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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 ²Π, ²Δ, and ²ɸ 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. [ABSTRACT FROM AUTHOR]

Stereodynamics of dissociative electron attachment to CO2 is investigated using O- anion velocity imaging experiments. Here 2&Pgr;g as a Feshbach resonant state of C02- is confirmed to play a role in the dissociation CO2- → CO(1&Sgr;+) + 0-(2P) around 8.0 eV. At the lower energy, 7.7 eV, two split states of 2Ilg due to the Renner-Teller effect are found to couple with the dissociation path; while above this energy, at 8.2 and 8.7 eV, the coupling between the dissociation and the C-O bond stretching becomes predominant. The evolutions of the potential energy surface around this Feshbach resonant state result in the dramatically different angular distributions of the O- momentum. [ABSTRACT FROM AUTHOR]

Atom cooling and trapping by partially spatially coherent lasers is investigated both experimentally and theoretically. The degree of spatial coherence of the laser beams is controlled by the electro-optic crystal. The characteristics of the trapped atomic cloud are studied. The experimental results indicate that the atom number and atomic Gaussian density distribution stay unchanged due to the fact that the average photon scattering rate is independent of the spatial coherence of the laser beams. However, the measured temperature of the atomic cloud increases as the degree of spatial coherence of the laser beams decreases. The reason is that the scattering force of the partially spatially coherent lasers acting on the atoms fluctuates temporally and spatially, which broadens the velocity distribution of the atoms. [ABSTRACT FROM AUTHOR]