So who were these physicists?
I notice that the Wiki entry you linked on Gamow says that an expert’s attention is needed on that subject. (In other words, there are questions about that article.)
From what I remember when taking pchem, quantum tunneling is a random event and not very likely to occur. It also describes the movement of a particle through a physical barrier, not through a charge barrier.
Not even a neutron star or black hole would have the energy to overcome the Coulomb barrier of a large nucleus like Nickel, according to the physics blog. I don’t happen to know the blog off-hand; it was something that JohnnyB linked a while back. The large atoms are not made through fusion; they are made through another process that also happens inside stars, which involves shoving neutrons into the nucleus. Since neutrons have no charge, there is no Coulomb barrier to overcome. Since shoving neutrons into a nucleus is very likely to make unstable isotopes, those isotopes undergo various forms of radioactive decay, which ends up producing all of the elements that we know (with exception of the extremely unstable radioactive elements which have only been made in labs). That non-fusion process I just described does NOT describe what Rossi claims to be doing in his “eCat”. He is claiming to have achieved cold fusion... sure, he calls it “LENR”, but it’s cold fusion.
BTW, when you slip another proton into a hydrogen nucleus, you get helium, not deuterium. The nucleus of a hydrogen atom is a single proton. The nucleus of a deuterium atom is a proton and a neutron. Tritium consists of a proton and two neutrons. The identity of a chemical element is determined by the number of protons in the nucleus, and the isotope is determined by the number of neutrons.
Are there any other basic chemistry questions you would like answered?