The Dependence of Electron Impact Excitation and Ionization Cross Sections of H2 and D2 Molecules on Vibrational Quantum Number

Capitelli, M.; Celiberto, R.

doi:10.1007/978-1-4757-9319-2_8

Cited by 7 publications

(7 citation statements)

References 26 publications

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“…It is noteworthy that the measured maximum ionization cross sections were essentially unaffected by the presence of the vibrationally target molecules. This is an observation which agrees with other recent experimental and theoretical findings (Cacciatore et al 1982, Celiberto and Rescigno 1993, Capitelli and Celiberto 1995, Kühn et al 1995. Our results for the CD 3 and CD 2 free radicals were found to agree with earlier measurements of Baiocchi et al (1984) which were carried out under different experimental conditions.…”

Section: Discussionsupporting

confidence: 93%

“…below about 30 eV in our case. This observation is supported by other recent experimental and theoretical studies which support the notion that vibrational excitation of the target molecule affects the ionization cross section primarily in the near-threshold region, but has little impact on the cross section shape at energies above about twice the ionization threshold in most cases (Cacciatore et al 1982, Celiberto and Rescigno 1993, Capitelli and Celiberto 1995, Kühn et al 1995.…”

Section: Ionization Cross Sections For the CD 4 Moleculesupporting

confidence: 68%

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Electron impact ionization of (x= 1 - 4)

Tarnovsky

Levin

Deutsch

et al. 1996

J. Phys. B: At. Mol. Opt. Phys.

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We report measurements of absolute cross sections for the electron-impact ionization and dissociative ionization of the deuterated methane molecule and the (x = 1 - 3) free radicals from threshold to 200 eV using the fast-neutral beam technique. We used the deuterated rather than the protonated target species to facilitate a better separation of the various product ions from a given parent molecule in our apparatus. Good agreement was found between our results and the most recent measurements in . Our results for and agree well with earlier measurements carried out under different experimental conditions. The present results for the CD free radical are the first ionization cross section measurements for this target. A common feature of all four targets studied in this work was a dominant parent ionization cross section with essentially the same absolute value of 1.6 - at 70 eV. A comparison of the experimentally determined total single ionization cross sections with calculated cross sections using a modified additivity rule showed very good agreement for all four targets.

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Section: Discussionsupporting

confidence: 93%

Section: Ionization Cross Sections For the CD 4 Moleculesupporting

confidence: 68%

Electron impact ionization of (x= 1 - 4)

Tarnovsky

Levin

Deutsch

et al. 1996

J. Phys. B: At. Mol. Opt. Phys.

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“…Other reaction paths open up for vibrationally excited H 2 [19,27]. The impact of these processes is just beginning to be assessed in experiments and theory.…”

Section: Hydrogenic Speciesmentioning

confidence: 99%

“…which can proceed either through the formation of H − , or the formation of H + 2 [26,28]. While it is too early to confirm the role of this process, it has the potential to increase the volume recombination rate by several orders of magnitude [26][27][28][29][30].…”

Section: Hydrogenic Speciesmentioning

confidence: 99%

Chapter 4: Power and particle control

Divertor¹,

Database²,

Editors³

1999

Nucl. Fusion

280

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Abstract.Progress, since the ITER Physics Basis publication, in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are : energy transport in the SOL in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main chamber material elements, ELM energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low and high Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma-materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas : refinement of the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a 2 major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral-neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma-materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed. Introduction.This chapter outlines the significant progress achieved since the ITER Physics Basis in understanding basic scrape-off layer (SOL) and divertor processes in a tokamak. The interaction of plasma with first-wall surfaces will have considerable impact on the performance of fusion plasmas, the lifetime of plasma facing components, and the retention of tritium in next step Burning Plasma E...

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“…Under many circumstances, such as multicusp magnetic plasmas or fusion edge plasmas, the vibrational excitation of H 2 , D 2 and T 2 cannot be neglected, so that complete sets of cross sections involving the whole vibrational manifold of the diatoms should be known (Capitelli and Celiberto 1995). Indeed, subtle effects in the detailed physics can have consequences for the plasma.…”

Section: Introductionmentioning

confidence: 99%

Calculated rates for the electron impact dissociation of molecular hydrogen, deuterium and tritium

Trevisan

Tennyson

2002

Plasma Phys. Control. Fusion

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At temperatures below 15 000 K, the major pathway for the electron impact dissociation of H 2 is through excitation to the b 3 + u excited electronic state. Total cross sections and energy differential cross sections for threshold energies as a function of vibrational states (v) for H 2 v = 0-4, D 2 v = 0-6 and T 2 v = 0-7 are calculated. The rates of dissociation as a function of electron temperature for each state are parametrized. Near-threshold rates are shown to be so critically dependent on the vibrational level that dissociation from very high-lying vibrational levels must be included in calculations of the rate at local thermal equilibrium (LTE) even at low temperature. An adapted version of the extrapolation procedure of Stibbe and Tennyson (1999 Astrophys. J. 513 L147) is used to approximate the rates for all of the higher vibrational levels, which are then used to calculate the LTE rate. The LTE rate is an order of magnitude greater than the v = 0 rate. Calculations of energy differential cross sections suggest that impact dissociation of vibrationally excited molecules could be the source of low energy H atoms observed in tokamak plasmas.

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The Dependence of Electron Impact Excitation and Ionization Cross Sections of H2 and D2 Molecules on Vibrational Quantum Number

Cited by 7 publications

References 26 publications

Electron impact ionization of (x= 1 - 4)

Electron impact ionization of (x= 1 - 4)

Chapter 4: Power and particle control

Calculated rates for the electron impact dissociation of molecular hydrogen, deuterium and tritium

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