| From conceptual modern,nearby laser crystal to ancient,remote lunar and martian soil,the topic of this thesis seems to have made a big jump.However,the spectroscopy of them link all these dramatic things together.The author was supported as a training student between Shandong University and Washington University in St.Louis,where he studied planetary spectroscopy guided by Dr.Alian Wang.Before that,the author's major interest was spectroscopy of tungstate laser crystal by the guidance of Professor Xia Hairui,and then he did some research on the spectroscopy of lunar soil and Mar's related ferric sulfates.1)Spectroscopic and Thermal Properties of Tungstates Laser CrystalsIt's nearly 50 years since the discovery of laser,which have been widely used in our life such as optical storage,optical communications and medical treatment,etc. Nowadays,a series of tungstate crystals including KGdWO4,CaWO4,and BaWO4, etc,have attracting more and more attentions due to their large nonlinear optical susceptibilityχ3,making them to be efficient frequency converters by SRS.The Yb3+ doped double tungstates have show their great potential for building practical diode-pumped continuous wave and ultra-short pulsed lasers due to their advantages of simple manifold,broad absorption and emission cross sections,negligible concentration quenching,low thermal load,etc.The first part of this thesis is the systematic investigations of lattice vibration spectra and thermal properties for three typical tungstate laser crystals SrWO4. Yb:K(LuWO4)2(Yb:KLuW)and Yb:NaGd(WO4)2(Yb:NGW).Detailed work as follows,1)Large size SrWO4 single crystal was grown by Czochralski method.Raman scattering and infrared absorbance spectra measurement was performed to assign the phonons properties of the crystal combined with the help of Space group analysis based on C4h6(I41/α).The experiments show that the characteristic lattice vibrational modes of SrWO4 arise mainly from the internal vibrations of the WO4 tetrahedra and partly by the external SrO8 polyhedra modes.Two of the strongest peaks 923 cm-1(v1)and 841 cm-1(v3),which obtain narrow peak width, can be used in steady SRS experiments.Thermal properties including thermal expansion,specific heat,thermal diffusion and conductivities of the crystal were obtained.The specific heat remains almost constant with a value of 0.30-0.34 J·g-1·K-1in the temperature range from 333.15 to 1063.15K,which is in compliance with the Dulong-Petit law.The average thermal expansion coefficient in between 373.15 and 1173.15K are as follows,,αa=5.1×10-6/K,αb=5.4×10-6/K,αc=17.2×10-6/K.The value along c is 3 times larger than that of a or b direction, which suggest a large anisotropy of thermal expansion.However,the thermal diffusion and conductivity show small anisotropy as shown by ka/kc=1.06.We explained those anisotropies from the viewpoint of crystal structure and its correlation with lattice vibration spectra.The external modes derived from Sr atoms in the crystal play an important role in the thermal expansion and especially the thermal diffusion and conductivity properties.From the point views of lattice vibration and thermal properties,SrWO4 crystal is a promising candidate for Raman lasers.2)Monoclinic 5at%Yb doped KLuW crystal was sucessfully grown by TSSG. Space group analysis was conducted based on C2h6(C2/c),which agrees with the results of polarized Raman spectra and infrared spectra.The all-symmetric vibration was ascribed by WO6 octahedron's six modes.Due to the large anisotropy of KLuW,the v6 was observed in the spectra,v6 is a silent mode due to the selection rule of octahedron,however,in a crystal field,it was activated by the large distortion of octahedrons.As a self-Raman crystal,the linewidth of Raman peaks 908 cm-1(v1)and 756cm-1(v3)reach to 12.5cm-1and 16.6cm-1,with a relaxation time to be 849.4fs and 639.6fs respectively,indicating that it is a promising SRS Raman crystal.The specific heat of Yb:KLuW,which seems lower than that of SrWO4,varies between 0.27 and 0.32 J·g-1·K-1in the temperature range from 303.15 to 723.15K,which also agrees with the Dulong-Petit law.We got the ellipsoid of thermal expansion coefficient for Yb:KLuW.The calculated principal thermal expansion coefficients of Yb:KLuW between 323.15 and 723.15K are:Î±â… =8.366×10-6/K,αⅡ=3.2×10-6/K, aâ…¢=14.934×10-6/K.The angle betweenαⅢand c axis is as small as 4.134°and the value ofαⅢis 4 times larger thanαⅡ,which suggests a very large anisotropy of thermal expansion.We got the ellipsoid of thermal expansion diffusion coefficients.At 303.15K.the principal thermal diffusion coefficients of Yb:KLuW are:kâ… =2.698 Wm-1K-1,kâ…¡=2.361 Wm-1K-1,kâ…¢=4.225 Wm-1K-1,which also show large anisotropy.Those large anisotropy,which was ascribed by the different link ways of the WO6 octahedrons.In a word,from our lattice studies especially the polarized Raman measurement,Yb doped KLuW is a promising medium for SRS operations.3)Large size Yb:NGW single crystal was grown by Czochralski method.We conducted the space group analysis on the Space group S42(I(?)).Raman scattering and infrared absorbance spectra analysis show that the Raman properties of Yb:NGW can be well explained by the space group I(?).The characteristic lattice vibrational modes of Yb:NGW arise mainly from the internal vibrations of the WO4 tetrahedra and partly by the external Na/GdO8 polyhedra modes.The new Raman peak E(LO)at 698 cm-1indicate noncentrosymmetrical structure,which in turn confirm the availability of the Space group analysis under space group I(?). The linewidth of Raman peaks 919cm-1(v1)and 814cm-1(v3)reach to 22.2 and 42.3cm-1,indicating a promising transient SRS Raman crystal.Comparing to SrWO4 and Yb:KLuW,the specific heat is higher with value 0.35 Jg-1K-1～0.58 Jg-1K-1between 323.15 and 1073.15K;The average thermal expansion coefficient in between 323.15 and 723.15K are as follows,αa=9.30×10-6K-1,αc=19.21×10-6K-1,which show relatively smaller anisotropy than the other two crystals.At 303.15K,the calculated thermal conductivity coefficients of Yb:NGW are 1.102 Wm-1K-1and 1.250Wm-1K-1along a and c direction,respectively,much smaller than those of SrWO4 and Yb:KLuW,which could also be interpreted from the viewpoint of crystal structure and its correlation with lattice vibration spectra. From the viewpoints of lattice vibration and thermal properties,Yb:NGW is a promising candidate for the SRS lasers in the femto-second regime.2.Spectroscopy,Mineralogy and Geochemistry Studies on Four Typical Apollo soilsAs we come into a new era for lunar exploration,it will be beneficial to examine the returned Apollo and Luna samples by various modern analytical techniques and newly developed methodologies.Comparing to the Vis-NIR spectra and thermal emission spectra,Laser Raman spectroscopy(LRS)can provide definitive mineralogical information,including mineral identification,mineral proportions,and major mineral chemistry thus is supposed to be one of the best scientific payload for landed planetary missions(for Moon,Mars,Venus,and asteroids,etc).Mid-IR spectroscopy yields additional information on fundamental vibrational modes under different selection rules.Vis-NIR spectroscopy(commonly used for orbital remote sensing)offers information on overtone and combinational modes,and electronic transition modes.A combination of these three spectroscopic methods will not only provide a comprehensive set of information at atomic and molecular levels of lunar samples,but will also contribute to a direct link between in situ surface exploration and orbital remote sensing.Four endmembers of lunar soils,Apollo 14163,15273, 67513 and 71501,were selected to investigate their mineralogy and geochemistry properties.Detailed work as follows,1)The grains size of four lunar are estimated in the range of 10-40μm,with Apollo 67513 as the coarsest(～30μm)and Apollo 14163 as the finest(10-20μm).The difference in grain size suggests the distinct maturity of the lunar soils.This agrees with the fact that Apollo 14163 is the most mature and Apollo 67513 as the most fresh soils among the four soils.2)Raman point-counting results indicate that plagioclase is the most abundant mineral in all four soils,with 67513 highest(56.6%)and 71501 lowest(25.6%). Orthorpyroxene is richer than clinopyroxene in Apollo 67513 and 14163,almost equal in soil 15273 whereas poorer in soil 71501.Further classification fo plagioclase feldspar indicate that,in Apollo 14163 and 15273,the plagioclase is more sodic than the other two.The shocked anorthite is rare in Apollo 67513, which also suggest it as a fresh soil.We also found quartz in Apollo 14163 and 15273.3)We extract the compositional information,i.e.,the Mg/(Mg+Ca+Fe), Ca/(Mg+Ca+Fe)in pyroxene and Mg/(Mg+Fe)in olivine,from the calibration of their Raman spectra.As shown in the pyroxene quadrilaterals,pyroxene grains in Apollo 67513(fresh anorthositic highland soil)are slightly richer in Mg;whereas in Apollo 71501(high Ti mare soil),they are slightly richer in Fe with more augite grains than pigeonite.The most reliable points locate in the region of pigeonite for Apollo 14163.For sample 15273,the compositional distribution of pyroxene is scattered more widely than the other three,which suggest the complexity for the source of soil.4)Compared with the ATR spectra of soil 67513,the spectra of soils 14613,15273 and 71501 all have a wide v3 band with much less spectral detail,which suggests low crystallinity,thus higher soil maturity.Among the four soils,Apollo 67513 has the lowest maturity.Adsorbed water and organic contaminants most likely associated with the Teflon sample containment material are evident in the in the diffusion reflectance spectra.5)The soil 67513 shows the highest albedo in the Vis-NIR region,with a strong orthopyroxene absorption band near 938 nm and plagioclase absorption at 1330 nm.This observation is consistent with Raman analyses,i.e.,a higher proportion of orthopyroxene.Spectra from soil 14163,15273 and 71501 have lower spectral contrast than soil 67513,which is a reflection of their maturity.3.Sulfates on Mars:Systematic Spectroscopic Studies and Stability Field of Hydrous Ferric Sulfates Sulfated have been identified on Mars by orbital missions(OMEGA on Mars Express and CRISM on MRO)and landing missins(Viking,Mars Pathfinder,Mars Exploration Rovers).However,Orbital observations clearly show evidence for Mg-and Ca-sulfates,but not Fe-sulfates,whereas the MER rovers have found Fe-sulfates at both landing sites.Nevertheless,there are still a large number of unknowns about ferric sulfates on Mars,especially the detailed mineralogy,hydration states,origins, pathways of formation under Mars surface conditions,and their significance to the current water budget on Mars and their role in Mars' hydrologic history.To address the unknowns related to ferric sulfates on Mars is the aim of this laboratory study.We prepared ferric sulfates in the laboratory and did a systematic characterization of their XRD,Raman,Mid-IR and Vis-NIR spectroscopic properties.After that,we started the stablitly field studies of five ferric sulfates using ten humidity buffers at three temperatures.Detailed work as follows,1)Seven hyedrated ferric sulfates were synthesized by humidity buffer technique. They are ferricopiate,rhomboclase,parqconquimbite,kornelite,lausenite, pentahydrate,and mikasaite.The lausenite is a new phase of hydrated ferric sulfates which we could not find the match of their XRD pattern in PDF 2006 database.By the mass loss calculation and comparing their Raman patter,we tentatively assigned it as lausenit.2)X ray diffraction(XRD)experiments were concucted on all the seven synthetic crystalline ferric sulfates and the amorphous phase(5w).The phase determintation results show that except for paracoquimbite and ferricopiapite, which containts very small amount of rhomboclase,the other ferric sulfates are pure.3)We have obtained Raman spectra,mid-IR,Vis-NIR(0.4-2.5μm & 1.0-5.0μm) spectra from the seven crystalline ferric sulfates,the amorphous(5w)phase,and the saturated solution.All these ferric sulfates show different Raman features, thus are diagnostic for in-situ phase identifications.The v1 peak of SO4 tetrahedra shift to a high frequency as the decrease of the hydration of these ferric sulfates, thus is especially suitable to identify the different hydrated ferric sulfates.Similar tendency appears in their ATR spectra.Kornelite and ferricopiapite show diagnostic features in the NIR region(located at 1428,1920,1995 nm and 1454, 1945,1979 nm,respectively)as indicated by diffuse reflectance spectra and Vis-NIR spectra.However,the water band(～1.9μm)of other ferric sulfates show minor changes.In the 0.7～1μm region of Vis-NIR spectra,the major absorption band of Fe3+shows a blue shift and becomes narrower for ferric sulfates with lower hydration degree.Notice the spectra of amorphous ferric sulfates and saturated solution do not follow well with these two trends4)We are conducting a set of experiments on the stability field and phase transition pathways of five ferric sulfates(amorphous(5w)phase,ferricopipiate, rhomboclase,kornelite,pentahydrate),using ten humidity buffers at 50℃,21℃, 5℃,respectively.The preliminary results show that the deliquescence sequence is as follows,amorphous(5w)＞rhomboclase＞kornelite＞pentahydrate＞ferricopipite. Furthermore,we found a new phase of ferric sulfates,which is 8 water hydrated phase by mass loss calculation.XRD results indicate it was kornelite,however, the Raman pattern is different from kornelite.Similarly,the hydrates state of amorphous phase can be variable from Fe2(SO4)3·4H2O to Fe2(SO4)3·11H2O。At 50℃and 5.5%RH,ferricopiapite can lose 3 structural water(can be wirrten as Fe4.67(SO4)6(OH)2·17.1H2O).All these changes can be monitored by in Situ Raman spectra but cannot by XRD.
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