T. Bergmark

Electron Spectroscopy of Open‐Shell Systems: Spectra of Ni(C5H5)2, Fe(C5H5)2, Mn(C5H5)2, and Cr(C5H5)2

The high resolution HeI electron spectra of Ni(C5H5)2, Fe(C5H5)2, Mn(C5H5)2, and Cr(C5H5)2 have been recorded and analyzed in terms of a molecular orbital description of the electronic structure. The ground state electronic configurations have been assigned by considering the feasible ground state configurations, determining the number and type of ionic states obtained from ionization of these configurations, and then comparing the predicted transitions with those observed experimentally. The ground state configuration and adiabatic first ionization potential of these molecules are: Cr(C5H5)2, ··· (e2g)3(a1g)1, 3E2g, I.P.=5.50 eV; Mn(C5H5)2, ··· (e2g)4 (a1g)1, 2A1g, I.P.=6.55 eV; Fe(C5H5)2, ··· (a1g)2 (e2g)4, 1A1g, I.P.=6.72; Ni(C5H5)2, ··· (a1g)2 (e2g)4 (e1g)2, 3A2g, I.P.=6.2 eV. Vibrational structure has been observed in the spectrum of ferrocene and is assigned to progressions in ν4, the symmetric ring‐metal stretching mode.

Analysis of vibrational structure and Jahn‐Teller effects in the electron spectrum of ammonia

The electron spectra of the 2A1←1A1 and the 2E←1A1 transitions of ammonia have been measured with sufficient resolution to observe considerable fine structure. The first transition, 2A1←1A1, contains two vibrational progressions which are assigned to the ν2 bending mode. The second transition 2E←1A1, consists of two overlapping electron bands due to Jahn‐Teller splitting of the 2E state. The vibronic structure accompanying this transition has been partially resolved and compared to the results of model calculations.

Isotopic and vibronic coupling effects in the valence electron spectra of H2 16O, H2 18O, and D2 16O

Isotopic shift data for Hei induced high resolution valence electron spectra of H2 16O, H2 18O, and D2 16O are presented. From the differences in the vibrational subspectra we were able to deduce adiabatic ionization energies and geometries of the ions and to assign the excited vibrations to normal modes. The ν2 progression in the 2A1 band was found to be affected by strong vibronic coupling.

The Jahn-Teller Effect in the Electron Spectrum of Methane

The high resolution He I photoelectron spectrum of the (a12t25)2T2 < - (a12t26)1A1 transition in methane has been recorded and analyzed and a value has been obtained for the adiabataic ionization potential. The electron spectrum resulting from ionization of a t2 electron is a composite of at least three overlapping electronic bands which are separated by several tenths of an eV. These bands are the split components of the 2T2 electronic state of the CH4+ ion which is distorted by strong Jahn-Teller forces. The symmetry of the molecule in these three electronic states is believed to be, in order of increasing energy, D2d<C3e<D2h. The active vibration which causes the Jahn-Teller splitting is the r2(e) mode. The adiabatic ionization potential of methane is certainly below 12.62 eV. Our extrapolated value is approx- 12.51 eV. Four different vibrational progressions have been found, one of which shows vibronic splittings.

Valence Electron Spectra of Benzene and the Hexafluorides of Sulphur, Molybdenum, Tungsten and Uranium. An Application of Multichannel Detector Technique to UV-Valence Electron Spectroscopy

HeI induced valence electron spectra of benzene and the hexafluorides of sulphur, molybdenum, tungsten and uranium are presented together with a HeII spectrum of sulphur hexafluoride. Vibrational band structure has been resolved in the spectra of all molecules and the energies of these bands are reported. A description is also given of the multichannel detector system which has facilitated the recordings of these spectra.

Electron Spectroscopic Investigation of Auger Processes in Bromine Substituted Methanes and Some Hydrocarbons

Auger spectra in gaseous CH4, CH3Br, CH2Br2, CHBr3, CBr4, C2H6, and C6H6 are excited by electron impact at about 5 keV energy and observed by means of a spherical electrostatic spectrometer at 90° to the primary electron beam. Besides the energies and the intensities of the Auger lines and the chemical shifts, the analysis of the spectra gives the energies and the lifetimes of the doubly ionized molecules. The line widths together with energy considerations indicate that some of these doubly ionized molecules rapidly dissociate. Comparisons are also made between the bromine and the carbon spectra.

The High Resolution L2,3 MM and M4,5 NN Auger Spectra from Krypton and M4,5 NN and N4,5 OO Auger Spectra from Xenon

The high resolution Auger spectra from krypton (L2,3 MM and M4,5 NN) and xenon (M4,5 NN and N4,5 OO) have been obtained. The Auger lines are assigned by comparison with energies obtained from optical spectroscopy and relativistic Hartree-Fock-Stater calculations and the energies of new atomic levels have been found. Some of the satellite lines have been assigned to shake-up processes. Comparison with calculations of Auger intensities has also been made.

The L2,3MM Auger Spectrum of Argon

The Ar L2,3MM Auger spectrum has been recorded. A great number of satellite lines are found many of which can be assigned to Auger transitions in doubly ionized argon. Several shake-up satellites are also found in the spectrum. The relative intensities of the spectral lines are given and the intensities are compared with previous experiments and calculations.

Vibrational and Vibronic Structure in the Valence Electron Spectrum of H2S

The high resolution HeI induced electron spectrum of H2S is presented and the energies of the observed vibrational and vibronic bands are reported. In the 2B1 electron band two progressions of vibrational bands have been measured. In the 2A1 electron band the vibronic structure associated with v2 bending vibrations has been partially resolved. Assignments of the vibronic bands are suggested from a comparison with electronic emission data in terms of the vibrational and angular momentum quantum numbers v2 and K.

The high resolution electron spectra of thiophene, 2-bkomothiophene and 3-bromothiophene

The high resolution HeI photoelectron spectra of thiophene, 2-bromothiophene and 3-bromothiophene have been recorded and vibrational analysis has been obtained. The vibrational analysis has shown that Br-sensitive, ring-stretching and ring-bending modes are excited together in many of the bands, indicating the mixing of Br atomic orbitals with the ring. Very sharp bands are obtained from ionization of the Br “lone pair” electrons. Vibrational analysis coupled with extended Huckel calculations indicate that these “lone pair” electrons exist in two different orbitals, the out-of-plane a″ orbital and the in-plane a′ orbital. The a″ electrons are more strongly bonding than the a′ electrons because of the “back-bonding” ability of the a″ orbital. Comparison of the thiophene and bromothiophene spectra indicate an intensification of the bands resulting from ionization of ring π electrons with respect to those resulting from ionization of ring σ electrons in the heavier molecules. This observation facilitates identification of bands resulting from π and σ electrons and suggests further experiments to determine if it is a general phenomenon.