fluxes, and proton double streams have been observed by a Helios solar probe survey of solar wind three-dimensional proton velocity distributions between 0.3 and 1 AU. It is found that a strong anisotropy in the core of proton distributions, with a temperature that is larger perpendicular rather than parallel to the magnetic field, is a persistent feature of high-speed streams, becoming most pronounced in the perihelion, or about 0.3 AU. Isotropic distributions have been detected only close to, and at, magnetic sector boundaries, and the flattest radial temperature profiles are found in high-speed streams. These observations indicate that local heating or proton heat conduction occurs in the solar wind.

Proton exchange for high‐index waveguides in LiNbO3

Abstract: We describe the fabrication and characterization of optical waveguides formed in LiNbO3 by proton exchange in benzoic acid melts at 200–250 °C. Proton exchange, in LiNbO3 the replacement of lithium ions with protons, takes place when the substrate is immersed in the molten acid. We observe a surface increase in the refractive index of 0.12, for the extraordinary polarization only, with a step function index profile. This is the highest index increase obtainable to date for LiNbO3. Measured diffusion rates for x‐cut crystals are 1.37 μm2/h at T = 249 °C and 0.37 μm2/h at T = 217 °C, so that very deep guides can be formed in short times. Diffusion is somewhat slower in the z direction. The process as described is not useful for y‐cut crystals, since it damgaes this surface. Losses, measured on x‐cut samples, were <0.5 dB/cm. All measurements were made at 0.633 μm.

Stabilization of methyl anions by first‐row substituents. The superiority of diffuse function‐augmented basis sets for anion calculations

Abstract: The entire set of methyl anions, XCH 2 - , substituted by first-row substituents, Li, BeH, BH 2 , CH 3 , NH 2 , OH, and F, was examined at various ab initio levels. Diffuse orbital-augmented basis sets, such as 4-31+G and 6-31+G ∗ , are needed to describe the energies of these anions adequately. Estimates of proton affinities are further improved by second-order Moller-Plesset (MP2) electron correlation corrections, but relative energies are less affected. The methyl group in the ethyl anion is destabilizing, the amino substituent is borderline, but all other groups are stabilizing. Very large π effects are exhibited by BH 2 and BeH groups; inductive stabilization by the electronegative F and OH groups is less effective. Lithium also is stabilizing, but the best singlet geometry of CH 2 Li - is not planar. A planar CH 2 Li - triplet with a π 1 configuration may be lower in energy.

The Role of the Big Flare Syndrome in Correlations of Solar Energetic Proton Fluxes and Associated Microwave Burst Parameters

Abstract: : In previous studies correlating E 10 MeV proton fluxes and spectra with various associated microwave burst parameters, the resulting high correlations were assumed to reflect a common acceleration process for the protons and the microwave-emitting electrons. We suggest and test an alternative explanation for these correlations, which we term the Big Flare Syndrome (BFS), that states that, statistically, energetic flare phenomena are more intense in larger flares, regardless of the detailed physics. Peak 1-8 A X-ray fluxes, characteristic of the thermal flare, are correlated with peak proton fluxes to derive correlation coefficients characteristics of the BFS. Of all microwave parameters tested for the 1973-1979 period, only the time-integrated flux densities at 8800 and 15400 MHz may be significantly larger than expected form the BFS. We fail to confirm previous results associating peak proton spectra with peak microwave spectral characteristics, thus finding no evidence that peak microwave fluxes are indicative of proton acceleration. We extend this conclusion to peak hard X-ray correlations. The strongly nonlinear relationship deduced between flare energy and proton production also appears invalid. (Author)

Proton radioactivity of 151 Lu

Abstract: A (1231±3) keV proton activity has been observed in the fusion reaction58Ni +96Ru→154Hf*. The production cross section peaks at 50 MeV of excitation energy with a value of about 70 μb. No coincidences with annihilation radiation or withK X-rays could be observed. The activity is assigned to direct proton decay of the new isotope151Lu. The measured half life is (85±10) ms.

Measurement of Elastic Electron-Neutron Cross Sections up to Q 2 =10 (GeV/c) 2

Abstract: The elastic electron-neutron cross sections were measured at values of the square of four-momentum transfer (Q/sup 2/) of 2.5, 4.0, 6.0, 8.0, and 10.0 (GeV/c)/sup 2/ using a deuterium target and detecting the scattered electrons at 10/sup 0/. The ratio of neutron to proton elastic cross sections decreases with Q/sup 2/. At high Q/sup 2/ this trend is inconsistent with the dipole law, form-factor scaling, and many vector dominance models, although it is consistent with some parton models.

Injection onsets of 2 GeV protons, 1 MeV electrons, and 100 keV electrons in solar cosmic ray flares

Abstract: We review the data for all 32 ground-level cosmic-ray events (GLEs) observed from 1942 through 1978 and infer injection onset times for the approx.2 GeV protons, approx.1 MeV electrons, and approx.100 keV electrons. Contrary to previous investigations, we find no compelling evidence for a systematic delay in GLE onset times. The most likely time of GeV proton injection onset in these large flares appears to be near the maximum of the first significant microwave peak. We note that GLEs with long delays to onset tend to be small in size. In addition, the data indicate a systematic phase relationship among the injection onsets of the three particle species considered, with the low-energy electron onset times proceding those of the relativistic protons by or approx. =5 min. This phase relationship holds even when the inferred injection times of all three species follow the flare flash phase by >20 min. To account for these observations, we suggest a picture in which the earliest observed particles are injected when an outward moving acceleration region at a shock front intersects the open field lines connecting to Earth.

Determination of the Rotational Correlation Time of Water by Proton NMR Relaxation in H217O and Some Related Results

Abstract: Analysis of the 1H-17O dipolar contribution to the proton longitudinal relaxation rate in 17O-enriched water yields a correlation time for re-orientation of the O–H vector τrOH = (1.71 ± 0.07) ps in H2O at 25 °C. This result is insensitive to uncertainties in the calculated intermolecular relaxation contribution. From 1H, D, and 17O relaxation rates in H2O/D2O mixtures deuterium isotope effects on the correlation times were estimated. The quadrupole coupling constants of D and 17O in liquid water were determined.

Energetic protons accelerated at corotating shocks: Pioneer 10 and 11 observations from 1 to 6 AU

Abstract: Vector helium magnetometer and proton telescope data are used to examine the relationship between low energy proton increases and corotating interaction regions (CIRs). A general correlation is noted between the maximum CIR field intensity and the maximum proton count rate. The minimum proton flux, located between the two proton maxima, appears to be correlated with the maximum field strength of the CIR. The evidence presented strongly supports shock acceleration as the primary source of the 1-MeV protons. A schematic figure incorporating many of the features deduced in the present study is given to illustrate the relationship between energetic protons, forward and reverse shocks, and the interplanetary magnetic field structure. The predictions of various theories and mechanisms for interplanetary nucleon acceleration are discussed in light of the experimental results presented.

The rotational spectrum and molecular structure of the ethylene–HF complex

Abstract: The microwave spectrum of the ethylene–HF complex in the ground vibrational state has been assigned using a Fourier transform microwave spectrometer, employing a Fabry–Perot cavity and a pulsed supersonic nozzle as a molecular source. Ethylene–HF is nonplanar, with the axis of the HF subunit oriented perpendicular to the plane of the ethylene molecule, and bisecting the carbon–carbon double bond. A hydrogen bond is formed between the HF proton and the π‐electron density of ethylene. The spectroscopic constants of ethylene–HF and ethylene–DF are:

Direct and beta-delayed proton decay of very neutron-deficient rare-earth isotopes produced in the reaction 58 Ni+ 92 Mo

Abstract: Using on-line mass separation of evaporation residues from the reaction58Ni +92Mo→150Yb*, a proton line of 1,055±6 keV energy and 0.42±0.10 s half-life was observed at mass number 147. The origin of this activity is very likely the direct proton decay of147Tm. Beta-delayed protons registered at the same mass position show a pronounced peak structure in their energy distribution. A lower limit of their half-life was set to 1 s.

Proton-sulfate co-transport: mechanism of H+ and sulfate addition to the chloride transporter of human red blood cells.

Abstract: Proton and sulfate inhibition of the obligatory chloride-chloride exchange of human erythrocytes was measured at 0 degrees C to determine their mechanism of reaction with the anion transporter. The proton and sulfate that are co-transported by this mechanism at higher temperatures behaved as nontransported inhibitors at 0 degrees C. We analyzed the data in terms of four molecular mechanisms: (1) HSO4- addition to the transporter; (2) ordered addition with the proton first; (3) ordered addition with the sulfate first; (4) random addition to the transporter. The Dixon plots of 1/MCl vs. [SO4] at different proton concentrations were not parallel. Thus protons and sulfate ions were not mutually exclusive inhibitors. The slope of these Dixon plots was independent of pH above 7.0, which indicates that sulfate could bind to the unprotonated carrier and excludes the first two mechanisms. Protons were inhibitors of chloride flux in the absence of sulfate, which indicates that protons could bind to the unloaded carrier and excludes mechanism 3. The KI for sulfate was 4.35 +/0 0.36 mM. The pK for the protonatable group was 5.03 +/- 0.02. The binding of either a proton or sulfate to the carrier decreased the KI of the other by ninefold. The only simple mechanism consistent with the data is a random-ordered mechanism with more transporters loaded with a sulfate than loaded with a proton at the pH and sulfate concentrations of plasma.

Energetic protons, alpha particles, and electrons in magnetic flux transfer events

Abstract: Energetic proton, alpha particle, and electron data are presented for two magnetopause crossings, which show magnetic field signatures characteristic of flux transfer events (FTEs). Energetic proton and alpha particles are observed streaming along the magnetic field within the magnetosheath in all events showing magnetic signatures characteristic of the FTEs. Flux ratios as high as about 180 parallel and antiparallel to the magnetic field are observed, which means that ions of about 30 keV per charge are at times streaming almost scatter-free from the magnetopause into the magnetosheath. Energetic ion bursts with signatures equal to those observed in FTEs are reduced by more than an order of magnitude as compared to the trapped particle flux.

Transport theoretic solutions for auroral proton and H atom fluxes and related quantities

Abstract: In this paper we show that linear transport theory may be used to solve for the auroral proton and H atom fluxes in plane-parallel geometry in the forward scattering and average discrete energy loss approximations. In this approximation, inelastic scattering is taken into account, but elastic scattering drops out and the solutions are approximations to the fluxes in the downward hemisphere. Using the multiple scattering method, we obtain the particle fluxes are finite sums of anlaytic functions of altitude, energy, and pitch angle. Closed form expressions are also found for the hemispherically averaged fluxes and the energy deposition and ionization rates. The notion of pseudoparticles is discussed and used to approximate the sums that occur in the above formulae. Results are presented for incident isotropic-Maxwellian proton fluxes.

The solitonic mechanism for proton transport in a hydrogen bonded chain

Abstract: We find that the proton transfer in a hydrogen bonded chain subjected to the appropriate electrostatic field behaves as a soliton. The energy of soliton and the rate constant for this proton transfer process are calculated by transition state theory. We obtain the results that the energy of soliton is considerably small compared with the band gap of the polypeptide chain and the rate constant is quite large which is enough to reveal the biological function. With these results, a few biological significances are discussed.

Primary kinetic HH/HD/DH/DD isotope effects and proton tunnelling in double proton-transfer reactions

Abstract: Double proton-transfer reactions are characterized by three primary kinetic H/D isotope effects (k.i.e.) involving a set of rate constants kHH, kHD, kDH and kDD. We have succeeded in measuring such sets for well defined symmetrical double proton-transfer reactions where kHD=kDH for the intramolecular hydrogen migration in meso-tetraphenylporphine (TPP) and for the intermolecular 1 : 1 proton exchange between acetic acid and methanol dissolved in tetrahydrofuran. In this system we also detected a triple proton transfer involving one methanol and two acetic acid molecules. Rate constants kHHH, kHHD, kHDD and kDDD of this reaction are reported. Additionally, we also observed an intramolecular double proton-transfer reaction in 2,5-dianilino-benzoquinone- 1,4-dianil (azophenine, AP) for which we have measured the HH/HD k.i.e. For the determination of rate constants dynamic n.m.r. spectroscopy was used.The predictions of the fractionation-factor theory, transition-state theory and different proton-tunnelling theories on the HH/HD/DH/DD k.i.e. of symmetrical double proton-transfer reactions are discussed with special emphasis on the rule of the geometric mean and compared with the experiments. The kinetic and the i.r. results for TPP and AP are well reproduced by the vibrational model of tunnelling as proposed previously by us. TPP is, therefore, the first proton-transfer system with NH-stretching levels not broadened by hydrogen-bond effects. The k.i.e. of the intermolecular proton exchange in the system acetic acid + methanol + tetrahydrofuran are consistent with tunnelling from the OH-stretching ground states. The energy of activation is associated with the enthalpy of formation of the cyclic complex in which the exchange takes place and the excited intermolecular vibrational states within this complex. The tunnelling theories are modified in order to take this enthalpy into account.