Polyatomic gas

McCourt F R, Beenakker J, Kohler W E and Kijscer I 1990 Nonequilibrium Phenomena In Polyatomic Gases. 1. Dilute Gases (Oxford Clarendon)... 

For polyatomic gases in porous media, however, the relaxation rate commonly decreases as the pore size decreases [18-19]. Given that the relaxation mechanism is entirely different, this result is not surprising. If collision frequency determines the Ti, then in pores whose dimensions are in the order of the typical mean free path of a gas, the additional gas-wall collisions should drastically alter the T,. For typical laboratory conditions, an increase in pressure (or collision frequency) causes a proportional lengthening of T1 so the change in T, from additional wall collisions should be a good measure of pore size. 

R. L. Armstrong 1987, (Magnetic resonance relaxation effects in polyatomic gases), Magn. Reson. Rev. 12, 91-135. 

According to Jellinek s deductions the differences in degradation rate expected for the diatomic and polyatomic gases should be smaller. A consideration of Tab. 5.8 shows that this is not observed in practise, the polyatomics having considerably lower rates. In fact, unlike the diatomics, the degradation rates for polyatomics are quite dissimilar, the rates decreasing with increase in solubility. If however solubility... 

Up to the time that one of the authors first began this investigation, the interpretation of the data on ionization potentials of polyatomic gases ha d been almost wholly a matter of conjecture, since no attempts had been made to resolve the group of ions, produced by impact electrons of various velocities, into their constituent parts. It was with the object of interpreting these data that the present investigation was started, and, while the work was in progress, several annoimcements of experimentations similar to that conducted by the authors have appeared. 

Eq 8 immediately tells us that the degree of ionization depends strongly on the shock velocity U. For strong shocks p constant 0.9 (see Fig 6 of Ref 2) for all monoatomic or even polyatomic gases. Thus the only important shock parameter is U. Similarly the only important gas parameters are the molecular weight M and the first Ionization potential 1,... 

A kinetic theory for dilute polyatomic gases has been developed by Wang-Chang and Uhlenbeck (W3, U3). No calculations have been made of the diffusion coefficients on the basis of this theory, however. For most polyatomic gases the results of the Chapman-Enskog monatomic gas theory seem to be adequate. 

With increasing energy of the incident photons the photoionization process is accompanied by a rupture of valence bonds, leading to various ionized fragments, the identification of which requires complementary methods of analysis. During the last decade much progress has been achieved in the mass spectrometry of the photoionization products in various diatomic or polyatomic gases under vacuum u.v. irradiation. 

F. R. McCourt, J. Beenakker, W. E. Kohler, and I. Kuscer Nonequilibrium phenomena in polyatomic gases, Volume I... 

For polyatomic gases, with rotational and vibrational degrees of freedom, Eq. 3.138 is not sufficiently accurate. Quite a number of theories have been developed to predict thermal conductivity, given the viscosity. The earliest is due to A. Eucken (1913), which is a semiempirical theory developed to accommodate polyatomic gases ... 

It turns out to be a surprisingly difficult task to determine accurately the thermal conductivity of polyatomic gases from the viscosity. Many of the approaches are motivated by the ideas of Eucken. The so-called Eucken factor is a nondimensional group determined by dividing the kinetic-theory expression for a monatomic gas by that for viscosity, yielding... 

If fu = 2.5, then, for a monatomic gas where Ctr/Cv = 1 and there are no internal degrees of freedom, Eq. 3.140 is recovered. For polyatomic gases, Eucken chose Fintemal = 1. Ctr = 3R/2, and Cinternai = Cv — Ctr, which lead to the widely used Eucken correction ... 

Here the subscript oo represents a reference property at the inlet condition, which may be at the inlet manifold or the far-held value for semi-infinite situations. The simple power-law dependence follows from kinetic theory. Typically the temperature dependence for polyatomic gases is n 0.645 (Section 3.3). 

The amount of theoretical and experimental research focused on the interaction, equilibrium and dynamical properties of noble, simple and polyatomic gases within quasi-one-dimensional nanotubes is still limited [6-13]. Experimental adsorption isotherms have been reported for simple gases (Ar,N2) and alkanes (methane [11], ethane [12], propane-butane-pentane [13]) in monodisperse nanotubes of aluminophosphates. It is expected that similar experiment could be carried out soon in bundles of monodispersed carbon nanotubes. 

The choice of ambient gas will also have a major impact on sonochemical reactivity. Monatomic gases give much more heating than diatomic, which aie much bcttei than polyatomic gases (including solvent vapor). The choice of the solvent also has a profound influence on the observed sonochemistry. In addition to vapor pressure, other liquid properlies, such as surface tension and viscosity, will alter the threshold of cavitation. The chemical reactivity of the solvent is often much more important. No solvent is inert under the high temperature conditions of cavitation. 

Polyatomic gases desensitize more than monatomic or diatomic gases... 

In starting the discussion of polyatomic gases it may be well to state concisely some respects in which they may be expected to differ from monatomic and diatomic gases. 

Experimental observation of relaxation phenomena in binary mixtures of polyatomic gases affords much more information about vibration-vibration transfer. The nature of the vibrational relaxation process for a mixture of a relaxing gas, A, with a non-relaxing gas, B, has been discussed in Section 4.3. It involves two collision processes... 

Alternatively, when process (3) is slower than (4) or (5), but faster than (1) or (2), A will again relax by the route (3) followed by (4) or (5), but now (3) will be rate determining. This will give a linear variation of 1// A with x. B will relax independently, and more rapidly, via (4) and (3), with linear dependence of 1// B on x. There will thus be a double relaxation phenomenon with two relaxation times, PA involving only the vibrational heat capacity of A, and / B only that of B, both showing linear concentration dependence. This mechanism is analogous to the relaxation behaviour discussed in Section 3.1 for pure polyatomic gases, which show double dispersion because vibration-vibration transfer between modes is slower than vibration-translation transfer from the lowest mode. 

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