the precursor to bohr's quantum theory

First edition of this significant work that lays out the empirical formulae governing the frequencies of atomic spectral lines, a precursor to Bohr's development of the quantum theory. A handsomely bound copy in excellent condition, and rare in commerce.

Atomic spectra are bright or dark lines that appear across the visible spectrum indicating the wavelengths of light emitted or absorbed when atoms are energised by photons. Each element produces a different series of lines, and these can be used to determine the chemical components of a substance on Earth, or even of a star or a distant planet's atmosphere. Inspired by Mendeleev's periodic table, Johannes Rydberg (1854-1919) was convinced that the electromagnetic spectra emitted by atoms could provide insight into atomic structure and theory. 'Notwithstanding the imperfect spectroscopic tables then at his disposal, Rydberg discovered most of the important properties of series spectra, including the relation between corresponding series in the spectra of related elements, and foreshadowed discoveries which were made later, when experimental work has sufficiently advanced. Some of the features noted by Rydberg were observed about the same time by Kayser and Runge, but his work had the special merit of connecting different series in the spectrum of the same element into one system, which could be represented by a set of simple formulae having but few adjustable constants. He especially insisted that the hydrogen constant, now generally called the "Rydberg constant," should appear in all series and, apart from slight variations from element to element suggested by the theoretical work of Bohr, nearly all subsequent attempts to improve the representation series have involved this supposition, and have had Rydberg's formula as a basis.' (Nature obituary, January 24, 1920). Rydberg's work was justified and expanded upon by Bohr's development of the quantum model of atomic structure in 1913, and Bohr was able to use his own theory to derive Rydberg's results, providing confirmation of both.

This uncommon publication represents the culmination of Rydberg's work. It 'mapped out Rydberg's total approach with remarkable clarity... While T.R. Thalen and Bernhard Hasselberg, Rydberg's major Swedish contemporaries in spectral studies, concentrated upon accurate measurements of the spectra of the elements, Rydberg's major spectral contributions were to theory and mathematical form, and those to form were the ones of enduring value' (Dictionary of Scientific Biography, vol. 12, p. 42).

First edition, first impression; tall 4to, (30 x 22.5 cms); 4 engraved plates of which 3 are double-page and 1 is folding; title page and plates faintly toned, contents clean otherwise; recent burgundy quarter morocco, marbled boards, titles to spine gilt, very good condition; 155pp.