It should be noted that fragmentation was not observed in the other experiments, presumably because the TNP ranges, and resulting sublimation or etching rates, were more modest. If fragmentation had occurred, it would have been obvious as secular frequency steps that did not match the step size expected for electron emission. The absence of such events, even for aggregate NPs, suggests that aggregates must be reasonably strongly bound, such that they break up only under conditions of rapid sublimation or etching.