Secondary collisions

Muschlitz E E 1957 Formation of negative ions in gases by secondary collision processes J. Appi. Rhys. 28 1414-18... 

An elementary reaction is defined as a reaction that takes place as written in the reaction scheme. We will here distinguish between a truly elementary reaction, where the reaction takes place in isolation without any secondary collisions, and the traditional definition of an elementary reaction, where inelastic collisions among the molecules in the reaction scheme (or with container walls) can take place. 

The visible chemiluminescence observed in the reactions of Y and Sc with F2, Cl2 and C1F was originally attributed [387] to emission from the metal monohalide, MX. However, more recent studies [388] suggest that the emitter is the metal dihalide, MXijf, which is formed by secondary collisions of vibrationally hot ground state monohalide, MXt, formed in the initial reaction, M + X2, with another halogen, viz. 

ADAS is centred on generalized collisional-radiative (GCR) theory. The theory recognizes relaxation time-scales of atomic processes and how these relate to plasma relaxation times, metastable states, secondary collisions etc. Attention to these aspects - rigorously specified in generalized collisional-radiative theory - allow an atomic description suitable for modeling and analyzing spectral emission from most static and dynamic plasmas in the fusion and astrophysical domains [3,4]. 

Breckenridge and Umemoto provided sample calculations based on the reaction of Mg( Pi) with H2 to demonstrate that the effective delay time for secondary collisions of the MgH product is different from the delay time... 

Hence there is no gas-phase experiment yet which fully encompasses all aspects of an electron-transfer reaction in solution. In solution, the solvent acts first as a polarization medium, which affects the energetics of direct transfers from the donor to the acceptor. It can also act as a transport medium for indirect electron transfers. The first aspect has been addressed in various cluster experiments [276]. The second aspect was addressed more recently by considering the femtosecond dynamics of iodide-(water) anion clusters, as reviewed below [277]. Finally, clusters present the advantage of isolating one reaction pair free from secondary collisions, except those, which are desired, with the solvent molecules (or atoms). The latter consideration motivated the cluster isolated chemical reaction (CICR) technique reviewed in Section 2.8.3. 

Nascent product state distributions have to be measured for a single photodissociation process, i.e., the products have to be analysed before they collide again with the residual gas. Otherwise the characteristic motion that emerges from the fragmentation process itself is changed by secondary collisions and the direct information about the fragmentation process is lost. 

Today two important techniques are used to avoid secondary collisions. The first technique is the molecular beam method, in which the density i kept so low that no collisions occur before the products reach the detector (for example a mass spectrometer). The second technique, that became more popular in the recent years, is based on time resolution. In this "pump and probe" technique, two short laser pulses... 

All passive safety measures implemented in the vehicle are only capable of addressing the so-called primary collision (i.e., contact with the vehicle). For example, only about 6 % of pedestrians impact with the head on the hood, which limits the efficacy of measures implemented there [48]. Secondary collisions, i.e., contacts with the road surface or other objects, are not addressed by those measures. In contrast active safety measures address the entire sequence of events and as a consequence have a much higher injury avoidance potential [17,49]. Preventive systems are at the moment in the state of development or already in the market [48, 50-52],... 

FIGURE 2 The microstructure of the different regions in implanted polymers. Toward the mean range of the ions, dangling bonds and one-dimensional tracks, formed by nuclear stopping and secondary collisions, dominate. Toward the surface of the polymer, where electronic stopping dominates, the hard amorphous carbon and graphite structures exist. 

An examination of energy flow in the trajectories pictured in Fig. 4 reveals that in both mechanisms, significant energy is initially deposited in the OH stretch and bending motions of HOCO. In the complex mechanism this energy is able to flow to the CO before the HOCO comes apart, but in the direct mechanism the CO is vibrationally and rotationally cold compared to that in the complex mechanism, while the OH is vibrationally and rotationally hot. The secondary collisions of OH with Br are therefore the only events by which OH can be cooled off in die direct mechanism. 

Secondary collision with another train on an adjacent line. 

The probability of a secondary collision depends on the time difference between the time that the train derails and the time that the next train arrives on an adjacent line. The GeoSRM is not a timetable simulation model, so this time is approximated, based on the timetable with random perturbations to ensure that the probability of a secondary collision is a smooth function. The time at which a train traverses a track section is based on the time the train departed the previous timing point, the time the train arrives at the next timing point, and an interpolation between these two times. It does not take into account the acceleration and braking characteristics of the train between these two points, if the timing points represent station stops. 

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