Analysis of a low-pressure mercury rare-gas positive column with a dynamic two-temperature representation of electron energy

Wani, Koichi

doi:10.1063/1.347067

Cited by 18 publications

(7 citation statements)

References 21 publications

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“…Van de Weijer and Cremers (1985) reported experimental trapped decay rates for Hg 6 3 P 1 atoms that showed the effect of buffer gas collisions, and used a modified version of Walsh's formulae to model their experimental results. Wani (1990) also studied the effect of buffer collisions on Hg 254 nm radiation trapping, and he presented an analytic formula for the trapped decay rate (as a function of Hg density and tube radius) with 400 Pa (∼3 Torr) of Ar. Monte Carlo results on Hg 254 nm radiation trapping with significant buffer gas broadening were recently reported by Baeva and Reiter (2003).…”

Section: Introductionmentioning

confidence: 99%

Radiation trapping of the Hg 254 nm resonance line

Herd¹,

Lawler²,

Menningen³

2005

J. Phys. D: Appl. Phys.

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The decay rate of Hg 6 3P1 atoms, due primarily to the escape of trapped 254 nm resonance radiation, was measured as a function of both Hg and Ar density in cylindrical, sealed fused silica cells. Time-resolved laser-induced fluorescence at 254 nm was used to obtain the decay rates for Hg densities from 5 × 1013 to 7 × 1015 cm−3 (22–101°C cold spot temperatures) and Ar densities from 0 to 9.7 × 1017 cm−3 in a cell of inner radius 1.05 cm. These new experimental data are compared to Monte Carlo results from a highly realistic code for simulating radiation trapping. This code includes Voigt profiles from a combination of Doppler, resonance, buffer gas and radiative line broadening, as well as hyperfine and isotopic structure with proper collisional redistribution. Upper limits on the rate constants for the quenching of Hg 6 3 P1 atoms by collisions with ground level Ar and Hg atoms were derived. Additional Monte Carlo simulations covering cell radii from 0.1 to 3.0 cm were performed. A broadly applicable engineering formula is derived from this study, which predicts the Hg 6 3P1 decay rate from 254 nm resonance radiation trapping as a function of Hg and Ar densities and cell radius.

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Section: Introductionmentioning

confidence: 99%

Radiation trapping of the Hg 254 nm resonance line

Herd¹,

Lawler²,

Menningen³

2005

J. Phys. D: Appl. Phys.

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“…[53][54][55][56][57] However, only in a recent study, Hadidi et al 58 reported the RT phenomena of the transition lines, 253.65 nm of the Hg (6p 3 P 1 → 6s 2 1 S 0 ) and 228.80 nm of the Cd (5p 1 P 1 → 5s 2 1 S 0 ) in the development of an online emission monitor using a similar microwave plasma. In that study the plasma power was 1.5 kW, sample concentration was 10 000 ppm, and the emission detector was located at the axial direction of the plasma torch.…”

Section: Effect Of Radiation Trapping Of 25365 Nm Transition Linementioning

confidence: 99%

A portable optical emission spectroscopy-cavity ringdown spectroscopy dual-mode plasma spectrometer for measurements of environmentally important trace heavy metals: Initial test with elemental Hg

Sahay

Scherrer

Wang

2012

Review of Scientific Instruments

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A portable optical emission spectroscopy-cavity ringdown spectroscopy (OES-CRDS) dual-mode plasma spectrometer is described. A compact, low-power, atmospheric argon microwave plasma torch (MPT) is utilized as the emission source when the spectrometer is operating in the OES mode. The same MPT serves as the atomization source for ringdown measurements in the CRDS mode. Initial demonstration of the instrument is carried out by observing OES of multiple elements including mercury (Hg) in the OES mode and by measuring absolute concentrations of Hg in the metastable state 6s6p (3)P(0) in the CRDS mode, in which a palm-size diode laser operating at a single wavelength 405 nm is incorporated in the spectrometer as the light source. In the OES mode, the detection limit for Hg is determined to be 44 parts per 10(9) (ppb). A strong radiation trapping effect on emission measurements of Hg at 254 nm is observed when the Hg solution concentration is higher than 50 parts per 10(6) (ppm). The radiation trapping effect suggests that two different transition lines of Hg at 253.65 nm and 365.01 nm be selected for emission measurements in lower (<50 ppm) and higher concentration ranges (>50 ppm), respectively. In the CRDS mode, the detection limit of Hg in the metastable state 6s6p (3)P(0) is achieved to be 2.24 parts per 10(12) (ppt) when the plasma is operating at 150 W with sample gas flow rate of 480 mL min(-1); the detection limit corresponds to 50 ppm in Hg sample solution. Advantage of this novel spectrometer has two-fold, it has a large measurement dynamic range, from a few ppt to hundreds ppm and the CRDS mode can serve as calibration for the OES mode as well as high sensitivity measurements. Measurements of seven other elements, As, Cd, Mn, Ni, P, Pb, and Sr, using the OES mode are also carried out with detection limits of 1100, 33, 30, 144, 576, 94, and 2 ppb, respectively. Matrix effect in the presence of other elements on Hg measurements has been found to increase the detection limit to 131 ppb. These elements in lower concentrations can also be measured in the CRDS mode when a compact laser source is available to be integrated into the spectrometer in the future. This exploratory study demonstrates a new instrument platform using an OES-CRDS dual-mode technique for potential field applications.

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“…In order to justify our assumption that the EEDF can be assumed to be Maxwellian, an analysis has been carried out along the lines of the two electron group model [5,6,15,16]. In this formalism, it is assumed that the EEDF consists of two parts.…”

Section: Maxwellian Distribution Functionmentioning

confidence: 99%

A collisional radiative model for mercury in high-current discharges

Dijk¹,

Hartgers²,

Jonkers³

et al. 2000

J. Phys. D: Appl. Phys.

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A collisional radiative model is presented for mercury discharges with electron temperatures between 0.75-2 eV and electron densities between 1018-1020 m-3. Such plasma parameters are encountered in a number of modern light sources, such as mercury-operated induction lamps and the compact fluorescent lamp. The analytical top model has been used, which allows the majority of the non-equilibrium levels to be taken into account implicitly. As a result, indirect ionization processes involving highly excited atomic mercury states are taken into account in spite of the relatively low number of levels (19) which has been considered. The influence of higher atomic mercury levels on the ionization rate coefficient has been carefully analysed, and has been found to contribute significantly. Furthermore, a consistent means of quantifying the production of radiation by the plasma will be presented by introducing the specific effective emissivities. These enable one to express the total radiated power in terms of the densities of the transport-dominated states and the electron density and temperature. These coefficients, as well as the net coefficients of ionization and recombination, will be presented and discussed, enabling their usage in plasma transport models.

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Analysis of a low-pressure mercury rare-gas positive column with a dynamic two-temperature representation of electron energy

Cited by 18 publications

References 21 publications

Radiation trapping of the Hg 254 nm resonance line

Radiation trapping of the Hg 254 nm resonance line

A portable optical emission spectroscopy-cavity ringdown spectroscopy dual-mode plasma spectrometer for measurements of environmentally important trace heavy metals: Initial test with elemental Hg

A collisional radiative model for mercury in high-current discharges

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