Femtosecond Dissociation of Core-Excited HCl Monitored by Frequency Detuning

Abstract

Core excitation of gaseous HCl to the dissociative s ‫ء‬ state leads to a deexcitation spectrum with two qualitatively different contributions -a broad molecular background and narrow atomic lines. The experiment demonstrates that the ratio of integrated intensities from these two contributions depends crucially on the excitation frequency; the molecular background is enhanced with increased detuning of the photon frequency. This is discussed in a time-dependent model, using the concept of an effective duration time for the resonant x-ray scattering process. [S0031-9007(97)

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].…”

Intramolecular Electron Scattering and Electron Transfer Following Autoionization in Dissociating Molecules

“…However, for values close to 180 the momentum transfer of the second scattering process can be neglected reducing the kinematical discussion to Eq. (1).…”

“…By that, dissociation of the nuclear framework and relaxation of the electronic shell are induced; they compete on a similar, femtosecond time scale. After discovery of this time scale, termed ''core-hole clock'' [1], interference effects of the outgoing nuclear wave packets [2,3] and most recently the momentum exchange of the fast accelerating fragments with the atomic autoionization electrons (also called resonant Auger electrons) [4,5] have been investigated.…”

Core-level spectroscopy and dynamics of free molecules

“…It has pioneeringly been observed for core-excited HBr [33], and has since then been found for other systems such as HCl [34,35], H 2 S [36,37], and many more, some of which we shall enlighten in this section and in the subsequent one.…”