Collision impulsive

The impulse can be due to sudden collision with particles or to exposure to electromagnetic radiation. The physical significance of tire fonn factoi n r transitions in atomic hydrogen,... 

Michaels C A, Lin Z, Mullin A S, Tapalian H C and Flynn G W 1997 Translational and rotational excitation of the C02(00°0) vibrationless state in the collisional quenching of highly vibrationally excited perfluorobenzene evidence for impulsive collisions accompanied by large energy transfers J. Chem. Phys. 106 7055-71... 

An alternative method, proposed by Andersen [23], shows that the coupling to the heat bath is represented by stochastic impulsive forces that act occasionally on randomly selected particles. Between stochastic collisions, the system evolves at constant energy according to the normal Newtonian laws of motion. The stochastic collisions ensure that all accessible constant-energy shells are visited according to their Boltzmann weight and therefore yield a canonical ensemble. 

Stoss, m. impulse, thrust, push, blow, stroke impact, collision, percussion, shock, jolt, blimp recoil pile, heap, (of papers) file joint blast (of a horn), stossartig, a. jolting, jerky, intermittent. Stossbutter, /. farm butter, stossdlimpfend, a. shock-absorbing, cushioning. Stoss ddmpfer, m. shock absorber dash pot. -dauer, /. duration of collision, of impact, etc. (see Stoss). 

The curve marked ion-dipole is based on the classical cross-section corresponding to trajectories which lead to intimate encounters (9, 13). The measured cross-sections differ more dramatically from the predictions of this theory than previously measured cross-sections for exothermic reactions (7). The fast fall-off of the cross-section at high energy is quite close to the theoretical prediction (E 5 5) (2) based on the assumption of a direct, impulsive collision and calculation of the probability that two particles out of three will stick together. The meaning of this is not clear, however, since neither the relative masses of the particles nor the energy is consistent with this theoretical assumption. This behavior is, however, probably understandable in terms of competition of different exit channels on the basis of available phase space (24). 

The earlier evaluation of the core radius was in terms of Bohr s impulse condition (see Sect. 2.3.3) at (relatively) high energies. This gives the core radius as 30 A at a particle energy of 10 MeV/amu. For much lower energies, this relation is unrealistic, since electrons ejected in glancing collisions penetrate... 

Schematic diagram of a reentry circuit that might occur in small bifurcating branches of the Purkinje system where they enter the ventricular wall. A Normally, electrical excitation branches around the circuit, is transmitted to the ventricular branches, and becomes extinguished at the other end of the circuit due to collision of impulses. B An area of unidirectional block develops in one of the branches, preventing anterograde impulse transmission at the site of block, but the retrograde impulse may be propagated through the site of block if the impulse finds excitable tissue that is, the refractory period is shorter than the conduction time. This impulse then reexcites tissue it had previously passed through, and a reentry arrhythmia is established.

The maximum impact parameter has to be estimated from different considerations. The basis of this process is that the ion rapidly moves past the electron and delivers a sharp impulse to the electron. The electrons are bound in atoms and thus are orbiting with their own characteristic frequencies or time scales. Thus, the time for the ion to cross the atom should be less than the average time for an electron orbit otherwise the collision will not be adiabatic or rapid. The time for the ion to move past can be estimated as the ratio of the impact parameter to the ion s velocity, the average orbital time for an electron will clearly depend on the chemical element, as there will be an average radius and velocity, thus... 

The reaction zone of a secondary expl can be subjected to an impulsive rise of pressure leading to deton within tens of microseconds by a technique termed ACP (augmented by collision pressure). This ACP method is claimed to have practical advantages of simplicity and reliability when compared with expl bridgewires and the known procedures for burning to deton. It has been applied to RDX (Ref 45a)... 

It may be verified that for a double quantum jump the steric factor is A precise treatment must consider simultaneous rotational transitions, because the impulse during collision depends not only on 0 but also on the manner in which 0 changes. However, the major part of the overall transition probability occurs where 6 is small, and coupling with rotation is then at its lowest efficiency. A detailed discussion of this complex problem is given by Herzfeld and Litovitz32. By integration of equation (14) through the velocity distribution, equation (13) takes the form... 

The simplest theory of impact, known as stereomechanics, deals with the impact between rigid bodies using the impulse-momentum law. This approach yields a quick estimation of the velocity after collision and the corresponding kinetic energy loss. However, it does not yield transient stresses, collisional forces, impact duration, or collisional deformation of the colliding objects. Because of its simplicity, the stereomechanical impact theory has been extensively used in the treatment of collisional contributions in the particle momentum equations and in the particle velocity boundary conditions in connection with the computation of gas-solid flows. 

Khare, V., Kouri, D.J. and Hoffman, D.K. (1981). On -preserving properties in molecular collisions. I. Quantal coupled states and classical impulsive approximation, J. Chem. Phys., 74, 2275-2286. 

We note from Fig. 9 that the individual bonded and nonbonded contributions to t — 22, as they vary with p, are approximately equal in absolute value although opposite in sign. A possible heuristic picture for this behavior is based on Fig (8a) because of the short range and strongly repulsive character of u b, a nonbonded interaction has the character of a classic collision—the duration of an individual interaction is very short. As a result, the impacted atom (fl in Fig. 8a) moves little and the resultant of the impulsive compressive forces in its bonds to oq and a2 balance that exerted by x ( on [>. However, a collision in the configuration shown in Fig. 8b would contribute an impulsive tensile force to its bonds, but a collision between y ( and fi in that configuration is less likely because of steric shielding and, as verified in simulations, occurs less frequently. 

The rotational and the translational freedom appear after desorption of adsorbed molecules and each energy is kept without any disturbance before detection in the present experimental condition, since there is no collision and the lifetime of the excited states for a desorbed molecule is long. The experimental data can be analyzed by a simple model using the impulse scheme, con fi ned to the momentum transferred from the substrate to an adsorbate atom, in which the form of the excited-state PES and the transition process need not be assumed [68, 69]. The energy released from the excited state is converted to the momentum and this energy is transferred impulsively. The desorption also occurs impulsively. This simple model sheds hght on the property of the intermediate excited state, and the intermediate excited state plays an important role in the DIET process. 

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