The New Quantum Mechanics

George Birtwistle (1877–1929) published The New Quantum Mechanics in 1928. His stated aim was to give a detailed account of work which had brought the relatively new subject of quantum mechanics to the fore in the previous few years. The earlier chapters give a restatement of Alfred Landé's theory of multiplets which reconciles it with the new mechanics which follow. Later chapters present the matrix theory of Heisenberg, the q-number theory of Dirac and the wave mechanics of Schroedinger, and synthesise new theories, statistics and controversies in the work of de Broglie, Bose, Einstein, Fermi and Dirac. The book gives a complete overview of the state of quantum mechanics at the end of the second decade of the twentieth century, making it a valuable benchmark for historians of science and mathematicians alike.

1. The origin and development of the new quantum mechanics; 2. The multiplets of series spectra and the l-s-j scheme of Landé; 3. The normal and anomalous Zeeman effect; 4. Atomic magnetism; 5. Interpretation of the g-formula; 6. X-ray spectra and their multiplet theory on the new mechanics; 7. The Paschen–Back effect and the Sommerfeld formula; 8. The new quantum kinematics of Heisenberg; 9. The theory of Dirac; 10. The harmonic oscillator; 11. The canonical transformation; 12. The anharmonic oscillator; 13. Angular momentum relations; 14. The theory of the Landé numbers; 15. Intensity formulae for the Zeeman effect; 16. The Dirac–Pauli calculations for hydrogen; 17. Schroedinger's wave equation; 18. Wave mechanics; 19. Schroedinger's theory of the oscillator and rotator; 20. The evaluation of the Heisenberg matrices by the use of the Schroedinger calculus; 21. Perturbation theory in wave mechanics; 22. Schroedinger's dispersion theory; 23. Light quanta; 24. The theory of the anomalous Zeeman effect on the new mechanics; 25. The calculation of the Zeeman intensities for the D-doublet of the alkalis; 26. Heisenberg's resonance theory of the ortho and para helium spectra; 27. The effect of the spin of the electrons upon the helium spectrum; 28. The new statistics of gases and radiation; 29. The Fermi–Dirac theory of an ideal gas; 30. Dirac's theory; 31. The Dirac matrix transformation theory; 32. The essential indefiniteness of quantum mechanics; Index.

Published in 1928, this book's aim was to give a complete overview of the development of quantum mechanics at the end of the second decade of the twentieth century, discussing the theories of Heisenberg, de Broglie, Bose, Einstein, Fermi, Dirac and Schroedinger.