Theory of Spectrochemical Excitation

Boumans, P.W.J.M.

doi:10.1007/978-1-4684-8428-1

Cited by 92 publications

(68 citation statements)

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“…(2), and can occur through possible de-excitation channels as almost simultaneously as the electron-impact excitation, so that the excited atom can rapidly fall down to the ground state while emitting the characteristic radiation. 9 Collisions with longlifetime species, such as argon metastable atom, called a collision of the second kind, 18 contribute less to the overall excitations of iron atom than does the electron collision. It is therefore considered that, when collisions with energetic electrons would be a dominant process for excitations of iron atom, the Boltzmann plot should follow a linear relationship over a wide range of the excitation energy, which is mainly determined by the average kinetic energy of the electrons.…”

Section: General Aspect Of Boltzmann Plotmentioning

confidence: 99%

Estimation Using an Enhancement Factor on Non Local Thermodynamic Equilibrium Behavior of High-lying Energy Levels of Neutral Atom in Argon Radio-Frequency Inductively-Coupled Plasma

Wagatsuma

Satoh

2016

ANAL. SCI.

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This paper describes a plasma-diagnostic method using an enhancement factor on the Boltzmann distribution among emission lines of iron atom in an argon radio-frequency inductively-coupled plasma (ICP). It indicated that Boltzmann plots of the atomic lines having lower excitation energies (3.4 to 4.8 eV) were well fitted on a straight line while those having more than 5.5 eV deviated upwards from a linear relationship. This observation could be explained by the fact that ICP is not in a complete thermodynamic equilibrium between direct excitation to energy levels of iron atom, ionization of iron atom, and radiative decay processes to the ground state. Especially, the recombination of iron ion with captured electron should accompany cascade de-excitations between closely-spaced excited levels just below the ionization limit, the rates of which become slower as a whole; as a result, these high-lying levels might be more populated than the low-lying levels as if a different LTE condition coexists on the high energy side. This overpopulation could be quantitatively estimated using an enhancement factor (EF), which was a ratio of the observed intensity to the expected value extrapolated from the normal distribution on the low energy side. The EFs were generally small (less than 3); therefore, the cascade de-excitation process would slightly contribute to the population of these excited levels. It could be considered from variations of the EF that the overpopulation proceeded to a larger extent at lower radio-frequency forward powers, at higher flow rates of the carrier gas, or at higher observation heights. The reason for this is that the kinetic energy of energetic particles, such as electrons, becomes reduced under all of these plasma conditions, thus enabling the high-lying levels to be more populated by cascade de-excitation processes from iron ion rather than by collisional excitation processes with the energetic particles. A similar Boltzmann analysis using the EF was also carried out in emission lines of nickel atom, which confirmed the conclusion concerning the atomic lines of iron.

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Section: General Aspect Of Boltzmann Plotmentioning

confidence: 99%

Estimation Using an Enhancement Factor on Non Local Thermodynamic Equilibrium Behavior of High-lying Energy Levels of Neutral Atom in Argon Radio-Frequency Inductively-Coupled Plasma

Wagatsuma

Satoh

2016

ANAL. SCI.

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“…From the intensities of lines of the same atom, ion or molecule, and detailed calculations of the transition probabilities, it is possible to determine the density and temperature of the region in which it arises [37].…”

Section: Excitation Temperature Measurementmentioning

confidence: 99%

“…These temperatures may differ from each other even if the individual velocity distributions are close to Maxwellians, because electron-electron energy transfer rates are much larger than electron-ion collision rates, as are ion-ion rates [37].…”

Section: Excitation Temperature Measurementmentioning

confidence: 99%

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Spectroscopic investigation of arc over an ice surface /

Nekahi¹

2011

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Ice accumulation on insulators of overhead transmission lines and substations has been recognized as a major problem which may cause insulator flashover and power outages. This phenomenon starts with corona discharge activity and continues with the formation of partial arcs which may result in flashover. Due to the complexity of the process, resulting from surface interaction of discharge with the water film on the ice surface, is not yet fully understood. As for any other type of discharge, the knowledge of some parameters such as temperature and concentration of different species is necessary in order to describe the mechanisms involved. Moreover, to develop mathematical models for discharge propagation, an estimation of discharge channel conductivity is necessary. The current flows through this conductive channel and supplies the energy needed to sustain the ionization activity inside the channel. The conductivity of discharge channel is directly related to its temperature, which illustrates the need for discharge temperature measurements. Up to now, for an arc over an ice surface the temperature has been assumed to have a constant value of 5,000 K, but without any experimental support.The existence of Local Thermodynamic Equilibrium (LTE) is another important aspect for proposing theories and models, but this has not yet been verified for flashover on icecovered insulators. The verification of LTE condition requires information about temperature and concentration of different species, electron density and ionization level.The objective of this research is to augment our knowledge of flashover on icecovered insulators by measuring and calculating several important discharge column parameters. Measurement of rotational and excitation temperatures, and electron density during arc propagation are the first steps. The effect of discharge current, voltage type and polarity on the variation of the mentioned arc parameters should be also studied.Based on these data, the LTE condition could be examined.Spectroscopic plasma diagnostic is a non-destructive test method used to achieve the stated objectives. The emitted light from an arc over an ice surface was transmitted to a spectrometer. The time-resolved recorded spectra of arc were used to study the nature and concentration of ionized species. The gas and electron temperatures and electron densities were also measured using Boltzmann and Stark broadening methods.Measured rotational temperatures were found to vary from 4,000 K to 6,500 K, while the current increased from 200 mA to 700 mA during the discharge propagation. It was observed that under similar experimental conditions, the arc current intensity of DC+ arcs were hotter than that of DC-. Moreover, arc temperatures under AC voltage were lower than those of DC+, and close to that of DC-. The excitation temperature was measured at about 9,000 K and does not vary significantly with discharge current. As current increases, electron densities increased as well. For currents ranging from 200 mA to 700 mA, ...

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“…A two-line method can provide a gas temperature under a local thermodynamic equilibrium condition. 13 Then, variations in the gas temperature can also be monitored during the atomization process occurring in the graphite furnace. 14 In order to estimate the gas temperature in the atomization furnace directly, the authors have reported a monitoring system by using a two-line method.…”

Section: Introductionmentioning

confidence: 99%

Temporal Variation in Gas Temperature at the Atomization Stage in Several Types of Graphite Furnaces for Atomic Absorption Spectrometry

et al. 2009

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In order to compare and evaluate the atomization process occurring in several types of graphite furnaces for atomic absorption spectrometry, the authors estimated temporal variations in the gas temperature by using a two-line method under the assumption of a Bolzmann distribution. The atomization furnaces employed were a graphite tube, a graphite tube coated with pyrolitic carbon, a graphite tube with a platform and a graphite cup. Differences in the temporal variation in the gas temperature among these graphite furnaces were observed.

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Theory of Spectrochemical Excitation

Cited by 92 publications

References 0 publications

Estimation Using an Enhancement Factor on Non Local Thermodynamic Equilibrium Behavior of High-lying Energy Levels of Neutral Atom in Argon Radio-Frequency Inductively-Coupled Plasma

Estimation Using an Enhancement Factor on Non Local Thermodynamic Equilibrium Behavior of High-lying Energy Levels of Neutral Atom in Argon Radio-Frequency Inductively-Coupled Plasma

Spectroscopic investigation of arc over an ice surface /

Temporal Variation in Gas Temperature at the Atomization Stage in Several Types of Graphite Furnaces for Atomic Absorption Spectrometry

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