Evidence against atomiclike resonant Auger decay inN2doubly excited core states by high-resolution experiments (original) (raw)
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Selective vibrational excitation in the resonant Auger decay following core-to- transitions in
Journal of Electron Spectroscopy and Related Phenomena, 2010
In N 2 O a detailed study of the vibrational distribution of theX state reached after decay of core-to- * excitation of N terminal, N central and O 1s core levels is reported. We observe a change in the relative intensity of bending versus stretching modes while scanning the photon energy across all three resonances. While this effect is known to be due to the Renner-Teller splitting in the core-excited states, we could derive that the antisymmetric stretching is excited mainly in the decay of the N terminal 1s-to- * excitation. An explanation for such selectivity is provided in terms of interplay of vibrational structure on potential energy surfaces of different electronic states involved in the process.
Dissociation of core-valence doubly excited states in NO followed by atomic Auger decay
The Journal of Chemical Physics, 2010
The decay processes of core-valence doubly excited states near the N K edge of NO have been studied using electron spectroscopy. Electron yields measured as a function of photon energy and kinetic energy enable the clear identification of atomic Auger lines associated with the dissociation of doubly excited states. The atomic Auger lines exhibit Doppler profiles, allowing the entire reaction scheme of such dissociation processes to be determined.
Bond-distance-dependent decay probability of the N 1s →π* core-excited state in N 2
Journal of Physics B: Atomic, Molecular and Optical Physics, 2000
We report the observation of the unusually weak decay of the N 1s → π * coreexcited N 2 molecule to theB 2 + u final state of N + 2 , which is only detectable in an experiment with high sensitivity. The resonant Auger spectra exhibit an unexpected dependence on the selected vibrational level of the intermediate state. Theoretical calculations show that the interference between direct and resonant photoemission as well as a strong geometry dependence of the decay probability on the bond distance give rise to the observed features.
Evidence of ultra-fast dissociation in ammonia observed by resonant Auger electron spectroscopy
Chemical Physics Letters, 2003
We present evidence for ultra-fast dissociation of molecular ammonia when photo-excited to the N1s ! 4a 1 corehole state. This finding is based on resonant Auger spectroscopical results as well as qualitative arguments concerning the photon energy dependence of the Auger structures. Calculations of the excited state potential based on the Z þ 1 approximation were performed. Both the calculations and the measurements indicate that the most likely fragmentation pathway for the core excited ammonia molecules leads to NH Ã 2 and H fragments.
The Journal of Chemical Physics, 2001
High-resolution Auger spectroscopy applied under resonant Auger Raman conditions is shown to be a powerful tool for characterizing complex potential energy surfaces in core-excited systems. Using the example of N t 1s Ϫ1 *→X 2 ⌸ resonant Auger transition in nitrous oxide we emphasize the interplay between the nuclear motion and the electronic decay. We show how the choice of excitation energy allows selection of core-excited species of different geometries. The nuclear dynamics of these species are mapped by measuring the resonant Auger decay spectra. In addition to the changes in vibrational structure observed for the resonant Auger decay spectra, a strong influence of nuclear motion on the electronic decay is revealed, inducing the so-called ''dynamical Auger emission.'' The experimental results are supported by ab initio quantum chemical calculations restricted to a linear geometry of the core-excited state.
Physical Review A, 2017
By theoretical calculation, we demonstrate the possibility to control and partially suppress the Coulomb explosion of N 2 molecules after core level photoionization by an x-ray laser and subsequent Auger decay. This is achieved by means of a femtosecond infrared laser pulse interacting with the N 2+ 2 dication produced by the x-ray pulse. Suppression of molecular fragmentation requires few-femtosecond IR pulses interacting with the system either during or shortly after the arrival of the x-ray pulse. The IR pulse suppresses fragmentation mostly by optically coupling the electronic routes to ultrafast molecular dissociation with electronic channels able to support long-lived vibrational resonances. The effect is strongly dependent on the orientation of the molecule with respect to the polarization axis of the IR field. Our calculations are motivated by x-ray pump-IR probe experiments performed at an x-ray free-electron laser [Optics Express 18, 17620 (2010)], where only enhancement of N 2+ 2 fragmentation as a function of the pump-probe delay time was reported. The opposite effect reported here becomes apparent when the various electronic channels are considered separately. In practice, this corresponds to a coincident measurement of the energy of the ejected Auger electron.
Physical Review Letters, 2002
An interference quenching of the 00 1 vibrational line in the resonant Auger decay of N 1s ! core-excited N 2 is observed and analyzed. The intensity ratio between the 00 1 and 00 0 vibrational levels of the X 2 g final state shows a surprising nonmonotonous variation as a function of frequency detuning, going through a minimum with a complete suppression of 00 1. We have developed a simple model which shows a linear relation between the value of the detuning frequency for this minimum and the equilibrium bond distance R 0 c of the core-excited state. A new way is thus established of determining the equilibrium bond distance for the core-excited state with a precision R 0 c < 10 ÿ3 A.
Is there interference in the resonant Auger electron spectra of N 1s and O 1s→2π core excited NO
Chemical Physics, 2003
High-resolution, angle-resolved resonant Auger electron spectra of the NO molecule in the regions of both N and O 1s ! 2p core electron excitations are presented. A large number of vibrational final states are resolved due to high energy resolution. Calculations based on lifetime vibrational interference (LVI) theory neglecting interference between different electronic intermediate states and between direct and resonant channels have been performed. A comparison between theoretical and experimental spectra shows that LVI theory describes the major spectroscopic features quite well. The same holds for the evolution of the angular averaged partial cross sections with the change of excitation energy. The angular distribution of particular vibrational final states are, however, not described successfully with LVI calculations at the present level of sophistication. A theoretical analysis supports that one reason for this deviation is electronic state interference.
Journal of Physics B Atomic Molecular and Optical Physics
We report the observation of the unusually weak decay of the N [iopmath latex="$1{\rm s}\to\pi^*$"] 1s* [/iopmath] core-excited N2 molecule to the [iopmath latex="$\tilde {\rm B}~^2\Sigma_{\rm u}^+$"] 2u+ [/iopmath] final state of N [iopmath latex="$_2^+$"] 2+ [/iopmath] , which is only detectable in an experiment with high sensitivity. The resonant Auger spectra exhibit an unexpected dependence on the selected vibrational level of the intermediate state. Theoretical calculations show that the interference between direct and resonant photoemission as well as a strong geometry dependence of the decay probability on the bond distance give rise to the observed features.