Requirements for Relative Intensity Correction of Raman Spectra Obtained by Column-Summing Charge-Coupled Device Data

Hurst, Wilbur S.; Choquette, Steven J.; Etz, Edgar S.

doi:10.1366/000370207781393235

Cited by 7 publications

(8 citation statements)

References 4 publications

(6 reference statements)

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“…The instrumental transfer function, or the wavelength dependent intensity sensitivity of the detector in the spectrograph, represents a source of uncertainty in these experiments. The transfer function can be estimated experimentally by exposing the spectrograph to a black-body source or spontaneous emission from luminescent glasses [39]. These systems are often expensive, difficult to implement properly, and correction calibrations need to be performed often.…”

Section: Additional Sources Of Uncertaintymentioning

confidence: 99%

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

et al. 2020

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We demonstrate precise determination of atmospheric temperature using vibro-rotational Raman (VRR) spectra of molecular nitrogen and oxygen in the range of 292–293 K. We used a continuous wave fiber laser operating at 10 W near 532 nm as an excitation source in conjunction with a multi-pass cell. First, we show that the approximation that nitrogen and oxygen molecules behave like rigid rotors leads to erroneous derivations of temperature values from VRR spectra. Then, we account for molecular non-rigidity and compare four different methods for the determination of air temperature. Each method requires no temperature calibration. The first method involves fitting the intensity of individual lines within the same branch to their respective transition energies. We also infer temperature by taking ratios of two isolated VRR lines; first from two lines of the same branch, and then one line from the S-branch and one from the O-branch. Finally, we take ratios of groups of lines. Comparing these methods, we found that a precision up to 0.1 K is possible. In the case of O2, a comparison between the different methods show that the inferred temperature was self-consistent to within 1 K. The temperature inferred from N2 differed by as much as 3 K depending on which VRR branch was used. Here we discuss the advantages and disadvantages of each method. Our methods can be extended to the development of instrumentation capable of non-invasive monitoring of gas temperature with broad potential applications, for example, in laboratory, ground-based, or airborne remote sensing.

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Section: Additional Sources Of Uncertaintymentioning

confidence: 99%

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

et al. 2020

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“…This stochastic intensity error may be intrinsic to uncontrolled factors in the data collection. These uncontrolled factors include variable polarization cross sections in a solid sample that can change the intensity when the sample is reoriented; 8 laser heating that can affect the scattering cross section and is a possible issue with spectra collected with different wavelength lasers; 12,31 changes in Raman cross sections that occur with absorption in nonheterogeneous samples; pixel-to-pixel sensitivities across a two-dimensional CCD that add to the signal noise; 16 and differences in the instrument response relating to sample alignment, laser focus, and depth of focus. 8,15 Baseline correction methods, if they are used, may add to the stochastic error (e.g., see the discussion of Fig.…”

Section: Spectral Mappingmentioning

confidence: 99%

“…In principle, Raman reference spectra can be acquired with calibration of the wavenumber axis and either absolute-response or relative-response calibration on the intensity axis so as to make spectra entirely portable between any system. 8,10,–17 Considerable work on spectral standardization has been applied to improve long-term data archiving of reference libraries. 9 However, although long-term data archiving of Raman spectra is making progress toward developing transferable Raman spectral libraries, 6,9,10 these libraries are only now being adapted to handheld systems.…”

Section: Introductionmentioning

confidence: 99%

Adapting Raman Spectra from Laboratory Spectrometers to Portable Detection Libraries

et al. 2013

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Raman spectral data collected with high-resolution laboratory spectrometers are processed into a format suitable for importing as a user library on a 1064 nm DeltaNu first generation, field-deployable spectrometer prototype. The two laboratory systems used are a 1064 nm Bruker Fourier transform (FT)-Raman spectrometer and a 785 nm Kaiser dispersive spectrometer. The steps taken to adapt for device-dependent spectral resolution, wavenumber shifts between instruments, and relative intensity response are described. Effects due to the differing excitation laser wavelengths were found to be minimal, indicating--at least for the near-infrared (NIR)--that data can be ported between different systems, so long as certain measures are taken with regard to the reference and field spectra.

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“…The merits of FT-spectrometers versus dispersive-instruments for specific applications can be deliberated elsewhere; this paper focuses only on the portability of the data. For both FT instruments [29] and for the dispersive instruments (especially smaller units) frequent and accurate wavelength calibration is paramount [30,31]. For this study, it is important to note that while both are FT instruments from the same manufacturer, the instruments are of different wavelength (785 and 1064 nm) and have differentétendues (numerical aperture), different interferometers (linear air-bearing versus mechanical flex-pivot), different detectors (though both are of the same type, power detection as opposed to photon counting), and differing optical components [7,22].…”

Section: Experimental and Calibrationmentioning

confidence: 99%

Demonstrated Wavelength Portability of Raman Reference Data for Explosives and Chemical Detection

Johnson

Jarman

et al. 2012

International Journal of Spectroscopy

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As Raman spectroscopy continues to evolve, questions arise as to the portability of Raman data: dispersive versus Fourier transform, wavelength calibration, intensity calibration, and in particular the frequency of the excitation laser. While concerns about fluorescence arise in the visible or ultraviolet, most modern (portable) systems use near-infrared excitation lasers, and many of these are relatively close in wavelength. We have investigated the possibility of porting reference data sets from one NIR wavelength system to another: We have constructed a reference library consisting of 145 spectra, including 20 explosives, as well as sundry other compounds and materials using a 1064 nm spectrometer. These data were used as a reference library to evaluate the same 145 compounds whose experimental spectra were recorded using a second 785 nm spectrometer. In 128 cases of 145 (or 88.3% including 20/20 for the explosives), the compounds were correctly identified with a mean “hit score” of 954 of 1000. Adding in criteria for when to declare a correct match versus when to declare uncertainty, the approach was able to correctly categorize 134 out of 145 spectra, giving a 92.4% accuracy. For the few that were incorrectly identified, either the matched spectra were spectroscopically similar to the target or the 785 nm signal was degraded due to fluorescence. The results indicate that imported data recorded at a different NIR wavelength can be successfully used as reference libraries, but key issues must be addressed: the reference data must be of equal or higher resolution than the resolution of the current sensor, the systems require rigorous wavelength calibration, and wavelength-dependent intensity response should be accounted for in the different systems.

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Requirements for Relative Intensity Correction of Raman Spectra Obtained by Column-Summing Charge-Coupled Device Data

Cited by 7 publications

References 4 publications

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

Toward Non-Invasive Measurement of Atmospheric Temperature Using Vibro-Rotational Raman Spectra of Diatomic Gases

Adapting Raman Spectra from Laboratory Spectrometers to Portable Detection Libraries

Demonstrated Wavelength Portability of Raman Reference Data for Explosives and Chemical Detection

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