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Chapter 1
Introduction
1.1 HISTORY: FROM DISCOVERY TO PRESENT
In the year 1923, Rutherford had discovered the proton but, in his subsequent
experiments, the atomic number was consistently less than the atomic mass.
is could not be due to the number of electrons, so Rutherford hypothesized
that there was another type of particle in the atomic nucleus—one with mass
but no charge. In another development in 1925, physicists proposed the idea of
nuclear spin to explain the Zeeman eect (shifts in atomic energy levels in a
magnetic eld), but this did not seem to t the prevailing model for the atomic
nucleus, believed to contain just protons and ...