Stray light in low wavenumber Raman spectra and secondary maxima of grating diffraction

The origin of the stray light appearing in the low wavenumber Raman spectra was studied on a double monochromator with a charge coupled device (CCD) detector by theoretical calculations and experimental observations. It is verified that the effect of the secondary maxima of the diffraction grating on the spectrum cannot be ignored, and the secondary maxima of Rayleigh scattering lead to the stray light in low wavenumber Raman spectra. The dependence of operating parameters for a double monochromator with a CCD detector working in the additive mode on the spectral feature has been calculated and experimentally observed. This may give a quantitative suggestion for proper choice of operating parameters that can efficiently suppress stray light in low wavenumber Raman spectra. Copyright © 2011 John Wiley & Sons, Ltd.     

Multiple Characterizations of Automotive Coatings in Forensic Analysis

The analysis of the organic and inorganic compositions is important in forensic characterization of automotive coatings in hit-and-run cases. The functional groups and the organic structures of coating samples could be easily analyzed from the FTIR and Raman spectrum. The elemental components and the possible additive types could be analyzed by the SEM-EDS and ICP-MS in a short time. All four instruments could present useful and unique information on the composition and structures of the coatings, so a method using the four instruments in combination to characterize the coating samples was introduced in this study. Two four-layered samples from a case were compared layer by layer as an example. FTIR, Raman, EDS, and ICP-MS provided similar results on the two samples. The results indicated that the method was accurate and reliable and could be used in real cases.     

Use of a handheld Raman spectrometer for fast screening of microbial pigments in cultures of halophilic microorganisms and in microbial communities in hypersaline environments in nature

A compact handheld Raman spectrometer equipped with a 532 nm excitation laser was used to detect pigments as possible biomarkers in autotrophic (cyanobacteria and purple sulfur bacteria) and heterotrophic halophilic microorganisms (Archaea of the family Halobacteriaceae, Salinibacter). Common as well as less common carotenoids, including α‐bacterioruberin, salinixanthin, and spirilloxanthin derivatives were detected in cell pellets of model organisms belonging to the genera Haloferax, Haloarcula, Halobacterium (Archaea), Salinibacter (Bacteroidetes), and Ectothiorhodospira (Gammaproteobacteria). Direct measurements on such cultures provide fast and reliable identification of pigments. Bacterioruberin was detected as the dominant carotenoid in pellets of cells collected from the saltern crystallizer ponds in Eilat, Israel. Raman analysis of the colored layered microbial communities in a benthic gypsum crust in the saltern evaporation ponds showed signals consistent with the presence of myxoxanthophyll and echinenone carotenoids in the upper orange and dark‐green cyanobacterial layers. Chlorophyll a and phycocyanin expected in the green layer were not detected using the green excitation. Spirilloxanthin dominates the red layer below, inhabited mainly by purple sulfur bacteria. To our best knowledge, this is the first attempt to detect and identify pigments in natural microbial communities consisting of different types of halophilic microorganisms by direct Raman spectrometric measurements using light compact handheld devices. Copyright © 2013 John Wiley & Sons, Ltd.     

Elemental Analyzer-Quadrupole MS Coupling—A Low Cost Equipment for the Simultaneous Determination of Carbon/13C and Nitrogen/15N in Isotopically Enriched Soil and Plant Samples

Abstract

Since the end of the 80s elemental analyzer-isotope ratio mass spectrometer connections have been used for the fast, automatic and highly precise determination of carbon and nitrogen content as well as their isotopic composition in one run. But for artificially enriched stable isotopes as tracer in biological processes and since these processes have a high biological variability anyway (e.g. soil processes) the use of these highly precise but also sophisticated and expensive instruments is not required. In this case the use of a quadrupole mass spectrometer connected with an elemental analyzer can offer a low cost alternative. As shown, such coupling is suitable for automatic simultaneous routine analysis of total nitrogen and carbon and their isotopic enrichment (¹⁵N, ¹³C) in plant material and soils. The relative standard deviation for ¹⁵N and ¹³C determination is 2% To meet this precision a careful sample homogenization by grinding is very important. The duration of one measurement is 6–8 min. depending on whether nitrogen alone or both nitrogen and carbon are determined. This enables a high sample throughput.     

Determining Ppb Mercury Concentrations Using a Spark-Source Mass Spectrometer Sample Changer

Abstract

A probe-type sample changer has been added to a spark-source mass spectrometer enabling the rapid determination of ppb levels of mercury by isotope dilution. The technique has also been used for determining Cd, Hg, and Zr in samples of air, water, and urine.     

Simple,Versatile, Pseudo “Double Beam” Photoacoustic Spectrometer

Abstract

We describe in this paper a “pseudo-double beam” photoacoustic spectrometer using a wide aperture monochromator (F/2) and a very sensitive cell. The double signals required to get the normalized value, i.e., the sample signal and a carbon black reference signal, are obtained by a slow (1.7 Hz) alternating movement of the two cells support, the sample and the reference being alternately placed at the focus point of the beam which is fixed in space and time. The modulation of the light flux is independently ensured by a mechanical chopper. Such an original device associates good performances in resolution (0.7 nm), signal-to-noise ratio (1200 for HO₂O₃ at 450 nm with a 5 nm bandwidth) and normalization in a wide spectral range.     

Reaction Of Nitrides And Oxide With Bath Metals In Gas Analysis In Metals

Abstract

Reactions of two nitrides, an oxide (α-SiaNi, A1N and α-AI2O3) and bath metals (platinum, iron and tin) in graphite capsules were investigated in vacuum fusion analysis by measuring gas extraction curves with a quadrupole mass spectrometer which can simultaneously measure nitrogen and carbon monoxide from the furnace. From the characteristic gas extraction patterns of each bath metals, gas release reaction mechanisms and their temperatures were studied.     

透射式矩形相位光栅的衍射光谱分析

提出了一种计算透射式矩形相位光栅衍射场的简便方法,计算并分析了透射式矩形相位光栅的衍射光谱,给出了相位光栅的衍射光谱与光栅材料的折射率、光栅厚度和入射波长的关系,得到了把衍射光能量集中到1级光谱的条件;并在相位光栅的应用方面作了探讨.     

Quantum fluctuations of superfluorescence delay observed with ultrashort optical excitations

We present an observation of fluctuations in delay times of the yoked-superfluorescence pulses generated in atomic rubidium. The yoked-superfluorescence was induced through two-photon excitation of cascade transitions by ultrashort (∼100 fs) laser pulses. A statistical distribution and fluctuations of delay times were studied as the pump pulse energy varied, effectively changing the number of participating atoms. The standard deviation in the delay-time statistics decreases when the pump power increases. The experimental data support the theoretical model of the quantum fluctuations of superfluorescence.     

X射线条纹相机阴极制备及其绝对标定

为了提升X射线条纹相机阴极性能,提出了一种X射线条纹相机阴极的制作方法,采用此方法制作的阴极衬底薄膜使用聚碳酸酯作为原材料,厚度仅为300 nm,可较大程度降低对X射线的C吸收边效应,对提升阴极性能具有较大益处。利用北京同步辐射光源（BSRF）对制作的Au阴极和CsI阴极进行了绝对标定,给出了两种阴极在60~5500 eV能区范围内的绝对谱响应灵敏度,标定结果表明CsI阴极在60~5500 eV整个能区范围内都具有较高的谱响应灵敏度,即使在C吸收边位置谱响应灵敏度也只降低了约90%,表明阴极性能得到较大提升。