Results 1 - 10 of 15276
Results 1 - 10 of 15276. Search took: 0.056 seconds
|Sort by: date | relevance|
[en] We developed a standoff Raman detection system for explosive molecules (EMs). Our system was composed of reflective telescope with 310 mm diameter lens, 532 nm pulse laser, and Intensified Charge-Coupled Device (ICCD) camera. In order to remove huge background noise coming from ambient light, laser pulses with nanosecond time width were fired to target sample and ICCD was gated to open only during the time when the scattered Raman signal from the sample arrived at ICCD camera. We performed standoff experiments with military EMs by putting the detector at 10, 20 and 30 m away from the source. The standoff results were compared with the confocal Raman results. Based on our standoff experiments, we were able to observe the peaks in the range of 1200 and 1600 cm-1, where vibrational modes of nitro groups were appeared. The wave numbers and shapes of these peaks may serve as good references in detecting and identifying various EMs
[en] Resonance Raman spectroscopy (RRS) potentially possesses many of the characteristics of an ideal verification technology. Some of these ideal traits are as follows: (1) very high selectivity and specificity to allow the deconvolution of a mixture of the chemicals of interest; (2) high sensitivity in order to measure a species at trace levels; (3) high reliability and long-term durability; (4) applicability to a wide range of chemicals (closely associated with item 1); (5) capability of sensing in a variety of environmental conditions; (6) independance of the physical state of the chemical; (7) capability of quantitative analysis; (8) capability for full signal development within seconds (response speed). In this paper, the authors assess the potential of RRS as a detection/identification technology for chemicals pertinent to nuclear materials production and processing. The basic principles behind this technique, both theoretical and experimental, are discussed, along with recent experimental results
[en] Laser Raman spectroscopy is the powerful tool to investigate the molecular structure. However, the conventional analog signal often causes some problems in many experiments. For high resolution, small signals, or background (solvent) subtraction, the computer interface of the Raman spectroscopy is the essential one. Here the interface work done in our laboratory is described and some results through the softwares developed are displayed. (Author)
[en] Pottery is one of the main productions of the pre-Columbian cultures in the Mesoamerican area. Among the others, the estucado pottery represents a very particular type of ceramic, widespread in Maya territory but still never investigated systematically. The peculiarity of this ceramic lies in the unusual application of the color decoration and in the excellent conservation conditions. Seventeen ceramic fragments from El Salvador have been analysed by Raman spectroscopy, SEM/EDS and XRPD, both as fragments and in cross-sections, in order to investigate the manufacturing technique and to understand the good and unexpected conservation state. In both cases, the presence and the chemical nature of a thin white layer (engobe) between the ceramic bulk and the colored decorations seems to be determinant.
[en] This book deals with historical background of a laser and characteristic of analytical chemistry laser spectrometry using diode laser, analytical chemistry application of laser induce plasma spectral of the law ; biochemical materials analysis using strengthening Raman spectroscopy such as resonance Raman scattering and surface-enhanced Raman scattering spectroscopy, resonant ionization mass spectrometry technology using a laser, remote analysis technique using a laser and realtime ingredient analysis of submicrometer practice in air.
[en] The aim of this study is to analyze the spectral characteristics of ascitic fluid using Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS). The utilization of SERS allows for detection the presence of ascitic fluid components that are not available for revealing when analyzed using conventional Raman spectroscopy. The potential to detect the spectral contribution of a number of pathogenic microorganisms utilizing the proposed SERS-based optical approach has been demonstrated. (paper)
[en] We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature
[en] The main focus of this work is on 2 spectroscopic techniques which enable the researcher to obtain information detailing the crystal structure of an actinide compound. This review presents useful cataloging of phonon Raman spectral data for selected binary actinide compounds. Included are the results from the literature with regard to both powder and single crystal data for various actinide oxides and halides. Where relevant data on the actinide compounds were unavailable , data has been included for actinide-related compounds, primarily lanthanide compounds. Another useful spectroscopic probe of crystal structure of an actinide compound is solid-state spectrophotometry. The electronic configurations of the actinide ions give rise to Laporte-forbidden f-f electronic transitions. These 5f electrons, although shielded, are affected by the crystal field about the actinide ion. In the case of a well-defined crystal, this effect is repeated over a long range. The selection rules which give rise to the intensities of these electronic f-f transitions are governed by the crystal symmetry. It has been found that the observed room-temperature absorption spectra of various trivalent actinide ions in different host matrices exhibiting the same crystal structure are reproducible and are, therefore, very dependent on the crystal structure. (author). 57 refs.; 21 figs.; 26 tabs
[en] Needle-like electromagnetic field has various advantages for the applications in high-resolution imaging, Raman spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device. Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We further produced an elongated focal line by concentrating the SAB via lenses with different NAs and achieved an ultralong longitudinal needle focus. The produced long needle focus will be applied in optical, chemical, and biological sciences
[en] Full text: Plasmonic nanogap arrays have been fabricated by EUV lithography to explore their use as sensing substrates for surface enhanced Raman scattering (SERS). SERS is a well-known effect offering the unique molecule signature of Raman spectroscopy with strongly enhanced signal strengths for detection as low as nanomolar concentrations. Because the signal enhancement often has its origin from randomly distributed hotspots, SERS substrates to-date lack reproducibility over large areas. Our fabrication process of nanogap arrays is found to lead to superior reproducibility with standard deviations well below 5 %. This evolves from the high density of well controlled nanogaps leading to a deterministic origin of SERS. Optimization procedures of fabrication will be presented, and we will discuss the obtained correlation between experiments and simulation enabling an accurate prediction of the sensor performance. (author)