Note: Coherent resonances observed in the dissociative electron attachment to carbon monoxide (original) (raw)
Related papers
Coherent interference in the resonant dissociative electron attachment to carbon monoxide
Physical Review A, 2013
Dissociative electron attachment to carbon monoxide, e − + CO → C + O − , at 9.5, 10.0, and 10.6 eV is investigated by using the anion velocity time-sliced map imaging technique. The completely backward scattering distributions of the fast O − fragment are observed at 10.0 and 10.6 eV. The single electron-molecule resonance model fails in interpretation to these unusual angular distributions, while a quantum interference model including two (at 10.0 eV) or three (at 10.6 eV) dissociative outgoing waves is consequently proposed and provides the satisfying results about the experimental data fittings. Moreover, coherent interference among the 2 , 2 , and 2 resonant states of CO − at 10.6 eV could be further established, based on the fact that the sum of the phase-shift fitting values equals π rad.
Dissociative electron attachment to carbon dioxide via the 8.2 eV Feshbach resonance
Journal of Physics B: Atomic, Molecular and Optical Physics, 2011
Momentum imaging experiments on dissociative electron attachment (DEA) to CO2 are combined with the results of ab initio calculations to provide a detailed and consistent picture of the dissociation dynamics through the 8.2 eV resonance, which is the major channel for DEA in CO2. The present study resolves several puzzling misconceptions about this system.
Dissociation dynamics in the dissociative electron attachment to carbon dioxide
Physical Review A, 2015
Dissociative electron attachment (DEA) to gas phase CO 2 has been probed using a velocity slice imaging technique. DEA to CO 2 produces only an O − ionic fragment and shows two major resonances located at 4.4 and 8.2 eV, respectively. The kinetic energy and angular distribution of the O − ions are measured around the second resonance with higher efficiency and sensitivity that provide details of the DEA dynamics. The kinetic energy distributions are in good agreement with the previous reports. However, the distinct angular distributions show substantial difference from the two recent studies within the limited electron energies. Our angular distribution results show two negative ion resonant states are involved in the underlying DEA process at the entire electron energies over the second resonance. We discussed the recent conflicting findings in the angular distribution results. The forward-backward asymmetry observed in the angular distributions is explained due to the interference effect of different partial waves associated with the attaching electron.
Dissociative electron attachment to CO molecule probed by velocity slice imaging technique
Journal of Physics: Conference Series, 2017
We have studied dissociative electron attachment to CO molecule using the well-established velocity slice imaging spectrometer. We have conclusively determined the symmetries of the TNI states involved in both the channels producing O − ions. In contrast to a recent report, we observed additional forwards lobes in the angular distribution data and we claim there is no need to invoke coherent interference between different states as introduced previously. Recent R-matrix calculations and momentum imaging study by other groups strongly support our claims.
Fragmentation dynamics in dissociative electron attachment to CO probed by velocity slice imaging
Physical chemistry chemical physics : PCCP, 2015
Complete dissociation dynamics in electron attachment to carbon monoxide (CO) have been studied using the newly developed velocity slice imaging (VSI) technique. Both kinetic energy and angular distributions of O(-) ions formed by dissociative electron attachment (DEA) to CO molecules have been measured for 9, 9.5, 10, 10.5, 11, and 11.5 eV incident electron energies around the resonance. Detailed observations conclusively show that two separate DEA reactions lead to the formation of O(-) ions in the ground (2)P state along with the neutral C atoms in the ground (3)P state and the first excited (1)D state, respectively. Within the axial recoil approximation and involving four partial waves, our angular distribution results clearly indicate that the two reactions leading to O(-) formation proceed through the specific resonant state(s). For the first process, more than one intermediate state is involved. On the other hand, for the second process, only one state is involved. The observ...
Renner-Teller effect on dissociative electron attachment to carbon dioxide
Physical Review A, 2012
Stereo-dynamics of dissociative electron attachments to CO 2 is investigated by the O − anion velocity imaging experiments combined with the R-matrix calculations. 2 Π g as a Feshbach resonant state of CO 2 − is confirmed to play roles in the dissociations around 8.0 eV. We find that the dynamic evolutions of the Renner-Teller effect lead to the dramatically different anisotropic O − momentum distributions.
arXiv: Atomic Physics, 2020
Ion-pair dissociation (IPD) to gas phase carbon dioxide molecule has been studied using time of flight (TOF) based mass spectroscopy in combination with the highly differential velocity slice imaging (VSI) technique. The appearance energy of the fragmented anion provides the experimental threshold energy value for ion-pair production. The kinetic energy (KE) distributions and angular distributions (AD) of the fragment anion dispense the detailed insight into the IPD dynamics. The KE distribution clearly reveals that the IPD dynamics may be due to the direct access to the ion-pair states. However, indirect mechanism can't be ruled out at higher incident electron energies. The angular distribution data unambiguously identified the involvement of the ion-pair state associated with Sigma symmetry and a minor contribution from Pi symmetric states. Computational calculations using density functional theory (DFT) strongly support the experimental observations.
Ion kinetic energy spectroscopy of the doubly charged ion of carbon monoxide
The Journal of Chemical Physics, 1984
Spontaneous and collision-induced dissociation processes of C02+ ions, formed by electron impact, have been studied in a double-focusing mass spectrometer using techniques of ion kinetic energy spectroscopy. The predissociation process, responsible for unimolecular dissociation of C02+ on the microsecond time scale, is almost certainly electronically adiabatic tunneling through a potential barrier, though predissociation via electronic curve crossing cannot be entirely ruled out. Semiempirical potential curves for states ofC0 2 + were revised in order to better accommodate all of the available data, including Auger spectra, appearance energies, and kinetic energy release. Collision induced dissociation processes with Ar, N 2 , and H2 proceed via charge exchange, and involve predissociation of the D 2II state by the C 2..1 state ofCO+. When He is used as collision gas, the dissociation processes involving charge exchange are different, and require an energetic contribution from the relative kinetic energy (kinetic energy loss). In addition, He is quite different in inducing dissociation of C0 2 + without prior charge exchange, from states ofC02+ up to 13 eV above the dissociation limit.
Collision-induced dissociation of CO 2 + cations: evidence for a long-lived excited state
Chemical Physics Letters, 1999
. q x Collision-induced dissociation of CO ions formed by 70 eV electrons CO Ar, CO q Ar O at 49 eV is 2 2 translationally exothermic. The intensity distribution of O q is symmetric about the ArrO q center-of-mass rather than that for ArrCO q , consistent with a spectator 'knock-out' mechanism. We propose that 70 eV electron ionization produces a 2 significant fraction of CO q ions in the a 4 P state with a lifetime of more than 30 msec and that collision induces 2 u curve-crossing between the 4 P and 4 S y states of CO q . The process becomes endothermic at low electron energy, u g 2 supporting the above conclusion. q 1999 Elsevier Science B.V. All rights reserved.