Search

Beam-splitter emission strongly influences the spectra measured with a Fourier transform spectrometer (FTS) as it affects the entire phase behavior, in particular in emission spectroscopy. The various radiation contributions of the scene and the FTS itself have different phases in the complex spectrum. As a specific feature, the radiation of the beam splitter is rotated by approximately [pi]/2 relative to the scene effective radiation. By classical methods of phase correction, the radiation components of different phases are mixed in the complex plane, which may lead to serious errors in the calibrated spectra. For this reason, the nature of the FTS phase has been studied, and a statistical phase determination method has been developed. It allows us to determine the phase function of the scene by minimizing the correlation between the imaginary and the real parts of the complex spectrum and by reducing the variance of the imaginary part. Thus phase accuracies of 10 to 30 mrad can be achieved. In addition, the remaining error of the phase can be calculated for each individual spectrum. The total phase error and its effect on the spectra are discussed. OCIS codes: 300.2140, 300.6300, 300.6340.

The nitro-assisted proton transfer (NAPT), responsible for the photoactivity of ortho-nitrobenzylpyridines and a model for the nitro-based caged compounds, is studied along with the parent compound 2-(2',4'-dinitrobnzyl)pyridine (DNBP) with polarized optical spectroscopy and theoretical calculations. The transition dipole moments of a DNBP single-crystal identified oriented molecules of the long-lived enamine tautomer, rather than of the aci-nitro tautomer.

Pink, Mn-bearing 'oxy-rossmanite' from a pegmatite in a quarry near Eibenstein an der Thaya, Lower Austria, has been characterized by crystal structure determination, chemical analyses (EMPA, SIMS), and optical absorption and infrared spectroscopy. Crystal structure refinements in combination with the chemical analyses give the optimized formulae [sup.x]([[??].sub.0.53][Na.sub.0.46][Ca.sub.0.01]) [sup.Y]([Al.sub.2.37][Mn.sup.2+.sub.0.25][Fe.sup.2+.sub.0.04] [Ti.sup.4+.sub.0.01]) [sup.Z][Al.sub.6] [sup.T]([Si.sub.5.47] [Al.sub.0.28][B.sub.0.25])[O.sub.18][(B[O.sub.3]).sub.3] [sup.v][[(OH).sub.2.85][O.sub.0.15]][sup.W][[O.sub.0.86] [(OH).sub.0.10][F.sub.0.04]], with a = 15.8031 (3), c= 7.0877(3) [Angstrom], and R = 0.017 for the sample with 2.05 wt% MnO, and [sup.x]([[??].sub.0.53][Na.sub.0.46][Ca.sub.0.01]) [sup.Y]([Al.sub.2.35][Li.sub.0.32][Mn.sup.2+.sub.0.28][Fe.sup.2+.sub.0.04] [Ti.sup.4+.sub.0.01])[sup.Z][Al.sub.6] [sup.T]([Si.sub.5.51][Al.sub.0.25][B.sub.0.24])[O.sub.18][(B[O.sub.3]).sub.3] [sup.v][[(OH).sub.2.80][O.sub.0.20]] [sup.w][[O.sub.0.86][(OH).sub.0.10][F.sub.0.04]] for a sample with a = 15.8171 (3), c = 7.0935(2) [Angstrom], R = 0.017, and 2.19 wt% MnO. Although the structure refinements show significant amounts of [sup.[4]]B, the bond-lengths (~ 1.620 [Angstrom]) mask the incorporation of [sup.[4]B because of the incorporation of [sup.[4]]Al. The distances, calculated using the optimized T site occupancies, are consistent with the measured distances. This 'oxy-rossmanite' shows that it is possible to have significant amounts of [sup.[4]]B and [sup.[4]]Al in an Al-rich tourmaline. The 'oxy-rossmanite' from Eibenstein has the highest known Al content of all natural tourmalines (-47 wt% [Al.sub.2][O.sub.3]; ~8.6 apfu Al). The near-infrared spectrum confirms both that hydroxyl groups are present in the Eibenstein tourmaline and that they are present at a lower concentration than commonly found in other lithian tourmalines. The integrated intensity (850 [cm.sup.2]) of the OH bands in the single-crystal spectrum of 'oxy-rossmanite' from Eibenstein is distinctly lower than for other Li-bearing tourmaline samples (970-1260 [cm.sup.-2]) with OH contents >3.0 pfu. These samples fall on the V site = 3 (OH) line in the figure defining covariance of the relationship between the bond-angle distortion ([[sigma].sub.oct.sup.2]) of the Z[O.sub.6] octahedron and the distance. On a bond-angle distortion- distance diagram 'oxy-rossmanite' from Eibenstein lies between the tourmalines that contain 3 (OH) at the V site, and natural buergerite, which contains 0.3 (OH) and 2.7 O at the V site. No H could be found at the O1 site by refinement, and the spherical electron density in the difference-Fourier map around the O1 site supports the conclusion that this site is mainly occupied by O. The pink color comes from the band at 555 nm that is associated with [Mn.sup.3+] produced by natural irradiation of [Mn.sup.2+]. This is the first time a tourmaline is described that has a composition that falls in the field of the previously proposed hypothetical species 'oxy-rossmanite'.

An analysis of optical heterodyne detected (OHD) two-photon absorption (TPA) resonant signals in transparent materials is presented. The OHD and TPA methodology explored here is another potential tool for the spectroscopic study of optical transition line shapes.

The ultrafast emission dynamics of a 1.3-micromillimeter (GaIn)(NaS)/GaAs vertical-cavity surface-emitting laser is examined, both experimentally and theoretically. Results indicate that (GaIn)(NAs) is a promising material for 1.3-micromillimeter VCSELs, and that the gain and emission dynamics of state-of-the-art (GaIn)(NAs)/GaAs material can be adequately described by the microscopic theory that has already been used for the description of standard semiconductor gain materials.

A Fourier-transform imaging spectrometer, believed to be novel, based on the Savart polariscope is presented. There is no slit in this instrument, which means that it has a high throughput. The principle and the system configuration are described. Several preliminary experimental results are shown. OCIS codes: 120.3180, 120.4640, 120.6200, 300.6190.

A relatively compact, lightweight, and programmable spectropolarimetric imager was used to collect spectral and polarization data from various objects and backgrounds, both in the laboratory and in field tests. This imager uses a tellurium dioxide (Te[O.sub.2]) acousto-optic tunable filter and a liquid-crystal retardation plate with a CCD camera. The spectral images were collected 450-1000 nm at 10- or 20-nm intervals at two or four polarization settings for each spectral interval. We analyzed a portion of these data to assess the effectiveness of this system for object detection. We present our measurements and discuss the analysis results. OCIS codes: 230.1040, 230.3720, 120.5410, 100.2960, 070.4790, 100.5010.

Fly ash, a fine gray powder, is filtered out of the flue gas in coal-fired power stations. It consists of silicon oxide, metal oxides, and unburned carbon. An optical sensor system for measurement of the carbon content of fly ash is described. Based on a mathematical model, an algorithm is deduced that allows the carbon content to be calculated from two measurements of the diffuse reflectivity of a fly ash sample before and after a surface-grinding process. In this model the fly ash sample is assumed to be composed of three types of cube: light-scattering cubes, soft absorbing cubes (carbon), and hard absorbing cubes (iron oxide).

The MASERATI (middle-atmosphere spectrometric experiment on rockets for analysis of trace-gas influences) instrument is, to our knowledge, the first rocket-borne tunable diode laser absorption spectrometer that was developed for in situ measurements of trace gases in the middle atmosphere. Infrared absorption spectroscopy with lead salt diode lasers is applied to measure water vapor and carbon dioxide in the altitude range from 50 to 90 km and 120 km, respectively. The laser beams are directed into an open multiple-pass absorption setup (total path length 31.7 m) that is mounted on top of a sounding rocket and that is directly exposed to ambient air. The two species are sampled alternately with a sampling time of 7.37 ms, each corresponding to an altitude resolution of approximately 15 m. Frequency-modulation and lock-in techniques are used to achieve high sensitivity. Tests in the laboratory have shown that the instrument is capable of detecting a very small relative absorbance of 10(- super 4) 10(- super 5) when integrating spectra for 1 s. The instrument is designed and qualified to resist the mechanical stress occurring during the start of a sounding rocket and to be operational during the cruising phase of the flight when accelerations are very small. Two almost identical versions of the MASERATI instrument were built and were launched on sounding rockets from the Andoya Rocket Range (69 degrees N) in northern Norway on 12 October 1997 and on January 1998. The good technical performance of the instruments during these flights has demonstrated the MASERATI is indeed a new suitable tool to perform rock-borne in situ measurements in the upper atmosphere.

The instrumental line shape (ILS) of two commercial high-resolution Fourier transform IR spectrometers has been analysed with gas cell measurements and a new ILS retrieval software LINEFIT. The instruments are used for atmospheric remote sounding, and the compatibility of the ILS deduced from laboratory gas cell measurements with the ILS in the atmospheric measurement itself is examined.

Laser-induced breakdown spectrometry (LIBS) has been used to detect atomic and molecular species in various environments. LIBS has the capability to be used as a continuous-emission monitor to monitor toxic-metal concentrations in stack emissions. Recently a mobile LIBS system was calibrated in our laboratory and tested as a multimetal continuous-emission monitor during a joint U.S. Department of Energy-Environmental Protection Agency (EPA) test. LIBS measurements were performed with three sets of metal concentrations at the EPA Rotary Kiln Incinerator Simulator. The LIBS system successfully measured concentrations of Cr, Pb, Cd, and Be in near real time in this test. Real-time LIBS data were averaged and compared with data obtained from an EPA reference method that was conducted concurrently with LIBS. The details of the LIBS calibration and results of these LIBS measurements are described.

We describe fluorescence spectral imaging results with the microscope computed-tomography imaging spectrometer ([Mu]CTIS). This imaging spectrometer is capable of recording spatial and spectral data simultaneously. Consequently, [Mu]CTIS can be used to image dynamic phenomena. The results presented consist of proof-of-concept imaging results with static targets composed of 6-[Mu]m fluorescing microspheres, Image data were collected with integration times of 16 ms, comparable with video-framerate integration times. Conversion of raw data acquired by the [Mu]CTIS to spatial and spectral data requires postprocessing. The emission spectra were sampled at 10-nm intervals between 420 and 710 nm. The smallest spatial sampling interval presented is 1.7 [[micro]meter].

The properties of convex gratings fabricated by electron-beam lithography are investigated. Three grating types are shown. The first is a single-panel, true blazed grating in which the blaze angle stays constant relative to the local surface normal. This grating provides high peak efficiencies of approximately 88% in the first order and 85% in the second order. The second grating has two concentric panels, with each panel blazed at a different angle. This type permits flexibility in matching the grating response to a desired form. The third type has a groove shape that departs from the sawtooth blazed profile to increase the second-order bandwidth. All these types are difficult or impossible to produce with conventional techniques. The gratings compare favorably with conventional (holographic and ruled) types in terms of efficiency and scatter. Simple scalar models are shown to predict the wavelength response accurately. These gratings allow the optical designer to realize fully the considerable advantages of concentric spectrometer forms.

The problem of retrieving minor concentrations of constituents by ground-based Fourier-transform infrared emission spectroscopy is addressed by means of the concept of differential optical emission spectroscopy in analogy to the concept of differential optical absorption spectroscopy. Using the prominent [[Nu].sub.3] ozone feature at 1043 [cm.sup.-1], we show that the strength of the spectral signature depends not only on the amount of ozone but also on the atmospheric thermal structure. This dependence can be described by a rather accurate approximation, which was used to construct a simple diagram to estimate the amount of column ozone between the instrument site and a cloud deck as well as to determine the detection limit. The detection limit is shown to depend on cloud base height. For a given thermal lapse rate it was found that the lower the detection limit, the higher the cloud base altitude. However, as shown in a case study with variable cloud base height, the concept fails for semitransparent clouds. Multiple scattering of the emitted radiation within the clouds yielded a path enhancement that simulated an enhanced amount of constituent. The path enhancement was estimated to be 2.4-4 km at 1000 [cm.sup.-1] for low-level clouds, equivalent to an enhancement factor of 6-21. The multiple scattering effect has considerable consequences for ground-based as well as for nadir satellite retrieval techniques in cloudy skies.

A simple and accurate wavemeter for measuring the wavelength of monochromatic light is described. The device uses the wavelength-dependent phase lag between principal polarization states of a length of birefringent material (retarder) as the basis for the measurement of the optical wavelength. The retarder is sandwiched between a polarizer and a polarizing beam splitter and is oriented such that its principal axes are 45 deg to the axis of the polarizer and the principal axes of the beam splitter. As a result of the disparity in propagation velocities between the principal polarization states of the retarder, the ratio of the optical power exiting the two ports of the polarizing beam splitter is wavelength dependent. If the input wavelength is known to be within a specified range, the measurement of the power ratio uniquely determines the input wavelength. The device offers the advantage of trading wavelength coverage for increased resolution simply through the choice of the retarder length. Implementations of the device employing both bulk-optic components and fiber-optic components are described, and the results of a laboratory test of a fiber-optic prototype are presented. The prototype had a wavelength accuracy of [+ or -]0.03 nm. Key words: Wavemeter, wavelength measurement, polarization interferometer, retarder.

We describe a new all-sky imaging spectrometer using a separation scanned Fabry-Perot etalon. It is intended for ground-based mapping of upper atmospheric wind and temperature fields in the auroral zone. Its major advantage is that recorded spectra are not distorted by spatial and temporal brightness fluctuations in the aurora. We present a discussion of previous approaches to field widening a Fabry-Perot spectrometer, then describe the principles underlying our method. This enables comparisons with the throughput and the response to brightness fluctuations provided by previous instruments. We also describe our instrument's optical layout, its calibration, and data analysis.

We report the design, construction, and evaluation of a static Fourier-transform ultraviolet spectrometer. The spectrometer is based on Wollaston prisms that form an interferogram in the spatial domain, which is recorded with a detector array. We demonstrate the application of the spectrometer to gas detection. Using a deuterium light source, we measured a detection limit, with a 1-s integration time, for hydrogen sulfide and sulfur dioxide, corresponding to 0.2 ppm over a 5-m path length. Key words: Open-path gas detection, ultraviolet Fourier-transform spectrometer, sulfur dioxide, hydrogen sulfide.

One of the primary goals of imaging spectrometry in earth remote sensing applications is to determine identities and abundances of surface materials. In a recent study, an orthogonal subspace projection (OSP) was proposed for image classification. However, it was developed for an a priori linear spectral mixture model which did not take advantage of a posteriori knowledge of observations. In this paper, an a posterior least squares orthogonal subspace projection (LSOSP) derived from OSP is presented on the basis of an a posteriori model so that the abundances of signatures can be estimated through observations rather than assumed to be known as in the a priori model. In order to evaluate the OSP and LSOSP approaches, a Neyman-Pearson detection theory is developed where a receiver operating characteristic (ROC) curve is used for performance analysis. In particular, a locally optimal Neyman-Pearson's detector is also designed for the case where the global abundance is very small with energy close to zero a case to which both LSOSP and OSP cannot be applied. It is shown through computer simulations that the presented LSOSP approach significantly improves the performance of OSP. Index Terms - A priori (pr), A posterior (ps), detection power, false alarm probability, least-squares estimate, Neyman-Pearson (N-P) detectors, orthogonal subspace projection, ROC curve.

We describe a sensitive and inexpensive vibrometer based on optical feedback by diffuse scattering to a single-mode diode laser. Fluctuations in the diode laser's operating frequency that are due to scattered light from a vibrating surface are used to detect the amplitude and frequency of surface vibrations. An additional physical vibration of the laser provides an absolute amplitude calibration. The fundamental bandwidth is determined by the laser response time of roughly [10.sup.-9] s. A noise floor of 0.23 nm/[Hz.sup.1/2] at 30 kHz with 5 x [10.sup.-5] of the incident light returning is demonstrated. This instrument provides an inexpensive and sensitive method of noncontact measurement in solid materials with low or uneven reflectivity. It can be used as a vibration or velocity sensor. Key words: Vibrometer, optical sensor, noncontact measurement, surface displacement.

An integrated transmission diffraction grating in a planar optical waveguide is presented for broadband spectroscopic analysis of liquids and gases. Silicon oxynitride slab waveguides on silicon substrates with low optical loss in the visible range are combined with a phase transmission grating exhibiting a blaze effect at 500 nm to achieve high-efficiency diffraction and high spectral dispersion. Collimated white light propagates through the waveguide and couples into air at a stepped formed planar grating. The beams of each adjacent step interfere constructively at the focal line of a cylindrical lens, its focal line positioned perpendicular to the waveguide plane. We used a common silicon photodiode array to detect the spectral data. Our approach is to develop a compact and economic spectrometer without moving parts that can be applied for UV-visible analysis and near-infrared industrial process control as well. Key words: Microspectrometer, transmission grating, microsystem, grating, diffraction, microanalysis system, photometer.

Calculations are presented for a set of aberration-corrected holographic concave gratings for possible use in space mission instruments. It is concluded that, for the visible range 0.26-1.02 [[micro]meter] when detectors with a 15-[[micro]meter] pixel size are used, a total field of view of [approximately]1 [degrees] is possible at an aperture of f/7.0. For the infrared regions 0.9-2.5 [[micro]meter] and 2.4-4.2 [[micro]meter], in which detector arrays have larger pixel sizes of 30-40 [[micro]meter], a spatial field of view of [approximately]2 [degrees] at f/7.0 and [approximately]1.0 [degrees] at f/3.5 can be achieved. An exploration of spectrum lengths showed that performance starts to fall off sharply for lengths over 15 mm at a focal length of 150 mm (i.e., a spectral angular extent of [approximately]6 [degrees]). Key words: Optical instrumentation, spectrometers, gratings.

UV-visible measurements of stratospheric constituents require the ratio of a pair of spectra to be determined. If their wavelength calibrations differ and if an array detector is used, at least one spectrum must be interpolated. This introduces error if the spectrum is undersampled; the error is smaller if wavelength stability is good. Increasing the sampling ratio by making the spectral resolution poorer reduces the optical depths of absorption by constituents. Exact values of interpolation errors from real spectra are a difficult topic, but with a theoretical study with a simulated spectrum we show that the sampling ratio should exceed [approximately]4.5 pixels/FWHM but need not exceed 6.5 pixels/FWHM. To avoid significant reduction in the optical depth of N[O.sub.2], the resolution should be smaller than [approximately]1.0 nm FWHM. Hence a spectrometer system that measures both OClO and NOs by observing one order from one stationary grating should have more than [approximately]1500 pixels, more than many currently available array detectors.

A temporally and spatially nonscanning imaging spectrometer is described in terms of computed-tomography concepts, specifically the central-slice theorem. A sequence of three transmission sinusoidal-phase gratings rotated in 60 [degrees] increments achieves dispersion in multiple directions and into multiple orders. The dispersed images of the system's field stop are interpreted as two-dimensional projections of a three-dimensional (x, y, [Lambda]) object cube. Because of the size of the finite focal-plane array, this imaging spectrometer is an example of a limited-view-angle tomographic system. The imaging spectrometer's point spread function is measured experimentally as a function of wavelength and position in the field of view. Reconstruction of the object cube is then achieved through the maximum-likelihood, expectation-maximization algorithm under the assumption of a Poisson likelihood law. Experimental results indicate that the instrument performs well in the case of broadband and narrow-band emitters. Key words: Imaging spectrometry, computed tomography, experimental point-spread-function characterization, central-slice theorem, missing cones.

Remote-sensing reflectance is easier to interpret for the open ocean than for coastal regions because the optical signals are highly coupled to the phytoplankton (e.g., chlorophyll) concentrations. For estuarine or coastal waters, variable terrigenous colored dissolved organic matter (CDOM), suspended sediments, and bottom reflectance, all factors that do not covary with the pigment concentration, confound data interpretation. In this research, remote-sensing reflectance models are suggested for coastal waters, to which contributions that are due to bottom reflectance, CDOM fluorescence, and water Raman scattering are included. Through the use of two parameters to model the combination of the backscattering coefficient and the Q factor, excellent agreement was achieved between the measured and modeled remote-sensing reflectance for waters from the West Florida Shelf to the Mississippi River plume. These waters cover a range of chlorophyll of 0.2-40 mg/[m.sup.3] and gelbstoff absorption at 440 nm from 0.02-0.4 [m.sup.-1]. Data with a spectral resolution of 10 nm or better, which is consistent with that provided by the airborne visible and infrared imaging spectrometer (AVIRIS) and spacecraft spectrometers, were used in the model evaluation.

The influence of electrical interference induced by the easily ionized sodium matrix upon the laser-enhanced ionization (LEI) detection of indium analyte is studied. As the LEI signal is electrically suppressed but still detectable, the original sample concentration may be effectively recovered by using the standard addition method. Nevertheless, this method fails to apply when the added Na matrix reaches a threshold level, at which the LEI signal is completely suppressed. Under such a condition of severe electrical interference, our design of an LEI device interfaced by a flow injection analysis (FIA) can be a successful substitute to recover a significant LEI signal, so that the standard addition method may be resumed. The FIA-LEI technique is capable of detecting the In sample in a solution containing a Na matrix of more than 40 ppm ([[micro]gram]/mL), about 20-fold that the conventional LEI apparatus can tolerate. It possesses another remarkable advantage, having a much wider range of linear dependence of indium concentration than that achieved by the conventional LEI. For instance, the linearity of indium concentration dependence measured by the conventional LEI method is restricted within 5 ppm, which can extend to 30 ppm with a mixture of 8 ppm of Na by means of the FIA-LEI apparatus. A good reproducibility and a rapid sampling rate are also advantages possessed. In addition, the new technique is able to be integrated with those methods used previously for reduction of the electrical interference to make the best use of this apparatus.

Double modulation - in frequency and intensity - of the power spectral distribution of a light beam is proposed for interferometric profilometry. The procedure is based on two facts: (1) the continuous spectrum of a light source is frequency modulated by the path difference in an interferometric device, (2) the continuous spectrum of a light source is intensity modulated by the transparency of an object placed in the exit plane of a spectroscopic device. Both procedures can be used to measure the profile of a surface with high precision. Moreover, phase shifting is automatically performed by the continuous wavelength variation along the spectrum, so that no piezoelectric transducers are necessary. The method is adaptable for the analysis of remote surfaces through optical fibers.

The performance and the characteristics of an interferometric double-mirror spectrometer with uncollimated light are studied by measuring spectra of different radiation sources. The stationary interferometer is fabricated without a beam splitter or moving components. The measured interferogra visibilities, which are limited by the size of the source aperture, agree with the theoretical predictions for a slit and a circular source aperture. By background subtraction the effect of detection nonuniformity can be radically reduced to increase the dynamics and the resolving power of the spectrometer. We used a mercury pencil lamp for measurement and found that the dynamic range was [difference] 80 dBm. When isolated spectral lines are measured, the resolving power can be improved by squeezing more than half of a spatial interference cycle onto one pixel. The maximum resolving power reached in measuring the spectra of a diode laser was 1600. The instrument is applicable to a wide range of measurements, such as the recording of temporally variant, wideband radiation sources and the monitoring of laser wavelength. Key words: Stationary interferometer, Fourier-transform spectrometer, interferometry.

Thermal (blackbody-like) radiation that originated from laser-heated tungsten nanoparicles was measured using optical emission spectroscopy. The cooling rate and temperature data indicate that depending on experimental parameters, evaporation and surface reactions can have a definite effect on the growth of particles.

Different combinations of electronic and vibronic perturbations are investigated to show evidence that both contribute equally to the observed Q-band split. It was found that vibronic perturbations give rise to different Q-and B-band splitting, in agreement with what was experimentally observed for asymmetrically distorted hemes and porphyrins.

A short-wave infrared (700-2500-nm) radiometer has been designed and built to calibrate and cross calibrate spherical-integrating sources used in the calibration of satellite sensors residing on NASA's Earth Observing System platforms. We describe the design, predicted and measured performance, and calibration of the transfer radiometer. [C] 2000 Optical Society of America OCIS codes: 120.5630, 120.4640, 040.3060, 040.5160, 040.0040, 280.0280.

We report a fully automated mid-IR difference-frequency spectrometer with a spectral resolution under 70 MHz pumped by a pair of conventional room-temperature 800-900-nm diode lasers. 0.1 [micro]W of tunable cw radiation is produced from incident-diode powers of 120 and 75 mW. The system has computer-controlled beam alignment with compact CCD cameras, motorized mirrors and positioners to obtain 0.01 [degrees] crystal-angle positioning, 4-[[micro]meter] beam overlap at the nonlinear crystal, and automated diode laser beam collimation. Computer-operated frequency control uses temperature tuning and current tuning of the free-running diode lasers. The system has been demonstrated by successfully scanning, without any human intervention, 64 randomly selected acetylene absorption lines between 12 and 15 [[micro]meter]. Spectral scans of ammonia are also presented. This mid-IR spectrometer is suitable for fully automated spectroscopy of an unlimited list of mid-IR frequencies and has the potential to detect any trace gas that has an acceptable absorption line within the large tuning range.