23 August 1955

To: Martin Karplus

From: Linus Pauling

Subject: Revision of Introduction to Quantum Mechanics

Here are my comments on your preliminary suggestion about the revision of the book.

I think that the revision that you propose is more extensive than we want. In particular, you propose great changes in the first few chapters. I think that these chapters should be retained, with some small changes and perhaps some additions.

In general, I think that we should proceed on the assumption that everything in the book as it stands now (as written twenty years ago) has been shown to be good by the fact that the book has been widely used. I suggest that we retain the present structure of the book and the present material in each chapter, unless a good argument can be presented to justify a change. I do not think that any section of chapter should be rewritten unless there is such an argument.

Also, I do not think that we should adopt the policy of rewriting the book in the way that a mathematician would – that is, of deriving early in the book (by matrix methods, say) some valuable theorems, and then making later discussions as succinct as possible with use of these theorems. Instead I favor deriving the theorems at the place where they are used. For example, you suggest revising the discussion of many-electron atoms by basing it upon previously derived theorems; I should prefer to have the theorems derived here.

You also suggest doing first and second order perturbation theory and degenerate theory in the same formulation. I think that there is an advantage to taking these up in succession, for the sake of clarity and emphasis, even though the treatment is less efficient.

I suggest that you check through the chapters and suggest deletions, changes, and additions.

We have agreed that something about matrices and general quantum mechanics should be introduced rather early. I think that your suggestion of a brief discussion of simple experiments showing duality of matter and light, uncertainty principle, complementarity, etc., may be introduced early, and suggest the end of Chapter 2 and the beginning of Chapter 3 as the proper place.

In Chapter 12 you suggest leaving out the Burrau treatment. I think that this treatment should be retained, partially because of its historical significance, but also because it involves the introduction of confocal elliptic coordinates.

You also suggest leaving out the treatment of the helium molecule ion, the interaction of two normal helium atoms, and the discussion of the one-electron bond, the electron-pair bond, and the three-electron bond. These matters seem to me to be important.

Your suggestions about other topics – virial theorem and applications, Feynman theorem and applications, solid state theory, book list – seem to me to be excellent. I agree that probably the section on statistical mechanics should be deleted.

Linus Pauling:W

cc: Professor Wilson