P. Sauvageau

Vacuum ultraviolet and photoelectron spectra of fluoro‐chloro derivatives of methane

The photoelectron and vacuum ultraviolet absorption spectra (200–120 nm) of CF3Cl, CF3Br, CF2HCl, CFH2Cl, CFHCl2, CF2Cl2, and CFCl3 are reported and discussed. The lowest ionization potentials belong to the chlorine or bromine lone pair orbitals, the next highest ones to the bonding orbitals of mainly C–Cl or C–Br character. In the absorption spectra the lowest freuqency bands are due to weak valence‐shell type transitions. At higher freuqencies we find much stronger Rydberg type bands related to the first ionization potential. All absorption bands up to 84 000 cm−1 depart from chlorine or bromine lone pair orbitals. Some of the bands exhibit vibrational fine structure. An increase in the number of the fluorine atoms causes a shift to either higher or lower energies of the ionization potentials belonging to orbitals of mainly C–H or C–Cl character according to the cases while the lone pair ionization potentials and the absorption spectra shift to higher energies in all cases.

THE ELECTRONIC SPECTRA OF n-ALKANES,

Abstract The far ultraviolet absorption spectra of the eight first normal paraffin hydrocarbons were measured down to 1150 angstroms with a MePherson model 225 normal incidence vacuum monochromator completed with a model 665 double beam attachment under approximately 0.2 A resolution. Methane has a diffuse but not entirely structureless band system with a maximum at 1277 A. According to its intensity it should be relating to an allowed transition and must therefore be of the 1 F 2 ← 1 A 1 type. The other seven molecules all seem to have a weak which was predicted by Mulliken in the case of ethane and probably has similar origins in all these molecules. Towards shorter wavelengths strong bands follow. The first strong band system of ethane exhibits a relatively well-resolved vibrational fine structure. The transition is very probably of the 1 E ← 1 A 1 type. The first and second strong bands (and probably the following ones) show a systematic shift toward longer wavelengths and a corresponding increase in intensity. An attempt is made to interpret the spectra in terms of Mullikens united atom treatment of the excited configurations of methane and ethane and of the Pariser- and Parr-type calculations of Katagiri and Sandorfy.

Photoelectron and far‐ultraviolet spectra of CF3Br, CF2BrCl, and CF2Br2

The Hei photoelectron and vacuum ultraviolet spectra up to about 20 eV of CF3Be, CF2Br2, and CF2BrCl have been measured. In both spectra, we find bands at energies lower than in the corresponding chlorine derivatives. Otherwise, the spectra can be interpreted along similar lines. The lowest ionization potentials and the lowest frequency bands in the ultraviolet spectra are due to transitions from the bromine lone pair orbitals.

The electronic spectra of normal paraffin hydrocarbons

Abstract The far ultraviolet absorption spectra of the normal paraffin hydrocarbons from C 1 to C 8 were photoelectrically recorded with a double beam instrument down to 1150 A under 0.2 A resolution. An attempt is made to interpret the spectra in terms of Mullikens united atom treatment of the excited states of methane and ethane.

Vacuum ultraviolet and photoelectron spectra of fluoroethanes

The photoelectron and vacuum ultraviolet absorption spectra of ethylfluoride, 1,1‐difluoroethane, 1,1,1‐trifluoroethane, and hexafluoroethane have been measured up to 20 eV. The photoelectron spectra show that the highest filled orbital in the ground state is an orbital mainly populated in the C–C bond in the molecules containing two or more fluorine atoms; for ethane itself and for ethylfluoride a mainly C–H and a mainly C–C orbital are almost degenerate. The ultraviolet absorption spectra can be interpreted in terms of Rydberg bands, some of which are superimposed on the ionization continuum.

The far-ultraviolet spectra of perfluoro-normal-paraffins☆

Abstract The far-ultraviolet spectra of the perfluoro- n -paraffins (C 1 to C 6 ) were measured from 2000 to 1150A. The spectra are compared to those of the related n -paraffins and a tentative interpretation is given.

Vacuum ultraviolet absorption spectra of fluoromethanes

The electronic absorption spectra of tetrafluoromethane, fluoroform, methylene fluoride, and methylfluoride were measured between 120 and 60 nm. Except for intenstities the spectra are found to be essentially the same as the electron impact spectra published previously by Harshbarger, Robin, and Lassettre. An experimental setup is described whereby absorption spectra can be measured in this part of the spectrum with relative ease.

The vacuum-ultraviolet absorption spectra of boron-trihalides

The vacuum-ultraviolet spectra from 200 to 120 nm of BF3, BCl3 and BBr3 are reported. Tentative assignments are made. The lowest frequency band of BCl3 and BBr3 can be assigned to a valence-shell transition of the π* ← π type of the σ* ← σ type. The strongest bands found at higher frequencies in the spectrum of BBr3 can be assigned to transitions to p-type Rydberg orbitals related to the three lowest (close lying) ionization potentials. Some weaker bands are likely to result from spin-orbit coupling.

Photoelectron and far‐ultraviolet absorption spectra of chlorofluoro derivatives of ethane

The Hei photoelectron and vacuum ultraviolet absorption spectra of the following chlorofluoro derivatives of ethane have been measured: C2F5Cl, CH3CF2Cl, CF2Cl−Cf2Cl, CF2Cl−CFHCL, and CF2CL−CFCl2. The lowest ionization potentials (12−13 eV) and all absorption bands from 50 000−84 000 cm−1 are due to transitions from the chlorine lone pair orbitals (Cl). The I.P.’s between 14 and 16 eV are due to ionization from orbitals mainly populated in the C−Cl, C−C, and C−H bonds, while at higher energies, ionization from orbitals of F lone pair (F) and C−F bonding character takes place. The lowest electronic transition is of the valence−shell type; at higher frequencies, Rydberg bands are found due to 4s→Cl and 4p→Cl type transitions.

Far-UV and photoelectron spectra of 1,3,5-trifluorobenzene

Abstract The photoelectron and vacuum-ultraviolet absorption spectra of 1,3,5-trifluorobenzene and its fully deuterated analog were measured. The two lowest ionisation potentials correspond to the π levels. We find two Rydberg series converging to the first IP and one converging to the second IP. The assignments are confirmed by the similarities between the vibrational fine structures of the photoelectron and the related Rydberg bands. These fine structures exhibit significant differences with respect to benzene.