Kinetic emission model

S Kinetic Emission Model The Kinetic Emission model proposed by Joyes (.loyes 1963, 1969a, 1969b) was developed to explain the yield trends exhibited by the positive multiply charged atomic ions from elements lighter than Phosphorus. This mechanism describes the formation of multiply charged ions as being formed as a result of the de-excitation of core holes present in the sputtered atomic/ionic populations, i.e. an auto-ionization process. 

The core holes responsible are believed to be formed as a result of sufficiently energetic atomic collisions occurring within the collision cascade. As a result, this should display a primary ion energy threshold as is indeed observed ( 900 eV for Ar impact on Aluminum surfaces). The threshold is present as the energy transfer from atoms/ions involved in collisions with electrons is an inefficient process. Also of note is the fact that collision threshold energy scales with the masses of the colliding partners. Indeed, those between the atoms of the same mass, otherwise referred to as symmetric collisions, yield the lowest threshold. Collisions between atoms of different masses are referred to as asymmetric collisions. This variation can be traced back to the fact that the efficiency of momentum transfer increases as the atomic masses approach each other (see Section 3.2.1.1 and relations contained within). 

Positive multiply charged atomic ions from elements heavier than Phosphorus appear to be formed via a collisional process active in the gas phase, i.e. at distances greater than 10 ran from the surface (van der Heide et al. 1993). This is realized through the observations that these emissions reveal energy-deficient populations in their respective energy distributions when collected under high-exiraction fields. 

---

In an attempt to simplify the foregoing discussions, only a select few models are covered. This starts, for historical reasons, with a brief overview of the Local Thermal Equilibrium model. This is covered in Section 3.3.2.I. The Bond Breaking model is then discussed in Section 3.3.2.2, followed by the Electron Tunneling model in Section 3.3.2.3. For completeness sake, the Kinetic Emission model is presented in Section 3.3.2.4 as this appears to be responsible for the production of multiply charged atomic ions from the elements hghter than Phosphoras. Although many other models have also been put forward, only these are covered as the latter three, in particular, represent those currendy accepted for the respective systems described. 

Kinetic emission model A model describing multiply charged atomic secondary ion emission... 

At this time a few comments about the model of Parilis et al. is appropriate. Their theory predicts that no kinetic emission can occur up to a certain threshold energy the yield then increases linearly with energy until at higher energy the slope again changes and the yield finally becomes linear with velocity. The majority of experimental results appear to confirm these trends suggesting that there is some truth in the basic assumptions. 

This illustrative study, using the new approach to CDPF emissions modelling, shows that PGM distribution can have a significant effect on emissions. In later work, with improved kinetics that more closely describe the real-world system performance, it has been shown that very great cost savings can be achieved by correctly zoning the CDPF (York et al., 2008). 

Sintering kinetics of model-suppoted catalysts are generally coielated by a GPLE of the form -d(D/Djj)/dt = kjCD/D -Dg /Dg) where m = 2. This result has important mechanistic implications since a number of fundamental processes such as emission of atoms frcnn crystallites, diffusion of adatoms on a support, collision of crystallites, w recmibination metal atoms may involve second-order processes. 

Balthasar M. and M. Frenklach (2005) Detailed kinetic soot modeling of soot aggregate formation in laminar premixed flames. Combustion and Flame 140, 130-145 Bange, H. W. (2006) The importance of oceanic nitrons oxide emissions. Atmospheric Environment 40, 198-199... 

The IIEC model was also used to study the importance of various design parameters. Variations in gas flow rates and channeling in the bed are not the important variables in a set of first-order kinetics. The location of the catalytic bed from the exhaust manifold is a very important variable when the bed is moved from the exhaust manifold location to a position below the passenger compartment, the CO emission averaged over the cycle rose from 0.14% to 0.29% while the maximum temperature encountered dropped from 1350 to 808°F. The other important variables discovered are the activation energy of the reactions, the density and heat... 

In this paper, we first briefly describe both the single-channel 1-D model and the more comprehensive 3-D model, with particular emphasis on the comparison of the features included and their capabilities/limitations. We then discuss some examples of model applications to illustrate how the monolith models can be used to provide guidance in emission control system design and implementation. This will be followed by brief discussion of future research needs and directions in catalytic converter modeling, including the development of elementary reaction step-based kinetic models. 

In Fig. 1, a comparison can be observed for the prediction by the honeycomb reactor model developed with the parameters directly obtained from the kinetic study over the packed-bed flow reactor [6] and from the extruded honeycomb reactor for the 10 and 100 CPSI honeycomb reactors. The model with both parameters well describes the performance of both reactors although the parameters estimated from the honeycomb reactor more closely predict the experiment data than the parameters estimated from the kinetic study over the packed-bed reactor. The model with the parameters from the packed-bed reactor predicts slightly higher conversion of NO and lower emission of NHj as the reaction temperature decreases. The discrepancy also varies with respect to the reactor space velocity. 

Ultrafast ESPT from the neutral form readily explains why excitation into the A and B bands of AvGFP leads to a similar green anionic fluorescence emission [84], Simplistic thermodynamic analysis, by way of the Forster cycle, indicates that the excited state protonation pK.J of the chromophore is lowered by about 9 units as compared to its ground state. However, because the green anionic emission is slightly different when it arises from excitation into band A or band B (Fig. 5) and because these differences are even more pronounced at low temperatures [81, 118], fluorescence after excitation of the neutral A state must occur from an intermediate anionic form I not exactly equivalent to B. State I is usually viewed as an excited anionic chromophore surrounded by an unrelaxed, neutral-like protein conformation. The kinetic and thermodynamic system formed by the respective ground and excited states of A, B, and I is sometimes called the three state model (Fig. 7). 

---