The first evidence. A simple experiment

On the other hand, it is easily shown that the secondary ion XHj, produced by the stripping of a proton from an incident ion XH by a stationary molecule XH, has very little kinetic energy in the direction of the incident ion, amounting to 

Since is generally much smaller than 1/4, we can discriminate the 

Henglein and Muccini [85—87] studied the systems CH4 + CH4 and CD4 + CD4 in this way and obtained the results shown in Fig. 5, where 

According to eqn. (66), the kinetic energies of the secondary ions CH5, at, for example, 20 eV voltage between the chamber and trap, are expected to be around 5 eV if they are produced via an intermediate complex. These energies are well above the detection limit mentioned above. The fact that CH ions are still detected in considerable amounts at even higher voltages shows that at least a part of the ions are formed by H stripping 

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