Gerhard Herzberg

"Atomic Spectra and Atomic Structure"
"Molecular Spectra and Molecular Structure I. Spectra of Diatomic Molecules"
"Molecular Spectra and Molecular Structure II. Infrared and Raman Spectra of Polyatomic Molecules"
"Molecular Spectra and Molecular Structure III. Electronic Spectra and Electronic Structure of Polyatomic Molecules"
"Molecular Spectra and Molecular Structure IV. Constants of Diatomic Molecules"
"The Spectra and Structures of Simple Free Radicals: An introduction to Molecular Spectroscopy"

Discovery of new spectra of known and (at the time) unknown diatomic molecules CO, N₂, PN, CP, B₂, H₂, HD, D₂ and others, and molecular ions especially CH⁺, and C₂^-. Observation of forbidden transitions of O₂, CO and particularly H₂ (the quadrupole infrared spectrum). Early (1929) recognition with Heitler from Rasetti's Raman spectra of N₂ that the N nuclei obey Bose statistics, that is, that electrons are not present in nuclei, leading to Heisenberg's recognition that nuclei are made up of neutrons and protons. Study of the spectra of simple polyatomic molecules H₂CO, C₂H₂, HCN, C₃ etc. Use of isotope effect to establish their precise geometric structures. Herzberg–Teller selection rules for electronic transitions. First observation of -type doubling. Variation of C–C single bond distance depending on the nature of neighbouring bonds. Study of electronic spectra of simple free radicals : NH₂, HCO, CH₃, CH₂, BH₂ and others. First observation of Rydberg molecules especially H₃ and NH₄. Precise spectroscopic determination of dissociation energies especially of O₂, H₂, HD, D₂ and of ionization potentials of H₂ and D₂, comparison with theoretical values. First experimental determination of the Lamb shifts of the ground states of the deuterium and helium atoms. Repeated contributions over many years to the study of predissociation.