[A Simple but Effective Device to Avoid Objective Lens Overheating: An Air Blower Device].

The interior of the Earth is a high temperature and high pressure environment. High temperatures cause important changes in the physical and chemical properties of minerals. An increase in temperature leads to significant changes in the molecular and lattice vibrations, elasticity, and seismic velocity of minerals. The high temperature vibrational spectroscopy (infrared and Raman) used to study these changes can provide highly significant understanding of the Earth's interior. During high temperature spectroscopy, the heating device that is used to heat the sample can work at a very high temperature (e.g., 1 500 ℃) because it has a cooling device surrounding it that is used to prevent the temperature of its environments from getting too high. However, radiation from its heating elements is intense and this will shine on and heat the objective lens of the focusing system for the spectroscopic light source, and this would result in damage to the lens. Thus, to avoid damage to the objective lens, an upper limit is placed on the heater temperature. The significance of this work is that it presents a method to exceed the present instrument's temperature limit so that we can perform in situ spectroscopy on samples at higher temperatures. This work extended the temperature limit for the sample to a higher temperature by using an air blower around the objective lens to create a gas flow around it. The gas flow serves to remove heat from the objective lens by forced convection and its turbulent flow also served to increase the rate of heat transport from the lens to the moving gas stream, which together prevented overheating of the objective lens. Our results have shown that although this device is simple, it was highly effective: for a sample temperature of 1 000 ℃, the objective lens temperature was reduced from ～235 to ～68 ℃. Using this device, we performed in situ high temperature Raman spectroscopy of forsterite up to a sample temperature of 1 300 ℃. The results agreed well with previous studies and demonstrated that with our simple air blower device, we can perform in situ high temperature spectroscopy up to 1 300 ℃ without damaging the objective lens and without expensive components like a high temperature composite objective lens or a long focus objective lens.

[Raman Spectroscopic Study on the Determination of SO4(2-) Concentration in Aqueous Solution under High Temperature and Pressure].

In the present work, the Raman spectra of SO4(2-) ions in aqueous solutions were studied. The quantitative analysis shows that there is a significant correlation between the Raman intensity ratio(R) and the SO4(2-) concentration. The SO4(2-) concentration in aqueous solution at ambient temperature and pressure can be determined by the Raman intensity according to the linear fitting equation c (SO4(2-) = 4.779 6R (r2 = 0.999 4). Furthermore, the research proves that the temperature and pressure will af- fect the relationship between the Raman intensity ratio and the concentration of SO4(2-) ions. The quantitative equation for measur- ing the SO4(2-) concentration in aqueous solution at high temperature and high pressure is c(SO4(2-)) = 4.779 6(R + 1.469 x 10(-4)ΔT + 1.340 x 10(-4)ΔP), where R is defined as the ratio of the SO4(2-) ions band intensity to the OH stretching single band intensity, T is the temperature relative to 23 °C, ΔP is the pressure relative to 0.1 MPa, 23 °C ≤ T ≤ 390 °C, the concentration range of the SO4(2-) ions is 0.5-1.5 mol · L(-1), and the uncertainty of the equation is 6.5%. Raman spectroscopy can be used to measure the concentration of the Raman-active species in aqueous solutions.

[Research on Raman spectra of chalcopyrite under 0-1400 MPa and ambient temperature].

The variation characters of the A1 mode Raman spectra of chalcopyrite under 0.1-1400 MPa and ambient temperature were researched using diamond anvil cell. The results show that the shape and intensity of the Raman peak remains constant under experimental conditions, indicating that the chemical bounds of Cu-S and Fe-S remain unchanged. The authors have also noticed that the position of the Raman peak shifts to higher frequency with increasing pressure, which could be described as: nu(290) = 0.031 2p + 290.60 (0.1< or =p<58.8 MPa) and nu(290) = 0.00572p+292.10 (58.8 < or =p<1400 MPa). The rate of the Raman peak shifting with increasing pressure changed abruptly at about 58.8 MPa, the d(nu)/dp is 31.2 and 5.72 cm(-1) x GPa(-1) below and above 58.8 MPa respectively, which perhaps indicate that some structural changes occurred in the chalcopyrite.

Raman spectroscopic quantitative study of NaCl-CaCl2-H2O system at high temperatures and pressures.

Raman spectra features of the ternary system NaCl-CaCl2-H2O under high temperatures and high pressures were systematically studied in the present work by using hydrothermal diamond anvil cell (HDAC) and Raman shifts of quartz to determine pressures, and it has been obtained for the quantitative relationship between Raman shifts of the O-H stretching band of water, mass fractions of solutes and pressures was obtained. The mass fractions of salts, where salinity of NaCl equal to that of CaCl2, are 4.0 mass %, 8.0 mass %, and 12.0 mass %, respectively. Experimental results indicate that the standardized Raman frequency shift differences of the O-H stretching vibration (deltav(O0H)) rise with the increasing temperatures when the mass fractions of salts and pressures of the NaCl-CaCl2-H2O system remain constant. deltav(O-H) increases with the increase in mass fractions of salts in the system when the temperatures and pressures are constant. Linear relationship between deltav(O-H) and pressure with similar slopes can be found for the NaCl-CaCl2-H2O system with different salinities. The quantitative relationship between deltav(O-H), temperature (T), pressure (P), and mass fraction of solute (M) is P = -31.892 deltav(O-H) + 10.131T + 222.816M - 3 183.567, where the valid PTM range of the equation is 200 MPa < or = P < or = 1 700 MPa, 273 K < or = T < or = 539 K and M < or = 12 mass %. The equation can be used as a geobarometer in the studies of fluid inclusions of NaCl-CaCl2-H2O system with equal salinities. The method, as a direct geological detecting technique, has a potential application value.

[Research on Raman spectra of oxalic acid during decarboxylation under high temperature and high pressure].

The present research studied the thermal stability of oxalic acid under high temperature and pressure and its in-situ transformation by Raman spectroscopy using a hydrothermal diamond anvil cell. Raman spectra allow the detection of ionic and covalent atomic aggregates through the acquisition of vibrational spectra that are characteristic of their structures and molecular bond types. The result showed that there was no change in characteristic vibrational Raman peaks of oxalic acid in the low-temperature stage. With the increase in temperature and pressure, the characteristic vibrational Raman peaks of oxalic acid became weaker and the peaks disappeared at a certain high temperature, and decarboxylation happened. Oxalic acid decomposes to produce CO2 and H2, according to the reaction: C2 H2O4-2CO2 + H2. It was found that the decarboxylation was highly related with pressure and that the decarboxylation would be hindered at high pressure. Decarboxylation of oxalic acid under high temperature and pressure showed a linear relationship between temperature and pressure. The data fitting generated the formula: P(MPa) = 12. 839T(K)-5 953.7, R2 = 0.99. The molar volume change of decarboxylation of oxalic acid can be described by deltaV(cm(-3) x mol(-1)) = 16.69-0.002P (MPa) + 0.005 2T(K), R = 0.99.

[Raman spectroscopic study on the fluid effects in dissolution and phase transition mechanisms of gypsum].

Raman spectroscopic studies on the process of dissolution and phase transition of gypsum in different fluids were taken. Gypsum took phase transition to be anhydrite in the range from 170 degrees C to 190 degrees C in pure water, and no more change happened with decreasing temperature to room temperature. Gypsum took phase transition to be anhydrite in the range from 170 degrees C to 190 degrees C too in Na2 SO4 solution, but anhydrite can regain to be gypsum when temperature decreases to room temperature. The process of phase transition of gypsum in pure water is not reversible, but it happens in Na2 SO4 solution. The study shows that fluid effects can influence the dissolution and phase transition mechanisms of minerals and cannot be ignored.

[Research on Raman spectra of isooctane at ambient temperature and ambient pressure to 1. 2 GPa].

The experimental study of the Raman spectral character for liquid isooctane (2,2,4-trimethylpentane, ATM) was con ducted by moissanite anvil cell at the pressure of 0-1.2 GPa and the ambient temperature. The results show that the Raman peaks of the C-H stretching vibration shift to higher frenquencies with increasing pressures. The relations between the system pressure and peaks positions is given as following: v2 873 = 0.002 8P+2 873.3; v2 905 = 0.004 8P+2 905.4; v2 935 = 0.002 7P+ 2 935.0; v2 960 = 0.012P+2 960.9. The Raman spectra of isooctane abruptly changed at the pressure about 1.0 GPa and the liquid-solid phase transition was observed by microscope. With the freezing pressure at ambient temperature and the melting temperature available at 1 atm, the authors got the liquid-solid phase diagram of isooctane. According to Clapeyron equation, the authors obtained the differences of volume and entropy for the liquid-solid phase transition of isooctane: deltaV(m) = 4.46 x 10(-6) m3 x mol-1 and deltaS = -30.32 J x K(-1) x mol(-1).

[In situ experimental study of phase transition of calcite by Raman spectroscopy at high temperature and high pressure].

The phase transitions of calcite at high temperature and high pressure were investigated by using hydrothermal diamond anvil cell combined with Raman spectroscopy. The result showed that the Raman peak of 155 cm(-1) disappeared, the peak of 1 087 cm(-1) splited into 1083 and 1 090 cm(-1) peaks and the peak of 282 cm(-1) abruptly reduced to 231 cm(-1) at ambient temperature when the system pressure increased to 1 666 and 2 127 MPa respectively, which proved that calcite transformed to calcite-II and calcite-III. In the heating process at the initial pressure of 2 761 MPa and below 171 degrees C, there was no change in Raman characteristic peaks of calcite-III. As the temperature increased to 171 degrees C, the color of calcite crystal became opaque completely and the symmetric stretching vibration peak of 1 087 cm(-1), in-plane bending vibration peak of 713 cm(-1) and lattice vibration peaks of 155 and 282 cm(-1) began to mutate, showing that the calcite-III transformed to a new phase of calcium carbonate at the moment. When the temperature dropped to room temperature, this new phase remained stable all along. It also indicated that the process of phase transformation from calcite to the new phase of calcium carbonate was irreversible. The equation of phase transition between calcite-III and new phase of calcium carbonate can be determined by P(MPa) = 9.09T x (degrees C) +1 880. The slopes of the Raman peak (v1 087) of symmetrical stretching vibration depending on pressure and temperature are dv/dP = 5.1 (cm(-1) x GPa(-1)) and dv/dT = -0.055 3(cm(-1) x degrees C(-1)), respectively.

[Research on the experiment of hydrogen isotope fractionation using diamond anvil cell and Raman spectra].

Hydrothermal diamond-anvil cell and Raman spectroscopy were used to measure the hydrogen isotope fractionation factor between gypsum and liquid water. Hydrogen isotopes of deuterium (D) and hydrogen (H) show the largest relative mass difference in all stable isotope systems. The exchange reaction between D and H would easily take place and the extent of exchange would be larger than others under same condition. So we selected the hydrogen isotopes for the investigation. The concept of fractionation factor is the quotient of ratios of heavy and light isotopes in different minerals, and can be expressed as alpha(A-B) = R(A)/R(B). There is a linear relationship between ratio of Raman peak intensities and ratio of corresponding amount of substances. So the fractionation factor between gypsum and heavy water can be expressed as [formula: see text] The experimental study for the isotope fractionation is based on the dissolution and recrystallization of minerals in aqueous solutions. The process can reach the total isotope fractionation equilibrium and get isotope fractionation factors with different temperatures. Compared with other methods, chemical synthesis one has following advantages: (1) short time for the experiment; (2) no problem about the equilibrium for isotope exchanges. It was proved that the new method would be more convenient and reliable for obtaining the isotopic fractionation factor compared with previous ways.

[Raman spectra of aragonite at the pressure of 0.1-2 GPa and ambient temperature].

Raman spectra of aragonite were studied at ambient temperature and pressure of 0.1 - 2 GPa in a moissanite anvil cell using Raman spectrum technique. The relations between the Raman shifts of aragonite and the system pressure are given as follows: v153 (cm(-1)) = 0.003 5p (MPa) +154.0, v206 = 0.006 0p + 206.3, v704 = 0.002 1p + 704.2, v1085 = 0.003 5p + 1 085.3. No phase transition occurred in aragonite within the range of experimental pressure. Similar to other carbonate minerals (magnesite, dolomite), the measured relative pressure-shift of the Raman line of the symmetric stretching vibration of aragonite is greater at 0.1-2 GPa than at ultrahigh pressure, which indicates that the C-O bond compressibility of the CO3 groups is related to the pressure, and it is more compressible at 0.1 - 2 GPa than at higher pressure.

[Raman spectra study of barite at the pressure of 0-1 GPa and ambient temperature].

The variation characters of Raman spectra of S-O symmetric stretching vibration v987 and symmetric bending vibration v452 and V462 of barite at high pressure were studied using moissanite anvil cell. The experimental results show that barite is stable at the pressure of 0-1 GPa and ambient temperature, and the Raman peak positions of barite shift to higher frequency with increasing pressure. The relations between the Raman shifts and system pressure are given as follows: v987 = 0.004 4p+987.42, v452 = 0.002 3p+452.6, v462 = 0.001 8p+ 462.42, and that stretching vibrations are more affected by pressure than bending vibrations. The intensity of 987 cm(-1) Raman peak of barite is six times greater than that of 464 cm(-1) Raman peak of quartz, so barite can be used as a good pressure gauge. Besides, the relation between the system pressure and Raman shift of 987 cm(-1) peak position of barite is given as follows: p(MPa) = 223.16 X (deltav(p))987 -90.35 (987 cm(-1) < v(p) < 992 cm(-1)). The difference in the measured relative pressure-shift of the Raman line of the symmetric stretching vibration among various sulfate minerals shows the compressibility and strength of the S-O bond in the SO4 group.

[Research on Raman spectra of calcite phase transition at high pressure].

The present research studied the process of phase transition from calcite-I to calcite-III under the condition of high hydrostatic pressure using hydrothermal diamond anvil cell and Raman spectrum technique. The hydrothermal diamond anvil cell is the most useful instrument to observe sample in-situation under high temperature and high pressure. The authors can get effective results from this instrument and pursue further research. The method of Raman spectra is the most useful measure tool and it can detect the material according to the spectrum. The result shows that three characteristic Raman peaks of calcite-I move to high-position with adding pressure. Water media in system becomes frozen at the pressure of 1103 MPa, and there is no change in the structure of calcite-I. The abrupt change of characteristic Raman peaks of calcite-I happens when the system pressure reaches 1752 MPa, and changed characteristic Raman peaks explain that calcite-I changes to calcite-III. There are two types of calcite-III, and type A happens in the system because of the effect of hydrostatic pressure. The characteristic Raman peak in different areas of minerals shows that the degree of phase transition becomes larger from inner part to edge part. The research also shows the advantage of hydrothermal diamond anvil cell and Raman spectrum for qualitative analysis of mineral structure using in-situ technique.

[In-situ research on Raman spectroscopy of 1-pentanol under high pressure].

Raman spectra in 800-3 000 cm(-1) of 1-pentanol were studied under high pressure and at ambient temperature (23 degrees C) using a cubic zirconia anvil cell. The Raman peaks become sharper at higher pressure so that each individual C-H stretching mode is difficult to be distinguished. The Raman frequencies of the C-H stretching modes shift to a higher position with increasing pressures ranging between 0.1 MPa and 1.75 GPa. And the pressure induced frequency shifts are described by P(MPa) = 69.652 65 x (deltanu(p)) (single, T = 23 degrees C) + 105.806 93 where 0 < (deltanu(p)) single (cm(-1) < or = 23 and P(MPa) =77.974 04 x (Anu(p))( 2 960, T = 23 degrees 95.390 5 where 0 < (deltanu(p))2 960 (cm(-1)) < or = 21 and P(MPa) =126.956 39 x (deltanu(p)) (2 863, T = 23 degrees) -110.648 09 where 0 < (deltanu(p)) 2 863(cm(-1)) < or = 13, respectively. The global slope is (thetanu(single)/thetaP)T (14+/- 1) cm(-)1 x GPa(-1), which can be used as a pressure sensor. Both the jumping of the frequencies and the figure under microscope indicate that the frozen pressure of the 1-pentanol at room temperature is 1.75 GPa. The molar volume change of the 1-pentanol is deltaVm = 1.84 x 10(-6) m3 x mol(-1) in the phase transformation from a liquid to a solid at 23 degrees C.

[Study on the accuracy of pressure determined by raman spectra of quartz].

Quartz as a pressure gauge and its accuracy were studied by Raman spectroscopy at 25 degrees C and ambient pressure. The result shows that even at same temperature and pressure, the Si-O vibrational mode for different grains of quartz varies between 463.59 and 464.65 cm(-1), with (+/- 0.1- +/- 0.3) cm(-1) error. The maximum difference of various grains of quartz is up to 1.06 cm(-1), much higher than the measurement error. The authors believe that the variety is resulted from the stress in the internal grains of quartz, which formed during crushing quartz into small grain. Therefore, Raman spectrum for quartz has to be firstly measured as a reference of zero pressure at ambient pressure and temperature in the experimental study by using diamond anvil cell. In addition, wavenumber drift of the spectrometer and the unstable temperature will also cause remarkable error for measuring pressure.

[Raman spectra of carbonate ions as pressure gauge at high pressure and room temperature].

Three aqueous solutions of sodium carbonate (1.5, 2.0 and 2.5 mol x L(-1)) were studied by in-situ Raman spectrum in a moissanite anvil cell in order to measure the Raman shift of symmetric stretching vibration of carbonate ion at around v1 066. The experiment was conducted from 0 to 1.7 GPa under quasihydrostatic conditions at temperature of 22 degrees C. The result showed that the increase in Raman wavenumber shift of in-plane bending vibration of carbonate ion is linearly proportional to the rise of pressure under room temperature. At the three concentrations mentioned above, the correlations between Raman shift ofthe v1 066 peak and the pressure are depicted as three nearly identical curves, with a slope error smaller than 1%. The deviation, being smaller than the systemic error, suggested that the concentration of carbonate ions, within experimental errors, has no detectable influence on the pressure-induced shift of v1 066 peak. Besides, the data fitting generated the formula: p/MPa = 174.13deltavl 066/cm(-1) -59.03 (deltav1 066 = v1 066 -v(0)1 066, where v(0)1 066 denotes the Raman shift of v1 006 peak of carbonate ion under the ambient pressure, which can be used as a pressure gauge in pure Na2CO3 solution.

[Research on Raman spectra of benzoic acid during decarboxylic process].

The present research studied benzoic acid change in water and its Raman spectra in temperature rising period using hydrothermal diamond anvil cell and Raman spectrum technique. The hydrothermal diamond anvil cell is the most useful instrument to observe sample in-situation under high temperature and high pressure. The authors can get effective results from this instrument and pursue further research. The method of Raman spectra is the most useful measure tool and it can detect the material according to the spectrum. The result showed that there was no change in characteristic vibrational Raman peak of benzoic acid in the lower temperature period and there was no reaction between benzoic acid and water. In the process of temperature rising period, the characteristic vibrational Raman peak of benzoic acid became weaker. During the process, benzoic acid began to dissolve in water, but no chemical reaction happened. The reason for weaker Raman peak of benzoic acid is the dissolution. The characteristic vibrational Raman peak of carboxyl disappeared at 150 degrees C, which showed that decarboxylic reaction occurred on benzoic acid. But the main Raman peak of benzoic acid existed which showed that no chemical reaction existed. And then benzoic acid disappeared when temperature ascended to 170 degrees C. When the temperature of system dropped to room temperature, a kind of crystal appeared. The characteristic vibrational Raman peak of this kind of crystal showed that the crystal contained benzene ring, showing that dutrex appeared. At the same time the authors did not find the characteristic vibrational Raman peak of carboxyl, so the crystal was not benzoic acid. The whole research showed that: dutrex can disappear and be regained in the process of dissolution and recrystallization, but carboxyl cannot.

[Research on Raman spectra of heavy water at high pressure].

The present work studies the Raman spectra of heavy water at pressure from 0.1 MPa to 800 MPa at ambient temperature using the method of diamond anvil cell and Raman spectrum technique. The result shows that the Raman peak of heavy water moves to lower frequency, and the linear relationship exists between Raman shift and pressure. There is no abrupt change in Raman shift, indicating that no phase transition occurs. Raman peak of heavy water is separated, corresponding to O-D vibration inside D2O molecule as the higher frequency peak and to hydrogen bond among D2O molecules as the lower frequency peak. Research on the characters of these two kinds of Raman spectra indicates that the area of lower frequency peak for hydrogen bond among D2O molecules exhibits different changes at different pressures, and the influence of pressure on hydrogen bond among D2O molecules is not unchangeable. The area of Raman spectra peak reflects the amount of vibrations which result in the Raman spectra peak, and the change in the area of Raman spectra peak reflects the change in the amount of special vibration. Because of the strong interaction between hydrogen bonds among D2O molecules, the molecules of D2O are apt to form the symmetrical dimensional structures of tetrahedron which consists of five molecules of D2O. So the biggest area of Raman spectra peak represents the most stable structure that is the symmetrical dimensional structures of tetrahedron consisting of five molecules of D2O. This result proves that the most stable structure is existent.

[Evidence of discontinuities in the Raman spectra of aqueous NaCl solution at high pressure].

In-situ Raman spectra measurement for aqueous NaCl solution was conducted at the temperature of 21 degrees C and the pressures of 50-1 100 MPa using a SiC anvil cell. It is shown that the decomposed bands of aqueous NaCl solution shift to lower wavenumber with increasing pressure initially and reaches the minimum at about 300 MPa, and increases at higher pressure up to about 800 MPa, then decreases again with increasing pressure. Similarly, the ratio of band-area and the width at half maximum of the decomposed bands of the solution exhibit discontinuities at about 300 and 800 MPa. This finding demonstrates that the structure of aqueous NaCl solution is discontinuous at high pressure and O-H...Cl- bonds change correspondingly, which suggests the existence of rearrangement and the appearance of more complicated configuration in the interior structrure of aqueous NaCl solution.

[Raman spectroscopic studies of n-pentadecane under high temperature].

The present paper investigates the Raman spectrum of n-pentadecane in diamond anvil cell under a temperature up to 350 degrees C. The result shows that the pressure increases at elevated temperature, but the effect of pressure on the stretching vibrational modes of CH3 and CH2 is inverse to that of temperature. The action of temperature is weaker than that of pressure. So the spectral profile of stretching vibrational modes of CH3 and CH2 gradually changes and the Raman shift moves to higher frequency with increasing temperature and pressure. It is indicated that the bonding energy of C-H bonding increases with temperature and pressure. In addition, the generation of a new substance resulted in a drastic fluorescence appearance, so the detection of the Raman spectrum of n-pentadecane failed. During the authors' experiment, the author observed a dependence of the drastic fluorescence occurrence time on temperature and pressure conditions.

[Research on Raman spectra of 2-methylpentaneat at pressure of 0-1.5 GPa and temperature of 26 degrees C].

The present paper investigates the Raman spectral character of liquid 2-methylpentane by an experiment at the pressure of 0-1.5 GPa and the temperature of 26 degrees C, and defines the relation between the pressure and the Raman peak of 2-methylpentane at ambient temperature. The result shows that there are five characteristic Raman peaks in 2-methylpentane defined as v (CH2) and v(CH3), and all of them move to high position as the system pressure increases. The relation between the system pressure and peaks positions is given as following: v(as), (CH3) = 0.013 1p + 2 960.1, v(s), (CH3) = 0.008 8p + 2 871.0, v(as) (CH2) = 0.008 9p + 2 930.2, v(as) (CH2), = 0.007 0p + 2 903 and v(s) (CH2) = 0.007 9p - 2 844.7. On the other hand, 2-methylpentane is reliable as a liquid pressure gauge for high pressure experiment. The equation applied to demarcate system pressure is also showed: p (MPa) = 76.2 (deltav(p))2 960 + 21.65(r2 = 0.995 8). This is probably the first organic liquid gauge, especially for systems not expected to emergence of Si, Al and hydroxyl matter.