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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1

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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