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Theoretical Spectra (theoretical + spectrum)
Selected AbstractsImprovement of rotational CARS thermometry in fuel-rich hydrocarbon flames by inclusion of N2 -H2 Raman line widthsJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2009Alexis Bohlin Abstract In rotational coherent anti-Stokes Raman spectroscopy (CARS) thermometry applied to air-fed flames, the temperature sensitivity mainly depends on the intensity distribution of the nitrogen spectral lines. Temperatures are estimated by numerical fitting of theoretical spectra to experimental ones, and one uncertainty in the calculation of theoretical CARS spectra for specific flame conditions is the accuracy in utilized line-broadening coefficients. In a previous article, self-broadened N2 -N2 line widths were considered in the spectral calculations as well as those of N2 -CO, N2 -CO2, N2 -H2O, and N2 -O2. In the present article, we also include N2 -H2 line widths calculated from a newly developed model, and it is shown that the evaluated temperature from flame spectra increases with increasing mole fractions of hydrogen. For example, in a very rich flame at , = 2.5, the use of available line-width data for all major species gives a temperature raise of 72 K at a temperature of ,1700 K, in comparison with using self-broadened N2 -N2 line widths only. Half of this temperature raise is related to the inclusion of N2 -H2 line widths. This article emphasizes the importance of using adequate line-broadening models for rotational CARS thermometry in flames. Copyright © 2009 John Wiley & Sons, Ltd. [source] X-ray excited optical luminescence from crystalline siliconPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 9 2009Paul Gundel Abstract Synchrotron based X-ray excited optical luminescence (XEOL) has been measured with many direct bandgap semiconductors. We present XEOL measurements on crystalline silicon (Si), obtained despite of its indirect bandgap and the consequently low luminescence efficiency. Spectra of monocrystalline and multicrystalline (mc) Si at room temperature are compared to theoretical spectra. A possible application in the synchrotron-based research on mc-Si is exemplified by combining XEOL, X-ray fluorescence (XRF) spectroscopy, photoluminescence (PL) spectroscopy, and microscope images of grain boundaries. This approach can be utilized to investigate the recombination activity of metal precipitates, to analyze areas of different lifetimes on mc-Si samples and to correlate additional material parameters to XRF measurements. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Properties of the fundamental absorption edge of InN crystals investigated by optical reflection and transmission spectraPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2004Y. Ishitani Abstract InN crystals are grown on sapphire substrates using a plasma-assisted MBE system. The carrier concentrations of the samples are 2 × 1018,1 × 1019 cm,3. Optical transmission and reflectance measurements are performed on these samples in the temperature range 5,300 K. The resultant spectra are analysed by theoretical spectra based on the LO-phonon,plasmon coupling scheme for the phonon-related factor and non-parabolic conduction band structure for the electronic transition factor. The observed absorption edge is estimated to originate from a valence band to conduction band transition rather than a defect- or impurity-related transition. It is estimated that InN has a bandgap energy in the range 0.59,0.65 eV. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Estimating false discovery rates for peptide and protein identification using randomized databasesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 12 2010Gregory Hather Abstract MS-based proteomics characterizes protein contents of biological samples. The most common approach is to first match observed MS/MS peptide spectra against theoretical spectra from a protein sequence database and then to score these matches. The false discovery rate (FDR) can be estimated as a function of the score by searching together the protein sequence database and its randomized version and comparing the score distributions of the randomized versus nonrandomized matches. This work introduces a straightforward isotonic regression-based method to estimate the cumulative FDRs and local FDRs (LFDRs) of peptide identification. Our isotonic method not only performed as well as other methods used for comparison, but also has the advantages of being: (i) monotonic in the score, (ii) computationally simple, and (iii) not dependent on assumptions about score distributions. We demonstrate the flexibility of our approach by using it to estimate FDRs and LFDRs for protein identification using summaries of the peptide spectra scores. We reconfirmed that several of these methods were superior to a two-peptide rule. Finally, by estimating both the FDRs and LFDRs, we showed for both peptide and protein identification, moderate FDR values (5%) corresponded to large LFDR values (53 and 60%). [source] Photochemistry of CH3Mn(CO)5: A multiconfigurational ab initio studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2006Leticia González Abstract The electronic spectroscopy of CH3Mn(CO)5 has been investigated by means of ab initio multiconfigurational MS-CASPT2/CASSCF calculations. The absorption spectrum is characterized by a series of Metal-Centered (MC) excited states in the UV energy domain (below 290 nm) that could be responsible for the observed photoreactivity starting at 308 nm. The upper part of the spectrum is overcrowded between 264 and 206 nm and dominated by a high density of Metal-to-Ligand-Charge-Transfer (MLCT) states corresponding mainly to 3dMn , ,*CO excitations. A non-negligible contribution of Metal-to-,-Bond-Charge-Transfer (MSBCT) states corresponding to 3dMn , ,*Mn-CH3 excitations is also present in the theoretical spectrum of CH3Mn(CO)5. However, in contrast to other transition metal hydrides and methyl substituted (HMn(CO)5, HCo(CO)4, and CH3Co(CO)4) these MSBCT transitions do not participate to the lowest bands of the spectrum as main contributions. The photochemistry of CH3Mn(CO)5, namely the loss of a CO ligand vs. the metal-methyl bond homolysis, is investigated by means of MS-CASPT2 states correlation diagrams. This study illustrates the complexity of the photodissociation mechanism of this class of molecules, which involves a large number of nearly degenerate electronic states with several channels for fragmentation. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006 [source] Optimal signal bandwidth for the recording of surface EMG activity of facial, jaw, oral, and neck musclesPSYCHOPHYSIOLOGY, Issue 1 2001A. van Boxtel Spontaneous pericranial electromyographic (EMG) activity is generally small and is contaminated by strong low-frequency artifacts. High-pass filtering should suppress artifacts but affect EMG signal power only minimally. In 24 subjects who performed a warned simple reaction time task, the optimal high-pass cut-off frequency was examined for nine different pericranial muscles. From four experimental conditions (visual and auditory reaction signals combined with hand and foot responses), 1-min EMG recordings were selected (bandwidth: 0.4,512 Hz) and divided into 60 1-s data segments. These segments were high-pass filtered, the ,3-dB cut-off frequency varying from 5 to 90 Hz, and subjected to power spectral analysis. Optimal high-pass filter frequencies were determined for the mean power spectra based on visual estimation or comparison with a theoretical spectrum of the artifact-free EMG signal. The optimal frequencies for the different muscles varied between 15 and 25 Hz and were not influenced by stimulus or response modality. For all muscles, a low-pass filter frequency between 400 and 500 Hz was appropriate. [source] Infrared spectrum of potassium-cationized triethylphosphate generated using tandem mass spectrometry and infrared multiple photon dissociationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2009Gary S. Groenewold Tandem mass spectrometry and wavelength-selective infrared photodissociation were used to generate an infrared spectrum of gas-phase triethylphosphate cationized by attachment of K+. Prominent absorptions were observed in the region of 900 to 1300,cm,1 that are characteristic of phosphate PO and POR stretches. The relative positions and intensities of the IR absorptions were reproduced well by density functional theory (DFT) calculations performed using the B3LYP functional and the 6-31+G(d), 6-311+G(d,p) and 6-311++G(3df,2pd) basis sets. Because of good correspondence between experiment and theory for the cation, DFT was then used to generate a theoretical spectrum for neutral triethylphosphate, which in turn accurately reproduces the IR spectrum of the neat liquid when solvent effects are included in the calculations. Copyright © 2009 John Wiley & Sons, Ltd. [source] | |||||||||||||