High velocity collision

Impaction (the direct, high-velocity collision force)... 

One very effective approach for partitioning the molecular Hamiltonian so as to simplify vibration-rotation interaction effects involves the use of classical rotational sudden approximations. These are primarily applicable to high-velocity collisions, and they have been applied quite effectively to the Li" + CO2 system.In... 

Each line iri an x-ray series thus has a common initial state and a different final state. (Note contrast with other spectra.) The initial state is characterized by a hole in an energy level. To create this hole, an electron is expelled by collision with a high-velocity electron in electron excitation, and by the absorption of a photon in x-ray excitation. The Einstein equivalence law must be satisfied in either of these elementary processes. 

Suslick KS, Doktyez SJ (1989) The sonochemistry of Zn powder. Am Chem Soc 111 2342-2344. Prfozorov T, Prozorov R, Suslick KS (2004) High velocity interparticle collisions driven by ultrasound. J Am Chem Soc 126 13890-13891... 

In the case of solid interfaces which are in the form of coarse powders, cavitation collapse can produce enough energy to cause fragmentation and activation through surface area increase. For very fine powders the partides are accelerated to high velocity by cavitational collapse and may collide to cause surface abrasion (Fig. 3.5). For some metal powders these collisions generate sufficient heat to cause particle fusion. 

The molecules of a dilule gas are sufficienlly far from each other so lhal each would execule free flighls with a very high velocity during periods between collisions. The mean velocity of a gaseous molecule is given by... 

High-Pressure Technique — The components of the formulation are pumped at high pressure (1500 to 3000 pounds/square inch) into an impingement mixer. As the name implies, the mixing is achieved by collisions of the ingredients at high velocity. 

Impacts and Explosives. The collision of high velocity bullets or other projectiles with solids causes rapid conversion of kinetic to thermal eneigy. Plasmas result incidentally, whereas the primary effects of impact are shock and mechanical effects in the target. Impact-produced plasmas are hot enough to cause thermonuclear bum (180). 

At high velocities, v/ve 1, these ion-atom collisions can be described by the Born approximation, and this description leads to a reasonable description of the observed Na nd —> ni results.4 For example, the results of Percival and Richards,4 shown in Fig. 13.3, are obtained by calculating the Born cross section for the nd — nf transition and using a sudden approximation to estimate the redistribution of population among the nearly degenerate higher angular momentum states. 

Fig. 4. Scanning electron micrograph of 5-Jim diameter Zn powder. Neck formation from localized melting is caused by high-velocity interparticle collisions. Similar micrographs and elemental composition maps (by Auger electron spectroscopy) of mixed metal collisions have also been made.

Fig. 5. The effect of ultrasonic irradiation on the surface morphology and particle size ofNi powder. Initial particle diameters (a) before ultrasound were 160 fim (b) after ultrasound, 80 fan. High velocity interparticle collisions caused by ultrasonic irradiation of slurries are responsible for the smoothing...

The constant motion and high velocities of gas particles lead to some important practical consequences. One such consequence is that gases mix rapidly when they come in contact. Take the stopper off a bottle of perfume, for instance, and the odor will spread rapidly through the room as perfume molecules mix with the molecules in the air. This mixing of different gases by random molecular motion with frequent collisions is called diffusion. A similar process in which gas molecules escape without collisions through a tiny hole into a vacuum is called effusion (Figure 9.13). 

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