Dublin: Royal Dublin Society, 1898. 1st Edition. FIRST EDITION OF THOMAS PRESTON’S DISCOVERY OF THE ANOMALOUS ZEEMAN EFFECT accompanied by photograph of his experimental results. Offered is an extract housed in a custom case. This was published concurrently (April 1898) in The London, Edinburgh, and Dublin Philosophical Magazine.
When studying the spectral lines of elements in the presence or absence of a magnetic field, the Irish scientist Thomas Preston noted a phenomenon, an effect, in which the use of a stronger magnetic field led to results that were clearly at variance with the normal triplet structure reported by Zeeman and predicted by the Lorentz theory. Preston presented his findings to the Royal Dublin Society in December 1897. In early 1898, he furthered his initial findings and published his findings [in the paper offered] describing the anomalous Zeeman effect completely for the first time, including additional spectral lines that he called the ‘weak middled quartet,’ ‘double doublet,’ and ‘sextet’ (History of Physics: The Wenner Collection).
The Zeeman effect -- the effect of splitting a spectral line into multiple closely spaced lines in the presence of an external magnetic field -- was first reported by Zeeman in 1896 and agreed with the classical theory as interpreted by Lorentz. Observed in atoms with no spin, the Zeeman effect, the splitting, is caused by the interaction between the magnetic field and the magnetic dipole moment when associated with the orbital momentum of the electrons; in these cases the magnetic fields “separating the energy levels associated with the angular momentum of the electrons in an atom into three parts. When they settle back to their normal state, they yield three spectral lines” (ibid).
The effect that Preston discovered, the anomalous Zeeman effect occurs in atoms with non-zero spin and involves further splitting of the spectral line into four, six, or even more lines (or triplets exhibiting wider spacing than the norm. This effect was a deviation – hence, ‘anomalous’ – and it was very puzzling to the scientific community. The explanation of these differing patterns of splitting took time to emerge because it depends on electron spin -- quantized electron spin – which had yet to be discovered when the effect was first observed. In other words, the deviations Preston discovered were explained by the quantum mechanics effects of spin. Item #1107
CONDITION & DETAILS: Dublin: Royal Dublin Society. 4to (10.5 x 9 inches). Institutional copy deaccessioned from the Chemical Society (single stamp on the title page). Handsomely bound extract from the Scientific Transactions of the Royal Dublin Society complete with title page and photographic plate. Bound in half calf over brown cloth boards; gilt-lettered at the spine and on the front board. Bright and clean. Near fine inside and out.