Equipment & location: B254

The Micro-Raman Spectroscopy Laboratory (Sections 3.1 and 3.2) uses a Horiba Jobin Yvon LabRAM HR Evolution Raman spectrometer equipped with a motordriven x-y table and an Olympus optical microscope. Depending on the experiment two different laser light sources can be used for investigations on gas hydrates: a Nd:YAG laser providing a 532 nm line and 785 nm wavelength-stabilized laser diode. The confocal technique provides an efficient way to obtain interference-free Raman spectra of specimens embedded in transparent matrix (grain mounts, thin sections) but also for gas hydrate crystals.

Application of Raman spectroscopy in earth sciences:

• identification of mineral phases
• composition of the gas phase in fluid and melt inclusions (qualitative and semi-quantitative)
• detection of anions in fluid inclusions (CO₃^2-, HCO₃^-, PO₄^3-, BO₄^3- , SO₄^2- , HS^-, OH^- )
• identification of crystalline dimorphs and polymorphs (e.g., calcite-aragonite; sillimanite- kyanite- andalusite)

Applications in gas hydrate research:

• determination of the composition of gas hydrates (qualitative and semi-quantitative) during formation, growth and equilibrium state
• determination of hydrate structure and cage occupancies
• investigation on hydrate formation kinetics
• mapping of natural and synthesized samples – determination of co-existing phases

For Raman studies at ambient pressure and temperatures between -196°C and 1500°C we use LINKAM stages. For Raman spectroscopic investigation of gas hydrates we use a custom made pressure cell with a volume of about 400 µl which can be used at pressures up to 10 MPa and in the temperature range between -30°C and about 60°C.