[en] The technique of threshold photoelectron spectroscopy using synchrotron radiation is described and recent technical developments are discussed. The sorts of information that such studies can provide about atoms and molecules are considered. Examples of recent experimental studies of both single and double photoionisation are given in the context of the high photon resolution now provided by synchrotron radiation sources

[en] In this work an inner-shell spin-forbidden transition in N₂ and a parity-forbidden transition in Ar were studied. These transitions were observed by using incident electron energies as low as 1.15 times the excitation energy of the inner-shell states. (Auth.)

[en] This chapter presents early inner-shell excitation studies and high-resolution studies. A comparison of the photoabsorption and electron energy-loss techniques for making spectroscopic measurements in atoms and molecules is presented. Experimental details are given for the electron energy-loss technique. High-resolution studies of both atoms and molecules are examined

No abstract available

[en] The interaction of gene 5 protein (G5P) with oligodeoxynucleotides is investigated by ¹H NMR methods, principally two-dimensional nuclear Overhauser effect spectroscopy (NOESY). Aromatic resonances of G5P are specifically assigned from crystallographic data, while the low-field resonances of nucleotides are assigned with sequential or other procedures. Chemical shift changes that accompany binding of d(pA)₄, d(A)₄, d(pT)₄, and d(pA)₈, combined with specific protein-nucleotide nuclear Overhauser effects (NOEs) obtained from NOESY spectra, suggest that Phe-73 and Tyr-26 are the only aromatic residues that stack significantly with nucleotide bases. Chemical shift data also imply a role for Leu-28, though this has not been confirmed with intermolecular NOEs. Binding of all four oligonucleotides causes marked upfield movements (0.1-0.6 ppm) of G5P NOESY cross peaks belonging to Tyr-26, Leu-28, and Phe-73. In the d(pA)₄-G5P complex an intermolecular NOE is observed between Tyr-26 and H1' of Ade-1, while Phe-73 has NOEs with the H2, H8, and H1' protons of Ade-2 and -3. Binding causes relatively small chemical shift changes for the base resonances in adenylyl nucleotides, suggesting that there is some, but not complete, unstacking of the bases. The view of the G5P-oligonucleotide interaction that emerges from this study is different from one previously proposed from model-building exercises. NMR data provide no support for this proposal. Rather, a comparison of the NMR data with the X-ray structure of native G5P suggests that Tyr-26, Leu-28, and Phe-73' form the major components of a dominant nucleotide interaction site that lies near a phosphate-binding electropositive cluster formed by the side chains of Arg-16, Arg-21, Lys-24, and Lys-46. Such an interaction mode creates a shorter nucleotide path across the protein surface than previously proposed

No abstract available

[en] The use of a threshold photoelectron/photoion coincidence spectrometer for the study of threshold photodouble ionization processes is described. This spectrometer has been used to determine the value of the exponent α in the Wannier law and its range of validity, and to investigate the behaviour of the asymmetry parameter β for near-threshold photoionization. The experimental results are compared with theoretical predictions. (orig.)

[en] Recent work devoted to the study of photo-double-ionization of atoms is reviewed. This process is of much current interest because it is completely dominated by electron-electron correlations. In particular, experimental studies based on the techniques of low energy electron spectroscopy are described in the region near the double ionization threshold, together with (γ, 2e) coincidence experiments performed above this threshold. By using selected examples from non-coincidence and coincidence experiments the various kinds of dynamic and spectroscopic information that can be obtained are illustrated. Recent results, mainly in the rare gases, are described and their interpretation discussed. Future perspectives are considered

No abstract available

[en] The differential cross sections for the excitation of the n=2 states of atomic hydrogen by high-energy-resolution electron impact have been measured at scattering angles of 33⁰, 54⁰, 70⁰ and 90 ⁰ over the energy range 11.5 to 12.2 eV, allowing the Feshbach resonances below the n=3 inelastic threshold to be studied. The lowest six of these resonances have been identified as ¹S, ³P, ¹D, ¹P, ³F and ³S/³D respectively, using previous classifications. At higher energies, the ³P, ¹D and ¹S states have been tentatively identified. All measured energies agree well with previous work. (author)