THE ESTABLISHMENT OF THE FIELD OF MOLECULAR BEAMS

STERN, OTTO (+) WERNER HEISENBERG.

Zur Methode der Molekularstrahlen. I. (Untersuchungen zur Molekularstrahlmethode aus dem Institut für physikalische Chemie der Hamburgischen Universität. Nr. 1.) (+) [Heisenberg:] Über die Spektra von Atomsystemen mit zwei Elektronen.

Berlin, Julius Springer, 1926. 8vo. Bound in a contemporary half cloth. Small Library label pasted on to pasted down front free end-paper. Library stamt to title-page. A nice and clean copy. [Heisenberg:] pp. 499-518. [Stern:] Pp. 751-763. [Entire volume: VIII, 948 pp.].

First printing of Stern's first publication of his famous and groundbreaking series of papers named UNTERSUCHUNGEN ZUR MOLEKULARSTRAHLMETHODE (U.z.M.), which established the field of molecular beams.

In the first of the U.z.M.-papers (the present), Stern explains the advantages and disadvantages of the method, discusses technical details, and then gives the program for future work. In this section he mentions 1, the measurement of magnetic moments of molecules, including those due to the electrons, to the nucleus, and those induced by diamagnetic action; 2, electric dipole moments, including the so-called permanent dipole moment as well as moments of higher order (quadrupoles); 3, the measurement of the field of force of molecules (molecular forces); 4, fundamental problems such as the recoil on emission of a quantum, the de Broglie waves of matter, and others. The execution of this immense program kept him busy and gave work to many assistants, students, postdoctoral fellows, and guests of his institute.
This series reached 30 papers before it ended prematurely due to interruption by Nazi Germany.

ÜBER DIE SPEKTRA VON ATOMSYSTEMEN MIT ZWEI ELEKTRONEN. First edition of this important paper in which Heisenberg - after inventing Quantum Mechanics the year before (1925) - investigates some of the fundamental aspects of the new theory. Heisenberg recognizes the invariance of the wave equation with respect to various transformations. "It is clear that such invariance exists with respect to an interchange of the coordinates of identical particles, e.g. of two electrons in an atom of two nuclei of the same kind in a molecule. As a consequence, the wave function of a non-degenerate stationary state must either remain unchanged or may only change sign when the transformation is applied to it....Indeed, in this way Pauli's exclusion principle for electrons found a formulation in terms of wave mechanics."(K. Kronik in Memorial Volume to Wolfgang Pauli).

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