Detection of traces in semiconductor materials by two-color laser-enhanced ionization spectroscopy in flames

Axner, Ove; Lejon, Mats; Magnusson, Ingemar; Rubinsztein‐Dunlop, Halina; Sjöström, Sten

doi:10.1364/ao.26.003521

Cited by 19 publications

(5 citation statements)

References 13 publications

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“…4 b. They constitute of such determinations as Ni in petroleum products [34], determinations of Cs in tap water [35], measurements of Cu in sea water [36], detection of traces in semiconductor materials [37] and detection of organotins in estuarine sediment samples ~381. This is illustrated in Fig.…”

Section: Detection Limits and Sensitivitiesmentioning

confidence: 99%

Analytical applications of laser-enhanced lonization spectrometry in flames and furnaces

1989

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This paper is concerned with a critical analysis of the analytical performance of laser-enhanced ionization (LEI) spectrometry in flames and furnaces as an ultra-sensitive trace-element technique. Updated tables of LEI detection limits, both in flames and furnaces, are given. Special attention is paid to interference phenomena which are unique to the LEI technique. Ways of reducing their influence on the analytical signals are proposed. Finally, advantages and disadvantages of LEI spectrometry as a tool for ultra-sensitive trace element analysis are discussed.Key words: laser-enhanced ionization (LEI), flame, furnace, trace element.Laser-enhanced ionization (LEI) spectrometry is a very powerful technique for detecting low concentrations of metal atoms in solutions I-1-23]. The major characteristics of the technique constitute of a high sensitivity and a rather high resistance to interferences. The general principle of the LEI technique is that an enhancement of the normal ionization processes (collisions) is obtained by optical excitation of the atoms under study by resonant laser light. The enhanced ionization rate is detected as a change in the current passing through a medium (atomic reservoir) exposed to a voltage by means of an electrode arrangement.When a sample is analyzed by LEI, the atomization can, in principle, be done in any of the conventional atomic reservoirs which previously have been developed for standard analytical techniques (absorption or emission techniques). However, LEI has so far most often been done in atmospheric pressure flames (primarily air/acetylene flames) and only recently LEI has been applied to graphite furnaces [8,16,17,[24][25][26].The atoms under study are excited from low lying, highly populated levels (primarily from the ground level) to high lying excited states by resonant laser light. Solution Boxcar Oscilloscope Fig. l. A typical experimental set-up for two-step LEI in flames. C = 10 nF and R = 50 k~This is almost exclusively done by using pulsed dye-laser systems for production of resonant laser light.Since the atomic reservoirs used for LEI are characterized by high temperatures in fairly dense media the collision rates between analyte atoms and buffer molecules are high. Hence, the atoms have certain probabilities of undergoing ionizing collisions. The probability of such collisional ionization is higher the less energy needed for ionization of the (excited) atoms. Therefore, the ionization probability increases the closer to the ionization limit the atoms are being excited [-27].The excitation of atoms in LEI spectrometry can be carried out in several ways. The most common excitation scheme is to excite the atoms from the ground state by absorption of one photon. By using ultra-violet light or by exciting the atoms in two consecutive steps a high ionization rate (efficiency) can be obtained. The two-step excitation is practically done by illuminating the atoms with light from two simultaneously pumped dye lasers, each tuned to a suitable transition wavelength in the...

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Section: Detection Limits and Sensitivitiesmentioning

confidence: 99%

Analytical applications of laser-enhanced lonization spectrometry in flames and furnaces

1989

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“…21,22 Among these concerns, employment of dual lasers through a stepwise excitation, causing more of the analyte to be promoted to its higher states, has proved to be a very efficient method to increase the ion yield. ~, [23][24][25][26][27] The col-3D2) transition, the detection limit is five times as large as that with the first-step excitation alone. 28 Obviously, changing the collisional ionization rate is not the only factor to affect the behavior of the ion yield.…”

Section: Introductionmentioning

confidence: 97%

Ion Enhancement Effect of Laser-Enhanced Ionization Induced by One-Step Excitation and Two-Step Excitation

Sü

Lin

1994

Appl Spectrosc

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The two-step laser-enhanced ionization (LEI) technique is believed to be more sensitive and selective in trace analysis than one-step LEI. As reported previously, for optimization of the two-step LEI configuration, factors involving laser intensity, transition probability of second-step excitation, collisional ionization rates, and transition linewidth should be taken into account. We have derived a simple theoretical model in relation to these parameters that is rough but suitable in practice for characterizing the ion yields enhanced by two-step LEI over one-step LEI. According to the model, each parameter affecting the ion enhancement has been systematically examined and compared to the theoretical evaluation. The findings of the relative ion enhancement as a function of each related parameter are consistent with the model prediction, except for the effect of transition linewidth, which is underestimated theoretically due to the difficulty of establishing the experimental conditions.

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“…In VECSELs, a dual-wavelength output with THz spacing has been generated using both: two mode-locked pulses centered with THz-spacing and with intracavity difference frequency generation (DFG). 11,12 Stable dualwavelength operation of VECSELs has many applications ranging from spectroscopy, 13,14 geological and atmospheric measurements using LIDAR, 15,16 semiconductor laser parameter measurement, 17,18 THz-imaging, [19][20][21][22] and THz-signal generation. 23,24 In general, stable dual-wavelength operation in semiconductor lasers has been a popular research topic both experimentally and theoretically.…”

Section: Introductionmentioning

confidence: 99%

Influence of microscopic many-body scattering on multi-wavelength VECSEL lasing

Kilen

Hader

Koch

et al. 2019

Vertical External Cavity Surface Emitting Lasers (VECSELs) IX

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Non-equilibrium multi-wavelength operation of vertical external-cavity surface-emitting lasers (VECSELs) is investigated numerically using a coupled system of Maxwell semiconductor Bloch equations. The propagation of the electromagnetic field is modeled using Maxwell's equations, and the semiconductor Bloch equations simulate the optically active quantum wells. Microscopic many-body carrier-carrier and carrier-phonon scattering are treated at the level of second Born-Markov approximation, polarization dephasing with a characteristic rate, and carrier screening with the static Lindhard formula. At first, an initialization scheme is constructed to study multi-wavelength operation in a time-resolved VECSEL. Intracavity dual-wavelength THz stabilization is examined using longitudinal modes and an intracavity etalon. In the latter, anti-correlated noise is observed for THz generation and investigated.

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Detection of traces in semiconductor materials by two-color laser-enhanced ionization spectroscopy in flames

Cited by 19 publications

References 13 publications

Analytical applications of laser-enhanced lonization spectrometry in flames and furnaces

Analytical applications of laser-enhanced lonization spectrometry in flames and furnaces

Ion Enhancement Effect of Laser-Enhanced Ionization Induced by One-Step Excitation and Two-Step Excitation

Influence of microscopic many-body scattering on multi-wavelength VECSEL lasing

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