1. Can any other atom besides helium be completely stripped of all its electrons? Are these ever encontered? Can they (C +12, or Fe +26, or U +92 etc.) be isolated and produced as a stream? How do these compare (stability) to alpha particles? 2. As for alpha particles themselves, how long do they last before becoming helium? There must be some half-life related to this and that would depend on local environment, especially the pressure of the gas in which it resides. Surely, an alpha particle would last longer in a vacuum than it would in 1 atm.