Plume collisions

Chondrules from metal-rich (CH, CB) chondrites formed significantly later than those in other classes (Fig. 9.9), with Pb-Pb measurements giving ages of -4562.7 Ma, 5.5 Myr after CAIs (Krot et al., 2005). These chondrules likely formed by a different mechanism than the chondrules in other classes. One model of their formation suggests they are products of a collision between two asteroid-sized bodies and that they formed by recondensation of a vapor plume generated in the collision. 

The Cl source operates at low pressure. Ion-molecule reactions occur and are needed for sample ionization. The MALDI source is under vacuum, but during the ionization process the pressure increases in the plume close to the target and ion-molecule reactions occur. The various sources operating at atmospheric pressure include ESI, APCI, APPI and AP-MALDI. All these sources operate at sufficient pressure to have numerous collisions between ions and molecules, and reactions between these species are observed. 

The difference between model and calculation undoubtedly comes from the effect of the free interface, which was not taken into account here. This model also lacks the interactions between bubbles in reality, the rising bubbles collide with each other and then lose kinetic energy. The numerous collisions between quasi-rigid bubbles probably explain the widening of the plume seen in fig. 11. Moreover, the numerical model did not take into account the interactions that might exist between the bubbles in the plume and those at the sparger outlet. Nor did the model take into account bubble diameter distribution. This poor description of a plume is not related to EA. 

The observed phenomenon was rationalized by considering the role of gas-phase collisions in the plume generated by laser irradiation. In this frame, two different kinetic energy regimes of the colliding ion must be considered The first is due to the initial translational energy related to the ion sputtering prior to the acceleration phase,... 

As a first approach to post-ionization of desorbed neutral pol5uners we discuss laser-generated cationization. This approach differs from other desorption/ cationization techniques because the desorption step and the cationization step are completely separate. First polymers are gently laser desorbed at low fluence wifh one laser. Independenfly atomic metal ions are generated by a second pulsed laser that is tightly focused on a metal surface fo creafe a plume of mefal ions. Gas phase collisions above the sample surface subsequenfly produce fhe cafionized complexes. Separation of fhe desorption and cationization processes allows independent optimization of fhe fwo laser/maferial interactions. This approach is especially useful in sifuations where ofher ionization methods fail, such as fhe example of PFPEs discussed here. ... 

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