Recherches sur la Constitution des Spectra d'Émission des Éléments Chimiques. Kongl. SV. Vet. Akademiens Handlinger Band 23. No. II.

Stockholm: Kongl. Boktryckeriet. P. A. Norstedt & Söner, 1890. Tall quarto (300 x 230 mm). Recent burgundy quarter morocco, marbled boards, titles to spine gilt. Title page just a little toned. Excellent condition. First edition of this significant work in which Rydberg lays out the empirical formulae governing the frequencies of spectral lines, a precursor to Bohr's development of the quantum theory. A handsomely bound copy in excellent condition. Johannes Rydberg (1854-1919) was a Swedish physicist at Lund University who studied atomic masses and electromagnetic radiation; inspired by Mendeleev's periodic table, he 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 Neils 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. He conceived of the spectrum of an element as composed of the superposition of three different types of series - one in which the lines were comparatively sharp, one in which the lines were more diffuse, and a third that he called the principle series even though they consisted mostly of lines in the ultraviolet. The first lines were located in the visible spectrum and were usually the most intense. The members of each series might be single, double, triple, or of higher multiplicity. Any particular elementary spectrum might contain any number (even zero) of a series of each of the basic types. While Rydberg observed and measured some spectral lines on his own, he was not particularly noted as an experimental physicist and did not publish any of his experimental investigations or spectroscopic measurements. Most of the data he needed were already available in the voluminous literature. 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).