Arthur Erich Haas (April 30, 1884, in Brno – February 20, 1941, in Chicago) was an Austrian physicist, noted for a 1910 paper[1] he submitted in support of his habilitation as Privatdocent at the University of Vienna that outlined a treatment of the hydrogen atom involving quantization of electronic orbitals, thus anticipating the Bohr model (1913) by three years.
Soon thereafter, however, by September 1911 at a physical science convention in Karlsruhe, former detractors of Haas's work acknowledged it with greater enthusiasm as noted in a footnote: "We do not know what caused [a] change of mind in 1911 and can merely suggest the general trend of thinking at the time: 1910 saw the beginning of a universal shift of opinion of the quantum concept.
"[2] The significance of Haas's work lay in the establishment of a relationship between the Planck constant and atomic dimensions, having been first to correctly estimate the magnitude of what is today known as the Bohr radius.
Max Planck's lecture ended with this remark: "... atoms or electrons subject to the molecular bond would obey the laws of quantum theory.
"[3] Hendrik Lorentz in the discussion of Planck's lecture raised the question of the composition of the atom based on Thompson's model with a great portion of the discussion around the Quantum atom developed by Arthur Erich Haas.