Pulsed Hollow Cathode Lamp Research Articles

Characterization of an Ar/N2 reactive amplified magnetron discharges by Atomic Absorption Spectroscopy and Glow Discharge Mass Spectrometry

The aim of this paper is the characterization of an inductively amplified magnetron discharge running in reactive mode (Ar/N2 gas mixture with titanium target) using Atomic Absorption Spectroscopy and Glow Discharge Mass Spectrometry. The first technique gives access to absolute densities of sputtered metal, usually neutrals. In this paper, ionic titanium densities are also estimated thanks to a pulsed hollow cathode lamp used as optical source for absorption measurements. The second technique deals with the relative behaviour of ions extracted from the plasma.At a given pressure, both diagnostic methods are correlated in describing the evolution of the metallic species as the target surface evolves, with the nitrogen content, from the metallic to the poisoned state. The transition is marked by the decrease of titanium neutral (measured by absorption spectroscopy) and relative ionic densities (by mass spectrometry). At 0.7 Pa, the transition happens for a gas mixture containing 6% of nitrogen. It happens for 4% of nitrogen at higher pressure (3.9 Pa). It confirms the validity of mass spectrometry to qualitatively follow titanium neutral density in reactive mode. Nevertheless, both techniques are not correlated in describing the evolution of Ti+ and Ti as the total pressure increases from 0.7 to 9.1 Pa.

Multi-step photoionization spectroscopy in uraniumbetween 5900 and 6060 Å using a pulsed hollow-cathodelamp

The observation of current in the afterglow of the discharge ina pulsed hollow-cathode lamp illuminated by tunable lasers,combined with optogalvanic techniques, provides a simple andreliable tool for multi-step photoionization spectroscopystudies. A three-photon photoionization spectroscopy study wasperformed in a uranium hollow-cathode lamp, using thiscombination of techniques. Single-, double- and triple-frequencyphotoionization paths were identified for uranium, in the rangebetween 5900 and 6060 Å.

Cluster formation and uranium photoionization in the afterglow of a pulsed hollow cathode lamp

Uranium photoionization was observed in the afterglow of pulsed hollow cathode lamps illuminated by a dye laser tuned near the electronic transition around 591.5 nm (L605−16 900 cm−1 M77). The photoionization signal was used to monitor the time evolution of the ground state uranium vapor density in the cathode hole. Lifetimes over 1 ms were measured for the uranium vapor; that makes this device attractive for multistep photoionization spectroscopy. The obtained results lead to the conclusion that these long times are due to cluster formation in the afterglow.

Roll-over effect in graphite furnace atomic absorption spectrometry with a gold pulsed hollow-cathode lamp

The presence of stray light in graphite furnace atomic absorption spectrometry causes errors in background correction at high analyte concentrations. The stray light level originates in the hollow-cathode lamp, but can be modified in the atomizer. Some differences were noted for both wall and platform atomization. Other factors, such as the presence of matrix components (copper) or chemical modifiers (vanadium), also affect the sensitivity for gold and consequently have an effect on the roll-over phenomenon. Experimental results show that the stray radiation depends on the wavelength region used for the determination of gold.

The effect of spectral line broadening on the shape of analytical curves obtained using pulsed hollow-cathode lamps for background correction

The cause of the calibration curve flattening or roll-over observed when using the Smith-Hieftje background correction technique in atomic absorption spectrometry has been investigated by high and low resolution spectral scans of the region around the resonance lines of several elements. These scans, together with computer modelling of line profiles, have shown the important influence of weak line-wings on the shape of absorbance curves at high analyte concentrations. The wings, which are due to natural and pressure broadening in the hollow-cathode lamp, are shown to be the main cause of curve flattening in the Smith-Hieftje technique. Close non-absorbable lines (especially gas lines, which decrease in relative intensity at higher currents) can behave as stray light and cause calibration curve roll-over. Metal lines with low absorption sensitivity have a similar effect to the line wings and only cause flattening of the calibration curve.

Stray light in Zeeman and pulsed hollow cathode lamp atomic absorption spectrometry

In atomic absorption spectrometry using the Zeeman effect or the pulsed hollow-cathode lamp for background correction, the presence of stray light can cause errors in background correction, when the stray light is not completely absorbed by the matrix arising from the sample. Fortunately, it can be concluded from experimental results that the stray radiation is located close to the resonance wavelength of the analyte. On the other hand, saturation of the electronics leads to a limiting absorbance of the gross AAS signal and to errors in the net absorbance in the presence of high-background absorbance.

Evaluation of ICP atomic fluorescence for the determination of mercury

Using a commercial atomic fluorescence instrument that employs an ICP as an atomization cell, a pulsed mercury hollow cathode lamp produced an unsatisfactory detection limit of only 0.5 mg l −1. Consequently, the hollow cathode lamp was replaced with a mercury vapor lamp operating in the pulsed mode. Using this source and sample introduction by pneumatic crossflow nebulization, a detection limit of 0.03 mg l −1 and an upper linearity limit of 300 mg l −1 were achieved. For lower level mercury determinations, a continuous cold vapor generator was developed that interfaces with the instrument to leave the nebulizer intact. The generator allows mercury to be determined with a detection limit of 0.2 μg l −1 while up to eleven other elements are simultaneously determined in the conventional manner. The cold vapor generator can also be used with the plasma off for single element mercury determinations. In this mode, a detection limit of 0.04 μg l −1 was achieved.

Roll-over of analytical curves in atomic absorption spectrometry arising from background correction with pulsed hollow-cathode lamps

A theoretical analysis of background correction systems in atomic absorption spectrometry reveals the interdependence of three phenomena: analytical sensitivity, roll-over of the analytical curve, and wavelength proximity of the background correction. The deuterium lamp system sacrifices wavelength proximity and the Zeeman technique is subject to roll-over. For the newly introduced correction technique using pulsed hollow-cathode lamps roll-over has also been observed, although the effect is reduced by sacrifices of both wavelength proximity and analytical sensitivity.

Characterization of a Commercial Gated Silicon Intensified Target Vidicon for Transient, Nonrepetitive Radiation Sources

Response linearity and dynamic range of a gated silicon intensified target vidicon multichannel detector are evaluated for applications involving short pulse, nonrepetitive exposure. A high intensity pulsed hollow cathode lamp and an electrically vaporized thin film plasma generator were used as radiation sources. Qualitative aspects of the vidicon are discussed by analogy with photographic emulsions. The effects of intensifier stage voltage on image intensity and focus are considered. Charging curves are presented for various electron beam scan times and for multiple as well as single interrogation scans. The effect of erase scans prior to the exposure on the shape of the charging curves also is considered. These charging curves suggest that target surface saturation effects result in very inefficient target charging, and multiple interrogation scans are required for quantitative information retrieval. The use of target preparation scans reduces charging efficiency. Using the intensifer gate pulse width for exposure control, plots of target response vs exposure are shown to be linear over at least two decades of exposure but only with multiple interrogation scans using long scan times on a small region of the target surface.

高周波再励起パルス動作ホローカソードランプの過渡発光特性

Transient emission characteristics of R. F. burst injecting pulsed hollow cathode lamps HCLs have been measured in detail and the applicability of conventional HCLs as an excitation source to time gated atomic fluorescence spectrometry has been discussed. For some elements of HCL, optimum operating conditions for providing maximum emission intensity were experimentally determined. By injecting 240 Vp-p R. F. burst with a duration of 20μs into the HCL operated at a few hundreds of milli-ampere pulse of 20 μs, analysis lines of which intensity being sevaral hundreds to a thousand times as large as that for lamps under 10 mA dc operation were obtained. The degree of analysis line broadening was also examined by means of intensity ratio measurement of the atomic fluorescence to excitation radiation.

Instrumental system for multidimensional spectroscopic characterization of a radio frequency boosted, pulsed hollow cathode lamp

Instrumental system for multidimensional spectroscopic characterization of a radio frequency boosted, pulsed hollow cathode lamp

Excitation processes in an r.f.-boosted, pulsed hollow cathode lamp

Time and space resolved emission spectroscopy was used to examine the excitation processes in an r.f.-boosted, pulsed hollow cathode lamp. Sealed commercial hollow cathode lamps with copper cathodes and neon or argon buffer gases were driven with temporally spaced unidirectional current pulses and radio frequency bursts. The neon filled lamp was studied most extensively; the argon lamp was used for comparison. Three excitation periods were considered: the current pulse, the r.f. burst, and the afterglow. Each of these periods was marked by a unique set of emission characteristics that suggested different combinations of excitation processes. Excitation during the current pulse appears to be a combination electron impact and charge exchange. Charge exchange excites the 3 d 95 s levels of Cull while electron impact excites the other ion levels and the neutral levels. Charge exchange continues to excite the ion spectrum during the afterglow. Afterglow emission from the neutral spectrum apparently results from two types of recombination processes. The exact recombination mechanisms could not be unambiguously assigned. Emission results from the r.f. burst suggest that electron impact is the dominant excitation process. Excitation of the neutral and ion spectra are from their respective ground states. There appears to be little ionization by electron impact. To evaluate the lamp's suitability as a line source for analytical atomic spectroscopy the profile of the 324.8 nm neutral resonance line was examined during the current pulse and the r.f. burst. The profile during the current pulse is strongly dependent on radial position in the cathode bore. Near the edges of the cathode the line is severely self-reversed. The profile during the r.f. burst is uniform across the cathode bore and is affected only slightly by self-absorption.

Atomic fluorescence spectrometry with an inductively coupled plasma as atomization cell and pulsed hollow cathode lamps for excitation

Atomic fluorescence spectrometry with an inductively coupled plasma as atomization cell and pulsed hollow cathode lamps for excitation

Time and spatially resolved atomic absorption measurements with a dye laser plume atomizer and pulsed hollow cathode lamps

Time and spatially resolved atomic absorption measurements with a dye laser plume atomizer and pulsed hollow cathode lamps

Laser-induced impedance changes in pulsed hollow cathode lamps

Laser-induced impedance changes in pulsed hollow cathode lamps

Générateur de vapeur d’uranium: la lampe à cathode creuse pulsée

The production of uranium vapors has been studied in the (5)L(0)(6)ground state using a pulsed hollow cathode lamp. The evolution of the (238)U ((5)L(0)(6)) concentration with time has been studied with Xe and Ar as buffer gases. A density of 2.7 x 10(13) atoms cm(-3) was obtained with Xe as a buffer gas. In addition, those measurements, obtained from the absorption of a laser beam tuned to the 5758.143 A ((5)L(0)(6)-17,361(7)L(6)) transition, allowed the determination of the transition probability A = 2.1 x 10(5) sec(-1) and of the branching ratio BR = 0.08 for this transition.

A Dual Wavelength Atomic Absorption Spectrophotometer Using a Pulsed Hollow Cathode Lamp

A novel use of pulsed hollow cathode lamps for the purpose of background correction with a dual wavelength atomic absorption spectrophotometer is described. The pulsed hollow cathode lamp in conjunction with a transient signal gating system behaves as if the analyte source and the background correction source are firing alternately in time. Determinations of Fe, Mg, and Cd are carried out in order to evaluate the performance in practical analyses. Procedures and results on the time-resolved measurement of emission spectra and resonance line profiles from several kinds of pulsed hollow cathode lamps are also demonstrated in detail.

Computer Controlled System for Study of Pulsed Hollow Cathode Lamps

A system for complete computer control of the important current waveform variables in the operation of pulsed hollow cathode lamps is described and characterized. The system is shown to provide a highly flexible approach for the rapid accumulation of data on lamp operating characteristics. By implementing a simplex optimization technique with the system, it is shown that a selected lamp response (average peak intensity or integrated peak intensity) can be observed as a function of one variable, while all other variables are at values which result in an optimized response. This procedure, which probably could not be carried out without a closed loop system such as that described, avoids the potential difficulties of the one-factor-at-a-time approach. Results are reported for optimization studies of two iron hollow cathode lamps, for a response surface mapping experiment, and for examination of the pulse shapes of iron, calcium, vanadium, and aluminum hollow cathode lamps.

Time- and wavelength-resolved emission line profiles for pulsed Cu and Ag hollow cathode lamps

Time-resolved, line emission wavelength profiles were obtained for a copper and a silver pulsed hollow cathode lamp with the use of a piezoelectrically driven interferometer. A computer was used to control the timing of the sweep of the interferometer, the pulsing of the source, and the acquisition, averaging, sorting and display of data. Minor manipulation of the data stored in core facilitated the presentation of intensity vs wavelength emission profiles in a time-resolved form. Ten sequential line profiles spaced at 21 μsec time intervals were obtained. The copper hollow cathode lamp was driven at 100 Hz with pulse currents of up to 400 mA. Pulses lasted for up to 300 μsec. Line profiles changed dramatically during a pulse and showed extreme self-reversal of the resonance emission lines after 100 μsec. Variations of line profile with dc background current level and spatial position within the discharge were also investigated. Uncorrected line widths of each of the doublets of the Cu(I) 324.7 nm resonance line measured during the first 21 μsec of the discharge, where they were narrowest, ranged from 0.0012 to 0.0022 nm, including an instrumental broadening contribution estimated to be less than 0.0004 nm. The silver lamp showed extreme self-reversal even during the first 21 μsec.

Self-reversal in a copper pulsed hollow cathode lamp

Self-reversal in a copper pulsed hollow cathode lamp