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David B Graves - One of the best experts on this subject based on the ideXlab platform.
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measurements of the electron energy distribution function in Molecular Gases in a shielded inductively coupled plasma
Journal of Applied Physics, 2000Co-Authors: Harmeet Singh, David B GravesAbstract:A cylindrical Langmuir probe has been used to measure the electron energy distribution function (EEDF) in atomic and Molecular Gases in a shielded inductively coupled plasma. We report the EEDFs in these Gases as a function of pressure. While the electron properties in a discharge depend on the product of the neutral number density (N0) and the effective discharge dimension (deff) for a given gas, this dependence is different for different Gases. We find that pressure is a convenient parameter for comparison of the EEDFs in these Gases. The EEDFs in inert (Ar, Kr, Xe) and Molecular Gases (H2,N2,O2,H2O,CO2,CF4) in the low pressure limit (below 1 mTorr) show a “three-temperature” structure. Since this wide range of Gases display similar EEDF shape, we propose this structure to be common to all gas discharges in this limit. The EEDF in all of the Gases shows a two-temperature structure with apparent tail depletion at 3 mTorr. The similarity of the EEDFs in all of the above Gases is probably due to nonlocality of the electrons at these low pressures. The Molecular Gases exhibit a nearly Maxwellian EEDF between about 10 and 30 mTorr, while the EEDF in argon is non-Maxwellian in this range. At pressures above 30 mTorr, the EEDFs in Molecular Gases show deviations from a Maxwellian distribution, reflecting the electron-neutral collision cross sections of each gas. The EEDFs in Molecular Gases at 100 mTorr show significant deviations from a Maxwellian distribution. We find that the EEDF in Molecular Gases can be approximated by a Maxwellian distribution over a fairly large pressure range of 3–50 mTorr for the purposes of modeling these discharges.
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measurements of the electron energy distribution function in Molecular Gases in an inductively coupled plasma
Journal of Applied Physics, 2000Co-Authors: Harmeet Singh, David B GravesAbstract:A cylindrical Langmuir probe has been used to measure the electron energy distribution function (EEDF) in atomic and Molecular Gases in a shielded inductively coupled plasma. We report the EEDFs in these Gases as a function of pressure. While the electron properties in a discharge depend on the product of the neutral number density (N0) and the effective discharge dimension (deff) for a given gas, this dependence is different for different Gases. We find that pressure is a convenient parameter for comparison of the EEDFs in these Gases. The EEDFs in inert (Ar, Kr, Xe) and Molecular Gases (H2,N2,O2,H2O,CO2,CF4) in the low pressure limit (below 1 mTorr) show a “three-temperature” structure. Since this wide range of Gases display similar EEDF shape, we propose this structure to be common to all gas discharges in this limit. The EEDF in all of the Gases shows a two-temperature structure with apparent tail depletion at 3 mTorr. The similarity of the EEDFs in all of the above Gases is probably due to nonlocalit...
Kaito Ushio - One of the best experts on this subject based on the ideXlab platform.
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a large amount of diffuse Molecular Gases in the bar of the strongly barred galaxy ngc 1300 cause of the low star formation efficiency
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Fumiya Maeda, Kouji Ohta, Yusuke Fujimoto, Asao Habe, Kaito UshioAbstract:In many barred galaxies, star formation efficiency (SFE) in the bar is lower than those in the arm and bar-end, and its cause has still not been clear. Focusing on the strongly barred galaxy NGC 1300, we investigate the possibility that the presence of a large amount of diffuse Molecular gas, which would not contribute to the SF, makes the SFE low in appearance. We examine the relation between the SFE and the diffuse Molecular gas fraction ($f_{\rm dif}$), which is derived using the $^{12}$CO($1-0$) flux obtained from the interferometer of ALMA 12-m array, which has no sensitivity on diffuse (extended; FWHM $\gtrapprox 700$ pc) Molecular Gases due to the lack of ACA, and the total $^{12}$CO($1-0$) flux obtained from Nobeyama 45-m single-dish telescope. We find that the SFE decreases with increasing $f_{\rm dif}$. The $f_{\rm dif}$ and ${\rm SFE}$ are $0.74 - 0.91$ and $(0.06 - 0.16) ~\rm Gyr^{-1}$ in the bar regions, and $0.28 - 0.65$ and $(0.23 - 0.96) ~\rm Gyr^{-1}$ in the arm and bar-end regions. This result supports the idea that the presence of a large amount of diffuse Molecular gas makes the SFE low. The suppression of the SFE in the bar has also been seen even when we exclude the diffuse Molecular gas components. This suggests that the low SFE appears to be caused not only by a large amount of diffuse Molecular Gases but also by other mechanisms such as fast cloud-cloud collisions.
Fumiya Maeda - One of the best experts on this subject based on the ideXlab platform.
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a large amount of diffuse Molecular Gases in the bar of the strongly barred galaxy ngc 1300 cause of the low star formation efficiency
Monthly Notices of the Royal Astronomical Society, 2020Co-Authors: Fumiya Maeda, Kouji Ohta, Yusuke Fujimoto, Asao Habe, Kaito UshioAbstract:In many barred galaxies, star formation efficiency (SFE) in the bar is lower than those in the arm and bar-end, and its cause has still not been clear. Focusing on the strongly barred galaxy NGC 1300, we investigate the possibility that the presence of a large amount of diffuse Molecular gas, which would not contribute to the SF, makes the SFE low in appearance. We examine the relation between the SFE and the diffuse Molecular gas fraction ($f_{\rm dif}$), which is derived using the $^{12}$CO($1-0$) flux obtained from the interferometer of ALMA 12-m array, which has no sensitivity on diffuse (extended; FWHM $\gtrapprox 700$ pc) Molecular Gases due to the lack of ACA, and the total $^{12}$CO($1-0$) flux obtained from Nobeyama 45-m single-dish telescope. We find that the SFE decreases with increasing $f_{\rm dif}$. The $f_{\rm dif}$ and ${\rm SFE}$ are $0.74 - 0.91$ and $(0.06 - 0.16) ~\rm Gyr^{-1}$ in the bar regions, and $0.28 - 0.65$ and $(0.23 - 0.96) ~\rm Gyr^{-1}$ in the arm and bar-end regions. This result supports the idea that the presence of a large amount of diffuse Molecular gas makes the SFE low. The suppression of the SFE in the bar has also been seen even when we exclude the diffuse Molecular gas components. This suggests that the low SFE appears to be caused not only by a large amount of diffuse Molecular Gases but also by other mechanisms such as fast cloud-cloud collisions.
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large velocity dispersion of Molecular gas in bars of strongly barred galaxies ngc 1300 and ngc 5383
arXiv: Astrophysics of Galaxies, 2018Co-Authors: Fumiya Maeda, Kouji Ohta, Yusuke Fujimoto, Asao Habe, Junichi BabaAbstract:We carried out $^{12}$CO(J = 1 -0) observations toward bar and arm regions of strongly barred galaxies, NGC 1300 and NGC 5383, with the Nobeyama 45-m radio telescope (beamsize of 1-2 kpc in the galaxies). The aim of the observations is to qualitatively examine a new scenario for the suppression of star formation in bars based on recent high-resolution numerical simulations: higher speed collisions between Molecular clouds in the bar region compared with the arm region suppress the massive star formation. CO emissions were detected from all the regions, indicating the presence of the Molecular Gases in the strong bars without associating clear HII regions. In both galaxies, the velocity width of the CO line profile tends to be larger in the bar region than in the arm region, which is qualitatively consistent with the new scenario.
Harmeet Singh - One of the best experts on this subject based on the ideXlab platform.
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measurements of the electron energy distribution function in Molecular Gases in a shielded inductively coupled plasma
Journal of Applied Physics, 2000Co-Authors: Harmeet Singh, David B GravesAbstract:A cylindrical Langmuir probe has been used to measure the electron energy distribution function (EEDF) in atomic and Molecular Gases in a shielded inductively coupled plasma. We report the EEDFs in these Gases as a function of pressure. While the electron properties in a discharge depend on the product of the neutral number density (N0) and the effective discharge dimension (deff) for a given gas, this dependence is different for different Gases. We find that pressure is a convenient parameter for comparison of the EEDFs in these Gases. The EEDFs in inert (Ar, Kr, Xe) and Molecular Gases (H2,N2,O2,H2O,CO2,CF4) in the low pressure limit (below 1 mTorr) show a “three-temperature” structure. Since this wide range of Gases display similar EEDF shape, we propose this structure to be common to all gas discharges in this limit. The EEDF in all of the Gases shows a two-temperature structure with apparent tail depletion at 3 mTorr. The similarity of the EEDFs in all of the above Gases is probably due to nonlocality of the electrons at these low pressures. The Molecular Gases exhibit a nearly Maxwellian EEDF between about 10 and 30 mTorr, while the EEDF in argon is non-Maxwellian in this range. At pressures above 30 mTorr, the EEDFs in Molecular Gases show deviations from a Maxwellian distribution, reflecting the electron-neutral collision cross sections of each gas. The EEDFs in Molecular Gases at 100 mTorr show significant deviations from a Maxwellian distribution. We find that the EEDF in Molecular Gases can be approximated by a Maxwellian distribution over a fairly large pressure range of 3–50 mTorr for the purposes of modeling these discharges.
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measurements of the electron energy distribution function in Molecular Gases in an inductively coupled plasma
Journal of Applied Physics, 2000Co-Authors: Harmeet Singh, David B GravesAbstract:A cylindrical Langmuir probe has been used to measure the electron energy distribution function (EEDF) in atomic and Molecular Gases in a shielded inductively coupled plasma. We report the EEDFs in these Gases as a function of pressure. While the electron properties in a discharge depend on the product of the neutral number density (N0) and the effective discharge dimension (deff) for a given gas, this dependence is different for different Gases. We find that pressure is a convenient parameter for comparison of the EEDFs in these Gases. The EEDFs in inert (Ar, Kr, Xe) and Molecular Gases (H2,N2,O2,H2O,CO2,CF4) in the low pressure limit (below 1 mTorr) show a “three-temperature” structure. Since this wide range of Gases display similar EEDF shape, we propose this structure to be common to all gas discharges in this limit. The EEDF in all of the Gases shows a two-temperature structure with apparent tail depletion at 3 mTorr. The similarity of the EEDFs in all of the above Gases is probably due to nonlocalit...
Gilberto Teobaldi - One of the best experts on this subject based on the ideXlab platform.
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density functional theory screening of gas treatment strategies for stabilization of high energy density lithium metal anodes
Journal of Power Sources, 2015Co-Authors: Stephan L Koch, Benjamin J Morgan, Stefano Passerini, Gilberto TeobaldiAbstract:Abstract To explore the potential of Molecular gas treatment of freshly cut lithium foils in non-electrolyte-based passivation of high-energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of Molecular Gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different Molecular Gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered Gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages ≤1 mono-layer. The substantial Li → adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.
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density functional theory screening of gas treatment strategies for stabilization of high energy density lithium metal anodes
arXiv: Materials Science, 2015Co-Authors: Stephan L Koch, Benjamin J Morgan, Stefano Passerini, Gilberto TeobaldiAbstract:To explore the potential of Molecular gas treatment of freshly cut lithium foils in non-electrolyte based passivation of high energy-density Li anodes, density functional theory (DFT) has been used to study the decomposition of Molecular Gases on metallic lithium surfaces. By combining DFT geometry optimization and Molecular Dynamics, the effects of atmospheric (N2, O2, CO2) and hazardous (F2, SO2) gas decomposition on Li(bcc) (100), (110), and (111) surfaces on relative surface energies, work functions, and emerging electronic and elastic properties are investigated. The simulations suggest that exposure to different Molecular Gases can be used to induce and control reconstructions of the metal Li surface and substantial changes (up to over 1 eV) in the work function of the passivated system. Contrary to the other considered Gases, which form metallic adlayers, SO2 treatment emerges as the most effective in creating an insulating passivation layer for dosages adsorbate charge transfer and adlayer relaxation produce marked elastic stiffening of the interface, with the smallest change shown by nitrogen-treated adlayers.