Atomic Autoionization Following Very Fast Dissociation of Core-Excited HBr

On the production of N+2ions at the N 1s edge of the nitrogen molecule

“…At the N 1s → 3sσ excitation, soft x-ray emission only reaches the 3σ −1 g 3sσ 1 state, which is located below the first ionization potential of 15.581 eV. At the N 1s → 3pπ excitation, a small part of x-ray fluorescence intensity goes to the 2σ −1 u 3pπ 1 u state, which, as judged by the transition energy, should be located above the IP and could thus be followed by autoionization to the ground state of N + 2 . The soft x-ray emission energies are expected to remain practically constant at higher core-to-Rydberg excitations because the N 1s → 3pπ soft x-ray emission spectrum is shifted from the non-resonant spectrum, resulting from the (N 1s) −1 states, by only 0.05 eV [26].…”

“…Those resonances represent the creation of highly excited neutral states, where an inner-shell (or core) electron has been transferred to an unoccupied (or virtual) valence or Rydberg orbital. The resulting core-excited states decay very fast-typically in the fs range-by emitting x-ray photons or electrons or, in some cases, they may dissociate before the decay of the core hole (ultrafast dissociation [1]). Electron emission is by far the predominant decay channel in molecules composed of light elements such as carbon, nitrogen and oxygen.…”

Potential Energy Surface Reconstruction and Lifetime Determination of Molecular Double-Core-Hole States in the Hard X-Ray Regime

“…In the case of resonant excitation to a dissociative molecular state, the time evolution of the relaxation process is determined by the potential energy surface (PES) and the lifetime of the excited state. The so called "core-hole clock" spectroscopy (CHCS) allows probing ultrafast dynamics, occurring in a resonantly core-excited molecule within the core-hole lifetime, through control over the photon energy [1][2][3][4].Resonant inelastic x-ray scattering (RIXS) and resonant Auger electron spectroscopy (RAS) are the two CHCS techniques relevant, respectively, to the measurements of x-ray photons or Auger electrons emitted in the course of relaxation of core-excited molecular states. As the probability of radiative relaxation of core-excited atoms increases with atomic number, both RIXS and RAS become equally relevant in the hard x-ray regime [5][6][7][8][9][10][11][12][13][14].…”

“…In the case of resonant excitation to a dissociative molecular state, the time evolution of the relaxation process is determined by the potential energy surface (PES) and the lifetime of the excited state. The so called "core-hole clock" spectroscopy (CHCS) allows probing ultrafast dynamics, occurring in a resonantly core-excited molecule within the core-hole lifetime, through control over the photon energy [1][2][3][4].…”

Design of a lens table for a double toroidal electron spectrometer

“…The spectral line profiles in the electron energy spectra can also provide information on the ultrafast processes, such as the competition between the electronic decay and the nuclear motion. [13][14][15][16][17][18] Information on the interferences and phase shifts of the partial waves that describe the photoionization process itself 19 can also be retrieved by measuring the angular distribution of the ejected electrons with respect to the light polarization axis or to the propagation direction of the photon beam. 20 The combination of electrons and ions spectrometers in a sophisticated coincidence technique constitutes a powerful way to provide a direct view on a molecular reaction process by correlating all physical parameters of the emitted eleca) Electronic mail: liu@synchrotron-soleil.fr.…”