Various Types Of Collisions Research Articles

On the calculation of pressure-broadened linewidths for symmetric-top molecules using the modified Anderson theory

An approximation, accurate to better than 0.5%, to the Anderson-Tsao-Curnutte theory of linewidth is presented. This approximation is shown to be suitable for calculating linewidths of symmetric top molecules where dipole-dipole forces are dominant, but higher-order multipole terms are not negligible. Some insight is gained as to the relative importance of various types of collisions between interacting molecules from this approach to the calculation of the spectral linewidths for rotational states of molecules. Experimental results for CH 3 35Cl and CH 3 127I are presented for comparison with the calculated results.

Subduction zones: An introduction to comparative subductology

Abstract The subduction model for trench-arc-back arc systems was deduced more or less as a logical consequence of sea-floor spreading. Many features in these systems, such as thrust-type inter-plate earthquakes and deep earthquakes along Wadati-Benioff zones, are readily explained by the subduction model. But, other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain. An approach to solve these problems may be to recognize the existence of the two basically different modes of subduction: one Chilean-type — causing a compressional stress regime in the arc and back arc regions; the other — Mariana-type — causing a tensional stress regime. Implications of the two types of the mode of subduction for some tectonic problems, such as vertical movement and sediment accretion at trenches are discussed, with special reference to the results of recent DSDP active margin drilling. In discussing the possible causes of the two modes, it is suggested that the large-scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction, but of some additional factors involving much greater energy, such as mantle flow associated with the motion of major plates. Finally, the possible great importance of various types of collision, accretion and erosion at subduction zones is emphasized.

A Monte-Carlo calculation of the secondary electron emission of normal metals: I. The model

A model is proposed to describe the secondary electron emission (SEE) of pure normal metals. The various types of collisions suffered by an electron travelling in the solid are analyzed. The dielectric theory is used to account for the collisions with the jellium, including surface effects in an approximate way. The different damping mechanisms for plasmons are reviewed and their influence on SEE is emphasized. The elastic and ionizing collisions with the ionic cores are described by a randium model. The relative importance of each of the above processes for the SEE of normal metals is discussed.

Chemiluminescence in reactions of N+ ions with hydrogen and hydrocarbons. II. Dependence of total reaction cross sections on the collision energy

Chemiluminescent reactions between N+ ions and H2 as well as some hydrocarbons were studied up to ∼450 eVCM collision energy. Emission from NH(A 3Π) and, with hydrocarbons, from CH(A, B, and C) as well as from C and H atoms was observed. Except in the H2 case, the formation of NH(A) in a bimolecular exchange reaction occurs up to 150 eVCM. Below 20 eVCM this reaction appears to proceed by direct interaction between the N+ projectile and an H atom, while at high energies the primary interaction is between N+ and a C atom. The approximately exponential falloff of the cross section for NH(A) formation above 50 eVCM was explained in the case of CH4 using a soft-sphere collision model. A hard-sphere model was used in an attempt to explain the measured ratio of the N++C2H4 and N++CH4 cross sections. Computer trajectory studies revealed the relative importance of various types of collision and led to semiquantitative agreement with experiment.

Acoustical Studies. II. The Behavior of a Gas with Several Independent Internal Energy States

The method founded by Einstein for the description of the acoustical behavior of a dissociating gas has been extended to cover a nondissociating gas in which five groups of internal energy states have different relaxation times. Since the resulting expressions are unwieldly, approximations based on them, which permit the rough description of experiment, have been given. The study of the variation of the velocity of sound with frequency demonstrates differences in the relaxation times of the various states. The variation of the velocity of sound with pressure shows in addition effects due to three-body collisions or to radiation from optically active states. It has been suggested to treat the temperature coefficient of the kinetic relaxation time by the introduction of an expirical quantity which may be called ``the activation energy of collision.'' By this means a rough kinetic analysis of the transition probability is possible. In gaseous mixtures, the relative spatial and energetic effectiveness of various types of collisions in exciting internal energy may be compared.

Collisions Between Electrons and Gas Molecules

Using a simple method in which positive ion sheaths serve as perfect grids we have obtained data on the probability of various types of collisions occurring between Hg, ${\mathrm{H}}_{2}$, ${\mathrm{N}}_{2}$, He, Ne and A molecules and electrons of moderate velocity, i.e., 30-250 volts. A theory has been developed and the mean angular deflection for elastic and inelastic collisions between electrons and gas molecules has been calculated. Evidence on the mechanism of ionization is presented. The current densities of the various Maxwellian groups of electrons and the average temperatures of these groups are calculated from the data and are shown to be in good agreement with data obtained by us using Langmuir and Mott Smith's probe wire method. The current density of positive ions has been measured by both plane and probe wire collectors and the space potential both measured and calculated. The evidence in support of negative anode drops has been pointed out and the ions flowing to the anode measured separately by means of a perforated collector. The maximum number of positive ions produced by an electron with a given velocity before losing its ionizing power has been measured and shown to be independent of current density and pressure being dependent only on the velocity of the electron and the nature of the gas.The mean free path of high velocity electrons (i.e., above the ionizing potential) for various types of collision can be evaluated from the probability data. The mean free path for inelastic impact has been calculated separately and independently of the reflection of electrons from the collectors. The small angular scattering of electrons is discussed in detail. Phenomena, similar to Langmuir's high speed electrons in mercury vapor, have been observed and the curves showing the energy transfer between primary electrons in ${\mathrm{H}}_{2}$ and A are given. The resonance and ionization potentials observed in the work are also tabulated.