Second Generation Laser Raman Spectrometer for the Deep Ocean Alana Sherman 1, Rachel M. Dunk 1,...
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Transcript of Second Generation Laser Raman Spectrometer for the Deep Ocean Alana Sherman 1, Rachel M. Dunk 1,...
Second Generation Laser Raman Spectrometer for the Deep Ocean Second Generation Laser Raman Spectrometer for the Deep Ocean
Alana Sherman1, Rachel M. Dunk1, Sheri N. White2, William Kirkwood1, Edward T. Peltzer1, Peter Walz1, Farley Shane1, Richard Henthorn1, Karen A. Salamy1, Peter
G. Brewer1
1 Monterey Bay Aquarium Research Institute, Moss Landing, CA2 Woods Hole Oceanographic Institution, Woods Hole, MA
Raman SpectroscopyRaman Spectroscopy• Vibrational spectroscopy
– Based on Raman scattering• The inelastic scattering of
monochromatic radiation
– The shift in energy of the scattered light is equal to the change in the vibrational energy of the molecule
– The Raman spectrum serves as a fingerprint of a substance based on molecular composition and local environment
• Vibrational spectroscopy– Based on Raman scattering
• The inelastic scattering of monochromatic radiation
– The shift in energy of the scattered light is equal to the change in the vibrational energy of the molecule
– The Raman spectrum serves as a fingerprint of a substance based on molecular composition and local environment
• The technique provides the ability to make in situ geochemical measurements in the deep ocean.
• Advantages of Raman Spectroscopy:– Can analyze solids, liquids and gases – Rapid analysis– Can perform in situ analysis targets with
stability zones confined to the deep ocean – Generally non-destructive, and requires
little or no sample preparation
• The technique provides the ability to make in situ geochemical measurements in the deep ocean.
• Advantages of Raman Spectroscopy:– Can analyze solids, liquids and gases – Rapid analysis– Can perform in situ analysis targets with
stability zones confined to the deep ocean – Generally non-destructive, and requires
little or no sample preparation
Raman Spectroscopy in the Ocean
Raman Spectroscopy in the Ocean
• A number of oceanic targets are Raman active:– Gases
•CO2, CH4, N2, O2, H2S, etc.– Minerals
•Sulfides, anhydrite, calcium carbonates, silicates, feldspars, magnetite, etc.
– CO2 and CH4 hydrates
• A number of oceanic targets are Raman active:– Gases
•CO2, CH4, N2, O2, H2S, etc.– Minerals
•Sulfides, anhydrite, calcium carbonates, silicates, feldspars, magnetite, etc.
– CO2 and CH4 hydrates
Raman Spectroscopy in the Ocean
Raman Spectroscopy in the Ocean
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DORISS 1Deep Ocean Raman In Situ Spectrometer
DORISS 1Deep Ocean Raman In Situ Spectrometer
40”
10”
20”
12”
15”
6”
OperationsOperationsROV deployed instrument• The instrument housing is
mounted in the rear drawer of the ROV
• The probe head is carried in front of the ROV
• Communications between Doriss and shipboard computer via Ethernet
• Spectra of targets, video, and environmental data are transmitted back to the operator
ROV deployed instrument• The instrument housing is
mounted in the rear drawer of the ROV
• The probe head is carried in front of the ROV
• Communications between Doriss and shipboard computer via Ethernet
• Spectra of targets, video, and environmental data are transmitted back to the operator
Doriss2
Probe head
Spectrum
Raman Shift (cm-1)
Inte
nsit
y (
Cou
nts
)
DORISS1DORISS1• Scientific Successes
– First deep ocean Raman spectra – 3 years of successful deployments– Collected data from hydrothermal vents at Gorda Ridge,
natural hydrates from Hydrate Ridge– Demonstrated worth of technique– 8 papers published
• Scientific Successes– First deep ocean Raman spectra – 3 years of successful deployments– Collected data from hydrothermal vents at Gorda Ridge,
natural hydrates from Hydrate Ridge– Demonstrated worth of technique– 8 papers published
• Technical Challenges– Prototype instrument not suitable for routine
expeditionary use• Weight and size• Sensitivity• Reliability and robustness
• Technical Challenges– Prototype instrument not suitable for routine
expeditionary use• Weight and size• Sensitivity• Reliability and robustness
DORISS2DORISS2Power SupplyLaser
CCD camera Spectrometer(Kaiser Optical Systems NXRN model)
Computer
DORISS2DORISS2
• Improvements:– U-shaped spectrometer
simplifies housings – 90 lbs lighter than DORISS1
• Can be deployed on vehicles with limited payload
– Increased sensitivity, due to new back illuminated CCD camera
– More robust and reliable
• Improvements:– U-shaped spectrometer
simplifies housings – 90 lbs lighter than DORISS1
• Can be deployed on vehicles with limited payload
– Increased sensitivity, due to new back illuminated CCD camera
– More robust and reliable12” diameter, 30” long
DORISS2 DataCH4-H2S FractionationDORISS2 Data
CH4-H2S Fractionation
CH4-H2S FractionationCH4-H2S Fractionation
Disappearance of the 2610 Δcm-1 H2S peak with time.
In Situ CalibrationIn Situ Calibration• Would like a way to
calibrate intensity and wavelength of the instrument in situ.
• Calibration module experiments:
– Relative intensity correction standard: NIST SRM 2242 luminescent glass
– Wavelength correction: Acrylic and Polystyrene
• Would like a way to calibrate intensity and wavelength of the instrument in situ.
• Calibration module experiments:
– Relative intensity correction standard: NIST SRM 2242 luminescent glass
– Wavelength correction: Acrylic and Polystyrene
NIST SRM2242
Acrylic Polystyrene
Hydraulic Ram
Calibration Module
Probe head
Calibration DataCalibration Data• Less than 2% error
between white light corrected and SRM 2242 corrected spectra
• Difficulty extracting water signal when using stand-off optic
• Less than 2% error between white light corrected and SRM 2242 corrected spectra
• Difficulty extracting water signal when using stand-off optic
Comparison of White Light corrected andSRM 2242 corrected Acrylic spectra
SRM2242 Corrected
WL Corrected
Inte
nsi
ty (
Norm
aliz
ed
)
Raman Shift (cm-1)
Future DevelopmentsFuture Developments
• Improve fiber optic cables
• Integrate new smaller probe head
• Smaller positioner
• Improve fiber optic cables
• Integrate new smaller probe head
• Smaller positioner
Kaiser Optical Systems, MultiRxn Probe
AcknowledgementsAcknowledgements
• Crew of the R/V Western Flyer and R/V Point Lobos• Pilots of the ROV Tiburon and ROV Ventana• Technical support of John Ferreira, Larry Bird, Jim
Scholfield, Cheri Everlove• Kaiser Optical Systems• Steve Choquette at NIST• David & Lucile Packard Foundation
• Crew of the R/V Western Flyer and R/V Point Lobos• Pilots of the ROV Tiburon and ROV Ventana• Technical support of John Ferreira, Larry Bird, Jim
Scholfield, Cheri Everlove• Kaiser Optical Systems• Steve Choquette at NIST• David & Lucile Packard Foundation
Probe head