Heitler and London’s hydrogen molecule paper was not, in Pauling’s view, followed
up with much of value. The German pair were physicists, after all, not chemists, so
they could not be expected to understand how their exchange-energy concept related
to the huge cornucopia of chemical phenomena, most of which they knew nothing about.
Even though they had beaten Pauling to the first successful quantum-mechanical attack
on the chemical bond, there was still much he could do to expand and rework their
One of the first things he did was to prepare a long article for Chemical Reviews
in which he introduced the Heitler-London chemical-bond work and added some new insights
of his own into its application to the one-electron hydrogen molecule-ion. This was
the first glimpse that most chemists had seen of the quantum mechanical approach to
their field, and it marked Pauling’s entrance onto the American scientific stage in
his new role of quantum-chemist.
Click images to enlarge
Linus and Ava Helen Pauling in Munich, with Walter Heitler (left) and Fritz London
"The application of the quantum mechanics to the structure of the hydrogen molecule
and hydrogen molecule-ion and to related problems." June 1928.
"I slept till very late in the morning, found I couldn’t do work at all, had a quick
lunch, went to sleep again in the afternoon and slept until five o’clock. When I woke
up...I had clearly...the picture before me of the two wave functions of two hydrogen
molecules joined together with a plus and minus and with the exchange in it. So I
was very excited, and I got up and thought it out. As soon as I was clear that the
exchange did play a role, I called London up, and he came to me as quickly as possible.
Meanwhile I had already started developing a sort of perturbation theory. We worked
together then until rather late at night, and then by that time most of the paper
was clear.... Well...at least it was not later than the following day that we had
the formation of the hydrogen molecule in our hands, and we also knew that there was
a second mode of interaction which meant repulsion between two hydrogen atoms, also
new at the time –- new to chemists, too."