This dissertation describes the first high-precision observation of the infrared spectrum of the helium hydride molecular ion HeH⁺. The frequencies of five vibrational-rotational transitions in the range 1700-1900 cm⁻¹ in the X¹Σ⁺ ground electronic state of ⁴HeH⁺ have been measured to ±0.002 cm⁻¹ (±1 ppm). The Doppler tuned ion beam laser spectroscopic method was used in making the measurements: In a region of constant electrostatic potential, an HeH⁺ ion beam of several keV energy is intercepted at a small angle by a beam from a carbon monoxide infrared gas laser. The energy of the ion beam is adjusted to Doppler-shift an ion transition into resonance with a nearby laser line. On resonance the laser light stimulates transitions to take place. If the resonating states differ in population, the laser-induced transitions produce a net population transfer. The occurrence of population transfer is detected by monitoring the transmission of the ion beam through a gas target downstream from the laser beam interaction region. The transmission through the target is dependent upon the ion beam vibrational-state population distribution and therefore is sensitive to changes in the population distribution, because the cross-section for charge-exchange neutralization of an incident ion is dependent upon the vibrational state of the ion. The current interest in molecular ions in general, and in HeH⁺ in particular, is explained. The existing theory of the structure of HeH⁺ is summarized and a comprehensive listing of theoretical treatments of the structure of HeH⁺ is given. The meager previous experimental work on HeH⁺ is reviewed. The principles of the Doppler tuned ion beam laser resonance method are discussed and the experimental apparatus used is described in detail. The acquisition and analysis of the data is described and the results are compared with the best existing theoretical predictions of the transition frequencies. The present experimental values (given by D. E. Tolliver, G. A. Kyrala, and W. H. Wing, Phys. Rev. Lett. 43, 1719) for the measured transitions are (with the corresponding values calculated by D. L. Bishop and L. M. Cheung, J. Mol. Spectrosc. 75, 462, given in parentheses): (v,J)=(1,11)↔(0,12), 1855.905 cm⁻¹ (1856.152 cm⁻¹); (1,12)↔(0,13), 1751.971 cm⁻¹ (1752.198 cm⁻¹); (2,8)↔(1,9), 1896.992 cm⁻¹ (1897.139 cm⁻¹); (2,9)↔(1,10), 1802.349 cm⁻¹ (1802.492 cm⁻¹); and (2,10)↔(1,11), 1705.543 cm⁻¹ (1705.684 cm⁻¹). It is seen that the present experimental values deviate from the theory by typically 0.2 cm⁻¹, and are two orders of magnitude more precise than the theoretical values.

High-resolution Fourier spectra in the 0.9-2.5 μm region were measured for sixteen asteroids. These data were combined with 0.3-1.1 μm spectrophotometry and 3.0-3.5 μm narrowband photometry for compositional analysis. Comparison spectra of meteorites and terrestrial minerals were measured in the laboratory, some under simulated asteroidal conditions of pressure and temperature. Spectra of eleven representative S-type asteroids show a range of olivine/pyroxene ratios overlapping those of ordinary and carbonaceous chondrites, but not approaching those of common differentiated meteorite types. The reddening in the asteroid spectra implies the presence of metallic iron, but if the metal is finely divided its abundance could be low. S-type asteroids have spectra most consistent with undifferentiated compositions, and some of them, especially 8 Flora, could be ordinary chondrite parent bodies. 4 Vesta and 349 Dembowska are unusual asteroids which have spectra resembling those of achondritic meteorites. Vesta has a pyroxene-feldspar mineralogy intermediate in composition between eucrites and howardites. If shergottite-like basalts are present, they must be in low abundance. Dembowska has an olivine-pyroxene mineralogy similar in some ways to ordinary chondrites, but there is considerable evidence that it is actually a fragment of the mantle of a differentiated Vesta-like parent body. The most diagnostic spectral feature seen on three low-albedo asteroids is the 3 μm band due to water of hydration. 1 Ceres must consist mostly of a low-iron clay mineral with some hydrated salts. 2 Pallas has a low abundance of hydrated minerals relative to Ceres, with the bulk of its composition being anhydrous iron-free silicates. 324 Bamberga probably contains clay minerals, but its spectrum is dominated by abundant magnetite. These and other C-type asteroids have surface compositions consistent with massive aqueous alteration of primary carbonaceous chondrite minerals. These results all indicate that the compositions of main belt asteroids are more closely related to the compositions of meteorites than was previously believed. S-type and C-type asteroids are undifferentiated assemblages of which ordinary and carbonaceous chondrites are an incomplete sample. Differentiated meteorites could be derived from the other relatively rare asteroid types.

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Protein-protein and ligand-protein interactions as well as the effect of temperature and applied pressure on protein conformation were investigated by Fourier transform infrared (FTIR) spectroscopy with the use of Fourier self-deconvolution, Fourier derivative, and two-dimensional correlation techniques. The effect of the binding of biotin to avidin on the conformation of the protein was examined. At a biotin concentration of 0.05% (w/v), avidin was stabilized against thermal and pressure-induced denaturation. The IR spectra of avidin recorded as a function of increasing hydrostatic pressure in the presence and the absence of biotin indicated that, in the presence of biotin, avidin adopts a very compact structure in solution. The 2D correlation analysis of the infrared spectra of avidin recorded as a function of increasing temperature over the range of 25--95°C revealed that the protein unfolded via different pathways in the presence and the absence of biotin. Furthermore, the thermally induced conformational changes observed in the absence of biotin were irreversible upon cooling of the protein solution, owing to aggregation of the thermally unfolded protein, whereas in the presence of biotin the protein unfolded and refolded via the same pathway. Variable-temperature FTIR spectroscopy and 2D correlation analysis were also employed to examine correlations between absorptions in the amide I and amide III regions in the spectra of four proteins. The results suggested that the band at 1284 cm-1 in the amide III region may be tentatively assigned to the intermolecular beta-sheet structure formed upon aggregation of thermally unfolded protein. FTIR studies were also conducted to investigate the interaction between the catalytic and regulatory subunits of the enzyme ATCase. The secondary structure of the ATCase holoenzyme was stable up to 60°C. The isolated regulatory subunit denatured at approximately 47°C while the isolated catalytic subunit was thermall

Variable-temperature Fourier transform infrared (VT-FTIR) and circular dichroism (far-UV CD) spectroscopy were employed to investigate the sequence of structural changes responsible for the thermally induced formation of myosin gels with various rheological properties, as measured by dynamic oscillatory rheology, as well as the effects of prior high-pressure processing (HPP) on thermally induced gel formation. The viscoelastic properties of the protein gels were monitored as a function of temperature and were also measured at three fixed temperatures (44, 48, and 68°C). Examination was done of changes in the secondary structure-sensitive amide l'band in the FTIR spectra of the protein in D2O buffer (0.6M KCl, pH 6.4) as a function of temperature, as well as far-UV CD spectra. Myosin solutions were exposed to increasing hydrostatic pressure (100--400 MPa for 10 min at 16°C). The extent of unfolding of the tail was shown to be proportional to the pressure treatment, suggesting that the slight increase of gel strength may partly originate from the facilitated tail-tail interaction. (Abstract shortened by UMI.)

Fourier transform infrared (FTIR) spectroscopy was employed to monitor the oxidation of edible oils in the absence and presence of antioxidants. Three synthetic antioxidants (butylated hydroxyanisole, propyl gallate and tert-butylhydroxyquinone) were added to menhaden oil at three different concentrations (1%, 0.1%, and 0.01%), and the FTIR spectra of the oils under conditions of oxidative stress were recorded as a function of time. The efficacy of each antioxidant was assessed by monitoring bands at 3444 cm$ sp{-1}$, characteristic of hydroperoxide formation, 971 cm$ sp{-1}$ for trans double bond formation, and 3008 cm$ sp{-1}$ for cis depletion. An FTIR spectroscopic method was also developed for the determination of the peroxide value of edible oils undergoing oxidation, based on the measurement of the 3444-cm$ sp{-1}$ band. The results of the FTIR method were compared to those from both the iodometric chemical method and the enzymatic hemoglobin-methylene blue assay for the determination of hydroperoxide content. The FTIR predictions were within $ pm$3% of the values obtained by both the chemical and the enzymatic method. Finally, the determination of the hydroxyl value of emulsifiers by FTIR spectroscopy was investigated. Both attenuated total reflectance (ATR) and transmission flow cell techniques were used to record the spectra of commercial monoglycerides. Calibration models for the prediction of hydroxyl value from the FTIR spectra were developed using partial-least-squares (PLS) regression for both the ATR and transmission spectra. Cross-validation of the calibration models yielded an overall average error in the predicted hydroxyl values of $ sim$3% for both the ATR and transmission flow cell methodologies. Linear regression of the FTIR-predicted versus the hydroxyl values determined by the reference chemical method yielded r = 0.998 for the ATR and r = 0.997 for the transmission flow cell method.

Current methods for the detection and quantitation of airborne asbestos are either tedious, time consuming, subjective, or too expensive for routine analysis. A FT-IR spectroscopic method for the identification and quantitation of airborne asbestos samples provides a relatively inexpensive, fast, and non-subjective alternative for routine analysis.Three methods are investigated for the separation of the asbestos fibers from the matrix of the collection filter, (a mixed cellulose ester) for infrared analysis: spectral subtraction, chemical digestion, and ashing. Problems associated with the handling of asbestos (sample loss and contamination), and band anomalies encountered during spectral subtractions are discussed.Calibration curves are presented using the asbestos Si-O absorptions to quantitate the amount of asbestos. The spectral subtraction method yields linear calibration curves down to 0.3% asbestos by weight (6 mg) for tremolite asbestos. Tremolite and amosite asbestos calibration curves are linear down to 8 µg and 3 µg asbestos respectively using the ashing method.The spectral subtraction method and the ashing method are applied to NIOSH prepared PAT samples previously analyzed by phase contrast microscopy.The spectra are analyzed for asbestos by band identity, and once identified, quantitated from the appropriate calibration curve. / Department of Chemistry

This thesis introduces a new route to control the structure of semiconductor nanowires using surface chemistry. Specifically, in Au-catalyzed Si nanowire growth using hydride species (Si₂H₆) as growth precursors, we demonstrate that the surface hydrogen existing on the nanowires sidewalls affects the growth morphology. First, we show the spectroscopic evidence of atomic hydrogen bonded to sidewall surface of Si nanowires in real-time in situ during growth and correlate their relative change with different growth orientations and planar defect generation. By introducing additional atomic hydrogen during the <111>-oriented nanowire growth with intrinsically low hydrogen concentration, we confirm that the growth orientation changes from <111> to <112> orientation. We also show that the transient change in the nanowire growth conditions (i.e., substrate temperature and precursor pressure) can rationally induce the planar defects such as twin boundary or stacking fault in Si nanowires at user-defined position. These findings provide important insight into the vapor-liquid-solid technique for nanowire growth and identify new possibilities for systematically controlling their structures in general.

In this work, a rapid Fourier transform near infrared (FT-NIR) spectroscopic peroxide value (PV) method was developed and a prototype Continuous Oil Analysis and Treatment (COAT) system was assessed for monitoring and analytical purposes. High erucic acid rapeseed oil, a principle representative of triglyceride based oils suitable for biodegradable lubricating applications and mineral oil were used to test the methodology developed. / The FT-NIR PV method is based on a well defined stoichiometric reaction of triphenylphospine (TPP) with hydroperoxides to form triphenylphospine oxide (TPPO). A partial least squares calibration model for the prediction of PV was developed using the NIR spectral region where TPP and TPPO co-absorb. The resulting calibration was highly linear over the analytical range of 100PV. Validation of the method carried out by comparing the PV of PLS prediction to the results of AOCS iodometric procedures indicated an excellent concurrence between the two methods. By programming the FT-NIR spectrometer, the analytical procedure simply consists of the addition of TPP stock solution to oil sample, mixing, taking its spectrum and predicting PV value. Through selected testing procedures, the prototype COAT system utilizing FTIR spectroscopy, advanced sample handling system designs, and computer programming was proved to be effective in monitoring the oil quality and behavior of antioxidants in real time. / Both approaches offer combined advantages of speed, accuracy, low labor cost, automation, and environmental friendliness mainly derived from FTIR spectroscopy, and can serve as convenient means for routine quality control applications in oils and fats industry. Potential application based on the joint usage of the two methods in the obtaining of true value of oil stability was also presented in this text. (Abstract shortened by UMI.)