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Spatial aperture coding is a technique used to improve throughput without sacrificing resolution both in optical spectroscopy and sector mass spectrometry (MS). Previous work demonstrated that aperture coding combined with a position-sensitive array detector in a miniature cycloidal mass spectrometer was successful in providing high-throughput, high-resolution measurements. However, due to poor alignment and field nonuniformities, reconstruction artifacts were present. Recently, significant progress was made in eliminating most of the reconstruction artifacts with improved field uniformity and alignment. However, artifacts as large as 1/3 of the main peak were still observed at low mass (<17 u). Such artifacts will reduce accuracy in identification and quantification of analytes, reducing the impact of the throughput advantage gained by using a coded aperture. The artifacts were hypothesized to be a result of a mass dependent in curvature of ions in the ion source. Ions with higher mass ( m / z > 17 u) and a larger curvature did not pass through all slits in the coded aperture. Therefore, when reconstructing with a system response derived from the aperture image from a higher mass m / z = 32 u ion, reconstruction artifacts appeared for m / z < 17 u. In this work, two methods were implemented to significantly reduce the presence of artifacts in reconstructed data. First, we modified the reconstruction algorithm to incorporate a mass-dependent system response function across the mass range (10-110 u). This method reduced the size of the artifacts by 82%. Second, to validate the hypothesis that the mass-dependent system response function was a result of differences in curvature of ions in the ion source, we modified the design of the ion source by shifting the coded aperture slits relative to the center of the ionization volume. This method resulted in ions of all masses passing through all slits in the coded aperture, a constant system response function across the entire mass range. Artifacts were reduced by 94%.

Rationale: Higher resolution in fieldable mass spectrometers (MS) is desirable in space flight applications to enable resolving isobaric interferences at m/z < 60 u. Resolution in portable cycloidal MS coupled with array detectors could be improved by reducing the slit width and/or by reducing the width of the detector pixels. However, these solutions are expensive and can result in reduced sensitivity. In this paper, we demonstrate high-resolution spectral reconstruction in a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) without changing the slit or detector pixel sizes using a class of signal processing techniques called super-resolution (SR)., Methods: We developed an SR reconstruction algorithm using a sampling SR approach whereby a set of spatially shifted low-resolution measurements are reconstructed into a higher-resolution spectrum. This algorithm was applied to experimental data collected using the C-CAMMS prototype. It was then applied to synthetic data with additive noise, system response variation, and spatial shift nonuniformity to investigate the source of reconstruction artifacts in the experimental data., Results: Experimental results using two ½ pixel shifted spectra resulted in a resolution of ¾ pixel full width at half maximum (FWHM) at m/z = 28 u. This resolution is equivalent to 0.013 u, six times better than the resolution previously published at m/z = 28 for N 2 + using C-CAMMS. However, the reconstructed spectra exhibited some artifacts. The results of the synthetic data study indicate that the artifacts are most likely caused by the system response variation., Conclusions: This paper demonstrates super-resolution spectral reconstruction in C-CAMMS without changing the slit or detector pixel sizes using a sampling SR approach. With improvements, this technique could be used to resolve isobaric interferences in a portable cycloidal MS for space flight applications., (© 2023 John Wiley & Sons Ltd.)

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high-resolution, and high-sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector., (© 2022 John Wiley & Sons Ltd.)

In 1938, Walker Bleakney and John A. Hipple first described the cycloidal mass analyzer as the only mass analyzer configuration capable of "perfect" ion focusing. Why has their geometry been largely neglected for many years and how might it earn a respectable place in the world of modern chemical analysis? This Perspective explores the properties of the cycloidal mass analyzer and identifies the lack of suitable ion array detectors as a significant reason why cycloidal mass analyzers are not widely used. The recent development of capacitive transimpedance amplifier array detectors can enable several techniques using cycloidal mass analyzers including spatially coded apertures and single particle mass analysis with a "virtual-slit", helping the cycloidal mass analyzer earn a respectable place in chemical analysis.

Cycloidal sector mass analyzers have, in principle, perfect focusing due to perpendicularly oriented uniform electric and magnetic fields, making them ideal candidates for incorporation of spatially coded apertures. We have previously demonstrated a proof-of-concept cycloidal-coded aperture miniature mass spectrometer (C-CAMMS) instrument and achieved a greater than 10-fold increase in throughput without sacrificing resolution, compared with a single slit instrument. However, artifacts were observed in the reconstructed mass spectrum due to nonuniformity in the electric field and misalignment of the detector and the ion source with the mass analyzer focal plane. In this work, we modified the mass analyzer design of the previous C-CAMMS instrument to improve electric field uniformity, improve the alignment of the ion source and the mass analyzer with the detector, and increase the depth-of-focus to further facilitate alignment. A comparison of reconstructed spectra of a mixture of dry air and toluene at different electric fields was performed using the improved C-CAMMS prototype. A reduction in reconstruction artifacts compared to our proof-of-concept C-CAMMS instrument highlights the improved performance enabled by the design changes.

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified. Graphical Abstract ᅟ.

Several forensic sciences, especially of the pattern-matching kind, are increasingly seen to lack the scientific foundation needed to justify continuing admission as trial evidence. Indeed, several have been abolished in the recent past. A likely next candidate for elimination is bitemark identification. A number of DNA exonerations have occurred in recent years for individuals convicted based on erroneous bitemark identifications. Intense scientific and legal scrutiny has resulted. An important National Academies review found little scientific support for the field. The Texas Forensic Science Commission recently recommended a moratorium on the admission of bitemark expert testimony. The California Supreme Court has a case before it that could start a national dismantling of forensic odontology. This article describes the (legal) basis for the rise of bitemark identification and the (scientific) basis for its impending fall. The article explains the general logic of forensic identification, the claims of bitemark identification, and reviews relevant empirical research on bitemark identification-highlighting both the lack of research and the lack of support provided by what research does exist. The rise and possible fall of bitemark identification evidence has broader implications-highlighting the weak scientific culture of forensic science and the law's difficulty in evaluating and responding to unreliable and unscientific evidence.

An ambient desorption/ionization (ADI) source, known as the flowing atmospheric pressure afterglow (FAPA), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) equipped with a focal plane camera (FPC) array detector. The FAPA ionization source enables direct mass spectral analysis of solids, liquids, and gases through either positive or negative ionization modes. In either case, spectra are generally simple with dominant peaks being the molecular ions or protonated molecular ions. Use of the FAPA source with the MHMS allows the FPC detector to be characterized for the determination of molecular species, whereas previously only atomic mass spectrometry (MS) has been demonstrated. Furthermore, the FPC is shown to be sensitive to negative ions without the need to change any detector parameters. The analysis of solid, liquid, and gaseous samples through positive and negative ionization is demonstrated with detection limits (1-25 fmol/s, approximately 0.3-10 pg of analyte per mL of helium) surpassing those obtained with the FAPA source coupled to a time-of-flight mass analyzer., (2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.)

The implementation of hand-held ion mobility spectrometers (IMS) requires the development and evaluation of miniature drift cells providing high sensitivity while maintaining reasonable resolution. This manuscript describes the construction of a miniature IMS designed for such an application and its characterization by evaluation of the detection limits and resolution of the system with seven explosive compounds including trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), pentaerythritol tetranitrate (PETN), 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl), nitroglycerin (NG), 2,4-dinitrotoluene (2,4 DNT), and 2,6-dinitrotoluene (2,6 DNT).

A 512-channel Faraday-strip array detector has been developed and fitted to a Mattauch-Herzog geometry mass spectrograph for the simultaneous acquisition of multiple mass-to-charge values. Several advantages are realized by using simultaneous detection methods, including higher duty cycles, removal of correlated noise, and multianalyte transient analyses independent of spectral skew. The new 512-channel version offers narrower, more closely spaced pixels, providing improved spectral peak sampling and resolution. In addition, the electronics in the amplification stage of the new detector array incorporate a sample-and-hold feature that enables truly simultaneous interrogation of all 512 channels. While sensitivity and linear dynamic range remain impressive for this Faraday-based detector system, limits of detection and isotope ratio data have suffered slightly from leaky p-n junctions produced during the manufacture of the semiconductor-based amplification and readout stages. This paper describes the new 512-channel detector array, the current dominant noise sources, and the figures of merit for the device as pertaining to inductively coupled plasma ionization.

The first observation of the vibrational spectrum of the synthetic pyroxene Li-kosmochlor (LiCrSi2O6) is reported herein. The Raman and visible spectra are reported as a function of pressure. Though the pyroxene retains its P21/c symmetry, changes in the Raman spectra are observed between 6.8 and 7.7 GPa, possibly due to the formation of an additional bond between Li and O3 or some other transition that retains the mineral's P21/c space group. Splitting of the peak appearing at approximately 700 cm(-1), used to characterize the P21/c phase in other studies, is not observed. Comparison is made with the Raman spectra of LiAlSi2O6 and LiFeSi2O6 in the P21/c phase and the visible spectra of NaCrSi2O6 at high pressures.

In mass spectrometry, several advantages can be derived when multiple mass-to-charge values are detected simultaneously and continuously. One such advantage is an improved duty cycle, which leads to superior limits of detection, better precision, shorter analysis times, and reduced sample sizes. A second advantage is the ability to reduce correlated noise by taking the ratio of two or more simultaneously collected signals, enabling greatly enhanced isotope ratio data. A final advantage is the elimination of spectral skew, leading to more accurate transient signal analysis. Here, these advantages are demonstrated by means of a novel Faraday-strip array detector coupled to a Mattauch-Herzog mass spectrograph. The same system is used to monitor elemental fractionation phenomena in laser ablation inductively coupled plasma mass spectrometry.

A second-generation Faraday-strip array detector has been coupled to an inductively coupled plasma Mattauch-Herzog geometry mass spectrograph, thereby offering simultaneous acquisition of a range of mass-to-charge ratios. The second-generation device incorporates narrower, more closely spaced collectors than the earlier system. Furthermore, the new camera can acquire signal on all collectors at a frequency greater than 2 kHz and has the ability to independently adjust the gain level of each collector. Each collector can also be reset independently. With these improvements, limits of detection in the hundreds of picograms per liter for metals in solution have been obtained. Some additional features, such as a broader linear dynamic range (over 7 orders of magnitude), greater resolving power (up to 600), and improved isotope ratio accuracy were attained. In addition, isotope ratio precision as low as 0.018% RSD was achieved.

Mean-variance analysis is described as a method for characterization of the read-noise and gain of focal plane array (FPA) detectors, including charge-coupled devices (CCDs), charge-injection devices (CIDs), and complementary metal-oxide-semiconductor (CMOS) multiplexers (infrared arrays). Practical FPA detector characterization is outlined. The nondestructive readout capability available in some CIDs and FPA devices is discussed as a means for signal-to-noise ratio improvement. Derivations of the equations are fully presented to unify understanding of this method by the spectroscopic community.

Improved focal plane array detector systems are described which can provide improved readout speeds, random addressing and even be employed to simultaneously measure position, intensity and energy. This latter capability promises to rekindle interests in Laue techniques. Simulations of three varieties of foil mask spectrometer in both on- and off-axis configurations indicate that systems of stacked silicon detectors can provide energy measurements within 1% of the true value based on the use of single 'foils' and approximately 10000 photons. An eight-detector hybrid design can provide energy coverage from 4 to 60 keV. Energy resolution can be improved by increased integration time or higher flux experiments. An off-axis spectrometer design in which the angle between the incident beam and the detector system is 45 degrees results in a shift in the optimum energy response of the spectrometer system. In the case of a 200 microm-thick silicon absorber, the energy optimum shifts from 8.7 keV to 10.3 keV as the angle of incidence goes from 0 to 45 degrees. These new designs make better use of incident photons, lower the impact of source flicker through simultaneous rather than sequential collection of intensities, and improve the energy range relative to previously reported systems.

A photoionization hydrogen laser time-of-flight mass spectrometer system (H2-TOFMS) has been evaluated for the rapid analysis of drugs of abuse and pharmaceutical agents extracted from prescription tablets and spiked urine samples. The spectra obtained using the H2-TOFMS showed primarily intact molecular ions (M+*) after introduction by a heated probe and irradiation with vacuum ultraviolet (VUV) photons from the laser. Samples analyzed by this technique required only a simple solid-phase extraction step; no chromatographic separation or derivatization was necessary to identify the drugs of abuse or pharmaceutical agents.

The use of a separation step, such as liquid chromatography, prior to inductively coupled plasma mass spectrometry (ICP-MS) has become a common tool for highly selective and sensitive analyses. This type of coupling has several benefits including the ability to perform speciation analysis or to remove isobaric interferences. Several limitations of conventional instruments result from the necessity to scan or pulse the mass spectrometer to obtain a complete mass spectrum. When the instrument is operated in such a non-continuous manner, duty cycle is reduced, resulting in poorer absolute limits of detection. Additionally, with scanning instruments, spectral skew can be introduced into the measurement, limiting quantitation accuracy. To address these shortcomings, a high-performance liquid chromatograph has been coupled to an ICP-MS capable of continuous sample introduction and simultaneous multimass detection. These features have been realized with a novel detector array, the focal plane camera. Instrument performance has been tested for both speciation analysis and for the elimination of isobaric interferences. Absolute limits of detection in the sub picogram to tens of picograms regime are obtainable, while the added mass dimension introduced by simultaneous detection dramatically increases chromatographic peak capacity.

Clinical chelation therapy of mercury poisoning generally uses one or both of two drugs--meso-dimercaptosuccinic acid (DMSA) and dimercaptopropanesulfonic acid (DMPS), commercially sold as Chemet and Dimaval, respectively. We have used a combination of mercury L(III)-edge X-ray absorption spectroscopy and density functional theory calculations to investigate the chemistry of interaction of mercuric ions with each of these chelation therapy drugs. We show that neither DMSA nor DMPS forms a true chelate complex with mercuric ions and that these drugs should be considered suboptimal for their clinical task of binding mercuric ions. We discuss the design criteria for a mercuric specific chelator molecule or "custom chelator", which might form the basis for an improved clinical treatment.

The use of laser ablation (LA) as a sample-introduction method for inductively coupled plasma mass spectrometry (ICP-MS) creates a powerful tool for trace elemental analysis. With this type of instrument, high analyte spatial resolution is possible in three dimensions with ng/g limits of detection and minimal sample consumption. Here, simultaneous detection is used to eliminate the correlated noise that plagues the ablation process. This benefit allows analyses to be performed with single laser pulses, resulting in improved depth resolution, even less sample consumption, and improved measurement precision. The new instrument includes an LA sample-introduction system coupled to an ICP ionization source and a Mattauch-Herzog mass spectrograph (MHMS) fitted with a novel array detector. With this instrument, absolute limits of detection are in the tens to hundreds of fg regime and isotope-ratio precision is better than 0.02% RSD with a one-hour integration period. Finally, depth-profile analysis has been performed with a depth resolution of 5 nm per ablation event.

A novel charge-sensitive detector array, termed the focal plane camera (FPC), has been coupled to a Mattauch-Herzog mass spectrograph (MHMS) with an inductively coupled plasma ionization source. The FPC employs an array of gold Faraday cups, each with its own charge-integrating circuit that allows the simultaneous detection of several m/z ratios. The ion-sampling interface of the MHMS has been redesigned to provide better heat transfer away from the sampler and skimmer cones and to reduce the negative effects of turbulent gas flows around the plasma. The instrument has produced limits of detection in the tens to hundreds of parts per quadrillion regime and isotope ratio accuracy and precision of 5% error and 0.007% RSD, respectively. Limits of detection with the FPC are comparable to those obtained with a single-channel secondary electron multiplier (SEM). However, the isotope ratio accuracy and precision are better with the FPC than when the SEM is employed. The dynamic range has been shown to be linear over 7 orders of magnitude.

The improvised explosive triacetone triperoxide (TATP) was synthesized and characterized by 1H-nuclear magnetic resonance (NMR), 13C-NMR, Raman and infrared (IR) spectroscopy. Triacetone triperoxide was subsequently analyzed by ion mobility spectrometry (IMS) in positive ion mode, and detected as a cluster of three peaks with a drift time of the most intense peak at 13.06 ms. Triacetone triperoxide was then analyzed after dissolution in toluene, where a dramatic increase in peak intensity was observed, at a flight time of 12.56 ms (K0=2.71 cm2V(-1)s(-1)). Triacetone triperoxide was subsequently analyzed by coupling the ion mobility spectrometer to a triple quadrupole mass spectrometer, where a single peak at m/z of 223 atomic mass units identified the species present in the ion mobility spectra as being triacetone triperoxide.

A novel arsenic-selenium solution species was synthesized by reacting equimolar sodium selenite and sodium dimethylarsinate with 10 mol equiv of glutathione (pH 7.5) in aqueous solution. The solution species showed a single (77)Se NMR resonance at 112.8 ppm. Size-exclusion chromatography (SEC) using an inductively coupled plasma atomic emission spectrometer (ICP-AES) as the simultaneous arsenic-, selenium-, sulfur-, and carbon-specific detector revealed an arsenic-selenium moiety with an As:Se molar ratio of 1:2. Electrospray ionization mass spectrometry (ESI-MS) of the chromatographically purified compound showed a molecular mass peak at m/z 263 in the negative ion mode. Fragmentation of the parent ion (ESI-MS-MS) produced (CH(3))(2)As(-) and Se(2)(-) fragments. Arsenic and selenium extended X-ray absorption fine structure spectroscopy (EXAFS) of the purified species revealed two As-C interactions at 1.943 A and two As-Se interactions at 2.279 A. On the basis of these results this novel solution species is identified as the dimethyldiselenoarsinate anion.

A Mattauch-Herzog geometry mass spectrograph (MHMS) has been equipped with a novel array detector, the focal plane camera (FPC). The FPC consists of an array of gold Faraday cups, each coupled to its own integrator, with interrogation of the integrators performed by a multiplexer. The initial coupling of this instrument with a pin-type glow discharge source has provided limits of detection in the single to hundreds of nanograms per gram regime; isotope ratio accuracy and precision better than 5% error and 0.2% RSD, respectively; and a linear dynamic range of at least 6 orders of magnitude. A current weakness of the FPC is its pixel size, which limits both sensitivity and baseline resolution (to R = 130). The minimum data acquisition time for multiple images at present is 1 ms/image, with a dead time of 3.2 ms between images, which will limit the ability of the FPC to monitor extremely short transient signals.

A scientifically operated charge-coupled device detector combined with fluorescence quenching high-performance thin-layer chromatographic plates was employed for the detection of organic compounds, The plates were excited with 254 nm light from a mercury lamp, and quantitative information was obtained from organic compounds that absorbed the optimum conditions for detection. The linear dynamic range, sensitivity, and reproducibility of the system were evaluated by quantitative analysis of famotidine, acetaminophen, caffeine, and acetylsalicylic acid. The detection limits of the system were found to be in the nanogram range.

Mercuric chloride toxicity in mammals can be overcome by co-administration of sodium selenite. We report a study of the mutual detoxification product in rabbit plasma, and of a Hg-Se-S-containing species synthesized by addition of equimolar mercuric chloride and sodium selenite to aqueous, buffered glutathione. Chromatographic purification of this Hg-Se-S species and subsequent structural analysis by Se and Hg extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of four-coordinate Se and Hg entities separated by 2.61 A. Hg and Se near-edge X-ray absorption spectroscopy of erythrocytes, plasma, and bile of rabbits that had been injected with solutions of sodium selenite and mercuric chloride showed that Hg and Se in plasma samples exhibited X-ray absorption spectra that were essentially identical to those of the synthetic Hg-Se-S species. Thus, the molecular detoxification product of sodium selenite and mercuric chloride in rabbits exhibits similarities to the synthetic Hg-Se-S species. The underlying molecular mechanism for the formation of the Hg-Se-S species is discussed.

A high-performance thin-layer chromatography (HPTLC) method using a scientifically operated charge-coupled device detector is described for the assay of tetracycline pharmaceutical products. Quantitative information can be obtained for all samples on a TLC plate within a few seconds. The separation efficiency and detection limits were determined on both normal phase and reverse phase TLC plates. Fluorescence detection mode offers higher sensitivity than fluorescence quenching mode. The dynamic range, sensitivity, accuracy and precision of the system were evaluated. Detection limits of the impurities are in the range of 0.1 to 0.5 ng or 0.3 to 1% of tetracycline, depending on the compound, with a recovery percentage over 85%. The existing impurities in tetracycline capsules were determined using both HPLC and HPTLC techniques. All of the impurities were below the regulation level.

The stability of tetracycline in methanol solution was investigated by UV-visible spectroscopy, HPLC and TLC methods. After dissolution in methanol, tetracycline decomposed rapidly under the influence of light and atmospheric oxygen, forming more than fourteen different degradation products. None of the previously reported degradation products, such as the epi- and anhydro-compounds, were detected as the final degradation products. The molecular structures for eight of the compounds were suggested by their product-ion mass spectra. A degradation sequence was proposed for the reactions of tetracycline with methanol. A new HPLC-MS mobile phase was developed, which solved the clogging problem at the interface between the HPLC and MS chamber and enabled a high separation efficiency.

The use of energy-resolved area detection of Laue diffraction patterns for the determination of unit-cell parameters and systematic absences is demonstrated. Seven different crystals having previously known unit cells were re-examined using Laue diffraction methods. These crystals included four different crystal systems including cubic, orthorhombic, tetragonal and monoclinic cells. The crystals had cell sizes ranging from 179.4 to 4588.3 A(3). Comparison of known and re-determined cells showed good agreement (ratio of known to measured cells = 0.987 +/- 0.18). A single procedure was suitable for all unit-cell determinations. The accuracy of the method is presently limited by the quality of the available energy measurements. Some of the crystals represent space groups containing systematic absences normally obscured by harmonic overlap when using the Laue method. These include absences due to 2(1) screw axes (h, k or 1 = 2n + 1) and cell centering (h + k = 2n + 1). All systematic absences were identified using a combination of multiple linear regression with either stepwise elimination or stepwise inclusion and an F test for assignment of systematic absence. The methods are discussed in detail and simulations are used to evaluate critical tolerances for future systems.

An X-ray spectrometer for simultaneous position, intensity and energy determinations suitable for Laue diffraction applications is described. The foil-mask spectrometer consists of a series of metal foils of varying composition and thickness which are used to modulate the energy distribution of an incident X-ray source. Three modes of operation are described: a high-resolution spectrometer for measurement of nearly monochromatic X-rays, an intensity discriminator for partitioning the intensity from a small number of spatially overlapped monochromatic X-ray sources, and a low-resolution spectrometer for polychromatic X-rays with broad spectral features. The first mode of operation is designed to allow the energy of monochromatic Laue reflections to be measured with a resolution suitable for determination of unit-cell parameters. The second mode of operation is designed to allow the intensity of each component in a spatial region containing overlapping orders or spatially overlapped reflections to be discriminated for use in refinements or space-group assignment. The third mode of operation is described for completeness. The theory behind each mode of operation is described. The energy resolution of the spectrometer improves with the square root of the intensity of the incident beam. It also increases linearly with the change in energy with respect to transmission efficiency of a particular foil. In theory, the resolution of the spectrometer can readily exceed 50 eV over a wide range of energies depending on the foils used and the incident X-ray photon flux. Determinations of the energies of Mo Kalpha and Cu Kalpha radiation using a first-generation ten-foil spectrometer gave values of 17.5 +/- 0.1 and 8.08 +/- 0.05 keV, respectively. Treatment of random error shows good correspondence with a Poisson model. The use of this spectrometer is demonstrated using a sample of tetraphenylphosphonium tetrachlorooxomolybdenum(V). Comparison of predicted and observed energies shows good agreement over a wide range of energies. The ratio of predicted to measured energy for the first 50 measurements was 0.9918+/-0.0344. Up to three components of a position having harmonic overlap were separated. This work demonstrates the feasibility of using Laue diffraction to completely determine the crystal structure of a molecule without recourse to monochromatic methods.

Charge-injection devices (CIDs) are versatile detectors having a number of features which recommend them for use in the imaging of X-ray diffraction patterns. They have a flexible nondestructive readout allowing for analysis of image quality during data collection and rapid readout of selected portions of the device. CIDs have full-well capacities in the range of 10(6) charge carriers giving them a high dynamic range for both direct and indirect imaging of X-rays. CIDs have peak quantum efficiencies in the optical region over 50% allowing for their incorporation into indirect detection systems. Rapid random single-pixel address allows for their use as single X-ray photon counters with energy discrimination. Three types of position-sensitive detectors for X-rays have been developed using CIDs. Two CID formats, the CID 17PPRA (388 x 256) and the CID 38SG (512 x 512), were incorporated into systems performing indirect imaging, direct imaging and single X-ray photon counting with energy discrimination. Indirect images of the Laue diffraction patterns from tetraphenylphosphonium tetrachlorooxomolybdenum(V) and natural MoS(2) were collected using a phosphor sheet to convert X-rays into optical photons which were detected with the CID 38SG. Directly detected images of spots from the Laue diffraction pattern of MoS(2) were recorded with the CID 17PPRA. Single photon counting with energy discrimination is demonstrated with the CID 17PPRA using a reflection from the Laue diffraction pattern of MoS(2). Useful information could be obtained from a single pixel at read rates over 7 kHz. Complete energy-dispersive analysis suitable for determination of space groups from Laue diffraction is currently limited due to incomplete charge collection and/or split events.

Studies into the use of simultaneous multiwavelength detection over a broad wavelength region (220-520 nm) demonstrate the power and flexibility offered by a charge-injection device for detection in atomic-emission spectrometry. An echelle monochromator and a charge-injection device utilizing the general electric CID17B array detector are used in conjunction with a direct current plasma source to perform multi-line analysis for Mg, Sr, Fe, Dy, Ho and Yb, increasing the sensitivity and limits of detection. By monitoring the 341-nm OH band and background Ar emission lines, changes in the nebulization and excitation conditions are easily detected. The presence of an organic matrix component not present in the standards is detected by observing the C(I) emission at 247.8 nm. These diagnostic tools can be combined with the use of an internal standard to obtain a reliability not previously available in automated AES instrumentation.

Simultaneous multielement atomic-emission spectrometry with a charge-inection device (CID) as a multichannel optical detector is described. The system used in this study employs a standard commercial D.C. plasma source, a modified echelle spectrometer, and a special digital camera system that uses a two-dimensional CID array sensor. A description of the modified spectrometer is given along with performance results. Computer algorithms for acquiring and analysing spectral information are described. Detection limits for several elements are determined simultaneously. Results of simultaneous determination of several elements in an NBS standard reference material (SRM 1643A) are given. These results indicate that the CID detector is capable of reasonably good accuracy and high sensitivity in the simultaneous determination of several elements in complex samples.