scholarly journals Dissociation Processes of SiCl4 and Plasma Parameters measured by Transient Spectroscopy at the Beginning of a SiCl4?Helium dc Discharge

1995 ◽  
Vol 48 (3) ◽  
pp. 515 ◽  
Author(s):  
Takeki Sakurai ◽  
Shigeru Kobayashi ◽  
Jun Ogura ◽  
Yukio Inoue ◽  
Hirokazu Hori
Keyword(s):  
Excited States ◽  
Single Step ◽  
Emission Lines ◽  
Plasma Parameters ◽  
Average Electron Energy ◽  
Transient Behaviour ◽  
Excited Atoms ◽  
Dc Discharge ◽  
Transient Spectroscopy ◽  
Average Electron

We propose that the excitation or the dissociation mechanism and plasma parameters in a discharge can be estimated by. spectroscopic methods, such as the measurement of the transient behaviour of fluorescences at the beginning of a pulsed de discharge. Fluorescences emitted from excited atoms and dissociated fragments from 270 to 640 nm in wavelength are measured as a function of time at the beginning of a discharge of a He-SiCl4 gas mixture. The transient waveform of fluorescence is calculated by considering the experimental results of discharge current and voltage between electrodes measured as a function of time. From a comparison of the experimental and calculated waveforms of fluorescence it is concluded that the fragment emitting the light, SiCb, is excited in a single-step from SiCl4 by electronic collisions and the fluorescence-emitting fragments of SiCI3, SiCI, C12, CI, Si and CI+ in a discharge can never be excited by electronic collisions in a single step. Furthermore, an average electron energy in the plasma at a steady state is simply estimated from a measurement of the transient behaviour of emission lines from helium excited states. The result is in fair agreement with the value measured by using an electric probe.

All that is known about Mars discrete aurorae so far

2021 ◽  
Author(s):  
Lauriane Soret ◽  
Zachariah Milby ◽  
Jean-Claude Gérard ◽  
Nick Schneider ◽  
Sonal Jain ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Emission Layer ◽  
Atmospheric Effect ◽  
Average Electron Energy ◽  
Mars Express ◽  
Spatially Correlated ◽  
Auroral Emissions ◽  
Average Electron ◽  
First Time ◽  
Imaging Spectrograph

<p>The discrete aurorae on Mars were discovered with the SPICAM spectrograph on board Mars Express. Now, they have been analyzed in detail using the much more sensitive MAVEN/IUVS imaging spectrograph.</p><p>This presentation gives a summary of the very latest results obtained by Schneider et al. and Soret et al. on this topic.</p><p>The main conclusions are the following:</p><ul><li>the number of auroral event detections has considerably increased since the Mars Express observations;</li> <li>many detections have been made outside of the Southern crustal magnetic field structures;</li> <li>the MUV spectrum shows the same emissions as those observed in the dayglow, with similar intensity ratios;</li> <li>the Vegard-Kaplan bands of N<sub>2</sub> have been observed for the first time in the Martian aurora;</li> <li>the CO Cameron and the CO<sub>2</sub><sup>+</sup> UVD emissions occur at the same altitude;</li> <li>the OI emission at 297.2 nm has been analyzed;</li> <li>the CO Cameron/CO<sub>2</sub><sup>+</sup> UVD ratio is quasi-constant;</li> <li>intensities are higher in B-field regions;</li> <li>auroral emissions are more frequent in the pre-midnight sector;</li> <li>the altitude of the emission layer is independent of local time and presence or absence of a crustal magnetic field;</li> <li>the altitude of the emission layer varies moderately with season (atmospheric effect);</li> <li>the events are spatially correlated with an increase in the flux of energetic electrons simultaneously measured by the MAVEN/SWEA (Solar Wind Electron Analyzer) detectors;</li> <li>the peak altitude of the emission is in good agreement with that expected from the average electron energy.</li> </ul>

scholarly journals Anisotropic relaxation in NADH excited states studied by polarization-modulation pump–probe transient spectroscopy

2020 ◽  
Vol 22 (32) ◽  
pp. 18155-18168
Author(s):  
Ioanna A. Gorbunova ◽  
Maxim E. Sasin ◽  
Yaroslav M. Beltukov ◽  
Alexander A. Semenov ◽  
Oleg S. Vasyutinskii
Keyword(s):  
Excited States ◽  
Polarization Modulation ◽  
Transient Method ◽  
Pump Probe ◽  
Water Solutions ◽  
Transient Spectroscopy ◽  
Anisotropic Relaxation

Fast anisotropic relaxation in excited NADH in ethanol–water solutions at various ethanol concentrations was studied by a novel polarization-modulation transient method.

VUV Radiation by Dissociative Excitation of NH3

1971 ◽  
Vol 26 (9) ◽  
pp. 1491-1495 ◽  
Author(s):  
N . Böse ◽  
W. Sroka
Keyword(s):  
Excitation Function ◽  
Single Step ◽  
Dissociative Excitation ◽  
Step Process ◽  
Excited Atoms

Abstract The NH3 molecule is dissociated in a single step process into excited atoms and ions, which emit a radiation in the VUV. We have observed the Ly series and several lines of N I and N II. Only for Ly α we have found a structure in the shape of the excitation function.

Excited-Atom Production by Electron Bombardment of Alkali-Halides

1986 ◽  
Vol 75 ◽  
Author(s):  
R. E. Walkup ◽  
Ph. Avouris ◽  
A. P. Ghosh
Keyword(s):  
Gas Phase ◽  
Excited States ◽  
Ground State ◽  
Excited Atom ◽  
Alkali Halides ◽  
Electron Bombardment ◽  
Secondary Electrons ◽  
Excited Atoms ◽  
Positive Ions ◽  
Electronically Excited

AbstractWe present experimental results which suggest a new mechanism for the production of excited atoms and ions by electron bombardment of alkali-halides. Doppler shift measurements show that the electronically excited atoms have a thermal velocity distribution in equilibrium with the surface temperature. Measurements of the absolute yield of excited atoms, the distribution of population among the excited states, and the dependence of yield on incident electron current support a model in which excited atoms are produced by gas-phase collisions between desorbed ground-state atoms and secondary electrons. Similarly, gas-phase ionization of ground-state neutrals by secondary electrons accounts for a substantial portion of the positive ions produced by electron bombardment of alkali-halides.

Determination of Ionization Efficiencies of Excited Atoms in a Flame by Laser-Enhanced Ionization Spectrometry

1989 ◽  
Vol 43 (6) ◽  
pp. 940-952 ◽  
Author(s):  
O. Axner ◽  
T. Berglind
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Energy Difference ◽  
Ionization Efficiency ◽  
Striking Feature ◽  
Boltzmann Factor ◽  
Excited Atoms ◽  
Ionization Limit

State-specific ionization efficiencies for excited Li and Na atoms in acetylene/air flames have been determined. The ionization efficiencies, i.e., the probability that the excited atoms ionize instead of returning to the ground state, are determined by relating collision-assisted Laser-Enhanced Ionization (LEI) signals from various excited states with laser-induced photoionization signals. The ionization efficiencies are found to decrease (from being one at the ionization limit) almost monotonically as the lower atoms are excited. The most striking feature, however, is that the decrease of the ionization efficiency values is generally found to be less than the decrease of the Boltzmann factor, exp(- δE/kT), when the energy difference, δE, between the excited state and the ionization limit is increased. The ionization efficiencies are found to be close to unity for states with δE < kT and approximately 50% for states with δE ≈ 2.5 kT ( np ≈ 6 p). For the lower states, the ionization efficiencies are found to be approximately five times larger than the Boltzmann factor.

Transient spectroscopy of the lowest excited states of binuclear rhodium(I) isocyanides

1986 ◽  
Vol 90 (22) ◽  
pp. 5567-5570 ◽  
Author(s):  
Steven J. Milder ◽  
David S. Kliger ◽  
Leslie G. Butler ◽  
Harry B. Gray
Keyword(s):  
Excited States ◽  
Transient Spectroscopy

Measurements of Electron Energy by Emission Spectroscopy in Pulsed Corona and Dielectric Barrier Discharges

2003 ◽  
Vol 6 (1) ◽  
Author(s):  
Yongho Kim ◽  
Sang Hee Hong ◽  
Min Suk Cha ◽  
Young-Hoon Song ◽  
Seock Joon Kim
Keyword(s):  
Electron Energy ◽  
Spectroscopic Method ◽  
Optical Emission ◽  
Dielectric Barrier Discharges ◽  
Time Resolved ◽  
Average Electron Energy ◽  
Dielectric Barrier ◽  
Pulsed Corona ◽  
Average Electron ◽  
Barrier Discharges

AbstractElectric field distributions and average electron energies are measured by an optical emission spectroscopic method to investigate streamer characteristics in a pulsed corona discharge (PCD) and a dielectric barrier discharge (DBD) in atmospheric air. In PCD, average electron energies appear to be in the range of 10 ~ 12 eV along the streamers. Time-resolved measurements show that streamers in DBD have a relatively low value of average electron energy of 9 ~ 10 eV. Enhancement of the electron energy is observed when DBD is operated in a non-uniform geometry, such as dielectric barrier with a hole.

scholarly journals Measurement of Some Argon Plasma Parameters Glow Discharge Under Axial Magnetic Field

2019 ◽  
Vol 7 (4) ◽  
pp. 158-166
Author(s):  
Pshtiwan M.A. Karim ◽  
Diyar S. Mayi ◽  
Shamo Kh. Al-Hakary
Keyword(s):  
Magnetic Field ◽  
Electrical Conductivity ◽  
Glow Discharge ◽  
Electron Temperature ◽  
Breakdown Voltage ◽  
Axial Magnetic Field ◽  
Argon Plasma ◽  
Emission Lines ◽  
Plasma Parameters ◽  
Gas Pressures

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

scholarly journals Филаментация и самофокусировка электронных пучков в вакуумных и газовых диодах

2019 ◽  
Vol 45 (7) ◽  
pp. 3
Author(s):  
В.И. Олешко ◽  
В.Ф. Тарасенко ◽  
А.Г. Бураченко ◽  
V.V. Nguyen
Keyword(s):  
Energy Density ◽  
Electron Beams ◽  
Local Density ◽  
Beam Current ◽  
Beam Current Density ◽  
Runaway Electrons ◽  
Beam Current Pulse ◽  
Average Electron Energy ◽  
Interelectrode Gap ◽  
Average Electron

AbstractIn this paper, we experimentally studied pulsed electron beams with a high local density. The conditions in which the energy density cumulation is observed during the interaction of electrons with the anode are shown to develop in vacuum and gas diodes at nanosecond and subnanosecond durations of a beam current pulse and a decrease in the interelectrode gap. The average electron energy in filamentation and self-focusing of an electron beam in a vacuum diode of an accelerator at a current of ~2 kA and a no-load voltage of ~400 kV was established to be 50–100 keV while the energy density was 10^9–10^10 J/cm^3. It is confirmed that the beam current density in a gas diode can exceed 1 kA/cm^2. It is hypothesized that superdense electron beams in vacuum and gas diodes are formed as a result of avalanche multiplication of runaway electrons in the cathode–anode gap plasma.

Sign in / Sign up

Export Citation Format

Share Document