O. Edqvist

On the Photoelectron Spectrum of O2

The photoelectron spectrum of molecular oxygen has been studied in the range 12-28 eV with the 584 A and 304 A He lines, and the O2+ states have been measured accurately. Due to the high resolution of our apparatus we have been able to observe the A2 Πu state which has been considered as absent in photoelectron spectroscopy work. Its ionization energy is 17.045 eV. Our result is compared with spectroscopic observations of the second negative band system A2Πu → X2Πg. The relative intensity of the A2Πu state is in good agreement with a recent calculation by Dixon and Hull.

Jahn-Teller effect in the vibrational structure of the photoelectron spectrum of benzene

Abstract The photoelectron spectrum of benzene has been measured with high resolution. The lowest band at 9.241 eV, which is due to ionization from a degenerate π orbital, exhibits several fundamental frequencies. Each of the two possible ionization processes has a characteristic vibrational structure which is shown by comparison with pyrazine (Jahn—Teller effect). The vibrational structure is used to identify other degenerate and non-degenerate orbitals in benzene.

RYDBERG SERIES IN SMALL MOLECULES

Abstract New Rydberg series have been identified in the ultraviolet spectrum of furan. The charge exchange mass spectrum has been measured as a function of energy, and the protection spectrum has been measured up to ionization potentials of 25 eV. This formation, together with quantum-chemical calculations, allows a description of the electronic structure of furan to be given.

The electronic structure of benzene

Abstract The orbital energies of benzene from photoelectron spectroscopy measurements have been discussed by use of electron impact energy loss measurements and mass-spectrometric measurements. Between the π-orbitals at 9.3 eV and 12.1 eV there is a σ-orbital at 11.4 eV. Also the remaining molecular orbitals have been identified.

Photoelectron-spectroscopical study of the vibrations of furan, thiophene, pyrrole and cyclopentadiene

Abstract It is shown that photoelectron spectroscopy is of considerable value in the interpretation of Raman and infrared spectra. On the basis of photoelectron-spectroscopical results, new assignments are made for the symmetric “ring distorting” vibrations in furan, pyrrole and cyclo pentadiene. The uncertainty concerning the assignments for the symmetric “hydrogen bending” vibrations of the molecules, furan, pyrrole and cyclo pentadiene is largely eliminated. The assignments for the “ring breathing” vibration of furan and the symmetric “double bond stretching” vibrations of furan, thiophene, pyrrole and cyclo pentadiene are confirmed.

Rydberg series of small molecules VIII. Photoelectron spectroscopy and electron spectroscopy of NO2

The photoelectron spectrum of NO2 has been measured with high resolution up to 27.5 eV and interpreted by use of molecular orbital theory, taking especially the vibrational structure into account. The electron impact energy loss spectrum has been measured with electron energy 100 eV. The spectrum above 6.5 eV has been interpreted as due to Rydberg transitions and comparison with spectroscopic measurements have been made.

Rydberg series in small molecules: XIII. Photoelectron spectroscopy and electronic structure of cyclopentadiene

Abstract The photoelectron spectrum of cyclopentadiene has been measured up to 25 eV and its charge exchange mass spectrum has been determined as a function of energy. New Rydberg series have been identified in the ultraviolet spectrum. This information together with quantum-chemical calculations allows a description of the electronic structure of cyclopentadiene to be given.

The photoelectron spectra of O2, N2 and CO

Abstract The A 2 Π u state of O+2 has been observed in the photoelectron spectrum of O2. Its ionization energy is 17.045 eV. The intensity is only 1 6 of the intensity of the a 4 Π u state. The C 2 ∑ 2 + state of N+2 does not appear in the photoelectron spectrum of N2 as is also the case with the corresponding state of CO+. The rules for the appearance of ionic states in photoelectron spectroscopy are discussed.