A New Technique for the Elimination of Fluorescence Interference in Raman Spectroscopy

1986 ◽  
Vol 40 (5) ◽  
pp. 583-587 ◽  
Author(s):  
Frank V. Bright ◽  
Gary M. Hieftje
Keyword(s):  
Raman Spectroscopy ◽  
Rhodamine 6G ◽  
Microwave Spectrum ◽  
New Instrument ◽  
Ion Laser ◽  
A New Technique ◽  
Relative Errors ◽  
Argon Ion ◽  
Raman Scatter ◽  
Good Agreement

A new instrument for Raman spectroscopy has been constructed with the use of a cw or mode-locked argon-ion laser as the excitation source and a microwave spectrum analyzer for discrimination between fluorescence and Raman scatter. To demonstrate the new instrument's capability, the weak Raman scatter of water was resolved from the intense fluorescence from rhodamine 6G. Theoretically predicted relative errors in the new procedure are calculated and experimental results are shown to be in good agreement with theory.

Determination of Subnanosecond Fluorescence Lifetimes with a UHF Television Tuner and a cw or Mode-Locked Laser

1986 ◽  
Vol 40 (5) ◽  
pp. 683-687 ◽  
Author(s):  
Frank V. Bright ◽  
Daniel A. Wilson ◽  
Gary M. Hieftje
Keyword(s):  
High Frequency ◽  
Rhodamine 6G ◽  
Instrument Design ◽  
Fluorescence Lifetimes ◽  
New Approach ◽  
Ion Laser ◽  
Subnanosecond Fluorescence ◽  
Argon Ion ◽  
Good Agreement

An inexpensive ultra-high-frequency (UHF) television tuner and an argon-ion laser are employed for the determination of excited-state lifetimes of a series of common fluorophores. Fluorescence lifetimes are determined in the frequency domain; the results are in good agreement with previously reported values and demonstrate the utility of the new approach for subnanosecond measurements. Binary mixtures of rhodamine 6G and rose bengal can also be resolved with the use of this novel instrument design.

Scattering Tomography and Its Application to Sooting Diffusion Flames

1994 ◽  
Vol 116 (1) ◽  
pp. 144-151 ◽  
Author(s):  
M. P. Mengu¨c¸ ◽  
P. Dutta
Keyword(s):  
Diffusion Flames ◽  
Tomographic Reconstruction ◽  
Scattering Coefficient ◽  
Reconstruction Technique ◽  
Transmission Tomography ◽  
Ion Laser ◽  
Series Of Experiments ◽  
Argon Ion ◽  
Good Agreement

A new analytical tomographic reconstruction technique was developed for the determination of the extinction and scattering coefficient distributions in axisymmetric media. This method, called “scattering tomography,” was tested for several particle concentration profiles corresponding to those for diffusion flames. After that, a series of experiments were performed on sooting acetylene flames using an argon-ion laser nephelometer. The experimental results were reduced using both the transmission and scattering tomography techniques to obtain the extinction coefficient profiles. It was shown that in the center of the flame, the results from these two approaches were in good agreement. Scattering tomography can be used to determine both the absorption and scattering coefficient distributions in the medium. In addition to that, it is preferable over the transmission tomography if the medium is optically very thin and particles are predominantly scattering.

Quantitative Analysis of Styrene Monomer in Styrene/Butadiene Latexes Using Raman Spectroscopy

1976 ◽  
Vol 30 (5) ◽  
pp. 542-544 ◽  
Author(s):  
Patricia L. Wancheck ◽  
Lynn E. Wolfram
Keyword(s):  
Raman Spectroscopy ◽  
Liquid Chromatography ◽  
Quantitative Analysis ◽  
Styrene Monomer ◽  
Argon Ion Laser ◽  
Ion Laser ◽  
Styrene Concentration ◽  
Styrene Butadiene ◽  
Argon Ion ◽  
Butadiene Styrene

A simple rapid method has been developed for the quantitative analysis of styrene monomer in butadiene/styrene latexes using Raman spectroscopy. The latex samples were sealed in capillary tubes and scanned under high resolution conditions using a Spex Ramalog 1401 with a Spectra Physics 2 W argon ion laser. The Raman method involves ratioing the olefinic C=C (1632 cm−1) band of styrene monomer to the trans 1:4 C=C (1668 cm−1) band of butadiene in the butadiene/styrene polymer. Typical samples were found to have as low an unreacted styrene concentration as 0.7 wt. %. Reproducibility between samples was found to be within 0.1%. The values of residual styrene obtained by the Raman technique agreed within 0.25% with those obtained by liquid chromatography.

Determination of Azo Dyes by Resonance-Enhanced Raman Spectroscopy

1987 ◽  
Vol 41 (1) ◽  
pp. 117-119 ◽  
Author(s):  
James D. Womack ◽  
Thomas J. Vickers ◽  
Charles K. Mann
Keyword(s):  
Raman Spectroscopy ◽  
Azo Dyes ◽  
Internal Standard ◽  
Nonlinear Behavior ◽  
Limits Of Detection ◽  
Eriochrome Black T ◽  
Exciting Beam ◽  
Ion Laser ◽  
Argon Ion

An examination of the feasibility of using Raman spectroscopy to determine strongly absorbing solutes has been made, with the use of the azo dyes Eriochrome Blue SE, Eriochrome Black T, and Eriochrome Blue Black B as target compounds. These compounds are representative of the large class of dyes which are not easily determined because of their low volatility. They also are examples of compounds which absorb strongly, causing pronounced nonlinear behavior when attempts are made to use resonance-enhanced bands to improve analytical limits of detection, and which produce intense fluorescence which interferes with Raman bands when the strong 514-nm band of the argon-ion laser is used for excitation. The efficacy of internal standard correction for eliminating the effects of self-reversal and variation in intensity of the exciting beam is demonstrated. Limits of detection for the three compounds listed above are 99 ppb, 340 ppb, and 1.5 ppm, respectively.

Growth Mechanism of Direct Writing of Silicon in AR+ Laser CVD

1988 ◽  
Vol 129 ◽  
Author(s):  
Takeshi Nagahori ◽  
Satoru Matsumoto
Keyword(s):  
Direct Writing ◽  
Large Area ◽  
Arrhenius Behavior ◽  
Average Growth Rate ◽  
Average Growth ◽  
Thickness Profile ◽  
Ion Laser ◽  
Laser Cvd ◽  
Argon Ion ◽  
Good Agreement

ABSTRACTSilicon lines are directly written using argon ion laser CVD. The thickness profile of the line has a Gaussian-like shape. The thickness profile is calculated with the model based on Arrhenius behavior. A good agreement is obtained.The effective exposure time is used to analyze the direct writing process. Using it, the average growth rate is estimated to be about 100 times faster than that of conventional large area CVD with the activation energy of 2.4± 0.4eV.

Raman Spectroscopic Identification of Bilirubin-Type Gallstone

1986 ◽  
Vol 40 (8) ◽  
pp. 1099-1103 ◽  
Author(s):  
Siding Zheng ◽  
Anthony T. Tu
Keyword(s):  
Raman Spectroscopy ◽  
Laser Raman Spectroscopy ◽  
Characteristic Line ◽  
Raman Spectroscopic ◽  
Laser Raman ◽  
Stretching Vibration ◽  
Ion Laser ◽  
Spectroscopic Identification ◽  
Spectral Patterns ◽  
Argon Ion

A gallstone from Egypt was examined by laser Raman spectroscopy and identified to be a bilirubin-type stone. The surface of the stone, the subsurface interior, and the center of the stone were irradiated with the 514.5-nm argon-ion laser line. Spectra from the three areas gave similar Raman spectral patterns. Moreover, Raman spectra from the interior of the gallstone were identical to that of bilirubin standard. However, the examination of a Raman spectrum from the outer surface of the stone indicated that it contained cholesterol in addition to bilirubin. Bilirubin has the characteristic line of C=C stretching vibration at 1615 cm−1. Cholesterol has the characteristic line of C(5)=C(6) stretching vibration at 1674 cm−1. Cholesterol also has a strong characteristic line at 1439 cm−1. Therefore, it is quite easy to identify the constituents of gallstone by Raman spectroscopy.

A New Dual-Channel Frequency-Domain Fluorometer for the Determination of Picosecond Rotational Correlation Times

1988 ◽  
Vol 42 (2) ◽  
pp. 272-277 ◽  
Author(s):  
Frank V. Bright ◽  
Curtis A. Monnig ◽  
Gary M. Hieftje
Keyword(s):  
Rhodamine 6G ◽  
Correlation Times ◽  
Dual Channel ◽  
Beta Cyclodextrin ◽  
Significant Difference ◽  
New Instrument ◽  
Rotational Correlation Times ◽  
Ion Laser ◽  
Rotational Correlation

A new dual-channel multifrequency fluorometer is described which employs a mode-locked argon-ion laser as a polarized excitation source. The laser produces high-frequency sinusoidal intensity modulations in the MHz to GHz regime which are used to simultaneously probe the fluorescent molecules. The resulting orthogonally polarized components of the emission are collected by two opposite matched detection channels. Because both the parallel [ I∥(ω)] and perpendicular [ I⊥(ω)] components of the emission are collected simultaneously and at all modulation frequencies, information about the molecules' rotational rate can be rapidly deduced. With the new instrument, rotational correlation times as short as 15 ps can be routinely determined with data-acquisition times as short as 10 ms. Commonly, however, we employ collection times of several seconds to permit the averaging of between 100 and 500 scans. Examples which demonstrate the utility of the new instrument include the determination of the rotational correlation times for rhodamine 6G, fluorescein, and rubrene as a function of solvent viscosity. In addition, results are presented for the resolution of rhodamine 6G associated with beta-cyclodextrin. In the beta-cyclodextrin studies, little spectral (excitation/emission) or temporal (fluorescence lifetime) change was noted upon association. However, a significant difference exists between rotational correlation times of the free fluorophore and the fluorophore included by beta-cyclodextrin. This difference enables the formation constant for the association to be determined, a measurement which would be impossible with conventional techniques.

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