Chronological Table for the Development of Atomic and Molecular Physics ≈ 440 Empedocles assumes, that the whole world is constant proportions”: Each chemical element BC composed of 4 basic elements: Fire, Water, Air consists of equal atoms which form with sim- and Soil. ple number ratios molecules as building blocks ≈ 400 Leucippos and his disciple Democritus claim, of chemical compounds. BC that the world consists of small indivisible 1811 Amedeo Avogadro derives from the laws particles, called atoms, which are stable and of Gay-Lussac (Δp/p = ΔT/T ) and Boyle- nondestructable. Marriot (p · V = constant for T = constant) ≈ 360 Plato attributes four regular regular geometric the conclusion that all gases contain under BC structures composed of triangles and squares equal conditions (pressure and temperature) (Platonic bodies) to the four elements and the same number of particles per volume. postulates that these structures and their inter- 1820 John Herapath publishes his conception of a change represent the real building blocks of the Kinetic theory of gases. world. 1857 Rudolf J.E. Clausius develops further the ki- ≈ 340 Aristotle contradicts the atomic theory and as- netic gas theory, founded by J. Herapath and BC sumes that the mater is continuous and does D. Bernoulli. not consist of particles. 1860 Gustav Robert Kirchhoff and Robert Bunsen 300 Epicurus revives the atomic model and as- create the foundations of spectral analysis of BC sumes that the atoms have weight and spatial the chemical elements. extension. 1865 Joseph Lohschmidt calculates the absolute 200 BC no real progress in atomic physics. number of molecules contained in 1 cm3 of –1600 AC a gas under normal conditions (p = 1atm, 1661 Robert Boyle fights in his book: “The Sceptical T = 300 K). Chemist” for the atomic model, which states, 1869 Lothar Meyer and D.I. Mendelejew estab- that all matter consists of atoms which differ lish (independent of each other) the Periodic in size and form for the different elements. System of the Elements. He defines the terms “chemical element” and 1869 Johann Wilhelm Hittorf discovers the cathode “chemical compound”. rays in gas discharges. 1738 Daniel Bernoulli assumes that heat can be ex- 1870 James Clark Maxwell gives the mathematical plained as the movement of small particles. He foundations to the kinetic gas theory. He de- may be regarded as the father of the kinetic gas fines the atoms as “absolute and unchangeable theory. building blocks of matter”. 1808 John Dalton supports in his book “ANew 1884 Ludwig Boltzmann develops from statistical System of Chemical Philosophy” the atomic grounds the distribution function for the en- hypothesis by describing his experiments on ergy of a system of free atoms in a constant careful weighing the masses of reactants and volume. Together with the Austrian physicist reaction products of a chemical reaction. The Josef Stefan he derives the Stefan–Boltzmann results of these experiments lead to the “law of radiation law. W. Demtröder, Atoms, Molecules and Photons, 2nd ed., Graduate Texts in Physics, DOI 10.1007/978-3-642-10298-1, c Springer-Verlag Berlin Heidelberg 2010 520 Chronological Table 1885 Johann Jakob Balmer finds the Balmer- shows that both the characteristic and the con- formula for the spectral lines of the hydrogen tinuum radiation could be polarized. atom. 1913 Niels Bohr (Nobelprize 1922) develops his 1886 Eugen Goldstein discovers the “Kanal- new atomic model, based on the Rutherford Strahlen” (anode rays). model and the quantum hypothesis of Planck. 1886 Heinrich Hertz detects experimentally the 1913 Henry Moseley finds periodic regularities for electromagnetic waves predicted by Maxwell’s the absorption frequencies of X-rays by differ- theory and discovers 1887 the photo-electric ent atoms and is able to determine the nuclear effect and performs first experiments on the charge number Z of the atoms from his mea- absorption of cathode rays. surements of absorption edges. 1888 Phillip Lenard further investigates the absorp- James Franck and Gustav L. Hertz investigate tion of the cathode rays. the inelastic collisions of electrons with atoms 1895 Wilhelm Conrad Röntgen discovers, while (Franck–Hertz experiment). Nobel prize 1925. working on the properties of cathode rays 1919 Arnold Sommerfeld comprises all known facts a new kind of radiation which he called X-rays and models of atoms in his famous textbook: (first Nobel Prize in Physics 1901). “Atombau und Spektrallinien” and refines the 1896 Henry Becquerel first discovers radioactivity atomic model of Bohr. (Nobel prize 1903). 1921 Otto Stern and Walter Gerlach investigate the 1898 Marie Curie separates different radioactive el- deflection of atoms in an inhomogeneous mag- ements (Polonium and Radium) from minerals netic field and demonstrate the quantization of (Nobel prizes for Physics 1903 and Chemistry the component of the atomic angular momen- 1911). tum. 1900 Max Planck presents his new theory of black 1923 Arthur Holly Compton (Nobel prize 1927) ex- body radiation, introducing the energy quanta plains the inelastic scattering of X-rays by h · ν of the radiation field. This is nowadays electrons (Compton effect) using the model of regarded as the birth year of quantum physics light quanta. (Nobel prize 1918). 1924 Louis de Broglie (Nobel prize 1929) introduces 1905 Albert Einstein develops his theory of Brow- the concept of matter waves. nian motion. He explains the photoelectric 1925 S.A. Goudsmit and G.E. Uhlenbeck explain the effect using Planck’s light quantum hypothesis anomalous Zeeman effect by introducing the (Nobel prize 1921). electron spin, postulated theoretical already 1906 Charles Glover Barkla discovers the charac- 1924 by W. Pauli. teristic X-rays of the elements (Nobel prize 1925 W. Pauli (Nobel prize 1945) introduces the ex- 1917). clusion principle (Pauli-principle) which states 1909 Robert Millikan measures the elementary that every existing atomic state occupied by charge e with his oil-droplet experiment more than on electron must be described by (Nobel prize 1923). a wavefunction (product of spatial part and 1911 Ernest Rutherford and his coworkers investi- spin function) which is antisymmetric with gate the scattering of α-particles by gold nuclei respect to the exchange of two electrons. and postulates his atomic model. This can be 1925 Erwin Schrödinger (Nobel prize 1933) ex- regarded as the foundation of modern atomic tends the ideas of deBroglie about matter physics (Nobel prize for Chemistry 1908). waves to a general wave-mechanics which is 1912 Max von Laue (Nobelprize 1914) and his based on a special wave equation, called the coworkers demonstrate, that X-rays repre- Schrödinger equation. sent electro-magnetic waves by observing the 1927 Wolfgang Pauli gives a mathematical descrip- diffraction of X-rays by crystals. tion of the electron spin in form of quadrat- Shortly later William Henry Bragg (Nobelprize ic “spin-matrices” with two rows and two 1915) confirms this result and furthermore columns. Werner Heisenberg (Nobel prize Chronological Table 521 1932) develops together with Max Born 1954 N.G. Basow, A.M. Prochorov and Ch. Townes (Nobel prize 1954) and Pascual Jordan the (Nobel prize 1964) develop the theoretical mathematical concept of quantum mechan- foundations of the maser principle, based on ics, represented by matrices. He derives the Kastler‘s idea of optical pumping. First exper- uncertainty relations. imental verification of the NH3-maser by J.P. 1928 J.C. Davisson (Nobel prize 1937) and L.H. Gordon, H.J. Zeiger and Ch. Townes. Germer prove experimentally the wave na- 1957 Explanation of supra-conductivity by John ture of electrons by observing the diffraction Bardeen, Leon Cooper and J. Robert Schrieffer pattern of electrons passing through thin crys- (BCS theory) Nobel prize 1972. talline foils. 1958 Rudolf Mößbauer: Recoil-free emission and Paul Dirac (Nobel prize 1933) develops a rel- absorption of γ -quants by atomic nuclei ativistic theory of Quantum Mechanics. (Mößbauer effect) (Nobel prize 1972). Chandrasekhara Venkata Raman (Nobel prize 1959 Arthur Schawlow (Nobel prize 1995) and 1930) discovers the inelastic scattering of light Charles Townes give detailed description for by molecules (Raman-effect). the extension of the maser principle to the 1932 E. Ruska (Nobel prize 1986) constructs the optical range. first electron microscope. 1960 First experimental realization of an optical 1936 I. Rabi (Nobel prize 1944) demonstrates a new maser (ruby laser) by Th. Maiman. techniques of radiofrequency spectroscopy in 1961 The first He-Ne-laser is constructed by W.R. molecular beams for the precise measurement Bennet and A. Javan, based on detailed inves- of magnet moments. tigations of atomic collision processes in gas 1944 G.Th. Seaborg (Nobelprize for Chemistry discharges. 1951) identifies the first tran-uranium ele- 1966 The dyelaser is developed indepently by F. P. ments. Schäfer and P.A. Sorokin. 1947 Polykarp Kusch (Nobel prize 1955): Mea- 1971 G. Herzberg receives the Nobel prize in surement of the magnetic moment of the Chemistry for his centennial work on molec- electron. ular spectroscopy. Willis Lamb (Nobel prize 1955): Measurement 1980 First proposals for optical cooling of atoms by of the energy difference (Lamb-shift) between photon recoil by Th.W. Hänsch, A. Schawlow the 2S1/2 and 2P1/2 levels in the hydrogen and V. Letokhov. atom. 1982 Development of tunnel microscopy by G. 1947 John Bardeen develops together with W.H. Binning and H. Rohrer, where single atoms Brattain and W. Shockley the transistor (Nobel on surfaces can be observed (Nobel prize prize 1956). 1986). 1948 Felix Bloch and Edward Mills Purcell (Nobel 1986 Discovery of high temperature supra conduc- prize 1952) demonstrate the nuclear magnetic tivity by J. Bednarz and K.A. Müller (Nobel resonance technique NMR. prize 1987). 1948 J. Schwinger, R.P. Feynman and S. Tomonaga 1988 Nobel prize to H. Michel, J. Deisenhofer and (Nobel prize 1965) Theoretical formulation R. Huber for the elucidation of the primary of quantum field theory (quantum Electro- process in the photosynthesis of green plants dynamics).