Nonequilibrium rovibrational energy distributions of hydrogen isotopologues in an expanding plasma jet

Gabriel, Onno; Dungen, van den Jja Jeroen; Schram, D.C.; Engeln, Rah Richard

doi:10.1063/1.3352550

Cited by 12 publications

(15 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From this model, the obtained rotational population distribution is very similar to the typical rotational distributions with an overpopulation of high rotational levels as observed in dissociative processes occurring in plasmas [98]. The very detailed H 2 , D 2 and HD ro-vibrational distributions measured by Gabriel et al [229] are an example of the possible influence of surface reactions in recombining plasmas.…”

Section: Surface Reactionssupporting

confidence: 76%

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Bruggeman

Sadeghi

Schram

et al. 2014

Plasma Sources Sci. Technol.

435

431

View full text Add to dashboard Cite

The gas temperature in non-equilibrium plasmas is often obtained from the plasma-induced emission by measuring the rotational temperature of a diatomic molecule in its excited state. This is motivated by both tradition and the availability of low budget spectrometers. However, non-thermal plasmas do not automatically guarantee that the rotational distribution in the monitored vibrational level of the diatomic molecule is in equilibrium with the translational (gas) temperature. Often non-Boltzmann rotational molecular spectra are found in non-equilibrium plasmas. The deduction of a gas temperature from these non-thermal distributions must be done with care as clearly the equilibrium between translational and rotational degrees of freedom cannot be achieved. In this contribution different methods and approaches to determine the gas temperature are evaluated and discussed. A detailed analysis of the gas temperature determination from rotational spectra is performed. The physical and chemical background of non-equilibrium rotational population distributions in molecular spectra is discussed and a large range of conditions for which non-equilibrium occurs are identified. Fitting procedures which are used to fit (non-equilibrium) rotational distributions are analyzed in detail. Lastly, recommendations concerning the conditions for which the gas temperatures can be obtained from diatomic spectra are formulated.

show abstract

Section: Surface Reactionssupporting

confidence: 76%

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Bruggeman

Sadeghi

Schram

et al. 2014

Plasma Sources Sci. Technol.

435

431

View full text Add to dashboard Cite

show abstract

“…The rotational temperature is commonly attributed to the kinetic gas temperature 56,93,94 and depends on the experimental conditions. Gabriel et al mentioned rotational temperature in the 3000-4000 K range 95 while Briefi et al indicated a two-temperature Boltzmann distribution with a low (564 K) and a high (5440 K) component 56 and Wagner et al 66 showed up lower rotational temperature, 380 K. In our reactor, in plasma-OFF condition it appears slightly above the temperature of the temperature-regulated walls of the reactor (283 K). In plasma-ON condition, it is surprisingly low even if at low pressure (8 µbar) and low electron density (∼3×10 15 m −3 ) energy transfer between electrons and neutrals through inelastic collisions is weak 96 .…”

Section: Distribution Of Energy Over Rotational and Translational Of The D2mentioning

confidence: 47%

“…Translational kinetic does also depend on the experimental condition and especially on the plasma expansion in the vacuum vessel. For example, Gabriel et al observed, in a cascaded arc 95 , kinetic energies higher than 1800 K (8 mm from the source nozzle); Wagner et al measured T trans = 300 K between 500 and 5000 W. Hence our 320 ± 20 K value, both with or without plasma, shows that the plasma expansion in our setup is low, of the same order as a thermal expansion.…”

Section: Distribution Of Energy Over Rotational and Translational Of The D2mentioning

confidence: 50%

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Béchu

Lemaire

Gavilan

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

View full text Add to dashboard Cite

Ro-vibrationally excited molecules of deuterium are involved in non-equilibrium chemical reactions in divertor region of tokamak, molecular assisted recombination, or in neutral beam injector to produce negative ion, dissociative electron attachment, for fusion plasmas. These molecules produced both in a plasma volume and on surfaces are no longer in their electronic ground state X 1 + g (v " 0, J " ) and populate non-uniformly different vibrational (v ) and rotational levels (J ). The high resolution VUV Fourier Transform spectrometer of the DESIRS beam line (SOLEIL synchrotron) is applied to directly scrutinize the ro-vibrationally excited levels of the D 2 ground state from v = 0 to 10 and J up to 8 in an electron cyclotron resonance (ECR) cold plasma. This is performed for different plasma-facing materials, i.e. quartz, tantalum, tungsten, and stainless steel, in order to compare their relative impact in molecular excitation through recombinative desorption from surfaces. A significant effect of these materials on the absolute distribution of the vibrationally states has been found above v > 3. The experimental detection limit for Quartz is v = 7 whereas tungsten and stainlees steel excite the molecules up to v = 9 and tantalum up to v = 10. The use of a bare, temperature-controlled surface of Quartz as a reference, compared to metallic surfaces, allows us to determine the relative production of these excited levels. The recombinative desorption rate on tungsten and stainless steel compared to quartz is ∼2.6 higher and reaches ∼5 for tantalum.

show abstract

“…Concerning the utilization of the Fulcher transition for determining the gas temperature, it is important to check which levels are described by the cold temperature and which are not. Often the first four to five rotational levels in the electronic ground state thermalize with the gas temperature (see for example [5,6,8,9,11,12]) but this strongly depends on the value of the gas temperature: When its value decreases -for example due to active cooling of the discharge vessel -the number of levels which are in thermal equilibrium with T gas also decreases due to the lower energy of the heavy particles [27,40]. As a a-priori assessment of the number of thermalized levels is hardly possible, a consideration of non-thermalized levels in the evaluation can lead to an overestimation of the gas temperature (this will be demonstrated in sections 5.1 and 5.2).…”

Section: The Fulcher-α Transition Of Molecular Hydrogenmentioning

confidence: 99%

“…In low pressure hydrogen discharges the rotational levels in the electronic ground state are known to be populated in a non-thermal way: Rotational states with low rotational quantum number follow a Boltzmann distribution according to the gas temperature of the discharge whereas those levels with high quantum number are overpopulated by several orders of magnitude (see for example [4,5,6,7,8,9] for hydrogen and [10,11,12] for deuterium). Different processes that could contribute to the overpopulation in general have been evaluated in detail in [9].…”

Section: Introductionmentioning

confidence: 99%

Determination of the rotational population of H2 and D2 including high-N states in low temperature plasmas via the Fulcher-α transition

Briefi

Rauner

Fantz

2017

Journal of Quantitative Spectroscopy and Radiative Transfer

View full text Add to dashboard Cite

Vibrational and rotational excitation of the hydrogen molecule can significantly effect molecular reaction rates in low pressure low temperature plasmas, for example for the creation of H − /D − ions via the dissociative attachment process. In general, the rotational population in these discharges is known to be non-thermal with an overpopulation of states with high rotational quantum number N. In contrast to a sophisticated direct measurement of the rotational distribution in the X 1 Σ + g , v = 0 state, it is demonstrated that the determination can also be carried out up to high-N levels rather easily via optical emission spectroscopy utilizing the Fulcher-α transition of H 2 and D 2. The measured rotational populations can be described with a two-temperature distribution where the cold part reflects the population according to the gas temperature of the discharge. This has been verified by using the emission of the second positive system of nitrogen as independent gas temperature diagnostic. The hot part where the rotational temperature reaches several thousand Kelvin arises most probably from recombinative desorption of hydrogen at the discharge vessel wall where parts of the binding energy are converted into rotational excitation. Neglecting the hot population-what is often done when using the Fulcher-α transition as gas temperature diagnostic-can lead to a strong overestimation of T gas. No fundamental differences in the rotational distributions between hydrogen and deuterium have been found, only the hot rotational temperature is smaller for D 2 indicating an isotope-dependency of the recombinative desorption process.

show abstract

Nonequilibrium rovibrational energy distributions of hydrogen isotopologues in an expanding plasma jet

Cited by 12 publications

References 26 publications

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Gas temperature determination from rotational lines in non-equilibrium plasmas: a review

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Determination of the rotational population of H2 and D2 including high-N states in low temperature plasmas via the Fulcher-α transition

Contact Info

Product

Resources

About