Monte-Carlo simulation of hydrogen-atom recombination

1973 ◽  
Vol 333 (1595) ◽  
pp. 419-434 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Cross Section ◽  
Rate Constant ◽  
Relative Velocity ◽  
Classical Trajectory ◽  
Hydrogen Atoms ◽  
Order Of Magnitude ◽  
The Cross ◽  
The Right ◽  
Right Order

Classical trajectory calculations have been used to calculate the cross-section (and hence the rate constant) for the recombination of hydrogen atoms on a third hydrogen atom, in the temperature range 500–6000 K. The model involves the stabilization of a quasi-bound molecule in an encounter with the third atom. The results indicate that the cross-section for direct stabilization is small and insensitive to the relative velocity, whereas the cross-section for exchange stabilization is large at low velocities and decreases rapidly as the relative velocity is increased. The calculated rate constant, although of the right order of magnitude at 500 K, does not exhibit the anomalous features previously observed experimentally at higher temperatures.

Nucleon-Nucleon Scattering Calculations in a Pole Regularized Spinor Theory

1974 ◽  
Vol 29 (7) ◽  
pp. 981-990
Author(s):  
K. Dammeier
Keyword(s):  
Quantum Theory ◽  
Cross Section ◽  
Test Object ◽  
Nucleon Nucleon ◽  
Coupling Constant ◽  
Nonlinear Spinor ◽  
Spinor Theory ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

A pole regularized nonlinear spinor theory may be a suitable test object to compare scattering calculations of Stumpf's functional quantum theory with LSZ-results. To apply the LSZ-technique in this theory, a dressing of the occurring massless Green's function is necessary. It is shown which special approximations allow for this dressing. The renormalized nucleon-nucleon coupling constant yields the right order of magnitude for the elastic nucleon cross section.

Longitudinal oscillation of a rod with a variable cross section

2019 ◽  
Vol 14 (2) ◽  
pp. 138-141
Author(s):  
I.M. Utyashev
Keyword(s):  
Cross Section ◽  
Natural Frequencies ◽  
Liouville Problem ◽  
Variable Cross Section ◽  
Variable Cross ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Independent Functions ◽  
The Cross ◽  
The Right

Variable cross-section rods are used in many parts and mechanisms. For example, conical rods are widely used in percussion mechanisms. The strength of such parts directly depends on the natural frequencies of longitudinal vibrations. The paper presents a method that allows numerically finding the natural frequencies of longitudinal vibrations of an elastic rod with a variable cross section. This method is based on representing the cross-sectional area as an exponential function of a polynomial of degree n. Based on this idea, it was possible to formulate the Sturm-Liouville problem with boundary conditions of the third kind. The linearly independent functions of the general solution have the form of a power series in the variables x and λ, as a result of which the order of the characteristic equation depends on the choice of the number of terms in the series. The presented approach differs from the works of other authors both in the formulation and in the solution method. In the work, a rod with a rigidly fixed left end is considered, fixing on the right end can be either free, or elastic or rigid. The first three natural frequencies for various cross-sectional profiles are given. From the analysis of the numerical results it follows that in a rigidly fixed rod with thinning in the middle part, the first natural frequency is noticeably higher than that of a conical rod. It is shown that with an increase in the rigidity of fixation at the right end, the natural frequencies increase for all cross section profiles. The results of the study can be used to solve inverse problems of restoring the cross-sectional profile from a finite set of natural frequencies.

ISOSPIN DECOMPOSITION OF pp → NNππ CROSS SECTIONS — DO WE SEE A SIGN OF Δ(1600) EXCITATION IN THE nnπ+π+ CHANNEL?

2009 ◽  
Vol 24 (02n03) ◽  
pp. 450-453
Author(s):  
◽  
T. SKORODKO ◽  
M. BASHKANOV ◽  
D. BOGOSLOWSKY ◽  
H. CALÉN ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Pion Production ◽  
Significant Contribution ◽  
Differential Cross Sections ◽  
Pp Collisions ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
The Cross

The two-pion production in pp-collisions has been investigated in exclusive measurements from threshold up to Tp = 1.36 GeV . Total and differential cross sections have been obtained for the channels pnπ+π0, ppπ+π-, ppπ0π0 and also nnπ+π+. For intermediate incident energies Tp > 1 GeV , i.e. in the region, which is beyond the Roper excitation but at the onset of ΔΔ excitation the total ppπ0π0 cross section falls behind theoretical predictions by as much as an order of magnitude near 1.2 GeV, whereas the nnπ+π+ cross section is a factor of five larger than predicted. A model-unconstrained isospin decompostion of the cross section points to a significant contribution of an isospin 3/2 resonance other than the Δ(1232). As a possible candidate the Δ(1600) is discussed.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

scholarly journals Berechnung der Oberfläche von Kernmaterie mit Hilfe spezieller Einteilchen-Wellenfunktionen

1962 ◽  
Vol 17 (8) ◽  
pp. 640-649
Author(s):  
Franz Lanzl
Keyword(s):  
Surface Energy ◽  
Plane Waves ◽  
Yukawa Interaction ◽  
Range Interaction ◽  
Zero Range ◽  
Volume Energy ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order ◽  
Surface Thickness

Using a YUKAWA interaction between the nucleons the volume energy per particle and the specific surface energy are calculated. These expressions assume a very simple form for a zero range interaction. The space parts of the applied orthogonal single particle wave functions are products of plane waves and a momentum independent function which brings about the decrease in density within the surface layer. First the volume energy per particle as a function of the density in the interior of nuclear matter is minimized. The interaction parameters are so selected that the values of the volume energy per particle and the density at the minimum agree with the experimental data. Then the surface energy as a function of the surface thickness is minimized. The values of the surface energy and the surface thickness in the minimum are compared with the empirical data. They are found to be of the right order of magnitude

scholarly journals Generation of Coronal Currents by the Solar Convection Zone

2001 ◽  
Vol 18 (4) ◽  
pp. 329-335 ◽  
Author(s):  
D. J. Galloway ◽  
Y. Uchida ◽  
N. O. Weiss
Keyword(s):  
Convection Zone ◽  
Energy State ◽  
Minimum Energy ◽  
Solar Convection Zone ◽  
Solar Convection ◽  
Poynting Flux ◽  
Available Energy ◽  
Order Of Magnitude ◽  
The Right ◽  
Right Order

AbstractSolar flares are thought to be caused by reconnection of magnetic fields and their associated electric currents in the solar corona. The currents have to be there to provide available energy over and above the current-free minimum energy state, but what generates them has been little discussed. This paper investigates the idea that twisting motions in the turbulent convection zone below may provide a natural source for the currents and explain some of their properties. The twists generate upward-propagating Alfvén waves with a Poynting flux of the right order of magnitude to power a flare. Depending on the depth it takes place, the twisting event that initiates a particular flare may occur hours, days or even months before the flare itself.

Importance of coupling for inelastic collisions between protons and hydrogen atoms

1965 ◽  
Vol 283 (1392) ◽  
pp. 100-114 ◽  
Keyword(s):  
Cross Sections ◽  
Intermediate State ◽  
Relative Velocity ◽  
Inelastic Collisions ◽  
Hydrogen Atoms ◽  
Resonance Reactions ◽  
The Cross ◽  
Good Agreement

The importance of coupling for fast collisions between protons and hydrogen atoms is examined with the two-centred expansion in atomic eigenfunctions proposed by Bates (1958 a ). Cross-sections are evaluated for reactions H + + H (I s ) → H(I s ) + H + , H + + H( I s ) → H(2 s ) + H + , and H + + H(l a ) → H + + H(2 s ). The effect of a single intermediate state, either I s or 2 s , is considered. For the non-resonance processes, it is found that the cross-sections may be substantially increased by passage through intermediate state for incident energies less than about 10 keV, tending towards equality with decrease in relative velocity. Results obtained for the symmetrical resonance reactions are in good agreement with the two-state solutions of McCarroll (1961).

Static and Dynamic Analysis of Aircraft Structures by Component-Wise Approach

2013 ◽  
Author(s):  
E. Carrera ◽  
A. Pagani ◽  
M. Petrolo
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Aircraft Structures ◽  
Static And Dynamic Analysis ◽  
Computational Costs ◽  
Commercial Code ◽  
Wing Structures ◽  
Order Of Magnitude ◽  
The Cross ◽  
Beam Theories

This paper proposes an advanced approach to the analysis of reinforced-shell aircraft structures. This approach, denoted as Component-Wise (CW), is developed by using the Carrera Unified Formulation (CUF). CUF is a hierarchical formulation allowing for the straightforward implementation of any-order one-dimensional (1D) beam theories. Lagrange-like polynomials are used to discretize the displacement field on the cross-section of each component of the structure. Depending on the geometrical and material characteristics of the component, the capabilities of the model can be enhanced and the computational costs can be kept low through smart discretization strategies. The global mathematical model of complex structures (e.g. wings or fuselages) is obtained by assembling each component model at the cross-section level. Next, a classical 1D finite element (FE) formulation is used to develop numerical applications. It is shown that MSC/PATRAN can be used as pre- and post-processor for the CW models, whereas MSC/NASTRAN DMAP alters can be used to solve both static and dynamic problems. A number of typical aeronautical structures are analyzed and CW results are compared to classical beam theories (Euler-Bernoulli and Timoshenko), refined models and classical solid/shell FE solutions from the commercial code MSC/NASTRAN. The results highlight the enhanced capabilities of the proposed formulation. In fact, the CW approach is clearly the natural tool to analyze wing structures, since it leads to results that can be only obtained through three-dimensional elasticity (solid) elements whose computational costs are at least one-order of magnitude higher than CW models.

The reaction of hydrogen atoms with ethylene

1970 ◽  
Vol 316 (1527) ◽  
pp. 575-591 ◽  
Keyword(s):  
Hydrogen Atom ◽  
Rate Constant ◽  
Recombination Reaction ◽  
Methyl Radicals ◽  
Methyl Radical ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Cracking Reaction ◽  
Computer Calculations ◽  
First Time

A detailed study has been made of the products from the reaction between hydrogen atoms and ethylene in a discharge-flow system at 290 ± 3 K. Total pressures in the range 8 to 16 Torr (1100 to 2200 Nm -2 ) of argon were used and the hydrogen atom and ethylene flow rates were in the ranges 5 to 10 and 0 to 20 μ mol s -1 , respectively. In agreement with previous work, the main products are methane and ethane ( ~ 95%) together with small amounts of propane and n -butane, measurements of which are reported for the first time. A detailed mechanism leading to formation of all the products is proposed. It is shown that the predominant source of ethane is the recombination of two methyl radicals, the rate of recombination of a hydrogen atom with an ethyl radical being negligible in comparison with the alternative, cracking reaction which produces two methyl radicals. A set of rate constants for the elementary steps in this mechanism has been derived with the aid of computer calculations, which gives an excellent fit with the experimental results. In this set, the values of the rate constant for the addition of a hydrogen atom to ethylene are at the low end of the range of previously measured values but are shown to lead to a more reasonable value for the rate constant of the cracking reaction of a hydrogen atom with an ethyl radical. It is shown that the recombination reaction of a hydrogen atom with a methyl radical, the source of methane, is close to its third-order region.

New Results on Double Charmonium Production in e+e- Annihilation at $\sqrt{s} \approx 10.6~{\rm GeV}$ with the Belle Detector

2005 ◽  
Vol 20 (16) ◽  
pp. 3617-3620
Author(s):  
◽  
T. Ziegler
Keyword(s):  
Cross Section ◽  
Strong Evidence ◽  
Previous Analysis ◽  
Charmonium State ◽  
Data Set ◽  
Charmonium Production ◽  
Belle Detector ◽  
Theoretical Predictions ◽  
Order Of Magnitude ◽  
The Cross

Extending a previous analysis1 the double charmonium production [Formula: see text] and [Formula: see text] has been investigated with a data set of 155 fb-1 with the Belle detector. Theoretical predictions for the cross section are one order of magnitude lower than the measured value and this discrepancy is still not understood. In a very recent update with a dataset of 285 fb-1 strong evidence for a new charmonium state at a mass of 3.940 GeV was found.

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