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Consistent field Monte Carlo method calculation for collision effect on electron-ion diode characteristics and for hard sphere electron- neutral collision effect for monoenergetic- thermionic emission
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Here, the dynamics of dissociative electron attachment to ethanol is experimentally investigated at the Feshbach resonance formed with incident electron energies near 9.5 eV. Highly differential laboratory-frame momentum distributions of OH – fragments are measured for a series of energies spanning the resonance width, using the velocity-map-imaging technique. The OH – kinetic-energy distribution indicates that the C-O breaking dissociation process could either be a three-body dissociation or a two-body dissociation with significant rovibrational excited fragments. The small, but significant, anisotropy in the OH – angular distribution provides signatures of the molecular symmetry of the associated resonant state under the axial recoil approximation, which assumes the dissociation is much faster than any rotation of the dissociation axis. Within these assumptions, the 9.5-eV Feshbach resonance can be assigned to the electronic transition from the ($10a'$) orbital with its ground-state C s symmetry to the empty ($4a''$) level, involving the simultaneous electron attachment. This dynamics could be a model for C-O dissociation in larger alcohols and ethers.
Thermal escape of neutral hydrogen and distribution in Earth thermosphere, noting collision in transition regions
Low collision energy charge transfer and dissociative charge transfer between rare gas ions and molecular nitrogen, measuring nitrogen ion kinetic energy distributions
First collision Monte Carlo method for calculating aerodynamic drag on hard sphere and Maxwell molecular models in near-free molecular flow
Diatomic Br molecular vibration-rotation coupling effects on energy transfer during Br-Ar collisions, determining probability distributions
Time-of-flight measurements for relationship between velocity, mass and temperature in molecular gas motion and electron-atom collision kinematics
One-dimensional systems, such as nanowires or electrons moving along strong magnetic field lines, have peculiar thermalization physics. The binary collision of pointlike particles, typically the dominant process for reaching thermal equilibrium in higher-dimensional systems, cannot thermalize a 1D system. We study how dilute classical 1D gases thermalize through three-body collisions. We consider a system of identical classical point particles with pairwise repulsive inverse power-law potential V ij ∝ 1/|x i –x j | n or the pairwise Lennard-Jones potential. Using Monte Carlo methods, we compute a collision kernel and use it in the Boltzmann equation to evolve a perturbed thermal state with temperature T toward equilibrium. We explain the shape of the kernel and its dependence on the system parameters. Additionally, we implement molecular dynamics simulations of a many-body gas and show agreement with the Boltzmann evolution in the low-density limit. For the inverse power-law potential, the rate of thermalization is proportional to ρ 2 T$\frac{1}{2}$ – $\frac{1}{n}$, where ρ is the number density. Furthermore, the corresponding proportionality constant decreases with increasing n.
CO observations of nearby galaxies with nuclear active star forming regions (and starburst galaxies) with angular resolutions around 7 seconds revealed that molecular bars with a length of a few kiloparsecs have been formed in the central regions of the galaxies. The molecular bar is interpreted as part of shock waves induced by an oval or barred potential field. By shock dissipation or dissipative cloud-cloud collisions, the molecular gas gains an infall motion and the nuclear star formation activity is fueled. But the distribution and kinematics of the molecular gas in the nuclear regions, which are sites of active star formation, remain unknown. Higher angular resolutions are needed to investigate the gas in the nuclear regions. Researchers made aperture synthesis observations of the nuclear region of the late-type spiral galaxies NGC 6946 and IC 342 with resolutions of 7.6 seconds x 4.2 seconds (P.A. = 147 deg) and 2.4 seconds x 2.3 seconds (P.A. = 149 deg), respectively. The distances to NGC 6496 and IC 342 are assumed to be 5.5 Mpc and 3.9 Mpc, respectively. Researchers have found 100-300 pc nuclear gas disk and ring inside a few kpc molecular gas bars. Researchers present the results of the observations and propose a possible mechanism of active star formation in the nuclear region.
Particle-in-cell, direct simulation Monte Carlo simulations reveal that ion-acoustic instabilities excited in presheaths can cause significant ion heating. Ion-acoustic instabilities are excited by the ion flow toward a sheath when the neutral gas pressure is small enough and the electron temperature is large enough. A series of 1D simulations were conducted in which neutral plasma (electrons and ions) was uniformly sourced with an ion temperature of 0.026 eV and different electron temperatures (0.1 eV–50 eV). Ion heating was observed when the electron-to-ion temperature ratio exceeded the minimum value predicted by linear response theory to excite ion-acoustic instabilities at the sheath edge (T e /T i ≈ 28). When this threshold was exceeded, the temperature equilibration rate between ions and electrons rapidly increased near the sheath so that the local temperature ratio did not significantly exceed the threshold for instability. This resulted in significant ion heating near the sheath edge, which also extended back into the bulk plasma; presumably due to wave reflection from the sheath. Furthermore, this ion-acoustic wave heating mechanism was found to decrease for higher neutral pressures, where ion-neutral collisions damp the ion-acoustic waves and ion heating is instead dominated by inelastic collisions in the presheath.
Numerical integration calculation of collision integrals for exponential attractive potential of gases
Numerical values describing molecular rainbow scattering in Airy approximation for 12-6 potential
Transition probabilities of nitrogen-nitrogen collision obtained with time-dependent wave functions of forced harmonic oscillator and by numerical methods
Collisions in inner region of cometary head, structure of emission bands and formation of free radicals
Vibrational energy transfer in high energy collisions of diatomic nitrogen, evaluating transition probabilities for forced harmonic oscillator
Collision-induced transitions can significantly affect molecular vibrational-rotational populations and energy transfer in atmospheres and gaseous systems. This, in turn. can strongly influence convective heat transfer through dissociation and recombination of diatomics. and radiative heat transfer due to strong vibrational coupling. It is necessary to know state-to-state rates to predict engine performance and aerothermodynamic behavior of hypersonic flows, to analyze diagnostic radiative data obtained from experimental test facilities, and to design heat shields and other thermal protective systems. Furthermore, transfer rates between vibrational and translational modes can strongly influence energy flow in various 'disturbed' environments, particularly where the vibrational and translational temperatures are not equilibrated.
The semi-classical molecular convergent close-coupling approach has been applied to proton collisions with molecular hydrogen in the ground electronic and vibrational state. Cross sections for electron loss and electron capture agree well with the experimental data in the intermediate energy range where coupling between electronic reaction channels is strong and previously available calculations produce inconsistent results. Results for elastic scattering and total excitation are compared with effective one-electron coupled-channel calculations, showing that accurate target structure makes an important difference to these cross sections at intermediate energies. The excitation cross sections are calculated using both the fixed-nuclei and adiabatic-nuclei approximations for transitions from the $X^1Σ^+_{\textrm{g}}$ state to the $B^1Σ^+_{\textrm{u}}$, $B'$$^1Σ^+_{\textrm{u}}$, $B''$$^1Σ^+_{\textrm{u}}$, $EF$$^1Σ^+_{\textrm{g}}$, $GK$$^1Σ^+_{\textrm{g}}$, $H$$^1Σ^+_{\textrm{g}}$, $C$$^1Π_{\textrm{u}}$, $D$$^1Π_{\textrm{u}}$, $D'$$^1Π_{\textrm{u}}$, $I$$^1Π_{\textrm{u}}$, and $J$$^1Δ_{\textrm{g}}$ states for proton energies from to keV. We find significant differences between the present ab initio calculations and the equivelocity scaled electron-scattering data that is currently used for collisional-radiative modelling. Furthermore, the adiabatic-nuclei calculations enable us to resolve the final vibrational level after excitation, producing a complete set of cross sections for excitation of ground-state molecular hydrogen for all electronic states up to $n = 3$, where $n$ is the united-atoms-limit principle quantum number.