It should be necessary to ask Theunknown who tight with QM. Uranium and all these radioactive particles can be resolved into some conjunctions, but I don't know any to Lewis acid. The previous conjunction might be found to solve it.
By the way, H+ in deuterium and tritium can be maintained as such element. Hydro in them are too radioactive.
The binding energy of the first electron of Helium is about -54 eV, and the second about -24 eV. The binding energy for a single electron and H+ is -13 eV, and a second electron has a binding energy of -0.75 eV.
H+ will pull one electron very strongly, but it will benefit more from sharing a second electron than from pulling it and keeping it for itself. This leads to the formation of hydronium ions and more complex structures which are considered a 'lewis adduct'.
Helium is not interested in sharing electrons. It has two protons that desperately want to find two electrons. The alpha particle will grab the first two electrons it sees to form neutral helium and a pair of anions or a dianion. Many different things can happen, so it is a dirty process. This response can give you an idea of the type or processes that can happen: chemistry.stackexchange.com/questions/8929/what-is-a-product-of-water-ionization
The alpha particles themselves are not lewis acids because they do not form a lewis adduct. If a lot of them are added, the solution might violently explode due to the exergonicity of the electron transfer (and alpha particles are usually moving at about 5% the speed of light when they are made).