Resonant photofragmentation of water at the oxygenKedge by high-resolution ion-yield spectroscopy

Abstract

Resonant photofragmentation of core-excited water molecules has been studied with high-resolution partialion-yield spectroscopy. Both the single and coincidence channels were monitored simultaneously. A steep increase in the coincidence yield curves above the ionization threshold, where the normal Auger decay produces doubly charged or multiply charged species that yield two or more charged fragments, has been observed. By comparing the single and coincidence channels the relative weight of H neutral fragments has been qualitatively assessed, and found to be higher for the O 1s→4a 1 primary excitation. The presented ion-yield data provide strong evidence for a branching between atomic Auger decay and molecular fragmentation in the O ϩ channel. The most unexpected result is the formation of H 2 ϩ species being detected and attributed to a highly excited bending mode. ͓S1050-2947͑99͒00601-0͔

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

“…The sum of the charge states of the fragments must equal +1; hence singly charged cations and neutral fragments are expected to be the most common dissociation products after resonant Auger decay, see e.g. [2,3]. More highly charged ions can be created when core-excited states decay by emitting two or more electrons simultaneously (double and triple Auger decay [4]) or when they decay to so highly excited ionic states that second-step Auger decay is energetically allowed (Auger cascades).…”

Infrared-pump–x-ray-probe spectroscopy of vibrationally excited molecules

“…The PESs for the ground, and the two lowest 4a 1 [12,13] and 2b 2 [13] core-excited states were computed at the RASSCF (restricted active space self-consistent field) theory level [27] implemented in the MOLCAS package [28] (see Fig. 1(b)).…”

“…In contrast, in this work we study changes in XAS and RIXS spectra when the process starts from a single excited vibrational state. The proposed method is applied to the water molecule, in the xray spectral region near the two lowest core-excited states of dissociative 1a −1 1 4a 1 and bound 1a −1 1 2b 2 character [12,13]. We show advantages of the proposed schemes with the help of numerical simulations using two-dimensional wave packet techniques [14,15] combined with high level ab initio calculations of the PESs.…”

Core Excitation and De-excitation Spectroscopies of Free Atoms and Molecules

“…15(b). A reasonable fitting is obtained in the case of 151 AE 5 and 80 AE 5 meV for 88) They suggested a key role of the bending motion in the core-excited state, though they could not resolve the vibrations with their limited resolution ($180 meV bandwidth) and thus could not exclude the possibility of the overlap with another electronic state. In a similar measurement with a bandwidth of $55 meV, 12) vibrations in the core-excited state are resolved and clear evidence is obtained for the role of the vibrations in the core-excited state.…”