Dissociative recombination and the decay of a molecular ultracold plasma
Double-resonant photoexcitation of nitric oxide in a molecular beam creates a dense ensemble of 51f(2) Rydberg states, which evolves to form a plasma of free electrons trapped in the potential well of an NO+ spacecharge. The plasma travels at the velocity of the molecular beam, and, on passing throu...
| Main Authors: | , , , , , , , |
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| Format: | Journal article |
| Language: | English |
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2011
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| _version_ | 1826265769058500608 |
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| author | Rennick, C Saquet, N Morrison, J Ortega-Arroyo, J Godin, P Fu, L Schulz-Weiling, M Grant, E |
| author_facet | Rennick, C Saquet, N Morrison, J Ortega-Arroyo, J Godin, P Fu, L Schulz-Weiling, M Grant, E |
| author_sort | Rennick, C |
| collection | OXFORD |
| description | Double-resonant photoexcitation of nitric oxide in a molecular beam creates a dense ensemble of 51f(2) Rydberg states, which evolves to form a plasma of free electrons trapped in the potential well of an NO+ spacecharge. The plasma travels at the velocity of the molecular beam, and, on passing through a grounded grid, yields an electron time-of-flight signal that gauges the plasma size and quantity of trapped electrons. This plasma expands at a rate that fits with an electron temperature as low as 5 K. Dissociative recombination of NO+ ions with electrons provides the primary dissipation mechanism for the plasma. We have identified three dissociation pathways, and quantified their relative contributions to the measured rate: Two-body dissociative recombination competes with direct three-body recombination to neutral dissociation products, and with a process in which three-body recombination and electron-impact ionization form an equilibrium population of high-Rydberg states that decays by predissociation. Using available collision-theory rate constants for three-body recombination and ionization, together with quantum mechanical estimates of predissociation rates, we predict that the relaxation of the plasma to a high-Rydberg equilibrium outpaces direct three-body dissociative recombination, and, among second-order processes, the rate of two-body electron-cation dissociative recombination substantially exceeds the rate at which the high-Rydberg equilibrium dissociatively relaxes. The rate constant for dissociative recombination extracted from these data conforms with predictions drawn from theory for isolated electron-ion collisions. Methods based on the dissipation of molecular ultracold plasmas may provide a means for estimating rates of dissociative recombination for a variety of complex molecules. |
| first_indexed | 2024-03-06T20:28:50Z |
| format | Journal article |
| id | oxford-uuid:305b1e16-4d06-47e6-afc6-cff833bd3f06 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T20:28:50Z |
| publishDate | 2011 |
| record_format | dspace |
| spelling | oxford-uuid:305b1e16-4d06-47e6-afc6-cff833bd3f062022-03-26T13:00:52ZDissociative recombination and the decay of a molecular ultracold plasmaJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:305b1e16-4d06-47e6-afc6-cff833bd3f06EnglishSymplectic Elements at Oxford2011Rennick, CSaquet, NMorrison, JOrtega-Arroyo, JGodin, PFu, LSchulz-Weiling, MGrant, EDouble-resonant photoexcitation of nitric oxide in a molecular beam creates a dense ensemble of 51f(2) Rydberg states, which evolves to form a plasma of free electrons trapped in the potential well of an NO+ spacecharge. The plasma travels at the velocity of the molecular beam, and, on passing through a grounded grid, yields an electron time-of-flight signal that gauges the plasma size and quantity of trapped electrons. This plasma expands at a rate that fits with an electron temperature as low as 5 K. Dissociative recombination of NO+ ions with electrons provides the primary dissipation mechanism for the plasma. We have identified three dissociation pathways, and quantified their relative contributions to the measured rate: Two-body dissociative recombination competes with direct three-body recombination to neutral dissociation products, and with a process in which three-body recombination and electron-impact ionization form an equilibrium population of high-Rydberg states that decays by predissociation. Using available collision-theory rate constants for three-body recombination and ionization, together with quantum mechanical estimates of predissociation rates, we predict that the relaxation of the plasma to a high-Rydberg equilibrium outpaces direct three-body dissociative recombination, and, among second-order processes, the rate of two-body electron-cation dissociative recombination substantially exceeds the rate at which the high-Rydberg equilibrium dissociatively relaxes. The rate constant for dissociative recombination extracted from these data conforms with predictions drawn from theory for isolated electron-ion collisions. Methods based on the dissipation of molecular ultracold plasmas may provide a means for estimating rates of dissociative recombination for a variety of complex molecules. |
| spellingShingle | Rennick, C Saquet, N Morrison, J Ortega-Arroyo, J Godin, P Fu, L Schulz-Weiling, M Grant, E Dissociative recombination and the decay of a molecular ultracold plasma |
| title | Dissociative recombination and the decay of a molecular ultracold plasma |
| title_full | Dissociative recombination and the decay of a molecular ultracold plasma |
| title_fullStr | Dissociative recombination and the decay of a molecular ultracold plasma |
| title_full_unstemmed | Dissociative recombination and the decay of a molecular ultracold plasma |
| title_short | Dissociative recombination and the decay of a molecular ultracold plasma |
| title_sort | dissociative recombination and the decay of a molecular ultracold plasma |
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