Evidence for cluster shape effects on the kinetic energy spectrum in thermionic emission

Calvo, F.; Lépine, F.; Baguenard, B.; Pagliarulo, F.; Concina, B; Bordas, C.; Parneix, P.

doi:10.1063/1.2804861

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…The interest of this type of fitting function is rather to characterize the KERD shape with the parameter. 32 Let us point out that our experimental result is at variance with detailed statistical rate calculations combined with electron capture theory and kinetic modeling reported in ref. 8 , which led to an exponent .…”

Section: Experimental and Comparison To The Langevin Modelcontrasting

confidence: 65%

Kinetic energy released in the vibrational autodetachment of sulfur hexafluoride anion

Concina

Montagne

Martin

et al. 2021

The Journal of Chemical Physics

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The kinetic energy release distribution (KERD) in the vibrational autodetachment (VAD) from sulfur hexafluoride anion SF 6 has been measured in a velocity map imaging spectrometer for delays in the range of a few tens of microseconds. The experimental KERD is analyzed within the framework of the detailed-balance: first using the standard Langevin model, subsequently using a more refined and realistic model based on the experimental attachment cross-section. A discussion on the processes involved in the attachment and the VAD is presented based on an empirical fit of the attachment cross section. The lifetime derived from the model is in good agreement with the experimental time window, strengthening this theoretical approach for this model system.

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Section: Experimental and Comparison To The Langevin Modelcontrasting

confidence: 65%

Kinetic energy released in the vibrational autodetachment of sulfur hexafluoride anion

Concina

Montagne

Martin

et al. 2021

The Journal of Chemical Physics

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“…For example, distributions with n = 0.15, 0.28, and 0.58 were observed for electron emission from C 10 − , C 15 − , and C 18 − cluster anions, respectively. 33 One may deduce from this observation that the distribution approaches a more thermal shape when the cluster size increases. However, this effect may also be due to other factors such as different contributions from higher partial waves ͑lϾ0͒.…”

Section: -5mentioning

confidence: 99%

“…It should be noted that the interpretation of the experimental distributions in Ref. 33 was done in terms of orbiting transition state/phase space theory, see Ref. 4.…”

Section: -5mentioning

confidence: 99%

On the accuracy of thermionic electron emission models. I. Electron detachment from SF6−

Troe

Miller

Viggiano

2009

The Journal of Chemical Physics

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Detailed statistical rate calculations combined with electron capture theory and kinetic modeling for the electron attachment to SF 6 and detachment from SF 6 − ͓Troe et al., J. Chem. Phys. 127, 244303 ͑2007͔͒ are used to test thermionic electron emission models. A new method to calculate the specific detachment rate constants k det ͑E͒ and the electron energy distributions f͑E , ͒ as functions of the total energy E of the anion and the energy of the emitted electrons is presented, which is computationally simple but neglects fine structures in the detailed k det ͑E͒. Reduced electron energy distributions f͑E , / ͗͒͘ were found to be of the form ͑ / ͗͒͘ n exp͑− / ͗͒͘ with n Ϸ 0.15, whose shape corresponds to thermal distributions only to a limited extent. In contrast, the average energies ͗͑E͒͘ can be roughly estimated within thermionic emission and finite heat bath concepts. An effective temperature T d ͑E͒ is determined from the relation E −EA=͗E SF 6 ͑T d ͒͘ + kT d , where ͗E SF 6 ͑T d ͒͘ denotes the thermal internal energy of the detachment product SF 6 at the temperature T d and EA is the electron affinity of SF 6 . The average electron energy is then approximately given by ͗͑E͒͘ = kT d ͑E͒, but dynamical details of the process are not accounted for by this approach. Simplified representations of k det ͑E͒ in terms of T d ͑E͒ from the literature are shown to lead to only semiquantitative agreement with the equally simple but more accurate calculations presented here. An effective "isokinetic" electron emission temperature T e ͑E͒ does not appear to be useful for the electron detachment system considered because it neither provides advantages over a representation of k det ͑E͒ as a function of T d ͑E͒, nor are recommended relations between T e ͑E͒ and T d ͑E͒ of sufficient accuracy.

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“…Thus, it became possible to record time-resolved KERD. In particular, with a delay of about 100 ns relative to the laser excitation, the recorded spectrum does not contain direct electron emission anymore. , Using this experimental approach over a decade, we have conducted a detailed study on the thermionic emission of various negatively charged molecules and small clusters excited by lasers, including small anionic tungsten clusters (as a prototype of metal clusters), fullerene anions, and dianions . This method has been recently extended to the measurement of the spontaneous delayed electron emission in the case of the sulfur hexafluoride anion …”

Section: Introductionmentioning

confidence: 99%

Thermionic Emission of Negative Ions of Molecules and Small Clusters as a Probe of Low-Energy Attachment

Concina

Bordas

2022

J. Phys. Chem. A

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We have been studying the thermionic emission of negatively charged molecules and small clusters for more than a decade. The kinetic energy released distribution (KERD) of mass-selected negative ions has been measured with a velocity map imaging spectrometer. A comparison of the experimental KERD to detailed balance models provided information on the reverse process, namely, the electron attachment to the parent. The electron attachment to neutral systems (reverse process of the electron emission from anions) is usually described in a simplified way as a single electron capture in the framework of the classical Langevin model. Our measurements show that this approach is insufficient and that, in addition to the capture step, an intramolecular vibrational redistribution (IVR) step should be included. As far as multiply charged anions are concerned, the electron attachment to anions (reverse process of the electron emission from dianions) is strongly affected by the repulsive Coulomb barrier (RCB). Previous studies assumed a pure over-the-barrier process, which is in disagreement with our study. Indeed, electron emission is measured below the RCB, revealing significant thermal tunneling. In the present review, we summarize these works on singly and doubly charged anions in an attempt to present a unified view of the involved processes. It is worth noting that the detailed measurements of KERDs in the very low kinetic energy region (typically around 0.1 eV) have been made possible thanks to electron imaging methods, without which all of this work could never have been done, with time-resolution capabilities allowing the disentangling of direct and delayed electron emission.

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Evidence for cluster shape effects on the kinetic energy spectrum in thermionic emission

Cited by 5 publications

References 28 publications

Kinetic energy released in the vibrational autodetachment of sulfur hexafluoride anion

Kinetic energy released in the vibrational autodetachment of sulfur hexafluoride anion

On the accuracy of thermionic electron emission models. I. Electron detachment from SF6−

Thermionic Emission of Negative Ions of Molecules and Small Clusters as a Probe of Low-Energy Attachment

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