Remote Raman spectroscopy of minerals at elevated temperature relevant to Venus exploration

Abstract

We have used a remote time-resolved telescopic Raman system equipped with 532 nm pulsed laser excitation and a gated intensified CCD (ICCD) detector for measuring Raman spectra of a number of minerals at high temperature to 970 K. Remote Raman measurements were made with samples at 9-meter in side a high-temperature furnace by gating the ICCD detector with 2 micro-sec gate to minimize interference from blackbody emission from mineral surfaces at high temperature as well as interference from ambient light. A comparison of Raman spectra of gypsum (CaSO 4 .2H 2 O), dolomite (CaMg(CO 3 ) 2 ), and olivine (Mg 2 Fe 2-x SiO 4 ), as a function of temperature shows that the Raman lines remains sharp and well defined even in the high-temperature spectra. In the case of gypsum, Raman spectral fingerprints of CaSO 4 .H 2 O at 518 K were observed due to dehydration of gypsum. In the case of dolomite, partial mineral dissociation was observed at 973 K at ambient pressure indicating that some of the dolomite might survive on Venus surface that is at ~750 K and 92 atmospheric pressure. Time-resolved Raman spectra of low clino-enstatite (MgSiO 3 ) measured at 75 mm from the sample in side the high-temperature furnace also show that the Raman lines remains sharp and well defined in the high temperature spectra. These high-temperature remote Raman spectra of minerals show that time-resolved Raman spectroscopy can be used as a potential tool for exploring Venus surface mineralogy at shorter (75 mm) and long (9 m) distances from the samples both during daytime and nighttime. The remote Raman system could also be used for measuring profiles of molecular species in the dense Venus atmosphere during descent as well as on the surface.

Assessment of the quality of calcination of marbles from Thassos Island using Raman spectroscopy and X-Ray Diffraction

“…Periclase (MgO) and Lime (CaO) crystallize both in the cubic system, with a the crystal lattice similar to the cubic arrangement of Sodium Chloride's (NaCl) structure (Boynton 1980); the latter forbids first-order Raman spectrum as it possesses inversion symmetry (Schlecht and Böckelmann 1973). It is therefore, not possible to detect MgO (or CaO) from the Raman spectrum (Sharma et al 1991). Thus remain controversial in the literature the assignment of the observed Raman bands.…”

Study of Chemical and Physical Characterization of the Natural Dolomite of Ain Mlila-Algeria

“…Thus, in the first stage, it is the beginning of the formation of MgO from ~ 600 °C which manifests itself and which ends at ~ 800 °C then the formation of CaO which continues and ends around ~ 920 °C. So, the carbonate decompositions occur in two steps [13][14][15][16][17][18][19][20][21][22][23][24][25], and the following equations illustrated these processes: CaMg(CO3)2MgO+CaCO3+CO2 step I CaCO3CaO + CO2 step II…”

Planetary Geochemical Investigations Using Raman and Laser-Induced Breakdown Spectroscopy

“…In situ and remote Raman spectroscopy instruments have also been developed for planetary mineralogical analysis. 13–32 The development of these instruments started with a green 532 nm frequency-doubled neodymium-doped yttrium aluminum garnet (Nd:YAG) laser; more recently researchers have started to use ultraviolet (UV) lasers to excite the Raman active vibrational modes. Raman spectroscopy has many advantages as a mineralogical analysis tool because a single laser is capable of exciting nearly any important mineral and the signal can be recorded using a single spectrometer.…”

“…Raman spectroscopy is also completely insensitive to the ambient pressure and is insignificantly sensitive to the atmospheric temperature. 24,28,30…”