Browsing by Author "Buathong, S."

Now showing 1 - 5 of 5
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    Dissociative electron attachment studies with hyperthermal Rydberg atoms
    (AIP Publishing, 2018) Buathong, S.; Dunning, F.B.
    Earlier studies of the velocity distributions of heavy-Rydberg ion-pair states formed in collisions between potassium Rydberg atoms with low-to-intermediate values of n, 10 ≲ n ≲ 15, and targets that attach free low-energy electrons have shown that such measurements can provide a window into the dynamics of dissociative electron capture. Here we propose that the reaction dynamics can be explored in much greater detail through studies using hyperthermal Rydberg atoms. This is demonstrated using, as an example, helium Rydberg atoms and a semi-classical Monte Carlo collision code developed specifically to model the dynamics of Rydberg electron transfer in collisions between Rydberg atoms and attaching targets. The simulations show that the outcome of collisions is sensitive not only to the lifetime and decay energetics of the excited intermediate negative ion formed upon initial Rydberg electron capture but also to the radial electron probability density distribution in the Rydberg atom itself, i.e., to its ℓ value.
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    Dynamics of heavy-Rydberg ion-pair formation in K(14p,20p)-SF6, CCl4ﾠcollisions
    (AIP Publishing, 2014) Wang, C.H.; Kelley, M.; Buathong, S.; Dunning, F.B.
    The dynamics of formation of heavy-Rydberg ion-pair states throughﾠelectron transferﾠin K(np)-SF6, CCl4ﾠcollisions is examined byﾠmeasuringﾠtheﾠvelocity,ﾠangular, and bindingﾠenergyﾠdistributions of the product ion pairs. The results areﾠanalyzedﾠwith the aid of a Monte Carlo collision code that models both the initial electron capture and the subsequent evolution of the ion pairs. The model simulations are in good agreement with the experimental data and highlight the factors such asﾠRydberg atomﾠsize, the kineticﾠenergyﾠof relativeﾠmotionﾠof theﾠRydberg atomﾠand target particle, and (in the case of attaching targets that dissociate) the energetics ofﾠdissociationﾠthat can be used to control the properties of the product ion-pair states.
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    Probing dissociative electron attachment through heavy-Rydberg ion-pair production in Rydberg atom collisions
    (AIP Publishing LLC., 2016) Buathong, S.; Kelley, M.; Dunning, F.B.
    Electron transfer in collisions between low-n, n = 12, Rydberg atoms and targets that attach low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a weakly-bound positive-negative ion pair that orbit each other at large separations. Measurements of the velocity and angular distribution of ion-pair states produced in collisions with 1,1,1-C2Cl3F3, CBrCl3, BrCN, and Fe(CO)5 are used to show that electron transfer reactions furnish a new technique with which to examine the lifetime and decay energetics of the excited intermediates formed during dissociative electron capture. The results are analyzed with the aid of Monte Carlo simulations based on the free electron model of Rydberg atom collisions. The data further highlight the capabilities of Rydberg atoms as a microscale laboratory in which to probe the dynamics of electron attachment reactions.
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    Rydberg atom scattering in K(12p)-CH3NO2 collisions: role of transient ion pair formation
    (IOP Publishing, 2017) Kelley, M.; Buathong, S.; Dunning, F.B.
    Studies of K(12p)-CH3NO2 collisions reveal unusually strong Rydberg atom scattering which is attributed to the formation of transient K+..CH3NO2 − ion-pair states.
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    Very strong Rydberg atom scattering in K(12p)–CH3NO2collisions: Role of transient ion pair formation
    (AIP Publishing, 2017) Kelley, M.; Buathong, S.; Dunning, F.B.
    Collisions between K(12p) Rydberg atoms and CH3NO2 target molecules are studied. Whereas CH3NO2 can form long-lived valence-bound CH3NO−2NO2− ions, the data provide no evidence for production of long-lived K+⋯⋯CH3NO−2NO2− ion pair states. Rather, the data show that collisions result in unusually strong Rydberg atom scattering. This behavior is attributed to ion-ion scattering resulting from formation of transient ion pair states through transitions between the covalent K(12p) + CH3NO2 and ionic K+ + (dipole bound) CH3NO−2NO2− terms in the quasimolecule formed during collisions. The ion-pair states are destroyed through rapid dissociation of the CH3NO−2NO2− ions induced by the field of the K+core ion, the detached electron remaining bound to the K+ ion in a Rydberg state. Analysis of the experimental data shows that ion pair lifetimes ≳10 ps are sufficient to account for the present observations. The present results are consistent with recent theoretical predictions that Rydberg collisions with CH3NO2 will result in strong collisional quenching. The work highlights a new mechanism for Rydberg atom scattering that could be important for collisions with other polar targets. For purposes of comparison, results obtained following K(12p)–SF6 collisions are also included.