J.B. Peel

Photoelectron spectra of sulfur dibromide and selenium dibromide

Abstract The photoelectron spectra of gaseous products from reactions of atomic/molecular bromine with powdered sulfur and selenium analysed with a visual assessment stripping program (VASP) yield the He(I) spectra of SBr 2 (sulfur dibromide) and SeBr 2 (selenium dibromide). The proposed assignments are consistent with the results of valence-electron-only model-potential (VEOMP) calculations.

Photoelectron spectroscopic studies of the monomers and dimers of acetic and trifluoracetic acids

Abstract Comparison of the He(I) and He(II) photoelectron spectra of acetic and trifluoracetic acids has clarified the assignments of their p -based ionization potentials. The He(I) spectra of the gas-phase homodimer of each molecule have been observed using a high-pressure nozzle inlet system operating at room temperature. Spectrum-stripping of the monomer—dimer mixed-spectra gives dimer spectra which are interpreted with the aid of molecular orbital calculations. Appropriate mixtures of the two acids have been analyzed to obtain the He(I) spectrum of the 1:1 heterodimer. Assignments of the three dimer spectra indicate that the inductive influences of the methyl and trifluoromethyl groups are transmitted across the hydrogen-bond bridges.

Photoelectron spectroscopic studies of the butylbenzenes

Abstract The He(I) photoelectron spectra of the geometrical isomers of butylbenzene have been compared. All the isomers have first ionization potentials within 0.08 eV but show variations in the higher ionization energy range. A valence-electron-only model potential (VEOMP-3G) method is employed to aid in the spectral assignment. Comparison with the spectra of benzene and the butyl moiety indicates that the spectra of the butylbenzenes can be interpreted according to a composite-molecule model, which indicates that CC as well as CH hyperconjugation must be invoked to adequately describe the benzene—butyl interactions.

Photoelectron spectroscopic assignment of the p-states of benzenethiol

Abstract He(I) anisotropy parameters and He(I)/He(II) relative band intensities have been determined and utilised to make a complete assignment of the benzenethiol p -electron-region photoelectron spectrum. The major S-atom contribution appears more so in the third band than in the first.

The photoelectron spectrum of bromamine

Abstract The He(I) photoelectron spectrum of bromamine, NH 2 Br, has been obtained from observation of the products of the gas-phase reaction of NH 3 and Br 2 . A satisfactory yield of NH 2 Br is obtained in the presence of excess NH 3 . Spectrum stripping was used to remove the NH 3 and N 2 bands, leaving a spectrum of mainly NH 2 Br which correlates well with a calculated molecular orbital description.

Photoelectron spectra of the gauche and trans conformers of 1,2-bromochloroethane

Abstract The HeI photoelectron spectra of the gauche and trans conformers of 1,2-bromochloroethane have been obtained by analysis of time-averaged spectra recorded at different temperatures. Variations in ionization potentials of the two conformers are consistent with data obtained from molecular orbital calculations. Analysis of a HEII spectrum and comparisons with the related molecules 1,2-dichloroethane and 1,2-dibromoethane shows that the ClBr non-bonded interactions include both through-bond and through-space contributions.

The photoelectron spectra of unstable intermediates : Dibromamine

Abstract The He(I) photoelectron spectrum of dibromamine, NHBr2, has been obtained from observation of the products of the room temperature gas-phase reaction of NH3 and Br2. Due to its extreme reactivity, only a small proportion of NHBr2 is present in various mixtures containing NH2Br and N2 as well as unreacted NH3 and Br2. Careful spectrum stripping is required to obtain a spectrum of NHBr2 which is identified by the relationship of its spectrum to those of NH2Br, NH2Cl and NHCl2.

Electronic structure of the valence bands of SnCl2 and SnBr2 studied by ultraviolet photoelectron spectroscopy

Abstract A photoelectron study of the outermost bands of solid-phase SnCl2 and SnBr2 using 40.81 eV photons is reported. The main features of the spectra are successfully interpreted in terms of molecular orbital theory for the appropriate isolated molecules.

A comparative He(I)/He(II) study of the photoelectron spectrum of benzoyl chloride

Abstract The He(I) and He(II) photoelectron spectra of benzoyl chloride have been subjected to a relative band intensity analysis. The spectral assignment, which is supported by theoretical ionization cross-sections calculated from a GAUSSIAN 70 wavefunction, illustrates the use of He(II) radiation for molecules containing heavy atoms. The low ionization potentials of benzoyl chloride are described in molecular orbital terms as π o Cl ∼ n Cl .

The photoelectron spectra of N-bromo-methylamine and N, N-dibromo-methylamine

Abstract The UV photoelectron spectra of the reactive halamines, CH 3 NHBr (N-bromo-methylamine) and CH 3 NBr 2 (N, N-dibromo-methylamine) have been obtained from measurements on the gas phase reaction products of CH 3 NH 2 and Br 2 . Spectrum-stripping was used to separate the two components from spectra obtained under different equilibrium conditions. The spectra correlate well with the results of molecular orbital calculations on the two molecules, and show that there is considerable pπ-pπ interaction in the NBr bond.