Walter Heitler

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In existographies, Walter Heitler (51 BE-26 AE) (1904-1981 ACM) (IQ:180|#208) (PR:26,598|65AE / physicist:415) (GPE:48) (CR:12) (LH:8) (TL:20) was a German physicist, noted for []


In 1927, Heitler, in his “Interaction of Neutral Atoms and Homopolar Bonding according to Quantum Mechanics”, co-authored with Fritz London (1900-1954), starting with Niels Bohr atom model (1913), Louis Broglie’s electron wave theory (1924), which marks the starting point for "wave mechanics"[1], the spinning electron theory (1925) of George Uhlenbeck and the Samuel Goudsmit, the "exclusion principle" (1925) of Wolfgang Paul, and the Hamiltonian-style wave equation (1926) of Erwin Schrodinger, derived equations showing that electrons with up and down "spin", confined by Paul's exclusion rules, can interact to yield and "exchange energy", which changes depending upon orbital interaction, therein yielding a quantum physical basis for the "chemical bond" between atoms; this model, supposedly, later led to the generalized model of the "exchange force".[2]

In 1956, Heitler, in his Elementary Wave Mechanics: with Applications to Quantum Chemistry, §9: “Theory of the Homopolar Bond”, stated the following:

“One of the great puzzles confronting physicists and chemists, in the days before wave mechanics was found, was the problem of the chemical bond.”
— Walter Heitler (1956), Elementary Wave Mechanics (pg. 123)

Then, after discussing the ionic bond, covalent bond, and "van der Waals forces", he states that the reason for the formation of the "H molecule", symbol: H2, is because of the "exchange energy" lowering effect that results from the overlap of the electron orbitals; specifically:

“The total energy of the system will then differ from the sum of the internal energies of the two atoms, i.e. twice the energy of the ground state of H, by a certain ‘interaction energy’, E(R), which will depend on the distance R.”
— Walter Heitler (1956), Elementary Wave Mechanics (pg. 124)

He then gives the following diagram of the "charge cloud of two H atoms",

Heitler (charge clouds of two H atoms).jpg

where R is the distance of the separation of their nuclei, wherein we see a certain amount of orbital overlap.



Heitler was influenced by: Gilbert Lewis, Niels Bohr, Louis Broglie, Max Born, Erwin Schrodinger, George Uhlenbeck, and Samuel Goudsmit.


Heitler influenced: Linus Pauling.[3]


Quotes | On

The following are quotes on Heitler:

“Although the chemical bond was first recognized and discussed at great length in classical terms, most physicists regarded the mature of the chemical bond as a profound mystery until Heitler and London qualitatively derived the exchange interaction [see: exchange force] and showed that this quantum mechanical behavior accounted for the observed properties of valency and stability. On the other hand, it is not uncommon to find molecular biologists using a classical description of DNA replication and coding to justify the statement that the living cells obey the laws of physics without ever once putting down a law of physics or showing quantitatively how these laws are obeyed by these processes.”
Howard Pattee (1967), “Physical Problems of Heredity and Evolution” [4]
“The paper of Heitler and London on H2 for the first time seemed to provide a basic understanding, which could be extended to other molecules. Linus Pauling at the California Institute of Technology in Pasadena soon used the valence bond method. . . . As a master salesman and showman, Linus persuaded chemists all over the world to think of typical molecular structures in terms of the valence bond method.”
Robert Mulliken (1989), Life of a Scientist (pgs. 60-61) [3]

Quotes | By

The following are quotes by Heitler:

“The reason for the formation of a ‘molecule’ is the quantum mechanical exchange phenomena, and the bulk of the ‘binding energy’ is the exchange energy A.”
— Walter Hitler (1956), Elementary Wave Mechanics (pg. 134)
“When two H atoms meet, a molecule is not always formed. The two atoms repel each other if the spins of the two electrons are parallel. Indeed, if two H atoms collide, and if we do not know their relative spin directions, the chance is only one in four that they will attract each other and three and four that they will repel each other. This is so because there are three spin wavefunctions for the triplet state but only one for the singlet state. The existence of a repulsive interaction between two H atoms has also been found experimentally.”
— Walter Hitler (1956),  Elementary Wave Mechanics (pg. 134)
“My interest in science awoke rather early, at the age of 10 or 12 or so. I don’t think it was stimulated by a special home atmosphere or by school. My father was a professor of engineering, and so the atmosphere at home was certainly not unfavorable, but it did not particularly stimulate interest in science. I was first interested in astronomy; at the age of 12 or so I made myself a telescope from an old camera lens and the objective of an old microscope. I was very happy then that I could see the ring of Saturn and so on. Well, later at the age of 14 or 15 I became interested in practically everything scientific — mathematics, physics and chemistry, even geology. I installed a chemical laboratory in the bathroom which was perhaps not always to the pleasure of my family, and so on. My school education was mainly classic, Latin and Greek. And for this I’m very grateful, in fact. Especially, I derived a great deal of pleasure and interest from Greek — Greek philosophy, Greek poetry. Plato was my favorite philosopher, and perhaps he still is. The science, teaching in school was rather poor; my mathematics teacher was a kindly old man, but as I usually was far in advance of his lessons, I used the mathematics lessons for preparing the next Latin lesson or so, and he didn’t object. The physics teacher’s main concern was to be against Einstein and against relativity. Well, I was not on very good terms with him, or he was not with me, to put it more precisely, especially since he once discovered that I was reading a book by Einstein secretly under my desk.”
— Walter Heitler (1963), “Interviewed by John Heilbron”, Mar 18 [5]
“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.... 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.”
— Walter Heitler (1963), “Interviewed by John Heilbron”, Mar 18 [5]

End matter


  1. Heitler, Walter. (1936). Elementary Wave Mechanics: with Application to Quantum Chemistry (starting point, pg. 4). Oxford, 1958.
  2. Heitler, Walter and London, Fritz. (1927). “Interaction of neutral atoms and homopolar bond according to quantum mechanics” (“Wechselwirkung neutraler Atome and homoopolare Bindung nach der Quantenmechanik”), Zeitschift fur Physik, 44: 455-72.
  3. 3.0 3.1 Walter Heitler (material) –
  4. (a) Pattee, Howard H. (1967). “Physical Problems of Heredity and Evolution”, in: Sketching Theoretical Biology: Towards a Theoretical Biology, Volume Two (editor: C.H. Waddington) (contents). Publisher.
    (b) Gatlin, Lila L. (1972). Information Theory and the Living System (pg. 15). Columbia University Press.
  5. 5.0 5.1 Heilbron, John. (1963). “Interview of Walter Heitler” (Session: One), Zurich, Mar 18.

External links

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