Vickie M. Hallmark

Bio: Vickie M. Hallmark is an academic researcher from IBM. The author has contributed to research in topics: Raman spectroscopy & Coherent anti-Stokes Raman spectroscopy. The author has an hindex of 4, co-authored 8 publications receiving 143 citations.

Fourier Transform Raman Spectroscopy of Long-Chain Molecules Containing Strongly Absorbing Chromophores

Abstract: Fourier transform Raman spectroscopy shows considerable promise as a new characterization technique for molecules which contain chromophores which absorb in the visible region, the region where conventional Raman measurements are made. With the use of near-infrared excitation, spectra in the absence of fluorescence and resonance enhancement are obtained. These advantages can be further enhanced if the collection of data using this technique becomes routine, requiring a level of complexity comparable to that of conventional Raman scattering. Toward that end, the implementation of a 90° scattering geometry in our FT-Raman measurements was undertaken, and the results are shown to be at least comparable to those obtained with the use of reflective optics in a 180° geometry. A number of results on both liquids and solids have also been obtained in order to compare FT-Raman with conventional scanning Raman measurements.

Applications of Fourier Transform Raman spectroscopy to studies of thin polymer films

Abstract: Raman spectroscopic studies of submicron-thick films have been accomplished through the use of integrated optical techniques. By using the film as an asymmetric slab waveguide for the laser excitation, and collecting the scattering emanating from the guided streak, the authors have obtained Raman spectra of organic films, polymer laminates, and molecular composites. The utility of the waveguide Raman spectroscopy technique has been limited by high levels of fluorescence when visible wavelength excitation is used. With the advent of FT-Raman spectroscopy, in which a near-infrared laser is used, Raman spectra of highly fluorescent and intensely colored materials could be easily obtained. In this study, waveguide Raman spectroscopic measurements using near-infrared excitation and a Michelson interferometer have been demonstrated. The use of a fiber optic bundle to collect the scattering and convert the image from a line to a circle has resulted in a 15-fold improvement over conventional lens collection. With the improved sensitivity, FT-Raman spectra of films containing small molecule chromophores imbedded in a polymer matrix have been obtained. In addition, extension of this method to polymers of low refractive index, by using a sublayer of very low refractive index material, such as MgF{sub 2}, has been outlined.

Fourier Transform Raman Spectroscopy Using a Tuneable Solid-State Laser and a Semiconductor Bandgap Filter

Abstract: The feasibility of using the optical absorption properties of a semiconductor crystal as a long wavelength pass filter for Fourier transform Raman spectroscopy applications has been demonstrated. Near-infrared excitation from a titanium: sapphire solid-state laser was selectively tuned to the edge of the bandgap absorption of an indium-doped cadmium telluride semiconductor filter. Raman spectra to within 30 cm−1 of the exciting line could be measured. Narrowing of the optical absorption of the semiconductor filter at low temperatures did not improve the

FT-Raman spectroscopy of biological molecules

Abstract: Raman spectroscopy of biological molecules is often very difficult if not impossible due to a large fluorescence background from absorbing species, either from the molecule itself or an impurity. Photobleaching is occasionally successful in photochemically removing fluorescent impurities, but the majority of samples are not responsive to such treatment. Resonance enhancement of an absorbing species allows acquisition of Raman spectra in spite of competing fluorescence. However, the resonance Raman spectrum is characteristic of the chromophore only and little structural information is obtained from the spectrum about other parts of the molecule which are not resonantly enhanced. The newly developed technique of FT-Raman spectroscopy proves to be a solution to both of these problems for biological materials. Excitation with infrared wavelengths prevents electronic absorptions which give rise to fluorescence. In addition, the obtained spectra are completely nonresonant, allowing detection of vibrational modes of all parts of the molecule including the chromophore. We will present nonresonant, fluorescence free spectra of a range of biologically significant molecules including phospholipids and porphyrins.

Handbook of Raman Spectroscopy: From the Research Laboratory to the Process Line

Abstract: Theory of Raman scattering evolution and revolution of Raman instrumentation - application of available technologies to spectroscopy and microscopy Raman spectroscopy and its adaptation to the industrial environment Raman microscopy - confocal and scanning near-field Raman imaging the quest for accuracy in Raman spectra chemometrics for Raman spectroscopy Raman spectra of gases Raman spectroscopy applied to crystals - phenomena and principles, concepts and conventions Raman scattering of glass Raman spectroscopic applications to gemmology Raman spectroscopy on II-IV-semiconductor nanostructures medical applications of Raman spectroscopy - in vivo Raman spectroscopy some pharmaceutical applications of Raman spectroscopy low-frequency Raman spectroscopy and biomolecular dynamics - a comparison between different low-frequency experimental techniques collectivity of vibrational modes Raman spectroscopic studies of ion-ion interactions in aqueous and non-aqueous electrolyte solutions environmental applications of Raman spectroscopy to aqueous solutions Raman and surface enhanced resonance Raman scattering - applications in forensic science application of Raman spectroscopy to organic fibres and films applications of IR and Raman spectra of quasi-elemental carbon process Raman spectroscopy the use of Raman spectroscopy to monitor the quality of carbon overcoats in the disk drive industry Raman spectroscopy in the undergraduate teaching laboratory Raman spectroscopy in the characterization of archaeological materials.

Raman Spectroscopy—A Prospective Tool in the Life Sciences

Abstract: Although the physics of Raman spectroscopy and its application to purely chemical problems is long established, it offers a noninvasive, nondestructive, and water-insensitive probe to problems in the life sciences. Starting from the principles of Raman spectroscopy, its advantages, and methods for signal enhancement, the bulk of the review highlights recent applications. Structural investigations of a hormone receptor, testing the biocompatibility of dental implants, probing soil components and plant tissue alkaloids, and localization of single bacteria are just four problems in which Raman spectroscopy offers a solution or complements existing methods.

Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions

Abstract: Resonance Raman (RR) spectroscopy has several advantages over the normal Raman spectroscopy (RS) widely used for in situ characterization of solid catalysts and catalytic reactions. Compared with RS, RR can provide much higher sensitivity and selectivity in detecting catalytically-significant surface metal oxides. RR can potentially give useful information on the nature of excited states relevant to photocatalysis and on the anharmonic potential of the ground state. In this critical review a detailed discussion is presented on several types of RR experimental systems, three distinct sources of so-called Raman (fluorescence) background, detection limits for RR compared to other techniques (EXAFS, PM-IRAS, SFG), and three well-known methods to assign UV-vis absorption bands and a band-specific unified method that is derived mainly from RR results. In addition, the virtues and challenges of surface-enhanced Raman spectroscopy (SERS) are discussed for detecting molecular adsorbates at catalytically relevant interfaces. Tip-enhanced Raman spectroscopy (TERS), which is a combination of SERS and near-field scanning probe microscopy and has the capability of probing molecular adsorbates at specific catalytic sites with an enormous surface sensitivity and nanometre spatial resolution, is also reviewed (300 references).