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1.
 Infrared absorption spectra of brucite Mg (OH)2 were measured under high pressure and high temperature from 0.1 MPa 25 °C to 16 GPa 360 °C using infrared synchrotron radiation at BL43IR of Spring-8 and a high-temperature diamond-anvil cell. Brucite originally has an absorption peak at 3700 cm−1, which is due to the OH dipole at ambient pressure. Over 3 GPa, brucite shows a pressure-induced absorption peak at 3650 cm−1. The pressure-induced peak can be assigned to a new OH dipole under pressure. The new peak indicates that brucite has a new proton site under pressure and undergoes a high-pressure phase transition. From observations of the pressure-induced peak under various P–T condition, a stable region of the high-pressure phase was determined. The original peak shifts to lower wavenumber at −0.25 cm−1 GPa−1, while the pressure-induced peak shifts at −5.1 cm−1 GPa−1. These negative dependences of original and pressure-induced peak shifts against pressure result from enhanced hydrogen bond by shortened O–H···O distance, and the two dependences must result from the differences of hydrogen bond types of the original and pressure-induced peaks, most likely from trifurcated and bent types, respectively. Under high pressure and high temperature, the pressure-induced peak disappears, but a broad absorption band between 3300 and 3500 cm−1 was observed. The broad absorption band may suggest free proton, and the possibility of proton conduction in brucite under high pressure and temperature. Received: 16 July 2001 / Accepted: 25 December 2001  相似文献   

2.
In order to investigate the behaviour of proton in brucite under pressure, polarized IR absorption spectra and polarized absorbance distributions of (001) and (110) oriented single crystal of brucite under high pressure were measured by Fourier transform polarized infrared microspectroscopy with diamond anvil cell. A pressure-induced absorption peak at 3645 cm−1 observed under pressures over 2.9 GPa was confirmed to be due to a secondarily formed OH dipole. Polarized absorbance distribution measured under pressure of (110) suggests that the secondary OH dipole is oriented 136.0° to c-axis under 5.3 GPa. Isotropic absorbance distribution of (001) suggests that the secondary OH dipole is disorderly trifurcated. Abrupt onset of the secondary peak and its reverse pleochroism suggest that the process of secondary OH dipole formation is due to proton transfer between layers in brucite. The calculated orientation of the secondary OH dipole consistent with the O-H···O′ angle revealed by neutron diffraction supports the existence of proton transfer along H···O′. The secondary OH dipole implies a new site of proton in brucite under pressure. Received: 6 March 1997 / Revised, accepted: 9 June 1997  相似文献   

3.
Vibrational properties of diaspore, α-AlOOH, have been re-investigated using room-temperature single-crystal Raman spectroscopy and low-temperature powder infrared (IR) transmission spectroscopy. First-principles harmonic calculations based on density functional theory provide a convincing assignment of the major Raman peaks and infrared absorption bands. The large width of the Raman band related to OH stretching modes is ascribed to mode–mode anharmonic coupling due to medium-strength H-bonding. Additional broadening in the powder IR spectrum arises from depolarization effects in powder particles. The temperature dependence of the IR spectrum provides a further insight into the anharmonic properties of diaspore. Based on their frequency and temperature behavior, narrow absorption features at ~2,000 cm−1 and anti-resonance at ~2,966 cm−1 in the IR spectrum are interpreted as overtones of fundamental bending bands.  相似文献   

4.
A single-crystal of topaz was studied by Raman spectroscopy to assign the internal modes of the high-frequency range and to compare with infrared data. All active modes exhibit an important Davydov splitting (150 cm?1) but we have found a small Bethe splitting (14.5 cm?1) consistent with a very regular SiO4 tetrahedron. Because of a high value of v 1 (～920 cm?1) the Raman active modes present a mixed v 1/v 3 character. Finally the substitution of OH for F splits an A g internal mode and lead to some proper modes at 3650 cm?1, 3639 cm?1 and 1165 cm?1.  相似文献   

5.
Near-infrared (NIR) absorption bands related to total water (4000 and 7050 cm−1), OH groups (4500 cm−1) and molecular H2O (5200 cm−1) were studied in two polymerised glasses, a synthetic albitic composition and a natural obsidian. The water contents of the glasses were determined using Karl Fischer titration. Molar absorption coefficients were calculated for each of the bands using albitic glasses containing between 0.54 and 9.16 wt.% H2O and rhyolitic glasses containing between 0.97 and 9.20 wt.% H2O. Different combinations of baseline type and intensity measure (peak height/area) for the combination bands at 4500 and 5200 cm−1 were used to investigate the effect of evaluation procedure on calculated hydrous species concentrations. Total water contents calculated using each of the baseline/molar absorption coefficient combinations agree to within 5.8% relative for rhyolitic and 6.5% relative for albitic glasses (maximum absolute differences of 0.08 and 0.15 wt.% H2O, respectively). In glasses with water contents >1 wt.%, calculated hydrous species concentrations vary by up to 17% relative for OH and 11% relative for H2O (maximum absolute differences of 0.33 and 0.43 wt.% H2O, respectively). This variation in calculated species concentrations is typically greater in rhyolitic glasses than albitic. In situ, micro-FTIR analysis at 300 and 100 K was used to investigate the effect of varying temperature on the NIR spectra of the glasses. The linear and integral molar absorption coefficients for each of the bands were recalculated from the 100 K spectra, and were found to vary systematically from the 300 K values. Linear molar absorption coefficients for the 4000 and 7050 cm−1 bands decrease by 16–20% and integral molar absorption coefficients by up to 30%. Depending on glass composition and baseline type, the integral molar absorption coefficients for the absorption bands related to OH groups and molecular H2O change by up to −5.8 and +7.4%, respectively, while linear molar absorption coefficients show less variation, with a maximum change of ∼4%. Using the new molar absorption coefficients for the combination bands to calculate species concentrations at 100 K, the maximum change in species concentration is 0.08 wt.% H2O, compared with 0.39 wt.% which would be calculated if constant values were assumed for the combination band molar absorption coefficients. Almost all the changes in the spectra can therefore be interpreted in terms of changing molar absorption coefficient, rather than interconversion between hydrous species. Received: 17 December 1998 / Revised, accepted 8 July 1999  相似文献   

6.
Raman spectra of monoclinic Fo90 hydrous wadsleyite with 2.4 wt% H2O have been measured in a diamond-anvil cell with helium as a pressure-transmitting medium to 58.4 GPa at room temperature. The most intense, characteristic wadsleyite modes, the Si–O–Si symmetric stretch at 721 cm−1 and the symmetric stretch of the SiO3 unit at 918 cm−1, shift continuously to 58.4 GPa showing no evidence of a first order change in the crystal structure despite compression well beyond the stability field of wadsleyite in terms of pressure. The pressure dependence of these two modes is nearly identical for Fo90 hydrous and Fo100 anhydrous wadsleyite. A striking feature in the high-pressure Raman spectra of Fo90 hydrous wadsleyite is the appearance of new Raman modes above 9 GPa in the mid-frequency range (300–650 cm−1 at 1-bar and shifted to 500–850 cm−1 at 58.4 GPa) accompanied by a significant growth in their intensities under further compression. In the OH stretching frequency range Fo90 hydrous wadsleyite exhibits a larger number of modes than the Mg end-member phase. The higher number of modes may be due to either additional protonation sites or simply that we observe a different subset of all possible OH modes for each sample. The high-pressure behaviour of the OH stretching modes of Fo90 and Fo100 hydrous wadsleyite is consistent: OH stretching modes with frequencies <3,530 cm−1 decrease with increasing pressure whereas the higher-frequency OH modes show a close to constant pressure dependence to at least 13.2 GPa. The approximately constant pressure dependence of the OH modes above 3,530 cm−1 is consistent with protons being located at the O1···O edges around M3.  相似文献   

7.
The IR spectrum of an alpine, hydrothermally formed diopside containing 17 wt ppm H2O consists of three main OH absorption bands centred at 3647, 3464 and 3359 cm−1. Jadeite from a Californian vein occurrence is characterised by bands at 3616 and 3557 cm−1 and contains about 197 wt ppm H2O. Based on the pleochroic scheme of the OH absorption bands in diopside, OH defect incorporation models are derived on the basis of fully occupied cation sites and under the assumption of M1 and M2 site vacancies; OH defects replacing O2 oxygen atoms are most common. The less pronounced OH pleochroism and the broad band absorption pattern of jadeite indicate a high degree of OH defect disordering. The pleochroic scheme of the main absorption bands at 3616 and 3557 cm−1 implies partial replacement of O2 oxygen atoms by OH dipoles pointing to vacant Si sites. Under the assumption of M1 and M2 site vacancies, O1–H and O2–H defects are also derivable. OH incorporation modes assuming Si-vacancies should be considered for jadeite-rich clinopyroxenes formed in deep crust and upper mantle regions.  相似文献   

8.
Neutron- and gamma irradiation-induced paramagnetic centers in natural colorless topaz from four different Brazilian localities were studied by electron paramagnetic resonance (EPR) and optical absorption as a function of irradiation dose and thermal treatment. Gamma irradiation doses were applied up to 1,000 kGy with a dose rate of 15 kGy h−1. For the neutron irradiation experiments, a neutron flux of 4 × 1012 cm−2 s−1 was used with an integrated flux of up to 1 × 1018 cm−2. From the experiments, it is concluded that brownish colors are induced by gamma-rays and may be associated with a single broad isotropic EPR line with g = 2.015(2). Both the EPR line and the related optical absorption band at 460 nm (2.7 eV) are lost during thermal treatments between 150 and 200°C. Fast neutrons create the paramagnetic peroxyl radicals O2 − and the paramagnetic O− hole centers. The O− centers have the same thermal stability as the optical absorption band at 620 nm (2.0 eV). It is confirmed that the absorption due to the O− center is responsible for the blue color in topaz. Both color centers and their absorption bands are discussed in the context of O− bound small polarons.  相似文献   

9.
 Infrared spectroscopy provides a reliable method for rapid, non-destructive quantitative analysis of volatile species in silicate glasses, with applications to geochemistry and volcanology. The technique has been extensively calibrated for transmission measurements, in which the species concentration present is correlated with the height or area of characteristic absorption peaks, for doubly polished samples of known thickness. There are several drawbacks associated with this method, including the need for double polishing of parallel faces on thin samples, the errors associated with sample thickness measurement, and total absorption of the IR beam intensity for samples with high volatile content. We have tested an alternative method for quantitative IR determination of volatile concentrations in silicate glasses, based on analysis of the IR reflectivity signal. The reflectivity method requires preparation of a single polished glass surface, and no thickness measurement of the sample is necessary. The technique is applied easily as a microbeam technique using apertures as small as a few μm in diameter. The method should be particularly useful for volatile analysis of glass inclusions in phenocrystals, or standard samples in thin section. We have developed the methodology for the technique using a series of basanite and leucitite glasses with high carbonate contents (>1 wt% CO2), which could not be easily analyzed via IR transmission. We have used SIMS to standardize the technique. Two features observed in the reflectance spectra near 1400 cm–1 and 1500 cm–1 are due to resonance of the infrared beam with the asymmetric stretching vibrations of carbonate groups. The contribution of these species to the total reflectivity is directly correlated with the carbon abundance in the samples. This forms the basis for an empirical quantitative analysis. The optical constants, including the IR absorption coefficients associated with the CO3 2– stretching vibrations, have been extracted by Kramers-Kronig analysis of the reflectivity data. The molar extinction coefficients are 1119 ± 138 L mol–1 cm–1 and 1198 ± 145 L mol–1 cm–1 for the 1400 and 1500 cm–1 bands, respectively, in excellent agreement with results of previous transmission studies, after orientation effects are taken into account. Received: 29 September 1995 / Accepted: 17 May 1996  相似文献   

10.
 In situ x-ray data on molar volumes of periclase and tungsten have been collected over the temperature range from 300 K to melting. We determine the temperature by combining the technique of spectroradiometry and electrical resistance wire heating. The thermal expansion (α) of periclase between 300 and 3100 K is given by α=2.6025 10−5+1.3535 10−8 T+6.5687 10−3 T−1−1.8281 T−2. For tungsten, we have (300 to 3600 K) α=7.862 10−6+6.392 10−9 T. The data at 298 K for periclase is: molar volume 11.246 (0.031) cm3, α=3.15 (0.07) 10−5 K−1, and for tungsten: molar volume 9.55 cm3, α=9.77 (10.08) 10−6 K−1. Received: July 18, 1996 / Revised, accepted: February 14, 1997  相似文献   

11.
Hydroxyl in mantle olivine xenocrysts from the Udachnaya kimberlite pipe   总被引：6，自引：1，他引：5  
The incorporation of hydrogen in mantle olivine xenocrysts from the Udachnaya kimberlite pipe was investigated by Fourier-transform infrared spectroscopy and secondary ion mass spectrometry (SIMS). IR spectra were collected in the OH stretching region on oriented single crystals using a conventional IR source at ambient conditions and in situ at temperatures down to −180°C as well as with IR synchrotron radiation. The IR spectra of the samples are complex containing more than 20 strongly polarized OH bands in the range 3,730–3,330 cm−1. Bands at high energies (3,730–3,670 cm−1) were assigned to inclusions of serpentine, talc and the 10 Å phase. All other bands are believed to be intrinsic to olivine. The corresponding point defects are (a) associated with vacant Si sites (3,607 cm−1 E || a, 3,597 E || a, 3,571 cm−1 E || c, 3,567 E || c, and 3,556 E || b), and (b) with vacant M1 sites (most of the bands polarized parallel to a). From the pleochroic behavior and position of the OH bands associated with the vacant M1 sites, we propose two types of hydrogen—one bonded to O1 and another to O2, so that both OH vectors are strongly aligned parallel to a. The O2–H groups may be responsible for the OH bands at higher wavenumbers than those for the O1–H groups. The multiplicity of the corresponding OH bands in the spectra can be explained by different chemical environments and by slightly different distortions of the M1 sites in these high-pressure olivines. Four samples were investigated by SIMS. The calculated integral molar absorption coefficient using the IR and SIMS results of 37,500±5,000 L mol H2O cm−2 is within the uncertainties slightly higher than the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003) (28,450±1,830 L mol H2O cm−2). The reason for the difference is the different distributions of the absorption intensity of the spectra of both studies (mean wavenumber 3,548 vs. 3,570 cm−1). Olivine samples with a mean wavenumber of about 3,548 cm−1 should be quantified with the absorption coefficient as determined in this study; those containing more bands at higher wavenumber (mean wavenumber 3,570 cm−1) should be quantified using the value determined by Bell et al. (J Geophys Res 108(B2):2105–2113, 2003).
Monika Koch-MüllerEmail: Phone: +49-331-2881492
  相似文献   

12.
Summary The infrared absorption spectrum of amethyst in the region of stretching vibrations of X–OH groups reveals several bands that have been used for the separation of natural from synthetic amethyst. The intensity and shape of these bands have been measured as a function of crystallographic orientation. Using a resolution of 0.5 cm−1 the 3595 cm−1 band is present in all infrared spectra of natural amethyst and in some rare synthetic ones. If present in synthetic amethyst, its full width at half maximum (FWHM) is about 7 cm−1 whereas it is about 3 cm−1 in all natural samples. This new criterion, unlike the previous ones, seems appropriate to separate natural from synthetic amethyst in all cases.  相似文献   

13.
A selected set of five different kyanite samples was analysed by electron microprobe and found to contain chromium between <0.001 and 0.055 per formula unit (pfu). Polarized electronic absorption spectroscopy on oriented single crystals, R1, R2-sharp line luminescence and spectra of excitation of λ3- and λ4-components of R1-line of Cr3+-emission had the following results: (1) The Fe2+–Ti4+ charge transfer in c-parallel chains of edge connected M(1) and M(2) octahedra shows up in the electronic absorption spectra as an almost exclusively c(||Z′)-polarized, very strong and broad band at 16000 cm−1 if <, in this case the only band in the spectrum, and at an invariably lower energy of 15400 cm−1 in crystals with  ≥ . The energy difference is explained by an expansion of the Of–Ok, and Ob–Om edges, by which the M(1) and M(2) octahedra are interconnected (Burnham 1963), when Cr3+ substitutes for Al compared to the chromium-free case. (2) The Cr3+ is proven in two greatly differing crystal fields a and b, giving rise to two sets of bands, derived from the well known dd transitions of Cr3+ 4A2g→4T2g(F)(I), →4T1g(F)(II), and →4T1g(P)(III). Band energies in the two sets a and b, as obtained by absorption, A, and excitation, E, agree well: I: 17300(a, A), 17200(a, E), 16000(b, A), 16200(b, E); II: 24800(a, A), 24400(a, E); 22300(b, A), 22200(b, E); III: 28800(b,A) cm−1. Evaluation of crystal field parameters from the bands in the electronic spectra yield Dq(a)=1730 cm−1, Dq(b)=1600 cm−1, B(a)=790 cm−1, B(b)=620 cm−1 (errors ca. ±10 cm−1), again in agreement with values extracted from the λ3, λ4 excitation spectra. The CF-values of set a are close to those typical of Cr3+ substituting for Al in octahedra of other silicate minerals without constitutional OH− as for sapphirine, mantle garnets or beryl, and are, therefore, interpreted as caused by Cr3+ substituting for Al in some or all of the M(1) to M(4) octaheda of the kyanite structure, which are crystallographically different but close in their mean Al–O distances, ranging from 1.896 to 1.919 A (Burnham 1963), and slight degrees of distortion. Hence, band set a originates from substitutive Cr3+ in the kyanite structural matrix. The CF-data of Cr3+ type b, expecially B, resemble those of Cr3+ in oxides, especially of corundum type solid solutions or eskolaite. This may be interpreted by the assumption that a fraction of the total chromium contents might be allocated in a precursor of a corundum type exsolution. Received: 3 January 1997 / Revised, accepted: 2 May 1997  相似文献   

14.
 Jurassic Ferrar rocks in Victoria Land (Antarctica) occur predominantly as basaltic or andesitic flows and sills. Both show characteristic petrographical and chemical variations, which can be related to in-situ differentiation processes. Such characteristics have been investigated at one flow (“Colonnade flow”) and one sill (“Thumb Point sill”) in the Prince Albert Mountains (Central Victoria Land) based on a statistical grain size analysis and the application of the crystal size distribution theory. A third magma body (“HiTi-unit”), which in previous literature was described as a flow, does not show clear similarities to either the flow or sill. Sill and flow are in-situ differentiated with accumulation of silicic residual melt in the latest cooled parts. For the flow this part is located in the lower half and for the sill in the upper third of their thickness. Thumb Point sill additionally shows an accumulation zone of olivine in the lower third. The position of the residual melt accumulation zone is an indicator for an origin as flow or sill. The HiTi-unit, by contrast, exhibits, only moderate petrographical and chemical variations. Growth and nucleation rates have been determined using, with some modifications, the CSD theory introduced by Marsh (1988). Growth rates of plagioclase for the flow vary from 10−11 to 10−10 cm/s and are comparable with literature values for basaltic lava lakes on Hawaii. Nucleation rates vary from 10−4 to 10−3 cm−3s−1, which are generally smaller than for Hawaiian basalts. Growth and nucleation rates for the sill cover a large range from 10−13 to 10−11 cm/s and 10−9 to 10−3 cm−3s−1, respectively. Systematic variations of these parameters with vertical position were obtained for the sill with its extensive differentiation history. Nucleation and growth rates are dependant on the mode of cooling. Nevertheless, small but significant differences between the flow and sill exist. Growth and nucleation rates of HiTi-unit (10−12 to 10−11 cm/s and 10−6 to 10−5 cm−3s−1) are intermediate between the flow and sill and thus do not allow a distinction of emplacement mode. Received: 6 December 1995 / Accepted: 3 May 1996  相似文献   

15.
High-pressure synchrotron infrared (IR) absorption spectra were collected between 650 and 4,000 cm−1 at ambient temperature for hydrous Mg-ringwoodite (γ-Mg2SiO4) up to 30 GPa. The main feature in the OH− stretching region is an extremely broad band centred at 3,150 cm−1. The hydrogen bond is strong for most protons and the most probable site for protonation is the tetrahedral edge. With increasing pressure, this band shifts downward while decreasing its integrated intensity until disappearance at a pressure of 25 GPa. Only one band at 2,450 cm−1 and an absorption plateau persist with a maximum wavenumber of 3,800 cm−1. This behaviour is reversible upon pressure release. We interpret this as a second-order phase transition occurring in hydrated Mg-ringwoodite at high pressure (beyond ∼ 25 GPa). This result is compatible with the observation by Kleppe et al. (Phys Chem Miner 29:473–476, 2002a) who suggested the presence of Si–O–Si linkages and/or partial increase in the coordination of Si. Beyond the phase transition, the protons are delocalized and their environment on the ringwoodite structure is probably quite different from that at low pressure. Data obtained in situ at high pressures and temperatures are needed to better understand the effect of protonation on the structure and to better constrain this phase transition.  相似文献   

16.
 Raman spectra of hydrous β-Mg2SiO4 (1.65 wt% H2O) have been measured in a diamond-anvil cell with helium as a pressure-transmitting medium at room temperature to 50 GPa. We observe three OH-stretching modes, a doublet with components at 3329 and 3373 cm−1, which decrease linearly with pressure, and a single mode at 3586 cm−1, which remains nearly constant up to 24 GPa before decreasing at higher pressures. Assessment of the mode frequencies and their pressure dependence, together with previous results from X-ray and IR data, are consistent with protonation of the O1 site in agreement with previous studies. Strict assignment of Raman activity awaits detailed structural models. The nature of the protonation in wadsleyite may require more specific experimental probes for full solution of the hydrogen-site problem. Received: 18 July 2000 / Accepted: 22 November 2000  相似文献   

17.
In situ unpolarized and polarized Fourier transform infrared spectra of a natural orthopyroxene at varying temperatures were obtained using a heating stage attached on an Infrared microscope. The three main bands (3,595, 3,520 and 3,410 cm−1) at room temperature are ascribed to OH fundamental stretching bands. With increasing temperature from room temperature to 500 °C, the 3,595 cm−1 band shifts 20 cm−1 to lower frequency. The total integral absorbance decreases with increasing temperature. These changes are reversible. Excluding the influences of dehydration, proton migration, thermal expansion, and changes in OH dipole direction, the change of integral absorbance with temperature reflects the temperature dependence of absorption coefficient due to the anharmonicity of OH vibration. Based on the integral absorption coefficient at room temperature (14.84 ppm−1 cm−2) from Bell et al. (Am Mineral 80:463–474, 1995), the integral absorption coefficients at other temperatures are calculated. The variation of integral absorption coefficient between room temperature and 500 °C obtained in this study is about 18.5 % and may be greater at higher temperature according to the proposed linear relationship.  相似文献   

18.
 The incorporation of hydrogen (deuterium) into the coesite structure was investigated at pressures from 3.1 to 7.5 GPa and temperatures of 700, 800, and 1100 °C. Hydrogen could only be incorporated into the coesite structure at pressures greater 5.0 GPa and 1100 °C . No correlation between the concentration of trace elements such as Al and B and the hydrogen content was observed based on ion probe analysis (1335 ± 16 H ppm and 17 ± 1 Al ppm at 7.5 GPa, 1100 °C). The FTIR spectra show three relatively intense bands at 3575, 3516, and 3459 cm−1 (ν1 to ν3, respectively) and two very weak bands at 3296 and 3210 cm−1 (ν4 and ν5, respectively). The band at 3516 cm−1 is strongly asymmetric and can be resolved into two bands, 3528 (ν2a) and 3508 (ν2b) cm−1, with nearly identical areas. Polarized infrared absorption spectra of coesite single-crystal slabs, cut parallel to (0 1 0) and (1 0 0), were collected to locate the OH dipoles in the structure and to calibrate the IR spectroscopy for quantitative analysis of OH in coesite (ɛ i ,tot=190 000 ± 30 000 l mol−1 H2O cm−2). The polarized spectra revealed a strong pleochroism of the OH bands. High-pressure FTIR spectra at pressures up to 8 GPa were performed in a diamond-anvil cell to gain further insight into incorporation mechanism of OH in coesite. The peak positions of the ν1, ν2, and ν3 bands decrease linearly with pressure. The mode Grüneisen parameters for ν1, ν2, and ν3 are −0.074, −0.144 and −0.398, respectively. There is a linear increase of the pressure derivatives with band position which follows the trend proposed by Hofmeister et al. (1999). The full widths at half maximum (FWHM) of the ν1, ν2, and ν3 bands increase from 35, 21, and 28 cm−1 in the spectra at ambient conditions to 71, 68, and 105 in the 8 GPa spectra, respectively. On the basis of these results, a model for the incorporation of hydrogen in coesite was developed: the OH defects are introduced into the structure by the substitution Si4+(Si2)+4O2−= [4]□(Si2) + 4OH−, which gives rise to four vibrations, ν1, ν2a, ν2b, and ν3. Because the OH(D)-bearing samples do contain traces of Al and B, the bands ν4 and ν5 may be coupled to Al and/or B substitution. Received: 19 December 2000 / Accepted: 23 April 2001  相似文献   

19.
Summary The OH content of four rutile and two cassiterite single-crystals was studied by nuclear reaction analysis (NRA) and by polarised FTIR microspectroscopy. The OH absorption bands of both minerals are centered around 3300 cm−1 with different absorption features. The analytical H2O content determined by NRA ranges from 70 to 820 wt.ppm. The integrated molar absorption coefficients deduced from the total integrated OH absorbances are equal to 38000 lċmol−1 H2Oċcm−2 for rutile and 65000 lċmol−1 H2Oċcm−2 for cassiterite. For both minerals the absorption coefficients are significantly smaller than those expected from the linear calibration curves given by Paterson (1982) and by Libowitzky and Rossman (1997).
Zusammenfassung OH-Absorptionskoeffizienten von Rutil und Cassiterit ermittelt durch Kernreaktions-Analyse und FTIR Spektroskopie Der OH-Gehalt von vier Rutil- und zwei Cassiterit-Einkristallen wurde mittels Kernreaktions-Analyse (NRA) und polarisierter FTIR Mikrospektroskopie untersucht. Die OH Absorptionsbanden beider Minerale sind um 3.300 cm−1 zentriert, mit unterschiedlichen Absorptionserscheinungen. Der analytische H2O-Gehalt, der mit NRA bestimmt wurde, schwankt von 70 bis 820 Gew.ppm. Die integrierten molaren Absorptionskoeffizienten, die auf den gesamten integrierten OH-Absorptionen basieren, betragen etwa 38.000 lċmol−1 H2Oċcm−2 für Rutil and 65.000 lċmol−1 H2Oċcm−2 für Cassiterit. Für beide Minerale sind die Absorptionskoeffizienten signifikant kleiner als die, die auf Grund der linearen Kalibrationskurven von Paterson (1982) und Libowitzky und Rossmann (1997) zu erwarten sind.

Received January 4, 2000; revised version accepted April 10, 2000  相似文献   

20.
The dominant O− hole center in natural and neutron irradiated blue topaz with general formula Al2SiO4(F,OH)2 has been investigated with electron paramagnetic resonance (EPR) and optical absorption. The analysis of the EPR spectra of the O− center yielded superhyperfine interactions with two equivalent Al neighbors in four magnetically inequivalent positions. From the g-factors it is found that the O− hole center is located in (8d) Wyckoff positions on fluoride sites that were substituted by hydroxyl molecules prior to the irradiation. The spin Hamiltonian parameters were successfully interpreted with the model of transferred hyperfine interaction by exchange polarization supporting the localization of O− in (F,OH)− sites. The O− center has the same thermal stability as the absorption band centered at 620 nm, which is responsible for the blue color. The intensity of the absorption band correlates linearly with the O− concentration. Its correlation with the blue color is discussed.  相似文献   

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