Vacuum ultraviolet assessment of ionization temperature by space-resolved emission spectroscopy

In this article, the electron ionization temperature in plasmas generated by 1064 nm laser pulses in the vacuum ultraviolet spectral range is evaluated as a function of the axial distance from a steel target surface using emission spectroscopy. The temperature was determined using the relative line intensities ratio of C II 90.41 nm and C III 97.7 nm spectral lines, applied to the Saha–Boltzmann equation. Ionization temperatures determined in this way changed from 33 900 K at the target surface to 26 800 K (2.92–2.31 eV) at 4.0 mm away from it. Large differences between the measured excitation and ionization temperatures suggest nonthermal equilibrium conditions between electrons and heavier ionic species. Based upon the results obtained from this and a previous study under the same operating conditions, the validity of the local thermal equilibrium condition in the plasmas investigated is presented and discussed.

Prominence Emission Lines Observed With SUMER and Two Ground-based Telescopes

Two sets of H, He, and Ca+ emission lines were observed in a quiescent prominence simultaneously with the VTT and the Gregory telescope on Tenerife. At the same time, SUMER took two scans of low-ionized EUV emission lines.The emission ratios of Ca+–to–Balmer lines from ground vary little in the prominence, indicating a largely constant gas-pressure. In contrast, the ratio of He–to–Balmer from the ground shows the (known) increase toward the prominence borders, indicating higher temperature there. Similarly, the two-dimensional distributions of the ratios S IV/N II and C III/He I show pronounced bright prominence rims.The reduced He 537Å and He 584Å line widths are 2.6 and 3.6 times larger, respectively, than those of He D3 and He 3888Å. Explaining this by the optical thickness yields τ0 = 104 and τ0 = 2 · 105 for the two EUV lines. The total He 584 emission amounts to 13 watt/m2 ster in the main prominence body where the D3 line yields 4 watt/m2 ster; existing models, however, predict a factor 0.18.The widths of simultaneously observed optical lines with different atomic weights yield thermal and non-thermal broadening parameters of Tkin ≈ 8000 K and 2.5 < ξ < 6.5 km/s. The EUV lines, however, show line widths which correspond to much higher temperatures and non-thermal velocities. Assuming for each ion the corresponding ionization temperature, the line widths require non-thermal velocities of 15–40 km/s which is similar to values for the quiet corona.

Optical Monitoring of Laser-Induced Plasma Derived from Graphite and Characterization of the Deposited Carbon Film

Mechanisms of the deposition of carbon thin films by the laser ablation of graphite were investigated by monitoring the plasma emission. Parameters such as electron density, ionization temperature, and vibrational temperature during plasma growth were evaluated as a function of the laser power density and the surrounding atmosphere. Also, Raman spectra of the deposited films were measured so that the particle size can be estimated from the intensity ratio of the Raman bands around 1360 and 1580 cm−1. The increase in power density caused an increase in ionization temperature and vibrational temperature of carbon species in the plasma but a decrease of particle size of the deposited thin films. The existence of 10 Torr of helium as a surrounding atmosphere caused drastic changes in the plasma parameters. The films deposited with helium atmosphere showed a low optical band gap, which indicates heat restructuring of ablated graphite particles in the hot plasma. The results can be explained with a simple model of laser ablation and the subsequent interaction of ablated particles with the laser-induced plasma.

Effect of Carbon Dioxide and Hydrogen on Nonmetal Emission Intensities in a Helium Microwave-Induced Plasma

The effect of the introduction of carbon dioxide and hydrogen on nonmetal atomic and ionic line intensities in a helium microwave-induced plasma is discussed. The addition of these gases is found to diminish the excitation properties of the 150-W He plasma. While the plasma excitation temperature, ionization temperature, and electron number density are not significantly affected by the introduction of these gases, decreases in the emission intensities of atomic and ionic analyte transitions of S, P, Cl, Br, and I are noted with the higher-energy ionic transitions being more greatly affected. A correlation between the energy of the excited state and the depressing effect of CO2 is found by examining the signals of atomic and ionic transitions of Cl. The greater signal depression of the higher-energy nonmetal transitions is found to be consistent with charge transfer theory. These findings emphasize the importance of analyte line selection when a He plasma is being employed for the purpose of element-specific detection of nonmetals in supercritical fluid chromatography.

Ionization Temperatures in the Inductively Coupled Plasma Determined by Mass Spectrometry

Ionization temperatures in the inductively coupled plasma are determined with the use of the ionization fraction for iodine obtained by mass-spectral sampling. Temperatures profiled at different heights and different positions across the plasma are between 6900 and 7800 K at relatively low heights. Power increases raise the measured ionization temperature, while changes in nebulizer gas flow and the addition of an easily ionized element to the plasma have no measurable effect. Desolvation of the sample aerosol causes a decrease of about 500 K in the ionization temperature.

O VI Profiles of Solar Quiet and Active Areas Recorded by OSO-8 L.P.S.P. Experiment

O VI resonance line (2s2S - 2p2PO , 103.19 nm) is formed in the chromosphere-corona transition zone with a temperature of maximum ionization of 350 000°C (Jordan, 1969). The OSO-8/LPSP experiment has observed this line with a 0.006 nm resolution, few arcseconds angular resolution and a time resolution up to few seconds. We present the shape of the line in different areas on the sun (quiet and active). As transition lines are used to determine propagation of wave from chromosphere to corona, we compare width of the O VI line with other measurements obtained with lines of lower ionization temperature. From successive profiles we consider the possibility of direct measurements of wave propagating.