Hg Discharge Lamp Research Articles

Nickel determination in oily sludge leachates using isotope dilution inductively coupled plasma mass spectrometry following photochemical vapor generation: A feasibility study

The feasibility of photochemical vapor generation for the production of volatile Ni species was evaluated and applied to the analysis of acetic acid leachates obtained from oily sludge samples. Sludge samples originating from a petrochemical plant were submitted to extraction using standardized procedures with solutions adjusted to pH 2.88 or 4.93, with acetic acid. The leachate solutions were subsequently treated with a mixture of acetic and formic acid and exposed to UV radiation from a Hg discharge lamp; the irradiated solution was pumped to a gas-liquid separator and the volatile species were transported by a stream of argon for detection using inductively coupled plasma mass spectrometry. Experimental variables, including the nature and concentration of low molecular weight acids, irradiation interval, carrier gas flow rate and the effect of concomitant species on the efficiency of photochemical production of volatile Ni species were systematically evaluated. Oxygenated anions, particularly nitrate, were found to suppress the analytical signal, whereas the effect of cationic species depended on the nature of the cation. Lead was found to induce substantial signal suppression even at ppb levels. Considering the significant influence of concomitant species on the overall efficacy of the photochemical process, isotope dilution calibration was adopted as a strategy to overcome non-spectral interferences. Under optimized conditions, relative standard deviations better than 8.5% were achieved, along with detection limits better than 40 μg L−1. The accuracy was statistically attested upon comparison of the results to those obtained from the analysis of leachates using sample introduction via pneumatic nebulization. The proposed photochemical vapor generation setup was proven efficient to carry out the determination of Ni in the leachates, although the technique is highly sensitive to the presence of concomitants.

240 nm UV LEDs for LISA test mass charge control

Test Masses inside the LISA Gravitational Reference Sensor must maintain almost pure geodesic motion for gravitational waves to be successfully detected. LISA requires residual test mass accelerations below 3 fm/s2/√Hz at all frequencies between 0.1 and 3 mHz. One of the well-known noise sources is associated with the charges on the test masses which couple to stray electrical potentials and external electromagnetic fields. LISA Pathfinder will use Hg-discharge lamps emitting mostly around 254 nm to discharge the test masses via photoemission in its 2015/16 flight. A future LISA mission launched around 2030 will likely replace the lamps with newer UV-LEDs. Presented here is a preliminary study of the effectiveness of charge control using latest generation UV-LEDs which produce light at 240 nm with energy above the work function of pure Au. Their lower mass, better power efficiency and small size make them an ideal replacement for Hg lamps.

Exciton sensitive microscopy of anthracene monolayers on Si(1 1 1)

Thin anthracene films were studied with photoemission electron microscopy, using both a Hg discharge lamp and a femtosecond Ti:Sapphire laser for generation of the photoelectrons. In threshold photoemission, under illumination of the surface with the Hg lamp, anthracene islands appear dark due to the high work function of anthracene. Under illumination with frequency doubled femtosecond laser pulses ( λ = 400 nm ) two photon photoemission takes place, and the anthracene islands each exhibit a characteristic brightness. We find that the brightness of the islands in two photon photoemission (2PPE) is modulated by the S 1 -exciton in anthracene that serves as the intermediate state in 2PPE. Whenever the b → -axis of the unit cell within a particular anthracene island is aligned with the in-plane component of the electric field of the laser pulses, the island exhibits a maximal two photon photoemission yield. Based on exciton sensitive microscopy we find that the orientation of molecules in each island is different and that the anthracene film as a whole is textured.

Three-dimensional characterization of extreme ultraviolet mask blank defects by interference contrast photoemission electron microscopy

A photoemission electron microscope based on a new contrast mechanism "interference contrast" is applied to characterize extreme ultraviolet lithography mask blank defects. Inspection results show that positioning of interference destructive condition (node of standing wave field) on surface of multilayer in the local region of a phase defect is necessary to obtain best visibility of the defect on mask blank. A comparative experiment reveals superiority of the interference contrast photoemission electron microscope (Extreme UV illumination) over a topographic contrast one (UV illumination with Hg discharge lamp) in detecting extreme ultraviolet mask blank phase defects. A depth-resolved detection of a mask blank defect, either by measuring anti-node peak shift in the EUV-PEEM image under varying inspection wavelength condition or by counting interference fringes with a fixed illumination wavelength, is discussed.

Measurement of Work Function of Electrodes in Low Pressure Hg Discharge Lamps Using Photoelectric Effect

The work function of an oxide-coated tungsten filament in low pressure Hg discharge lamps was measured using the photoelectric effect with and without discharge. The plasma had been excited in a lamp with 2.45-GHz microwaves to reduce the power loading to the electrodes, which made the measurement of photoelectric current from the electrodes possible in plasma. Lasers with wavelengths of 325, 405, 532, and 633 nm irradiated the surface of the electrodes to induce photoelectric current. The work function of the electrode of an as-received lamp was determined to be 2.5 eV. Discharge operation of the lamp reduced the work function by activating the oxide-coated materials. The lowest observed work function ranged from 2.2 to 2.3 eV.

Investigation of crystal structure and associated electronic structure of Sr 6BP 5O 20

Strontium borophosphate phosphate (Sr 6BP 5O 20, SrBP), activated by divalent europium ions is a bluish-green phosphor emitting in a broad band with the emission peak near 480 nm. In this paper, we report the crystal structure of SrBP determined from an analysis of the X-ray diffraction pattern of a prismatic single crystal (size 60 μm×50 μm×40 μm). This crystal was chosen from undoped phosphor powder samples prepared for this purpose by solid-state reaction. SrBP is observed to crystallize in a body-centered tetragonal lattice with the lattice parameters a = 9.7 8 9 5 ( 7 ) Å and c = 1 9.0 3 2 ( 3 ) Å , the associated space group being I 4 ¯ c 2 (space group 120). Using the structural data from this study, we have also calculated its electronic structure using the augmented spherical wave method and the local density approximation (LDA). We show the ordering of the electronic states by the density of states (DOS) and the partial DOS plots. The LDA gives a direct optical band gap at the Γ point of about 5 eV. The significance of the crystal structure and associated electronic structure is discussed with respect to maintenance of this phosphor in Hg-discharge lamps.

Thomson scattering on high pressure Hg discharge lamps

Thomson scattering (TS) experiments have been performed on high-pressure Hg discharge lamps. These lamps were filled with different amounts of Hg (15, 30, 50 and 70 mg) and were operating at different powers (150, 200 and 240 W) with a square-wave ballast. As in the previous studies (Zhu X et al 2004 J. Phys. D: Appl. Phys. 37 736–43) a triple grating spectrograph was used to suppress the false stray light and Rayleigh scattered photons. This set-up had to be modified for this special application. The collective TS spectra have been fitted using both a calibration using Raman scattering and a form fitting procedure. It was found that the electron temperature fluctuates around a certain value that seems rather constant in the central region. The value of electron temperature (Te) varies between 5500 and 7600 K in the central region (r ≤ 0.3 R). The spatial-averaged Te value increases with the lamp power. The electron density was found to be of the order of 1021 m−3 which is high at the centre and decreases as r increases. The ne value also increases with the lamp power. Moreover the results of TS are compared with those from x-ray absorption measurement. The comparison shows that the plasmas in such lamps are not in local thermal equilibrium in the sense that -gas temperature and locally the rate of ionization is much larger than that of three body recombination.

Time-dependent simulation of plasma and electrodes in high-intensity discharge lamps with different electrode shapes

The subject of this paper is the modelling of d.c. and a.c. high-intensity Hg-discharge lamps with differently shaped electrodes. Different arc attachments on the electrodes are studied and insight for the development of new electrodes is gained. The model includes the entire discharge plasma (plasma column, hot plasma spots in front of electrodes, near-electrode non-LTE-plasma) as well as anode and cathode. No subdivision of the discharge space into different regions is necessary (like space charge layer, ionization zone, plasma column). This is achieved by using a differential equation for a non-LTE electrical conductivity which is applicable for local thermal equilibrium (LTE-)regions as well as for non-LTE plasma regions close to the electrodes in a high pressure plasma. Modelling results for a 0.6 MPa mercury discharge considering six different electrode shapes (anode and cathode) are presented and compared with experimental results. The electrodes have different diameters and different electrode tips, such as hemispherical, flat, or conical tip with 60° or 90° apex angle. Furthermore, an electrode with a larger diameter in the mid section of the rod is investigated.

LCD backlights: with or without Hg?

Abstract—High luminance and efficacy vs. temperature independence and environmental protection: these are the determining factors for the choice of Hg or Xe for LCD backlights. A capacity‐coupled cylindrical Hg discharge lamp attains a luminance of 114,000 cd/m2 and an efficacy of 35 lm/W when driven at 5 MHz. On the other hand, a mercury‐free Xe flat discharge backlight produces 11,000 cd/m2 and 30 lm/W, with fast luminance response. This paper discusses the underlying limitations assessed to the Hg and Xe backlights, considering application to LC TVs.

A 100,000‐cd/m2 capacity‐coupled electrodeless discharge backlight with high efficacy for LC TVs

Abstract—A capacity‐coupled electrodeless Hg discharge lamp has been developed for LC TV backlightings. By applying sinusoidal voltages which are 180° out of phase with a pair of external electrodes, a luminous uniformity of over 84% is attained in two types of lamps whose lengths are 190 and 390 mm. Luminance, efficacy, and input power to the lamp are 114,000 cd/m2, 35 lm/W, and 21.5 W when the 390‐mm lamp is driven at 5 MHz. With a frequency below 1.1 MHz, eight 390‐mm lamps, connected in parallel to one another without external ballast impedance, can be driven by using a single inverter.

19.2: A 100,000‐cd/m2, Capacity Coupled Electrodeless Discharge Backlight with High Efficacy for LC TVs

AbstractA capacity coupled electrodeless Hg discharge lamp has been developed for LC‐TV backlightings. By applying sinusoidal voltages which are 180 degrees out of phase to a pair of external electrodes, luminous uniformity of over 84 % was attained in two types of lamps whose lengths are 190mm and 390mm. Luminance, efficacy, and input power to the lamp were 114,000cd/m2, 35 lm/W, and 21.5W when the 390mm lamp was driven at 5MHz with an inverter.

Single photo-electron and photon detection in a mercury resonance ionization photon detector (RID)

Avalanche detection of a laser enhanced ionization (LEI) signal has been studied in a resonance ionization detector (RID) cell containing mercury vapor at room temperature. An avalanche multiplication factor of more than 8000 was achieved. The limit of detection of Hg resonance radiation ( λ = 253.7 nm) was at the level of 0.5 quantum during the lifetime of the excited 6 3P 1 0 state. Detection of radiation from a conventional CW Hg discharge lamp source with a signal to noise ratio of more than 10 4 has been achieved.

Photochemical reactions in GeO2-SiO2 glasses induced by ultraviolet irradiation: Comparison between Hg lamp and excimer laser.

${\mathrm{GeO}}_{2\mathrm{\ensuremath{-}}}$${\mathrm{SiO}}_{2}$ glasses prepared by vapor-phase axial deposition were exposed to ultraviolet (uv) radiation from a Hg discharge lamp (4.9 eV) and excimer lasers (KrF laser: 5.0 eV, XeCl laser: 4.0 eV). Two photochemical reaction channels were ascertained: (1) The exposure of the glasses to the Hg lamp radiation (\ensuremath{\sim}16 mW/${\mathrm{cm}}^{2}$) induced Ge E' centers accompanied by bleaching of the absorption band due to oxygen-deficient defects near 5 eV (5-eV band) and the emergence of an intense band near 6.4 eV. (2) The irradiation with KrF and XeCl lasers (power densities of 10 and 90 mJ/${\mathrm{cm}}^{2}$/pulse, respectively, pulse duration of 20 ns) generated two types of paramagnetic defects, electron trapped centers associated with fourfold coordinated Ge ions (GEC) and a self-trapped hole center (STH: bridging oxygen trapping a hole). The former and the latter were considered to be caused via one-photon and two-photon absorption processes, respectively. These alternative reactions proceeded independently depending on the power densities of uv photons. The formation of GEC's was saturated easily by irradiation with KrF laser pulses, and then the conversion of GEC to Ge E' centers was caused by prolonged irradiation.

Growth and modeling of cw-UV induced oxidation of silicon

A report on the use of a low pressure Hg discharge lamp to grow 100 Å SiO2 layers on Si at 550 °C. The induced reaction rate is more than 12 times that for thermal oxidation of Si at 612 °C, indicating that the growth mechanism is photonically controlled. We tentatively suggest that the induced oxidation is based on space-charge controlled drift of ionic oxygen species created in the SiO2 by charge photoinjected from the Si. Simple modeling predicts a limiting thickness for film growth that is confirmed by experimental evidence. An activation energy of 0.56 eV extracted from the data compares with values of 0.14 – 0.7 eV previously reported for oxidation of silicon by O or O− species.

Modeling and diagnostics of silicon nitride deposition from 254-nm Hg photosensitization of SiH4-NH3 mixtures: Luminescence of HgNH3 excimer and laser-induced fluorescence of NH2(Ã 2A1)

Silicon nitride thin films are obtained from the Hg(63P1) -photosensitized decomposition of SiH4 and NH3 using the 254-nm radiation of a low-pressure Hg discharge lamp. Several diagnostics are associated to characterize the physicochemical mechanisms and measure the densities of reactive species or reaction products. The photon flux is obtained by radiometry, the Hg density is determined by absorption of the 254-nm radiation, and the SiH4 gas depletion is measured by mass spectrometry. The luminescence at 340 nm of HgNH3 excimers is used as a probe of the metastable Hg(63P0) density and the NH2 radical is detected by laser-induced fluorescence (LIF) using the 597.8-nm line to excite NH2(Ã2A1) Σ(0,9,0) vibronic states. The interpretation of LIF results in terms of NH2 density takes into account collisional transfer and quenching of NH2(Ã2A1) revealed by nonexponential time decay of the fluorescence. In addition, the silicon nitride film deposition rate is monitored and the N/Si stoichiometry is determined by x-ray photoelectron spectroscopy. All these data are used to validate a one-dimensional spatially resolved modeling of the photochemistry. The model involves radiative transfer of the 254-nm radiation from the lamp, excitation and quenching of Hg(63P1) and Hg(63P0) by photoabsorption and reactive collisions, dissociation of NH3 and SiH4 into H, NH2, and SiH3 radicals, gas-phase diffusion and secondary reactions of these radicals, and eventually surface reactions of SiH3 and NH2 on the growing silicon nitride film surface, in terms of sticking and recombination probabilities. It is shown that SiH4 diluted in NH3 is essentially dissociated by reactive collisions with Hg(63P0) metastables produced by collisional deexcitation of Hg(63P1) with NH3. Moreover, within the assumptions and the precision of the model, we derive from LIF data that the rate constant for the reaction of NH2 with SiH4 is lower or equal to 10−13 cm3 s−1, in agreement with a recent determination. It is also shown that the radical-radical reactions between SiH3, NH2, and H are the main cause for the limitation of radical gas-phase density and deposition rate.

2SrO · 3Al2 O 3 : Eu2 + and 1.29 ( Ba , Ca ) O , 6Al2 O 3 : Eu2 + : Two New Blue‐Emitting Phosphors

In the system a new compound was discovered with composition (SAL); its structure is related to the one of (SAE). The aluminate (BAL) belongs to the β‐alumina type compounds and is closely related to (BAM). The compounds SAL and BAL are good host lattices for highly efficient Eu2+ luminescence. The europium emission peaks at 460 nm in SAL and at 440 nm in BAL. Both phosphors show a high output and good maintenance in low pressure Hg discharge lamps and are ideally suited for use in tricolor lamps.

Low Temperature Interlevel SiO2 Layers by Photoinduced Processing

ABSTRACTPolysiloxane layers were deposited from the gas phase by photoinduced polymerization reaction of tetraethylorthosilicate (TEOS) and 02/N20. The deposition kinetics can be described by a gas phase polymerization and the subsequent condensation of the siloxane molecules. As UV light sources an ArF excimer laser (193 nm) anda 185/253 nm low pressure Hg—discharge lamp were used, the polysiloxane deposition rates are 2000 Å/min or 1200 Å/min respectively. Ina second thermal or combined thermal/ photoinduced process step the as deposited siloxane layers are transformed by hydrolysis and condensation reactions to pure Si02. The composition of the as deposited and transformed polysiloxane layers were investigated by FTIR spectroscopy. Typical examples of the step coverage and planarizing properties of the SiO2 layers for the use as interlevel dielectrics are presented.

Three-dimensional natural convection in a high-pressure mercury discharge lamp

A three-dimensional computer model is used to calculate the convective flow in a 400 W high-pressure Hg discharge lamp. The model gives the expected axisymmetric flow when the arc tube axis is vertical, and more complex three-dimensional flows when it is not.

Quecksilberbestimmung durch flammenlose ASS auf der Resonanzlinie 184,9 nm

A simple device is described for flameless atomic absorption of the Hg resonance line at 184.9 nm. A low pressure Hg discharge lamp made from quartz was combined with an absorption tube and a photocell. The photocathode material of this photocell was CsJ. The spectral sensitivity of CsJ is very low for wavelengths greater than 200 nm. Therefore it was possible only to measure the absorption of the resonance line 184.9 nm. The detection limit was 30 times better compared to the intercombination line at 253.7 nm.

Determination of the 63P1→63P0 Transition Rate of Hg in CO and NO by a Modulation Technique

Abstract In order to determine the branching ratio for Hg(63P1) deactivation to the 63P0 and 61S0 states in CO or NO, a modulation technique was utilized. The intensity of 253.7-nm radiation was modulated at a frequency in the range from 0.1 to 20 kHz, and the resulting a.c. component of the Hg(63P1 or 63P0) concentration was measured by monitoring the absorption of the 435.8- or the 404.7-nm emission line from an Hg discharge lamp. The lower detection limit of excited Hg atoms was 107 cm−3 in this experimental method. On the basis of the Hg(63P0) concentration relative to that of Hg(63P1) in an Ar+CO or NO mixture including information on the phase delay, the 63P1→63P0 transition rate could be determined; the 63P1→63P0 cross section was found to be 22.4 Å2 for CO and 7.1 Å2 for NO and the 63P0→61S0 cross section to be 1.80 Å2 for CO and 37 Å2 for NO at room temperature.