Pauli's letter of the 4th of December
1930
Dear Radioactive Ladies and Gentlemen,
As the bearer of these
lines, to whom I graciously ask you to listen, will explain to
you in more detail, how because of the "wrong" statistics
of the N and Li6 nuclei and the continuous beta spectrum,
I have hit upon a deseperate remedy to save the "exchange
theorem" of statistics and the law of conservation of energy.
Namely, the possibility that there could exist in the nuclei electrically
neutral particles, that I wish to call neutrons, which have spin
1/2 and obey the exclusion principle and which further differ
from light quanta in that they do not travel with the velocity
of light. The mass of the neutrons should be of the same order
of magnitude as the electron mass and in any event not larger
than 0.01 proton masses> The continuous beta spectrum would
then become understandable by the assumption that in beta decay
a neutron is emitted in addition to the electron such that the
sum of the energies of the neutron and the electron is constant...
I agree that my remedy
could seem incredible because one should have seen those neutrons
very earlier if they really exist. But only the one who dare can
win and the difficult situation, due to the continuous structure
of the beta spectrum, is lighted by a remark of my honoured predecessor,
Mr Debye, who told me recently in Bruxelles: "Oh, It's well
better not to think to this at all, like new taxes". From
now on, every solution to the issue must be discussed. Thus, dear
radioactive people, look and judge. Unfortunately, I cannot appear
in Tubingen personally since I am indispensable here in Zurich
because of a ball on the night of 6/7 December. With my best regards
to you, and also to Mr Back.
Your humble servant
. W. Pauli