scholarly journals Optimizing the Raman signal for characterizing organic samples: The effect of slit aperture and exposure time

2009 ◽  
Vol 23 (2) ◽  
pp. 71-80 ◽  
Author(s):  
João Carlos Lázaro ◽  
Marcos Tadeu T. Pacheco ◽  
Kátia Calligaris Rodrigues ◽  
Carlos José de Lima ◽  
Leonardo Marmo Moreira ◽  
...  
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Exposure Time ◽  
Spectral Resolution ◽  
Spectral Intensity ◽  
Band Width ◽  
Infrared Light ◽  
Raman Signal ◽  
Specific Chemical ◽  
Time Exposure

The present work is focused on the influence of the slit aperture and time exposure of the infrared light on the Charge Coupled Device (CCD) in relation to their physical effects, in order to improve the Raman spectrum characteristics. Indeed, the alterations in slit aperture and CCD time exposure affect significantly important spectral properties, such as the spectral intensity, Signal to Noise Ratio (SNR) and band width resolution of the Raman spectra. Therefore, the present proposal has the aim of to found the optimum conditions of instrumental arrangement, involving the minimum collection time and maximum signal quality in dispersive Raman spectrometers. Samples of dehydrated human teeth and naphthalene were evaluated with a Raman dispersive spectrometer employing excitation wavelength of 830 nm in several integration times and spectrometer slit apertures. The analysis of the spectral intensity, SNR and band width of selected Raman peaks allowed to infer that these properties of a dispersive Raman spectrum depend directly of the exposure time on the detector as well as spectrograph slit aperture. It is important to register that the higher SNR was obtained with higher exposure time intervals. To the samples evaluated in the present article, the band width has lower values for slit apertures of 100–150 μm, i.e., in this aperture range the spectral resolution is maximum. On the publisher-id hand, the intensity and SNR of the Raman spectra becomes optimal for slit apertures of 150–200 μm, since this aperture does not affect significantly the integrity of the Raman signal. In this way, we can to propose that in approximately 150 μm, it is possible to obtain an optimum condition, involving spectral resolution as well as SNR and spectral intensity. In any case, depending of the priorities of each spectral measurement, the instrumental conditions can be altered according with the necessities of each specific chemical analysis involving a determined sample. The present data are discussed in details in agreement with recent data from literature.

Illumination- and Annealing-Induced Changes in the Infrared and Raman Spectra of a-Si:H

2001 ◽  
Vol 664 ◽  
Author(s):  
L.-F. Arsenault ◽  
S. Lebiba ◽  
E. Sacher ◽  
A. Yelon
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Qualitative Agreement ◽  
Raman Signal ◽  
Infrared And Raman Spectra ◽  
Matrix Elements ◽  
Short Term ◽  
Phonon Peak ◽  
Induced Changes ◽  
Ir And Raman

ABSTRACTWe have investigated the changes, produced by light-soaking, in both the IR and Raman responses of the Si-Hn stretching peaks in the 2000-2100 cm−1 range. Our observations of the IR response are in qualitative agreement with those of Kong and co-workers [1]: that is, short-term light soaking produces an increase in the intensity of the signal and a simultaneous shift to lower frequency. In contrast, short-term light soaking decreases the total intensity of the Raman signal in the 2000-2100 cm−1 range, when normalized to the TO phonon peak at about 480 cm−1. In both cases, these modifications are reversed on annealing at 200° C. We suggest that these changes are attributable to alterations in the environments of the Si-Hn bonds, with the resultant transfer of intensity between IR and Raman matrix elements. Details of the evolution of the components of the Raman spectrum in the 2000-2100 cm−1 range are presented, and compared with IR changes in the same range.

THE RAMAN SPECTRUM OF ETHANE

1955 ◽  
Vol 33 (10) ◽  
pp. 588-599 ◽  
Author(s):  
J. Romanko ◽  
T. Feldman ◽  
H. L. Welsh
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Spectral Resolution ◽  
Raman Band ◽  
Point Group ◽  
Infrared Band ◽  
Torsional Frequency

The rotational and rotation-vibrational Raman spectra of gaseous ethane at 1–3 atm. pressure have been photographed with a spectral resolution of approximately 1 cm.−1. Analyses of the rotational structures of the ν1 and ν2 totally symmetric bands were carried out; only the Q branch of the ν2 band was observed. The structures of the degenerate ν10 and ν11 bands were analyzed; however, no trace of ν12 was found. The structure of the ν10 band shows beyond doubt that the point group of the molecule is D3d. From the ν11+ν4 infrared band, and the ν11 Raman band, the value, 278.4 cm.−1, is deduced for the torsional frequency ν4.

Quantitative Analysis of Raman Spectra in Si/SiGe Nanostructures

2013 ◽  
Vol 1510 ◽  
Author(s):  
Selina Mala ◽  
Leonid Tsybeskov ◽  
Jean-Marc Baribeau ◽  
Xiaohua Wu ◽  
David J. Lockwood
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Quantitative Analysis ◽  
Raman Spectra ◽  
Instrumental Response ◽  
Sample Surface ◽  
Stray Light ◽  
Raman Signal ◽  
Longitudinal Acoustic ◽  
Local Sample

ABSTRACTWe present comprehensive quantitative analysis of Raman spectra in two-(Si/SiGe superlattices) and three-(Si/SiGe cluster multilayers) dimensional nanostructures. We find that the Raman spectra baseline is due to the sample surface imperfection and instrumental response associated with the stray light. The Raman signal intensity is analyzed, and Ge composition is calculated and compared with the experimental data. The local sample temperature and thermal conductivity are calculated, and the spectrum of longitudinal acoustic phonons is explained.

scholarly journals Raman Spectra of Nanodiamonds: New Treatment Procedure Directed for Improved Raman Signal Marker Detection

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Raoul R. Nigmatullin ◽  
Dumitru Baleanu ◽  
Diana Povarova ◽  
Numan Salah ◽  
Sami S. Habib ◽  
...  
Keyword(s):  
Raman Spectra ◽  
High Refractive Index ◽  
Spectroscopic Studies ◽  
Raman Signal ◽  
Heating Rates ◽  
Inert Core ◽  
Optimal Linear ◽  
Linear Smoothing ◽  
New Treatment ◽  
Increasing Temperature

Detonation nanodiamonds (NDs) have shown to be promising agents in several industries, ranging from electronic to biomedical applications. These NDs are characterized by small particle size ranging from 3 to 6 nm, while having a reactive surface and a stable inert core. Nanodiamonds can exhibit novel intrinsic properties such as fluorescence, high refractive index, and unique Raman signal making them very attractive imaging agents. In this work, we used several nanodiamond preparations for Raman spectroscopic studies. We exposed these nanodiamonds to increasing temperature treatments at constant heating rates (425–575°C) aiding graphite release. We wanted to correlate changes in the nanodiamond surface and properties with Raman signal which could be used as adetection marker. These observations would hold potential utility in biomedical imaging applications. First, the procedure of optimal linear smoothing was applied successfully to eliminate the high-frequency fluctuations and to extract the smoothed Raman spectra. After that we applied the secondary Fourier transform as the fitting function based on some significant set of frequencies. The remnant noise was described in terms of the beta-distribution function. We expect this data treatment to provide better results in biomolecule tracking using nanodiamond base Raman labeling.

The resonance Raman spectra and excitation profiles of some 4-sulfamylazobenzenes

1977 ◽  
Vol 55 (9) ◽  
pp. 1444-1453 ◽  
Author(s):  
Kamal Kumar ◽  
P. R. Carey
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Resonance Raman ◽  
Valence Bond ◽  
Wavelength Dependence ◽  
Accurate Estimation ◽  
Intensity Changes ◽  
Stretching Vibration ◽  
Resonance Raman Spectra ◽  
Frequency Changes

The resonance Raman spectra of three pharmacologically important sulfonamides, 4-sulfamyl-4′-dimethylaminoazobenzene (1), 4-sulfamyl-4′-hydroxyazobenzene (2), and 4-sulfamyl-4′-aminoazobenzene (3), are compared with those of analogues lacking the sulfonamide group. The —SO2NH2 moiety does not directly contribute intense or moderately intense bands to the resonance Raman spectra of 1, 2, and 3. However, —SO2NH2 ionization is reflected by frequency changes in a band near 1140 cm−1 and intensity changes in the 1420 cm−1 region. The normal Raman spectrum of 2 confirms that the intensity changes reflect —SO2NH2 ionization rather than unrelated changes in vibronic coupling. The effect of —OH ionization on the resonance Raman spectrum of 2 emphasizes that caution must be exercised when relating spectral perturbations to changes in contributions from valence bond type structures. Resonance Raman excitation profiles for the 1138, 1387, and 1416 cm−1 bands of 2 show that these bands gain intensity by coupling with the electronic transitions in the 240 to 450 nm region and that, more than 1000 cm−1 to the red of λmax, the wavelength dependence can be closely reproduced by the FB type terms of Albrecht and Hutley. The excitation profile for each band shows evidence for structure in the 470 nm region, although lack of sufficient excitation wavelengths prevents accurate estimation of the spacing. Under conditions of rigorous resonance the intense Raman lines all occur in the 1400 cm−1 region, i.e. they are 'bunched' in the region known to contain the —N=N— stretching vibration.

Studies of the Jahn - Teller effect IV. The vibrational spectra of spin-degenerate molecules

1962 ◽  
Vol 255 (1050) ◽  
pp. 31-53 ◽  
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Vibrational Spectra ◽  
Physical Theory ◽  
Vibronic Coupling ◽  
Infra Red ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Active Vibration ◽  
Degenerate States

The physical theory necessary for interpreting the vibrational spectra of spin-degenerate molecules is developed in this paper. Particular attention is paid to those molecules whose behaviour is expected to be markedly different from that of both orbitally non-degenerate molecules and those with purely spatial degeneracy. These include certain Kramers degenerate molecules, whose Raman spectra are expected to contain reverse-polarized contributions, and also tetrahedral and octahedral molecules in fourfold degenerate states. The case of a fourfold degenerate octahedral molecule is investigated in the limits of strong vibronic coupling by one of the Jahn—Teller active vibrations (e g and t 2g ). It turns out that the forbidden t 2u vibration may be infra-red active, that the Raman spectrum may contain reverse-polarized contributions and that both infra-red and Raman spectra may contain strong progressions of bands involving multiple excitations of the vibronically active vibration.

Laser Induced Oxidation Effects in Bismuth Thin Films

2012 ◽  
Vol 1477 ◽  
Author(s):  
Marco A. Zepeda ◽  
Michel Picquart ◽  
Emmanuel Haro-Poniatowski
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Laser Irradiation ◽  
Raman Spectra ◽  
Exposure Time ◽  
Oxidation Process ◽  
Energy Dispersion Spectroscopy ◽  
Irradiation Power ◽  
Pure Bismuth ◽  
532 Nm

ABSTRACTThe Laser induced oxidation process of bismuth was investigated using Raman spectroscopy. Upon laser irradiation (λ = 532 nm) pure Bismuth was transformed gradually into Bi2O3. Raman spectra of the samples showed the characteristics peaks for pure Bi located at 71 cm-1 and 96 cm-1. The oxidation process was monitored by Raman spectra with four additional bands located at about 127 cm-1, 241 cm-1, 313 cm-1 and 455 cm-1. Maintaining constant the exposure time of irradiation, the intensity of these bands depended on laser irradiation power. The presence of Bi2O3 in the sample was confirmed through by energy dispersion spectroscopy (EDS).

The Change in the Raman Spectra of Chloroprene and Isoprene in the Polymerization Process

1943 ◽  
Vol 16 (4) ◽  
pp. 841-847
Author(s):  
A. Gantmacher ◽  
S. Medvedev
Keyword(s):  
Raman Spectrum ◽  
Double Bond ◽  
Raman Spectra ◽  
Polymer Molecule ◽  
Polymerization Process ◽  
High Polymer ◽  
Single Bond ◽  
Double Bonds ◽  
Continuous Background ◽  
Single Bonds

Abstract 1. When chloroprene and isoprene polymerize, besides the frequency characterizing the conjugate double bond in the monomer, there appears a higher frequency corresponding to the isolated double bond in the polymer. In the polymerization process, the intensity of the frequency of the conjugate double bond decreases and the intensity of the frequency of the isolated double bond increases. Because of the increase in the number of single bonds in the polymer, the intensity of the frequency of the single bond 1005 in the polymer is considerably greater than in the monomer. 2. Even in the case of the samples with high polymer contents (greater than 50 per cent), the intensity of the frequency of the conjugate double bond is considerably greater than the intensity of the frequency of the isolated double bond. This is attributable to the fact that part of double bonds disappear during polymerization. 3. The Raman spectra of the chloroprene and isoprene polymers differ essentially from those of the monomers. To characterize the frequencies of vibration in the polymer molecule, it is essential to investigate its Raman spectrum in a medium free of the monomer. 4. The formation of highly polymeric molecules on polymerization does not result in an increase in the intensity of the continuous background in spectrograms.

Theoretical calculations of electronic Raman effects of the NO and O2 molecules

1970 ◽  
Vol 48 (14) ◽  
pp. 1664-1674 ◽  
Author(s):  
D. W. Lepard
Keyword(s):  
Raman Spectrum ◽  
Raman Spectra ◽  
Theoretical Calculations ◽  
Diatomic Molecules ◽  
Wave Functions ◽  
Rotational Structure ◽  
Intermediate Case ◽  
First Time

This paper presents a method for calculating the relative intensities and Raman shifts of the rotational structure in electronic Raman spectra of diatomic molecules. The method is exact in the sense that the wave functions used for the calculations may belong to any intermediate case of Hund's coupling schemes. Using this method, theoretical calculations of the pure rotational and electronic Raman spectrum of NO, and the pure rotational Raman spectrum of O2, are presented. Although a calculated stick spectrum for NO was previously shown by Fast et al., the details of this calculation are given here for the first time.

Spectroscopic requirements for Raman instrumentation on a planetary lander: potential for the remote detection of biosignatures on Mars

2004 ◽  
Vol 3 (2) ◽  
pp. 165-174 ◽  
Author(s):  
S.E. Jorge Villar ◽  
H.G.M. Edwards
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Spectral Resolution ◽  
Detection Sensitivity ◽  
Remote Detection ◽  
Spectral Identification ◽  
Scan Time ◽  
Time Parameters ◽  
Raman Spectral ◽  
Non Destructive

The special characteristics of Raman spectroscopy (relative insensitivity to water, non-destructive detection, sensitivity to bio- and geosignatures, molecular structural composition information, etc.) together with the development of miniaturized Raman spectrometers make the consideration of this technique for future robotic landers on planetary surfaces, particularly Mars, a very interesting option. The development of light and rugged Raman spectrometers limits the possible scope of the instrumentation which has particular importance in the recognition of biomolecular and mineral signatures. In this work, we evaluate the spectral resolution and scan time parameters and the effect that they have on the Raman spectra of extremophilic biomolecules, together with the wavenumber ranges which are critical for the detection of life signals. This is of vital relevance for the design of miniaturized Raman spectrometer systems. From our results, we conclude that for extraterrestrial biological signatures unambiguous Raman spectral identification provided with a minimum of 16 cm−1 spectral resolution is required for the most significant biosignature wavenumber range in the 1700–700 cm−1 region.

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