Importance of Nonresonant Scattering in Low-Energy Dissociative Electron Attachment to Molecular Hydrogen

Rabli, Djamal; Morrison, Michael A.

doi:10.1103/physrevlett.97.013201

Cited by 5 publications

(3 citation statements)

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“…Thus the present experimental CS is lower than that of Horacek et al by 20%-30%. Our results are in better agreement with more recent calculations employing an alternative method which also included contribution from the direct scattering [17]. Recent measurements of the rate coefficient for AD in hydrogen, [2,24], agreed very well with theoretical ones based on the same model as the one used in [15].…”

Section: Fig 1 (Color Online) Momentum Image Of Hsupporting

confidence: 90%

“…This is also well recognized in modeling the edge plasma in tokamak fusion reactors, e.g., [16], where, besides the strong increase of CS with excitation, the pronounced isotope effect will also influence the plasma behavior. Besides its importance in the various research fields of physics mentioned before, the availability of accurate DEA cross section is also crucial for numerous theoretical studies of DEA in hydrogen, e.g., [15,17,18]. …”

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confidence: 99%

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Dissociative Electron Attachment Cross Sections forH2andD2

et al. 2011

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New measurements of the absolute cross sections for dissociative electron attachment (DEA) in molecular hydrogen and deuterium are presented which resolve previous ambiguities and provide a test bed for theory. The experimental methodology is based upon a momentum imaging time-of-flight spectrometer that allowed us to eliminate any contributions due to electronically excited metastable neutrals and ultraviolet light while ensuring detection of all the ions. The isotope effect in the DEA process in the two molecules is found to be considerably larger than previously observed. More importantly, it is found to manifest in the polar dissociation process (also known as ion pair production) as well. DOI: 10.1103/PhysRevLett.106.243201 PACS numbers: 34.80.Ht Dissociative electron attachment (DEA) in hydrogen is of fundamental importance as one of the benchmark cases in atomic collisions. Together with its reverse process of associative detachment (AD), it is also relevant to the studies in astrophysics [1-3], development of ion sources [4], and in fusion edge plasmas [5,6]. Three distinct resonant processes leading to negative ion production (H À and/ or D À ) were studied and absolute cross sections (CSs)À , and its isotopologues HD and D 2 have been reported. These three processes are believed to proceed through the lowest attractive X 2 AE þ u state (4 eV process), the repulsive B 2 AE þ g state (7-13 eV process), and the attractive Rydberg excited state, 2AE þ g (14 eV process) leading to excited H (D). The peak cross section for the most abundant process at 14 eV in H 2 DEA was determined in two independent measurements to be 3:5 Â 10 À20 cm 2 [7] and 2:1 Â 10 À20 cm 2 [8]. These two CS values were the only ones available until now and therefore have been widely quoted and used in many applications. More recently, the CS for the 14 eV process was used to normalize the CS for the 4 eV process in relative CS studies [9,10]. It should be noted that the unusually small number of DEA CS measurements in hydrogen and the still high uncertainty in the CS is mainly due to its very low value. For example, the peak CS for H 2 DEA is 2 orders of magnitude smaller as compared to O 2 DEA. Another important characteristic of DEA in hydrogen is a strong decrease in the CS for heavier isotopologues, HD and D 2 [8,9], due to the strongly reduced survival probability of the dissociative channel.Additional data on DEA in hydrogen have been provided by other experiments: H À angular distributions [11], the strong dependence of DEA at 4 eV on rovibrational excitation [12], and the appearance of interference structures in the CS between 8-12 eV [11] and at 14 eV [13].Two more studies on the relative DEA cross section have been performed with emphasis on the vibrational excitation dependency of the 14 eV resonance in H 2 and D 2 [14] and on the electron energy resolution dependency of the experimental CS for the 4 eV process in H 2 [10]. Because of the increase of the DEA CS by orders of magnitude with vibrational excitation of the t...

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Section: Fig 1 (Color Online) Momentum Image Of Hsupporting

confidence: 90%

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confidence: 99%

Dissociative Electron Attachment Cross Sections forH2andD2

et al. 2011

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“…According to this model, it is pointed out that non-resonant scattering enhances the rate coefficient [72] and, although a complete dataset including it is not available, this effect may enhance the effective rate coefficient of (P1-P3) by an approximate factor of two beyond the value calculated here.…”

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confidence: 69%

Rovibrationally Resolved Time-Dependent Collisional-Radiative Model of Molecular Hydrogen and Its Application to a Fusion Detached Plasma

Sawada

Goto

2016

Atoms

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Abstract:A novel rovibrationally resolved collisional-radiative model of molecular hydrogen that includes 4,133 rovibrational levels for electronic states whose united atom principal quantum number is below six is developed. The rovibrational X 1 Σ + g population distribution in a SlimCS fusion demo detached divertor plasma is investigated by solving the model time dependently with an initial 300 K Boltzmann distribution. The effective reaction rate coefficients of molecular assisted recombination and of other processes in which atomic hydrogen is produced are calculated using the obtained time-dependent population distribution.

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