Control of nuclear motion in the B 2b₂ionic state of water via an Auger resonant Raman process

Abstract

Resonant Auger spectra of H2O are recorded with unprecedented resolution, for excitation energies tuned across the O 1s→2b2 resonance. Electron emission spectra for decay to the 1b2-1 final state show a partially resolved vibrational envelope whose overall appearance is photon energy dependent. Comparison with ab initio calculations indicates that the two-dimensional nuclear motion of the Auger final state can be controlled by sampling different portions of the potential curve and changing the nuclear motion in the core-excited state.

Core-level spectroscopy and dynamics of free molecules

“…The most interesting finding is that this mode selectivity decreases when the excitation energy is increased. At the hν = 535.95 eV excitation, in addition to the (1,ν 2 ) main progression, also the (0,ν 2 ) and (2,ν 2 ) progressions were identified [11]. At the hν = 536.12 eV excitation, the intensity of the (2,ν 2 ) components is comparable to those of the other components.…”

“…In the work of De Fanis et al [11], the observed vibrational structure is attributed mostly to the ν 2 mode. The vibrational structure becomes less resolved at the O1s → 2b 2 (1,0) excitation (cf.…”

“…In this way, complex twodimensional nuclear motion is stimulated in the Auger final state by the Auger resonant process via the (ν 1 , 0) components in the core-excited state. In the work of De Fanis et al [11] it was confirmed that indeed the two-dimensional nuclear motion of the Auger final state is mediated by tuning the incident energy to different portions of the core-excited state.…”

“…Another example of nuclear motion being reflected in the vibrational distribution of Auger decay spectra is the core excitation-decay in water. It has been shown that the two-dimensional nuclear motion of the Auger final state can be probed by resonant Auger spectroscopy, and furthermore that it can be mediated by sampling a different portion of the potential curve and changing the nuclear motion in the core-excited state [11]. Fig.…”

“…2 taken from Ref. [11] shows the electron emission spectra of H 2 O recorded at four different photon energies across the O1s → 2b 2 resonance together with calculated vibrational progressions. The spectra cover the binding energy region 17.0 -20.0 eV, where the B band corresponding to electron emission from the 1b 2 orbital is present.…”