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Oct 1991

Volume 62, Issue 10, pp. 2307-2502

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Spatial distributions of the emitting species in a Penning surface‐plasma source

H. Vernon Smith, Paul Allison, J. David Schneider, and Kourosh Saadatmand

Rev. Sci. Instrum. 62, 2307 (1991); http://dx.doi.org/10.1063/1.1142290 (7 pages) | Cited 6 times

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Using optical spectroscopy we study the spatial and temporal distributions of the Hα, Cs i(4555 Å), Cs ii(4604 Å), and Mo i(3903 Å) emission lines in a Penning surface‐plasma source (SPS). A diagnostic slit exposes the entire SPS discharge gap either parallel or perpendicular to the magnetic field. The spatial and temporal distributions of the emitting species are recorded using a 1‐m monochromator. In addition, the visible light and the Hα and Cs ii(4604 Å) spatial distributions are recorded with a video camera. The cesium atomic and ionic light, and the molybdenum atomic light, is strongly concentrated near the cathodes; the visible light and the Hα light is almost uniform in both directions. Electron‐impact ionization of atoms sputtered from the cathodes and the return of the ions to the cathodes by residual plasma fields is probably the mechanism which concentrates cesium near the cathodes. The Cs0 mean free path is estimated to be 16 and 0.43 mm for 2 and 400 A discharges, respectively.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements

H− temperature measurements by a slit diagnostic technique

Joseph D. Sherman, H. Vernon Smith, Carl Geisik, and Paul Allison

Rev. Sci. Instrum. 62, 2314 (1991); http://dx.doi.org/10.1063/1.1142291 (4 pages) | Cited 5 times

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H− ion beams are extracted at 5–25 kV from a long, narrow slit on a Penning surface‐plasma source (the 8X source). The extraction geometry produces negligible transverse electric fields (focusing effects) along the slit length. Therefore, the ion angular spread reflects the distribution of ion energies at the plasma surface. The angular distributions are measured with an electric‐sweep emittance scanner whose slits are oriented normal to the long dimension of the emission slit. The nearly Maxwellian angular distributions measured over the central portions of the ribbon beam give kTH− of 0.1–0.2 eV for a 2‐A dc discharge and 0.8–1.0 eV for 350–500 A pulsed discharges. This diagnostic technique has sufficient position resolution to allow measurement of the kTH− spatial distributions. It also allows study of the kTH− dependencies on ion source parameters (e.g., increasing the H2 gas flow lowers kTH−).
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Nc Particle measurements

GaAsP spin‐polarized electron source for a 300 keV accelerator

E. Mergl, E. Geisenhofer, and W. Nakel

Rev. Sci. Instrum. 62, 2318 (1991); http://dx.doi.org/10.1063/1.1142292 (4 pages) | Cited 5 times

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We report on a GaAsP spin polarized electron source designed to operate in high voltage terminals of electrostatic accelerators of several hundred kV. The small source of simple mechanical and electron‐optical design can easily be connected to an accelerator tube. A stable beam of 35%–40% degree of polarization can be produced with a lifetime of several weeks. A measurement of the asymmetry in the emission of bremsstrahlung by transversely polarized electrons has been performed.
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29.25.Bx Electron sources
29.20.Ba Electrostatic accelerators
34.80.Nz Spin dependence of cross sections; polarized beam experiments
81.65.-b Surface treatments

Construction and applications of a dual mass‐selected low‐energy ion beam system

Fuguang Qin, Xiangming Wang, Zhikai Liu, Zhenyu Yao, Zhizhang Ren, Lanying Lin, Shijun Su, Weisheng Jiang, and W. M. Lau

Rev. Sci. Instrum. 62, 2322 (1991); http://dx.doi.org/10.1063/1.1142293 (4 pages) | Cited 19 times

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A direct ion beam deposition system designed for heteroepitaxy at a low substrate temperature and for the growth of metastable compounds has been constructed and tested. The system consists of two mass‐resolved low‐energy ion beams which merge at the target with an incident energy range 50–25 000 eV. Each ion beam uses a Freeman ion source for ion production and a magnetic sector for mass filtering. While a magnetic quadrupole lens is used in one beam for ion optics, an electrostatic quadrupole lens focuses the other beam. Both focusing approaches provide a current density more than 100 μA/cm2, although the magnetic quadrupole gives a better performance for ion energies below 200 eV. The typical current of each beam reaches more than 0.3 mA at 100 eV, with a ribbon beam of about 0.3–0.5×2 cm2. The target is housed in an ultrahigh vacuum chamber with a base pressure of 1×10−7 Pa and a typical pressure of 5×10−6 Pa when a noncondensable beam like argon is brought into the chamber. During deposition, the target can be heated to 800 °C and scanned mechanically with an electronic scanning control unit. The dual beam system has been used to grow GaN using a Ga+ and a N+ beam, and to study the oxygen and hydrogen ion beam bombardment effects during carbon ion beam deposition. The results showed that the simultaneous arrival of two beams at the target is particularly useful in compound formation and in elucidation of growth mechanisms.
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81.15.Jj Ion and electron beam-assisted deposition; ion plating
07.77.-n Atomic, molecular, and charged-particle sources and detectors

Probe measurements in the REPUTE‐1 reversed field pinch

H. Ji, H. Toyama, K. Yamagishi, S. Shinohara, A. Fujisawa, and K. Miyamoto

Rev. Sci. Instrum. 62, 2326 (1991); http://dx.doi.org/10.1063/1.1142294 (12 pages) | Cited 21 times

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A four‐channel triple‐probe and magnetic‐probe array, a complex probe which consists of three types of probes and two eight‐channel magnetic‐probe (poloidal and toroidal) arrays, has been installed in the revised field pinch University of Tokyo experiment (REPUTE‐1) reversed field pinch (RFP) device. Mean and fluctuation parts of plasma parameters, including the three components of magnetic fields, three components of electric fields, electron density, electron temperature, and space potential, are measured in 0.5a≲r≤a region. The triple‐probe method and the electric field measurement are described in detail, and effects due to the fast electrons, etc., are discussed. Some experimental examples obtained in the REPUTE‐1 RFP plasma are given, and the detailed results will be published elsewhere.
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52.70.Ds Electric and magnetic measurements

Formation of fast ‘‘notched’’ current waveforms through a high inductance

G. Spanjers, B. A. Nelson, and F. L. Ribe

Rev. Sci. Instrum. 62, 2338 (1991); http://dx.doi.org/10.1063/1.1142513 (4 pages) | Cited 1 time

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A fast ‘‘notch’’ current has been produced on the (4 μH) hardcore central conductor [C. M. Greenfield, M. E. Koepke, and F. L. Ribe, Phys. Fluids B 2, 133 (1990)] of the high beta Q machine, a 2.6 m theta pinch [S. O. Knox, H. Meuth, E. Sevillano, and F. L. Ribe, 3rd IEEE International Pulsed Power Conf., 1981, IEEE Publ. 81 CH1662/6, paper 3.1]. With the notch circuitry, the current can be slowly (τ1/4 = 14 μs) brought to a crowbarred dc value (20 kA) and then quickly (τ1/4 = 1.3 μs) ‘‘notched’’ to a different value (typically either 0 kA or twice the dc value) and then quickly returned to the dc value. The use of a new inductively loaded spark gap switch eliminates extraneous ringing in the final crowbarred current waveform. As described here, by driving the hardcore circuit with two isolated capacitor banks, and a voltage stepup transformer, the notch current is created using spark gaps and ignitrons for switching, resulting in an inexpensive and technically simple circuit.
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52.55.Ez Theta pinch
84.30.Ng Oscillators, pulse generators, and function generators
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
52.80.-s Electric discharges

Guiding of a gun plasma by a permanent magnet octupole field

Christian Barrett and Scott Robertson

Rev. Sci. Instrum. 62, 2342 (1991); http://dx.doi.org/10.1063/1.1142295 (3 pages)

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Plasma from a coaxial gun has been guided 1 m by a linear octupole magnetic field generated by an array of permanent magnets. Calorimetry indicates 30% efficiency. The technique is useful for removing the neutral gas component from the plasma.
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52.75.Di Ion and plasma propulsion
07.20.Fw Calorimeters
07.55.-w Magnetic instruments and components

Application of two‐photon‐excited laser‐induced fluorescence to atomic hydrogen measurements in the edge region of high‐temperature plasmas

Toshinori Kajiwara, Tatsuya Shinkawa, Kiichiro Uchino, Mitsuharu Masuda, Katsunori Muraoka, Tatsuo Okada, Mitsuo Maeda, Sigeru Sudo, and Tokuhiro Obiki

Rev. Sci. Instrum. 62, 2345 (1991); http://dx.doi.org/10.1063/1.1142296 (5 pages) | Cited 6 times

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A two‐photon‐excited laser‐induced fluorescence (LIF) was applied to measurement of atomic hydrogen densities in the edge region of high‐temperature plasmas of Heliotron E for the first time. In this application, fluorescence signals were observed coaxially to the laser beam. This was possible because, in two‐photon‐excitation LIF, the visible fluorescence is localized at the laser focus and stray light can be completely eliminated by optical spatial filters, allowing much easier optical access than in previous LIF experiments. The densities at the initiation of the discharge and at the quasisteady state of the discharge were determined to be 3×1016 and 1×1016 m−3, respectively within an error of a factor of 2. Optimization to maximize the signal‐to‐noise ratio of the observation and resulting detection limit were discussed and confirmed the above results.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Use of a silicon surface‐barrier detector for measurement of high‐energy end loss electrons in a tandem mirror

T. Saito, Y. Kiwamoto, T. Honda, A. Kasugai, K. Kurihara, and S. Miyoshi

Rev. Sci. Instrum. 62, 2350 (1991); http://dx.doi.org/10.1063/1.1142297 (6 pages) | Cited 2 times

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An apparatus for the measurement of high‐energy electrons (10–500 keV) with a silicon surface‐barrier detector is described. The apparatus has special features. In particular, a fast CAMAC transient digitizer is used to directly record the wave form of a pulse train from the detector and then pulse heights are analyzed with a computer instead of on a conventional pulse height analyzer. With this method the system is capable of detecting electrons with a count rate as high as ∼300–400 kilocounts/s without serious deterioration of performance. Moreover, piled up signals are reliably eliminated from analysis. The system has been applied to measure electron‐cyclotron‐resonance‐heating‐induced end loss electrons in the GAMMA 10 tandem mirror and has yielded information relating to electron heating and diffusion in velocity space.  
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28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
29.40.Wk Solid-state detectors
29.50.+v Computer interfaces

rf‐excited molecular jet plasma for reactive ion etching

Joachim Janes and Norbert Lutz

Rev. Sci. Instrum. 62, 2356 (1991); http://dx.doi.org/10.1063/1.1142298 (7 pages)

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A new apparatus has been constructed combining free‐jet molecular‐beam technology and radio‐frequency plasma production for reactive‐ion etching. The beam is formed in a laval‐type nozzle and is skimmed before entering the plasma chamber. The free jet enters a discharge region between two parallel plates, one of which is capacitively powered with 13.56 MHz radio frequency. The goal was to investigate the possibility of creating a high‐density plasma with a linear multinozzle array for large‐area wafer processing. Experiments were carried out with argon and oxygen as process gases. Jet plasma glows with lengths of about 10 cm downstream of the skimmer were detected. Jet beam profile analysis was performed measuring the distribution of dynamic pressures with the Pitot–Prandtl method.
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81.65.-b Surface treatments
52.75.-d Plasma devices
52.80.Hc Glow; corona

An exact analysis for beam centroid position monitors used in pulsed intense relativistic electron‐beam experiments

W. W. Rienstra and M. D. Haworth

Rev. Sci. Instrum. 62, 2363 (1991); http://dx.doi.org/10.1063/1.1142246 (5 pages)

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Azimuthal arrays of B‐dot loops are often used to measure the time‐resolved beam centroid location of a pulsed, intense relativistic electron beam propagating in a metallic drift tube. A new analytical analysis is presented which can solve for the beam centroid position exactly, even for large radial displacements near the drift tube wall. This exact method is compared with the traditional first‐order analysis.
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41.75.Ht Relativistic electron and positron beams
07.55.-w Magnetic instruments and components
52.70.Ds Electric and magnetic measurements

Converting a reflectron time‐of‐flight mass spectrometer into a tandem instrument

Hellmut Haberland, Hans Kornmeier, Christoph Ludewigt, and Andreas Risch

Rev. Sci. Instrum. 62, 2368 (1991); http://dx.doi.org/10.1063/1.1142247 (4 pages) | Cited 16 times

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Adding a simple mass gate at the first time focus of a reflectron‐type time‐of‐flight mass spectrometer, one mass can be selected and its further decay or interaction studied. A new type of mass gate is described that does not have any grids. It is especially suitable for cluster studies. Three processes are identified that lead to an undesirable high background in a reflectron time‐of‐flight mass spectrometer.
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07.75.+h Mass spectrometers
36.40.-c Atomic and molecular clusters

Simple, fast, puff valve

J. Kriesel, R. Prohaska, and A. Fisher

Rev. Sci. Instrum. 62, 2372 (1991); http://dx.doi.org/10.1063/1.1142248 (3 pages) | Cited 3 times

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A simple, fast, reliable diamagnetically driven gas puff valve is described. It offers an extremely quick rise time (∼100 μs) and a large pressure rise rate (∼270 Pa/μs at a distance of 13.5 cm) with an input energy of only 90 J (600 V on a 500 μF capacitor). Because the valve can be operated with such a small input energy, solid‐state switching devices are adequate and the operation of the valve will not produce the amount of electrical noise that other valves needing higher energy often do. Our valve achieves high‐density puffs at relatively low plenum pressure (380 kPa, 3.8 atm), permitting it to be extremely simple in design and easy to operate. The entire package (valve plus driving circuit) is small in size; it can fit in a volume 4 in. in diameter by 8 in. long. The valve holds about 60 cm3 of gas and has an outlet opening of 1/4 in. in diameter.
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07.50.-e Electrical and electronic instruments and components
52.75.-d Plasma devices

Cryogenic monocrystalline silicon Fabry–Perot cavity for the stabilization of laser frequency

J.‐P. Richard and J. J. Hamilton

Rev. Sci. Instrum. 62, 2375 (1991); http://dx.doi.org/10.1063/1.1142249 (4 pages) | Cited 10 times

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A 1.6 kg silicon monocrystal was used to make a Fabry–Perot optical cavity operated at cryogenic temperatures. High‐resolution thermal expansion measurements were made as the silicon cooled to 4.2 K in order to characterize the cavity as a length reference standard. A helium–neon laser was then locked to a transmission resonance at liquid‐helium temperatures, and the laser frequency tracked the cavity resonance with error fluctuations at the level of 10 Hz/√Hz in the bandwidth dc to 1 Hz. Implications of the combined set of data, thermal expansion plus frequency‐tracking fluctuations, for using such a system as a frequency standard are discussed.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking
06.20.F- Units and standards

Power stabilization of high‐power CO laser by gas composition control

Hirotaka Kanazawa, Naohito Yamaguchi, Takuro Nakajima, and Tatsuji Taira

Rev. Sci. Instrum. 62, 2379 (1991); http://dx.doi.org/10.1063/1.1142250 (6 pages)

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Long time, stable operation of a high‐power discharge‐excited CO laser has been attained by controlling the laser gas composition. Firstly, stable obtainable laser output power was measured against the quantities of CO2 and of O2 added to the laser gas. Next, laser gas composition was recorded during sealed‐off operation with various initial gas conditions and cooling conditions. Finally, the detractive effect of O2 (added to enhance attainable output power through discharge stabilization) of quickening CO2 generation and CO depletion, was counteracted through continuous extraction of the laser gas and parallel replacement with fresh gas of predetermined composition. The resulting stabilization of the laser gas composition reduced output power variations to ±3% at 3 kW power level.  
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
52.80.-s Electric discharges

Short‐external‐cavity module for enhanced single‐mode tuning of InGaAsP and AlGaAs semiconductor diode lasers

Daniel T. Cassidy, Douglas M. Bruce, and Brian F. Ventrudo

Rev. Sci. Instrum. 62, 2385 (1991); http://dx.doi.org/10.1063/1.1142251 (4 pages) | Cited 11 times

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The construction and single‐mode tuning characteristics of a short‐external‐cavity (SXC) module for InGaAsP and AlGaAs semiconductor diode lasers are presented. The SXC system is a cost effective, simple, and rugged means to achieve single‐mode tuning and complete spectral coverage over large spectral regions with normally multimode lasers. With AlGaAs lasers, complete spectral coverage in overlapping ∼5‐cm−1 intervals over ∼400 cm−1 is obtained, while with InGaAsP diode lasers, complete spectral coverage in overlapping ∼5‐cm−1 intervals of 100–200 cm−1 is obtained.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes

Controlling the propagation axes of an ion laser

S. C. Guggenheimer and David L. Wright

Rev. Sci. Instrum. 62, 2389 (1991); http://dx.doi.org/10.1063/1.1142252 (5 pages)

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The motion of the output beam from an ion laser is critical for most applications, including the pumping of other lasers. In this paper we show that for a stable ion laser cavity, the output coupler can be used to position the beam at a given point in space. In this case an actively controlled laser cavity maintains the beam position at the laser exit. For a typical ion laser with an 8 m radius output coupler optic, maintaining the output beam position reduces the total beam motion a factor of 8, 1 m from the laser. Besides reducing the total beam motion, eliminating the position offset translates to a better angular overlap of pump and a cavity modes in lasers pumped by ion lasers such as Ti:sapphire lasers.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings

An on‐line Kerr spectrometer

G. Mallet and D. Vasilescu

Rev. Sci. Instrum. 62, 2394 (1991); http://dx.doi.org/10.1063/1.1142253 (4 pages) | Cited 1 time

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A transient electric birefringence computerized spectrometer inducing Kerr effect in anisotropically polarizable solutions such as DNA is described. Rectangular unipolar or bipolar pulses up to 400 V (I<10 A) can be applied to solutions with relatively high conductivity. The software developed for recording the signal in a PC/AT computer, interpreting the shape of the signals and plotting the experimental and theoretical curves, is also described. The software is written in turbo Pascal 5.0, except for the Labcard driver, which is in 80286 assembly language. The performances of the apparatus have been checked on various DNA solutions.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
78.20.Jq Electro-optical effects
78.20.Fm Birefringence

Determination of thin‐film optical constants with an automatic reflectance and transmittance goniometer

G. Bader, P. V. Ashrit, S. Elouatik, F. E. Girouard, and Vo‐Van Truong

Rev. Sci. Instrum. 62, 2398 (1991); http://dx.doi.org/10.1063/1.1142254 (7 pages) | Cited 2 times

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An automatic goniometer has been built in order to simultaneously measure the reflectance and transmittance of films at different angles of incidence of the incoming light. The angle can be varied from 7° to 83° and the incident light can be either s or p polarized. Following a minimization procedure, optical constants for the deposited films can be accurately determined. Results for Nb2O5, WO3, LiBO2 are presented and the precision of the method is discussed.
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78.66.-w Optical properties of specific thin films
07.60.Hv Refractometers and reflectometers

Near‐infrared spark source excitation for fluorescence lifetime measurements

D. J. S. Birch, G. Hungerford, and R. E. Imhof

Rev. Sci. Instrum. 62, 2405 (1991); http://dx.doi.org/10.1063/1.1142255 (4 pages) | Cited 4 times

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We have extended the range of excitation wavelengths from spark sources used in single photon timing fluorometry into the near infrared by means of the all‐metal coaxial flashlamp filled with an argon‐hydrogen gas mixture. At 750 nm this mixture gives ∼15 times the intensity available from pure hydrogen for a comparable pulse duration. Measurements are demonstrated by using the laser dye IR‐140 in acetone, for which a fluorescence lifetime of 1.20 ns is recorded.
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33.50.-j Fluorescence and phosphorescence; radiationless transitions, quenching (intersystem crossing, internal conversion)
52.80.Mg Arcs; sparks; lightning; atmospheric electricity

Electron polarimeter based on spin‐polarized low‐energy electron diffraction

J. Sawler and D. Venus

Rev. Sci. Instrum. 62, 2409 (1991); http://dx.doi.org/10.1063/1.1142256 (10 pages) | Cited 11 times

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A compact electron polarimeter which operates at low scattering energies (100 eV) has been built and characterized. The polarimeter uses spin‐dependent diffraction from a W(001) single crystal to measure the electron spin polarization of an incident electron beam. The design obtains reliable operation by attention to the input optics, the crystal mount, and the alignment procedure. The transport lens delivers the electron beam to the analyzer over an acceleration range of at least 2.0–0.33 while simultaneously keeping the angular convergence of the beam less than ±1.5°, and the magnification constant to within ∼30%. The crystal mount allows both orientation of the crystal normal to within 0.2° and flashes to 2500 K. Geometric instrumental asymmetries are linear in displacement (AD = 4%/mm) and angular displacement (Aθ = 3%/deg) of the sample. The alignment procedure and performance of the polarimeter are illustrated using spin‐polarized low‐energy electron diffraction rotation curves. Preliminary results suggest that the polarimeter may be operated for 1 h between cleaning cycles without degradation of the figure of merit.
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41.75.Fr Electron and positron beams
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
61.05.J- Electron diffraction and scattering

A new scheme for x‐ray grazing incidence diffraction

S. F. Cui, Z. H. Mai, L. S. Wu, C. Y. Wang, and D. Y. Dai

Rev. Sci. Instrum. 62, 2419 (1991); http://dx.doi.org/10.1063/1.1142257 (5 pages) | Cited 3 times

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A new scheme for x‐ray grazing incidence diffraction (GID) under total external reflection conditions is presented. This simple scheme allows the grazing angles and the scattering angles to be adjusted independently so that the structural and/or the chemical profiles of materials can be determined at controlled depths. As an example, Si1−xGex/Si superlattice materials were studied. Both commensurate and incommensurate growths between the two quantum wells in the strained‐layer superlattice were observed by the GID technique.  
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61.05.C- X-ray diffraction and scattering
07.85.-m X- and γ-ray instruments
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties

A tunneling instrument for angle resolved tunneling spectroscopy

M. Suzuki, T. Fujii, M. Miyashita, T. Onuki, H. Enomoto, and H. Ozaki

Rev. Sci. Instrum. 62, 2424 (1991); http://dx.doi.org/10.1063/1.1142524 (3 pages)

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A new tunneling instrument has been developed to observe the anisotropy of the Fermi surface. This instrument has two advantageous mechanisms over the conventional scanning tunneling microscope (STM); a tilt mechanism to keep two crystals parallel to each other and a rotation mechanism of the proven crystal over the sample crystal. We have evaluated its performance.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor

Single‐input double‐tuned mutually coupled surface coil circuits: An analysis

Siew Kan and Patrick Gonord

Rev. Sci. Instrum. 62, 2427 (1991); http://dx.doi.org/10.1063/1.1142258 (3 pages) | Cited 3 times

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The input reactance of a pair of coupled coils is a function of the latter’s primary, secondary, and mutual inductances as well as the secondary tuned frequency. It is thus possible to synthesize two appropriate equivalent inductances for use in a double‐tuned probe by a judicious choice of these parameters. From a given coil configuration and hence the associated self and mutual inductances, the present note analyzes and derives the essential equations showing the possible values of the tuned secondary frequency to be used to design this type of probe circuit first proposed by Fitzsimmons, Brooker, and Beck [Magn. Resoh. Med. 10, 302 (1989)]. In cases where an intercoil coupling capacitor is needed, its value also can be calculated from a biquadratic equation. A numerical example is given to check the validity of the theoretical results.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Thermal lens technique for sensitive kinetic determinations of fast chemical reactions. Part I. Theory

Mladen Franko and Chieu D. Tran

Rev. Sci. Instrum. 62, 2430 (1991); http://dx.doi.org/10.1063/1.1142259 (8 pages) | Cited 10 times

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The thermal lens effect can be successfully explained by use of the presently available theories. However, the existing theories fail for cases where the sample concentration changes with time, i.e., when the sample undergoes a chemical reaction. The objective of this work is to demonstrate that the thermal lens technique can be used for the sensitive kinetic determination of fast chemical reactions. It is systematically approached from two different directions: the theoretical aspect which is described in this paper and the experimental section which will be reported in the following paper. Specifically, novel theories which are based on the parabolic as well as the aberrant model have been derived to describe the thermal lens signal for cases where the sample concentration changes with time. Based on the developed theories, computer calculations were then performed to simulate conditions for various chemical reactions. It was found that in all cases, both of the developed (parabolic and aberrant based) theories can be used successfully to determine not only the order of the reaction but also the reaction rate constant.  
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
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