Thermal degradation of organic material by portable laser Raman spectrometry

AbstractRaman spectrometry has been established as an instrument of choice for studying the structure and bond type of known molecules, and identifying the composition of unknown substances, whether geological or biological. This versatility has led to its strong consideration for planetary exploration. In the context of the ExoGeoLab and ExoHab pilot projects of ESA-ESTEC & ILEWG (International Lunar Exploration Working Group), we investigated samples of astrobiological interest using a portable Raman spectrometer lasing at 785 nm and discuss implications for planetary exploration. We find that biological samples are typically best observed at wavenumbers >1100 cm−1, but their Raman signals are often affected by fluorescence effects, which lowers their signal-to-noise ratio. Raman signals of minerals are typically found at wavenumbers <1100 cm−1, and tend to be less affected by fluorescence. While higher power and/or longer signal integration time improve Raman signals, such power settings are detrimental to biological samples due to sample thermal degradation. Care must be taken in selecting the laser wavelength, power level and integration time for unknown samples, particularly if Raman signatures of biological components are anticipated. We include in the Appendices tables of Raman signatures for astrobiologically relevant organic compounds and minerals.

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Determination of Free Silicon in Sintered Silicon Nitride by Laser Raman Spectrometry

Journal of the Ceramic Society of Japan ◽

10.2109/jcersj.97.1466 ◽

1989 ◽

Vol 97 (1132) ◽

pp. 1466-1470

Author(s):

Atsushi CHINO ◽

Hideo IWATA ◽

Sirou TORIZUKA ◽

Kazuya YABUTA

Keyword(s):

Silicon Nitride ◽

Raman Spectrometry ◽

Laser Raman ◽

Free Silicon ◽

Sintered Silicon

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Spectrochemical Analysis of Liquids Using Laser-Induced Plasma Emissions: Effects of Laser Wavelength

Applied Spectroscopy ◽

10.1366/0003702971938812 ◽

1997 ◽

Vol 51 (1) ◽

pp. 87-91 ◽

Cited By ~ 70

Author(s):

W. F. Ho ◽

C. W. Ng ◽

N. H. Cheung

Keyword(s):

Laser Pulse ◽

Signal To Noise Ratio ◽

Laser Wavelength ◽

Spectrochemical Analysis ◽

Liquid Jets ◽

Single Shot ◽

Transient Nature ◽

Vapor Plume ◽

193 Nm ◽

532 Nm

The plasma plume emissions produced by pulsed (∼ 10 ns) laser ablation of liquid jets were monitored for spectrochemical analysis. Laser wavelengths at 532 and 193 nm were used, and sodium was the test analyte. As expected, the 532-nm laser pulse produced very intense plasma continuum emissions that masked the sodium signal for the first hundred nanoseconds, especially near the bright core of the vapor plume. Neither time-gating nor spatial masking could significantly improve the single-shot signal-to-noise ratio, since the transient nature of the emissions placed stringent demands on timing precision while the small size of the plume required accurate mask positioning—both antithetical to the inherent instability of jet ablation. In sharp contrast, the 193-nm laser pulse produced relatively dim plasma flash but intense sodium emissions, rendering it ideal for analytical applications.

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Microdrilled tapers to enhance optical fiber lasers for sensing

Scientific Reports ◽

10.1038/s41598-021-00046-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

R. A. Perez-Herrera ◽

M. Bravo ◽

P. Roldan-Varona ◽

D. Leandro ◽

L. Rodriguez-Cobo ◽

...

Keyword(s):

Optical Fiber ◽

Optical Fibers ◽

Fiber Lasers ◽

Signal To Noise Ratio ◽

Power Level ◽

Single Mode ◽

Optical Signal ◽

Single Mode Fiber ◽

Output Power Level ◽

Linear Cavity

AbstractIn this work, an experimental analysis of the performance of different types of quasi-randomly distributed reflectors inscribed into a single-mode fiber as a sensing mirror is presented. These artificially-controlled backscattering fiber reflectors are used in short linear cavity fiber lasers. In particular, laser emission and sensor application features are analyzed when employing optical tapered fibers, micro-drilled optical fibers and 50 μm-waist or 100 μm-waist micro-drilled tapered fibers (MDTF). Single-wavelength laser with an output power level of about 8.2 dBm and an optical signal-to-noise ratio of 45 dB were measured when employing a 50 μm-waist micro-drilled tapered optical fiber. The achieved temperature sensitivities were similar to those of FBGs; however, the strain sensitivity improved more than one order of magnitude in comparison with FBG sensors, attaining slope sensitivities as good as 18.1 pm/με when using a 50 μm-waist MDTF as distributed reflector.

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Improved Semi-Bit Differential Acquisition Method for Navigation Bit Sign Transition and Code Doppler Compensation in Weak Signal Environment

Journal of Navigation ◽

10.1017/s0373463320000028 ◽

2020 ◽

Vol 73 (4) ◽

pp. 892-911 ◽

Cited By ~ 1

Author(s):

M. Nezhadshahbodaghi ◽

M. R. Mosavi ◽

N. Rahemi

Keyword(s):

Signal To Noise Ratio ◽

Integration Time ◽

Data Sets ◽

Weak Signal ◽

Differential Acquisition ◽

Global Positioning ◽

Signal Environment ◽

Correlation Techniques ◽

Transition Issues ◽

Acquisition Method

The presence of code Doppler and navigation bit sign transitions means that the acquisition of global positioning system (GPS) signals is difficult in weak signal environments where the output signal-to-noise ratio (SNR) is significantly reduced. Post-correlation techniques are typically utilised to solve these problems. Despite the advantages of these techniques, the post-correlation techniques suffer from problems caused by the code Doppler and the navigation bit sign transitions. We present an improved semi-bit differential acquisition method which can improve the code Doppler and the bit sign transition issues in the post-correlation techniques. In order to overcome the phenomenon of navigation bit sign transitions, the proposed method utilises the properties of the navigation bit. Since each navigation bit takes as long as 20 ms, there would be 10 ms correlations duration integration time between the received signal and the local coarse/acquisition (C/A) code in which the navigation bit sign transitions will not occur. Consequently, this problem can be cancelled by performing 10 ms correlations in even and odd units separately. Compensation of the code Doppler is also accomplished by shifting the code phase of the correlation results. To validate the performance of our suggested method, simulations are performed based on three data sets. The results show that the quantity of required input SNR to detect at least four satellites in the proposed method is − 48·3 dB, compared with − 20 dB and − 9 dB, respectively, in traditional differential and non-coherent methods.

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A Biomimetic Miniaturized Microphone Array for Sound Direction Finding Applications Based on a Phase-Enhanced Electrical Coupling Network

Sensors ◽

10.3390/s19163469 ◽

2019 ◽

Vol 19 (16) ◽

pp. 3469

Author(s):

Chien-Chang Huang ◽

Chien-Hao Liu

Keyword(s):

Signal To Noise Ratio ◽

Microphone Array ◽

Incident Angle ◽

Power Level ◽

Electrical Coupling ◽

Direction Finding ◽

Separation Distance ◽

Mechanical Coupling ◽

Sound Direction ◽

Good Signal

In this research, we proposed a miniaturized two-element sensor array inspired by Ormia Ochracea for sound direction finding applications. In contrast to the convectional approach of using mechanical coupling structures for enlarging the intensity differences, we exploited an electrical coupling network circuit composed of lumped elements to enhance the phase differences and extract the optimized output power for good signal-to-noise ratio. The separation distance between two sensors could be reduced from 0.5 wavelength to 0.1 wavelength 3.43 mm at the operation frequency of 10 kHz) for determining the angle of arrivals. The main advantages of the proposed device include low power losses, flexible designs, and wide operation bandwidths. A prototype was designed, fabricated, and experiments examined within a sound anechoic chamber. It was demonstrated that the proposed device had a phase enhancement of 110 ∘ at the incident angle of 90 ∘ and the normalized power level of −2.16 dB at both output ports. The received power levels of our device were 3 dB higher than those of the transformer-type direction-finding system. In addition, our proposed device could operate in the frequency range from 8 kHz to 12 kHz with a tunable capacitor. The research results are expected to be beneficial for the compact sonar or radar systems.

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Diamond Deposition by a Nonequilibrium Plasma Jet

MRS Proceedings ◽

10.1557/proc-250-351 ◽

1991 ◽

Vol 250 ◽

Author(s):

D. G. Keil ◽

H. F. Calcote ◽

W. Felder

Keyword(s):

Substrate Surface ◽

Supersonic Nozzle ◽

Supersonic Jet ◽

Plasma Jet ◽

Nonequilibrium Plasma ◽

Hydrogen Atoms ◽

Raman Spectrometry ◽

Diamond Deposition ◽

Laser Raman ◽

Substrate Temperatures

AbstractA nonequilibrium plasma jet has been used to deposit diamond films on a number of substrates, including silicon, silicon nitride, alumina, and molybdenum. Hydrogen is passed through a glow discharge and expanded through a supersonic nozzle to produce a highly nonequilibrium jet. Methane is added downstream of the nozzle, where it mixes and reacts with the nonequilibrium concentration of hydrogen atoms. The resulting supersonic jet strikes the substrate surface producing a high quality (determined by laser Raman spectrometry) adherent diamond film. Because of the low jet temperature, substrate cooling is unnecessary. Diamond deposition rates have exceeded 2 mg/kWh and I μm/h averaged over 16 cm2 area; good quality films prepared at substrate temperatures below 600 K. have been

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Forward Degenerate Four-Wave Mixing as a Detection Method in Liquid Separation Systems: Improving Detection Limits by Means of a Fabry—Perot Interferometer

Applied Spectroscopy ◽

10.1366/0003702971941395 ◽

1997 ◽

Vol 51 (7) ◽

pp. 1008-1011 ◽

Cited By ~ 6

Author(s):

Gerard Ph. Hoornweg ◽

Tjipke De Beer ◽

Nel H. Velthorst ◽

Cees Gooijer

Keyword(s):

High Performance ◽

Limit Of Detection ◽

Signal To Noise Ratio ◽

Four Wave Mixing ◽

Laser Wavelength ◽

Stray Light ◽

Concentration Limit ◽

Wave Mixing ◽

Fabry Perot ◽

Degenerate Four Wave Mixing

A simple, small, and low-resolution confocal Fabry–Perot interferometer (CFP) has been developed to improve the signal-to-noise ratio (S/N) in forward degenerate four-wave mixing (F-D4WM) detection, coupled to high-performance liquid chromatography (HPLC). Its appropriateness is based on the difference in coherence between the F-D4WM signal and the background stray light. A detailed description of the specially designed CFP and its performance is presented. The improvement in S/N was calculated from the chromatographic peaks recorded after an HPLC separation of 1- and 2-aminoanthraquinone. The concentration limit of detection (LOD) was improved by a factor of 30; for 1-aminoanthraquinone it was 2 × 10−8 M injected (corresponding to about 3 × 10−9 M in the detector cell), which is quite favorable in view of its low molar extinction coefficient being 2000 M−1 cm−1 at the utilized laser wavelength (514.5 nm).

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Quantitative analysis and measurement of carbon isotopic compositions in individual fluid inclusions by micro-laser Raman spectrometry

Analytical Methods ◽

10.1039/c6ay01897a ◽

2016 ◽

Vol 8 (37) ◽

pp. 6730-6738 ◽

Cited By ~ 3

Author(s):

Jiajia Li ◽

Rongxi Li ◽

Bangsheng Zhao ◽

Ning Wang ◽

Jinghua Cheng

Keyword(s):

Raman Spectroscopy ◽

Quantitative Analysis ◽

Fluid Inclusions ◽

Laser Raman Spectroscopy ◽

Raman Spectrometry ◽

Laser Raman ◽

Isotopic Compositions ◽

Carbon Isotopic ◽

Non Destructive

Micro-laser Raman spectroscopy is a non-destructive technique to quantitatively determine the carbon isotopic compositions of CO2 in individual fluid inclusions.

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Laser wavelength selection for Raman spectroscopy of microbial pigments in situ in Antarctic desert ecosystem analogues of former habitats on Mars

International Journal of Astrobiology ◽

10.1017/s147355040300123x ◽

2002 ◽

Vol 1 (4) ◽

pp. 333-348 ◽

Cited By ~ 14

Author(s):

Howell G.M. Edwards ◽

Emma M. Newton ◽

David D. Wynn-Williams ◽

David Dickensheets ◽

Chris Schoen ◽

...

Keyword(s):

Raman Spectroscopy ◽

Raman Spectra ◽

Laser Wavelength ◽

Desert Ecosystem ◽

Nostoc Commune ◽

Raman Spectrometry ◽

Desert Ecosystems ◽

Long Wavelength ◽

Life On Earth

The vital ultraviolet- (UV-) protective and photosynthetic pigments of cyanobacteria and lichens (microbial symbioses) that dominate primary production in Antarctic desert ecosystems auto-fluoresce at short wavelengths. We therefore use a long-wavelength (1064 nm) infrared laser for non-intrusive in situ Raman spectrometry of their ecologically significant compounds (especially pigments). To confirm that the power loss at this longer wavelength is justified to avoid swamping by background fluorescence, we compared Raman spectra obtained with excitation at 1064, 852, 830, 785, 633 and 515 nm. These are typical of lasers used for Raman spectroscopy. We analysed communities of the cyanobacterium Nostoc commune and the highly pigmented lichens Acarospora chlorophana and Caloplaca saxicola. These require screening compounds (e.g. pigments such as scytonemin in cyanobacteria and rhizocarpic acid in the fungal symbiont of lichens). They are augmented by quenching pigments (e.g. carotenoids) to dissipate the energy of free radicals generated by penetrating UV. We also analysed organisms having avoidance strategies (e.g. endolithic communities within translucent rocks, including the common cyanobacterium Chroococcidiopsis). These require accessory pigments for photosynthesis at very low light intensities. Although some organisms gave useable Raman spectra with short-wavelength lasers, 1064 nm was the only excitation that was consistently excellent for all organisms. We conclude that a 1064 nm Raman spectrometer, miniaturized using an InGaAs detector, is the optimal instrument for in situ studies of pigmented microbial communities at the limits of life on Earth. This has practical potential for the quest for biomolecules residual from any former surface life on Mars.

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