In March 1994, members of the International Safeguards Department in the National Security Program Office (NSPO) hosted an environmental monitoring field trial workshop for International Atomic Energy Agency (IAEA) inspectors. The workshop was held at the Oak Ridge K-25 Site and its primary purpose was to train the inspectors in the techniques needed for effective environmental sample collection and handling. The workshop emphasized both sampling theory and practice. First, detailed techniques for swipe, vegetation, soil, biota, and water-associated sampling were covered in the classroom. Subsequently, the inspectors were divided into three groups for actual sample collection in and around the K-25 locale. The collected samples were processed by the Department of Energy (DOE) Network of Analytical Laboratories using established analytical techniques. This activity is part of the IAEA ``Programme 93+2 in. assessment of measures to enhance IAEA safeguards.
Ion implantation and thermal annealing have been used to produce a wide range of nanocrystals and quantum dots in amorphous (SiO{sub 2}) and crystalline (Al{sub 2}O{sub 3}) matrices. Nanocrystals of metals (Au), elemental semiconductors (Si and Ge), and even compound semiconductors (SiGe, CdSe, CdS) have been produced. In amorphous matrices, the nanocrystals are randomly oriented, but in crystalline matrices they are three dimensionally aligned. Evidence for photoluminescence and quantum confinement effects are presented.
Techniques for microsampling in infrared spectroscopy by matrix isolation are described. In the matrix isolation of liquid or solid compounds, the sample is vaporized and then diluted with a large excess of a matrix gas; the resulting gaseous mixture is deposited on a cold surface for spectroscopic examination as a solid. Detailed descriptions of the apparatus and procedures employed in the preparation of matrix-isolated samples for qualitative and quantitative analyses by Fourier transform infrared spectrometry are presented. Systems for “microsampling” (detection limits for specific compounds ∼0.5 to 1 μg) and “ultramicrosampling” (detection limits ∼50 to 100 ng) matrix isolation spectroscopy are described. Detection limits and Beer's law behavior for polycyclic aromatic hydrocarbons microsampled by matrix isolation are discussed. The advantages of matrix isolation as a technique for qualitative and quantitative infrared analysis of microsamples are itemized.
The role of hydrogen in enhancing the photoluminescence (PL) yield observed from Si nanocrystals embedded in SiO2 has been studied. SiO2 thermal oxides and bulk fused silica samples have been implanted with Si and subsequently annealed in various ambients including hydrogen or deuterium forming gases (Ar+4%H2 or Ar+4%D2) or pure Ar. Results are presented for annealing at temperatures between 200 and 1100 °C. Depth and concentration profiles of H and D at various stages of processing have been measured using elastic recoil detection. Hydrogen or deuterium is observed in the bulk after annealing in forming gas but not after high temperature (1100 °C) anneals in Ar. The presence of hydrogen dramatically increases the broad PL band centered in the near infrared after annealing at 1100 °C but has almost no effect on the PL spectral distribution. Hydrogen is found to selectively trap in the region where Si nanocrystals are formed, consistent with a model of H passivating surface states at the Si/SiO2 interface that leads to enhanced PL. The thermal stability of the trapped H and the PL yield observed after a high temperature anneal have been studied. The hydrogen concentration and PL yield are unchanged for subsequent anneals up to 400 °C. However, above 400 °C the PL decreases and a more complicated H chemistry is evident. Similar concentrations of H or D are trapped after annealing in H2 or D2 forming gas; however, no differences in the PL yield or spectral distribution are observed, indicating that the electronic transitions resulting in luminescence are not dependent on the mass of the hydrogen species.
A series of experiments designed to detect the by-products expected from deuterium fusion occurring in the palladium and titanium cathodes of heavy water (D{sub 2}O) electrolysis cells is reported. The primary purpose of this account is to outline the integrated experimental design developed to test the cold fusion hypothesis and to report preliminary results that support continuing the investigation. Apparent positive indicators of deuterium fusion were observed, but could not be repeated or proved to originate from the electrochemical cells. In one instance, two large increases in the neutron count rate, the largest of which exceeded the background by 27 standard deviations, were observed. In a separate experiment, one of the calorimetry cells appeared to be producing {approximately}18% more power that the input value, but thermistor failure prevented an accurate recording of the event as a function of time. In general, the tritium levels in most cells followed the slow enrichment expected from the electrolysis of D {sub 2}O containing a small amount of tritium. However, after 576 hours of electrolysis, one cell developed a tritium concentration approximately seven times greater than expected level. 3 refs., 6 figs., 1 tab.
Raman scattering studies were carried out to investigate the effects of ion implantation on the structure of diamond, graphite, and polymers. Carbon phases produced by chemical vapor deposition (CVD diamond) and rf discharge (diamondlike carbon or DLC) were also analyzed. Two types of amorphous carbon phases were distinguished with relevance to hardness. In general, amorphous carbon phases produced by electron beam evaporation and sputtering are soft (hardness \ensuremath{\ll}1 GPa), while DLC and some ion-beam-modified polymers are much harder. In all cases, the characteristic Raman bands of the starting material were lost upon ion implantation, and for the lowest fluences the one-phonon bands near 1360 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (D line) and 1580 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ (G line) of disordered polycrystalline graphite appeared. With increasing fluence these bands coalesced into a broad, asymmetric peak with the D line shifting to higher wave number and the G line shifting to lower wave number. This trend was clearly distinguishable from the finite crystallite size effect seen in graphite, where, in addition to the appearance of the D line, the G line shifts to higher wave number with decreasing crystallite sizes. Raman scattering could not distinguish between soft and hard amorphous carbon. There was also no indication that the hardness of DLC films and ion-beam-modified polymers was due to diamondlike ${\mathit{sp}}^{3}$ bonds. Instead, hardness in these materials is related to the three-dimensional interconnectivity of chemical bonds. Experimental results suggest that the amorphous carbons examined in this study are composed of random networks of distorted sp, ${\mathit{sp}}^{2}$, and ${\mathit{sp}}^{3}$ bonded atoms, sometimes in a hydrogenated state. The hard carbons such as DLC films and ion beam modified polymers have long-range chemical connectivity while the soft carbons such as damaged graphite, and carbon films prepared by sputter deposition lack such connectivity.
AbstractEarlier work in this laboratory' has shown matrix isolation Fourier transform infraredspectrometry (MI FTIR) to possess several advantages over conventional sampling techniquesfor the qualitative analysis of complex samples. The ability to obtain very sharp spectrausing MI makes it possible to distinguish between very similar compounds, including isomers,present in a sample.Instrumentation to couple capillary column gas chromatography (GC) to MI FTIR has beendeveloped as an alternative to on- the -fly gas -phase GC FTIR measurements. This techniqueallows leisurely study of chromatographic fractions at medium resolution (1 cm-1). A gold - plated disk is cooled to 15K with a closed -cycle helium refrigerator and used to collectcompounds eluting from the GC. Nitrogen is used as both GC carrier gas and matrix material.Beam condensing optics and KRS -5 rods are used to reflect the IR beam from the individualsample deposition surfaces.IntroductionConsiderable interest has developed recently in the use of FTII spectrometry for detec-tion in gas chromatography (GC), as reviewed by Erickson.2 At least two commercial GC -FTIRsystems are available which yield gas phase on- the -fly or vapor phase stopped -flow spectra.A major drawback of the on- the -fly systems is the limited resolution (ca. 4 cm-1) andnumber of FTIR scans (ca. 4) possible in the short time GC effluent is in the beam of thespectrometer. Use of stopped -flow systems results in better spectra, but the chromatographicresolution may be severely degraded if the gas flow is stopped, and other compounds elutingmay be lost if a bypass is used. These experimental limitations result in a practicalrequirement to use sensitive, cooled IR detectors to obtain detection limits of about 100 ngper component.2Matrix isolation is most commonly used as a means of trapping unstable or reactivespecies in order to study them in a leisurely fashion. For a sample which is liquid orsolid at room temperature, matrix isolation involves vaporizing the sample. Accordingly,matrix isolation should be directly applicable to detection in gas chromatography, particu-larly if the same substance is used both as the GC carrier gas and the matrix gas.
