Raman spectroscopic study of the tellurite minerals: carlfriesite and spiroffite

Raman spectroscopy has been used to study the tellurite minerals spiroffite and carlfriesite, which are minerals of formula type A(2)(X(3)O(8)) where A is Ca(2+) for the mineral carlfriesite and is Zn(2+) and Mn(2+) for the mineral spiroffite. Raman bands for spiroffite observed at 721 and 743 cm(-1), and 650 cm(-1) are attributed to the nu(1) (Te(3)O(8))(2-) symmetric stretching mode and the nu(3) (Te(3)O(8))(2-) antisymmetric stretching modes, respectively. A second spiroffite mineral sample provided a Raman spectrum with bands at 727 cm(-1) assigned to the nu(1) (Te(3)O(8))(2-) symmetric stretching modes and the band at 640cm(-1) accounted for by the nu(3) (Te(3)O(8))(2-) antisymmetric stretching mode. The Raman spectrum of carlfriesite showed an intense band at 721 cm(-1). Raman bands for spiroffite, observed at (346, 394) and 466 cm(-1) are assigned to the (Te(3)O(8))(2-)nu(2) (A(1)) bending mode and nu(4) (E) bending modes. The Raman spectroscopy of the minerals carlfriesite and spiroffite are difficult because of the presence of impurities and other diagenetically related tellurite minerals.     

Raman spectroscopic study of the tellurite minerals: rajite and denningite

Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.     

Raman and infrared spectroscopy of selected vanadates

Raman and infrared spectroscopy has been used to study the structure of selected vanadates including pascoite, huemulite, barnesite, hewettite, metahewettite, hummerite. Pascoite, rauvite and huemulite are examples of simple salts involving the decavanadates anion (V10O28)6-. Decavanadate consists of four distinct VO6 units which are reflected in Raman bands at the higher wavenumbers. The Raman spectra of these minerals are characterised by two intense bands at 991 and 965 cm(-1). Four pascoite Raman bands are observed at 991, 965, 958 and 905 cm(-1) and originate from four distinct VO6 sites. The other minerals namely barnesite, hewettite, metahewettite and hummerite have similar layered structures to the decavanadates but are based upon (V5O14)3- units. Barnesite is characterised by a single Raman band at 1010 cm(-1), whilst hummerite has Raman bands at 999 and 962 cm(-1). The absence of four distinct bands indicates the overlap of the vibrational modes from two of the VO6 sites. Metarossite is characterised by a strong band at 953 cm(-1). These bands are assigned to nu1 symmetric stretching modes of (V6O16)2- units and terminal VO3 units. In the infrared spectra of these minerals, bands are observed in the 837-860 cm(-1) and in the 803-833 cm(-1) region. In some of the Raman spectra bands are observed for pascoite, hummerite and metahewettite in similar positions. These bands are assigned to nu3 antisymmetric stretching of (V10O28)6- units or (V5O14)3- units. Because of the complexity of the spectra in the low wavenumber region assignment of bands is difficult. Bands are observed in the 404-458 cm(-1) region and are assigned to the nu2 bending modes of (V10O28)6- units or (V5O14)3- units. Raman bands are observed in the 530-620 cm(-1) region and are assigned to the nu4 bending modes of (V10O28)6- units or (V5O14)3- units. The Raman spectra of the vanadates in the low wavenumber region are complex with multiple overlapping bands which are probably due to VO subunits and MO bonds.     

Infrared and infrared emission spectroscopy of the zinc carbonate mineral smithsonite

Infrared emission and infrared spectroscopy has been used to study a series of selected natural smithsonites from different origins. An intense broad infrared band at 1440cm(-1) is assigned to the nu(3) CO(3)(2-) antisymmetric stretching vibration. An additional band is resolved at 1335cm(-1). An intense sharp Raman band at 1092cm(-1) is assigned to the CO(3)(2-) symmetric stretching vibration. Infrared emission spectra show a broad antisymmetric band at 1442cm(-1) shifting to lower wavenumbers with thermal treatment. A band observed at 870cm(-1) with a band of lesser intensity at 842cm(-1) shifts to higher wavenumbers upon thermal treatment and is observed at 865cm(-1) at 400 degrees C and is assigned to the CO(3)(2-)nu(2) mode. No nu(2) bending modes are observed in the Raman spectra for smithsonite. The band at 746cm(-1) shifts to 743cm(-1) at 400 degrees C and is attributed to the CO(3)(2-)nu(4) in phase bending modes. Two infrared bands at 744 and around 729cm(-1) are assigned to the nu(4) in phase bending mode. Multiple bands may be attributed to the structural distortion ZnO(6) octahedron. This structural distortion is brought about by the substitution of Zn by some other cation. A number of bands at 2499, 2597, 2858, 2954 and 2991cm(-1) in both the IE and infrared spectra are attributed to combination bands.     

Vibrational spectroscopy of stichtite

Raman spectroscopy complimented with infrared spectroscopy has been used to study the mineral stitchtite, a hydrotalcite of formula Mg6Cr2(CO3)(OH)16.4H2O. Two bands are observed at 1087 and 1067 cm(-1) with an intensity ratio of approximately 2.5/1 and are attributed to the symmetric stretching vibrations of the carbonate anion. The observation of two bands is attributed to two species of carbonate in the interlayer, namely weakly hydrogen bonded and strongly hydrogen bonded. Two infrared bands are found at 1457 and 1381 cm(-1) and are assigned to the antisymmetric stretching modes. These bands were not observed in the Raman spectrum. Two infrared bands are observed at 744 and 685 cm(-1) and are assigned to the nu4 bending modes. Two Raman bands were observed at 539 and 531 cm(-1) attributed to the nu2 bending modes. Importantly the band positions of the paragenically related hydrotalcites stitchtite, iowaite, pyroaurite and reevesite all of which contain the carbonate anion occur at different wavenumbers. Consequently, Raman spectroscopy can be used to distinguish these minerals, particularly in the field where many of these hydrotalcites occur simultaneously in ore zones.     

Raman spectroscopy of the mineral rhodonite

The mineral rhodonite an orthosilicate has been characterised by Raman spectroscopy. The Raman spectra of three rhodonites from Broken Hill, Pachapaqui and Franklin were compared and found to be similar. The spectra are characterised by an intense band at around 1000 cm(-1) assigned to the nu(1) symmetric stretching mode and three bands at 989, 974 and 936 cm(-1) assigned to the nu(3) antisymmetric stretching modes of the SiO(4) units. An intense band at around 667 cm(-1) was assigned to the nu(4) bending mode and showed additional bands exhibiting loss of degeneracy of the SiO(4) units. The low wave number region of rhodonite is complex. A strong band at 421.9 cm(-1) is attributed to the nu(2) bending mode. The spectra of the three rhodonite mineral samples are similar but subtle differences are observed. It is proposed that these differences depend upon the cationic substitution of Mn by Ca and/or Fe(2+) and Mg.     

Raman spectroscopy of newberyite Mg(PO3OH)·3H2O: a cave mineral

Newberyite Mg(PO3OH)·3H2O is a mineral found in caves such as from Moorba Cave, Jurien Bay, Western Australia, the Skipton Lava Tubes (SW of Ballarat, Victoria, Australia) and in the Petrogale Cave (Madura, Eucla, Western Australia). Because these minerals contain oxyanions, hydroxyl units and water, the minerals lend themselves to spectroscopic analysis. Raman spectroscopy can investigate the complex paragenetic relationships existing between a number of 'cave' minerals. The intense sharp band at 982 cm(-1) is assigned to the PO4(3-)ν1 symmetric stretching mode. Low intensity Raman bands at 1152, 1263 and 1277 cm(-1) are assigned to the PO4(3-)ν3 antisymmetric stretching vibrations. Raman bands at 497 and 552 cm(-1) are attributed to the PO4(3-)ν4 bending modes. An intense Raman band for newberyite at 398 cm(-1) with a shoulder band at 413 cm(-1) is assigned to the PO4(3-)ν2 bending modes. The values for the OH stretching vibrations provide hydrogen bond distances of 2.728 ? (3267 cm(-1)), 2.781 ? (3374 cm(-1)), 2.868 ? (3479 cm(-1)), and 2.918 ? (3515 cm(-1)). Such hydrogen bond distances are typical of secondary minerals. Estimates of the hydrogen-bond distances have been made from the position of the OH stretching vibrations and show a wide range in both strong and weak bonds.     

Raman and infrared spectroscopy of arsenates of the roselite and fairfieldite mineral subgroups

Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the roselite arsenate minerals of the roselite and fairfieldite subgroups of formula Ca(2)B(AsO(4))(2).2H(2)O (where B may be Co, Fe(2+), Mg, Mn, Ni and Zn). The Raman arsenate (AsO(4))(2-) stretching region shows strong differences between the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists with multiple (AsO(4))(2-) antisymmetric stretching vibrations observed, indicating a reduction of the tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong Raman bands around 450 cm(-1) are assigned to nu(4) bending modes. Multiple bands in the 300-350 cm(-1) region assigned to nu(2) bending modes provide evidence of symmetry reduction of the arsenate anion. Three broad bands for roselite are found at 3450, 3208 and 3042 cm(-1) and are assigned to OH stretching bands. By using a Libowitzky empirical equation hydrogen bond distances of 2.75 and 2.67 A are estimated. Vibrational spectra enable the molecular structure of the roselite minerals to be determined and whilst similarities exist in the spectral patterns, sufficient differences exist to be able to determine the identification of the minerals.     

Raman microscopy of autunite minerals at liquid nitrogen temperature

Uranyl micas are based upon (UO(2)PO(4))(-) units in layered structures with hydrated counter cations between the interlayers. Uranyl micas also known as the autunite minerals are of general formula M(UO2)2(XO4)2 x 8-12H2O where M may be Ba, Ca, Cu, Fe(2+), Mg, Mn(2+) or 1/2(HA1) and X is As or P. The structures of these minerals have been studied using Raman microscopy at 298 and 77K. Six hydroxyl stretching bands are observed of which three are highly polarised. The hydroxyl stretching vibrations are related to the strength of hydrogen bonding of the water OH units. Bands in the Raman spectrum of autunite at 998, 842 and 820 cm(-1) are highly polarised. Low intensity band at 915 cm(-1) is attributed to the nu(3) antisymmetric stretching vibration of (UO(2))(2+) units. The band at 820 cm(-1) is attributed to the nu(1) symmetric stretching mode of the (UO(2))(2+) units. The (UO(2))(2+) bending modes are found at 295 and 222 m(-1). The presence of phosphate and arsenate anions and their isomorphic substitution are readily determined by Raman spectroscopy. The collection of Raman spectra at 77K enables excellent band separation.     

A vibrational spectroscopic study of perhamite, an unusual silico-phosphate

The silico-phosphate mineral perhamite has been studied using a combination of electron and vibrational spectroscopy. SEM photomicrographs reveal that perhamite morphology consists of very thin intergrown platelets that can form a variety of habits. Infrared spectroscopy in the hydroxyl-stretching region shows a number of overlapping bands which are observed in the range 3581-3078 cm(-1). These wavenumbers enable an estimation to be made of the hydrogen bond distances in perhamite: 3.176(0), 2.880(5), 2.779(6), 2.749(3), 2.668(1) and 2.599(7)A. Intense Raman bands are observed in the region 1110-1130 and 966-996 cm(-1) and are assigned to the SiO(4) and PO(4) symmetric stretching modes. Other bands are observed in the range 1005-1096 cm(-1) and are attributed to the nu(3) antisymmetric bending modes of PO(4). Some low intensity bands around 874 cm(-1) were discovered and remain unclassified. Bands in the low-wavenumber region are assigned to the nu(4) and nu(2) out-of-plane bending modes of the OSiO and PO(4) units. Raman spectroscopy is a useful tool in determining the vibrational spectroscopy of mixed hydrated multi-anion minerals such as perhamite. Information on such a mineral would be difficult to obtain by other means.     

Raman spectra of carotenoids in natural products

Resonance Raman spectra of naturally occurring carotenoids have been obtained from nautilus, periwinkle (Littorina littorea) and clam shells under 514.5 nm excitation and these spectra are compared with the resonance Raman spectra obtained in situ from tomatoes, carrots, red peppers and saffron. The tomatoes, carrots and red peppers gave rise to resonance Raman spectra exhibiting a nu1 band at ca. 1520 cm(-1), in keeping with its assignment to carotenoids with ca. nine conjugated carbon-carbon double bonds in their main chains, whereas the resonance Raman spectrum of saffron showed a nu1 band at 1537 cm(-1) which can be assigned to crocetin, having seven conjugated carbon-carbon double bonds. A correlation between nu1 wavenumber location and effective conjugated chain length has been used to interpret the data obtained from the shells, and the wavenumber position (1522 cm(-1)) of the nu1 band of the carotenoid in the orange clam shell suggests that it contains nine conjugated double bonds in the main chain. However, the black periwinkle and nautilus shells exhibit nu1 bands at 1504 and 1496 cm(-1), respectively. On the basis of the correlation between nu1 wavenumber location and effective conjugated chain length, this indicates that they contain carotenoids with longer conjugated chains, the former having ca. 11 double bonds and the latter ca. 13 or even more. Raman spectra of the nautilus, periwinkle and clam shells also exhibited a strong band at 1085 cm(-1) and a doublet with components at 701 and 705 cm(-1), which can be assigned to biogenic calcium carbonate in the aragonite crystallographic form.     

A Raman spectroscopic study of the uranyl sulphate mineral johannite

Raman spectroscopy at 298 and 77K has been used to study the secondary uranyl mineral johannite of formula (Cu(UO2)2(SO4)2(OH)2 x 8H2O). Four Raman bands are observed at 3593, 3523, 3387 and 3234cm(-1) and four infrared bands at 3589, 3518, 3389 and 3205cm(-1). The first two bands are assigned to OH- units (hydroxyls) and the second two bands to water units. Estimations of the hydrogen bond distances for these four bands are 3.35, 2.92, 2.79 and 2.70 A. A sharp intense band at 1042 cm(-1) is attributed to the (SO4)2- symmetric stretching vibration and the three Raman bands at 1147, 1100 and 1090cm(-1) to the (SO4)2- anti-symmetric stretching vibrations. The nu2 bending modes were at 469, 425 and 388 cm(-1) at 77K confirming the reduction in symmetry of the (SO4)2- units. At 77K two bands at 811 and 786 cm(-1) are attributed to the nu1 symmetric stretching modes of the (UO2)2+ units suggesting the non-equivalence of the UO bonds in the (UO2)2+ units. The band at 786cm(-1), however, may be related to water molecules libration modes. In the 77K Raman spectrum, bands are observed at 306, 282, 231 and 210cm(-1) with other low intensity bands found at 191, 170 and 149cm(-1). The two bands at 282 and 210 cm(-1) are attributed to the doubly degenerate nu2 bending vibration of the (UO2)2+ units. Raman spectroscopy can contribute significant knowledge in the study of uranyl minerals because of better band separation with significantly narrower bands, avoiding the complex spectral profiles as observed with infrared spectroscopy.     

Peisleyite an unusual mixed anion mineral--a vibrational spectroscopic study

The mineral peisleyite has been studied using a combination of electron microscopy and vibrational spectroscopy. Scanning electron microscope (SEM) photomicrographs reveal that the peisleyite morphology consists of an array of small needle-like crystals of around 1 microm in length with a thickness of less than 0.1 microm. Raman spectroscopy in the hydroxyl stretching region shows an intense band at 3506 cm(-1) assigned to the symmetric stretching mode of the OH units. Four bands are observed at 3564, 3404, 3250 and 3135 cm(-1) in the infrared spectrum. These wavenumbers enable an estimation of the hydrogen bond distances 3.052(5), 2.801(0), 2.705(6) and 2.683(6)A. Two intense Raman bands are observed at 1023 and 989 cm(-1) and are assigned to the SO(4) and PO(4) symmetric stretching modes. Other bands are observed at 1356, 1252, 1235, 1152, 1128, 1098 and 1067 cm(-1). The bands at 1067 cm(-1) is attributed to AlOH deformation vibrations. Bands in the low wavenumber region are assigned to the nu(4) and nu(2) out of plane bending modes of the SO(4) and PO(4) units. Raman spectroscopy is a useful tool in determining the vibrational spectroscopy of mixed hydrated multianion minerals such as peisleyite. Information on such a mineral would be difficult to obtain by other means.     

UV near-resonance Raman spectroscopic study of 1,1'-bi-2-naphthol solutions

The normal and UV near-resonance Raman (UVRR) spectra of 1,1'-bi-2-naphthol (BN) in basic solution were measured and analyzed. Density functional theory (DFT) calculations were carried out to study the ground state geometry structure, vibrational frequencies nu, off-resonance Raman intensities I, and depolarization ratios rho of 1,1'-bi-2-naphtholate dianion (BN(2-)). On the basis of the calculated and experimental results of nu, I, and rho, the observed Raman bands were assigned in detail. The 1612 cm(-1) Raman band of BN in basic solution was found dramatically enhanced in the UV resonance Raman spectrum in comparison with the normal Raman spectrum. Analyzing the depolarization ratios of the 1366 and 1612 cm(-1) bands in the RR spectra manifests that both the symmetric and antisymmetric parts of transition polarizabilities contribute to the 1366 cm(-1) band, but that only the symmetric part contributes to the 1612 cm(-1) band.     

Raman spectroscopy of uranyl rare earth carbonate kamotoite-(Y)

Raman spectroscopy at 298 and 77K has been used to study the mineral kamotoite-(Y), a uranyl rare earth carbonate mineral of formula Y(2)(UO(2))(4)(CO(3))(3)(OH)(8).10-11H(2)O. The mineral is characterised by two Raman bands at 1130.9 and 1124.6 cm(-1) assigned to the nu(1) symmetric stretching mode of the (CO(3))(2-) units, while those at 1170.4 and 862.3 cm(-1) (77K) to the deltaU-OH bending vibrations. The assignment of the two bands at 814.7 and 809.6 cm(-1) is difficult because of the potential overlap between the symmetric stretching modes of the (UO(2))(2+) units and the nu(2) bending modes of the (CO(3))(2-) units. Only a single band is observed in the 77K spectrum at 811.6 cm(-1). One possible assignment is that the band at 814.7 cm(-1) is attributable to the nu(1) symmetric stretching mode of the (UO(2))(2+) units and the second band at 809.6 cm(-1) is due to the nu(2) bending modes of the (CO(3))(2-) units. Bands observed at 584 and 547.3 cm(-1) are attributed to water librational modes. An intense band at 417.7 cm(-1) resolved into two components at 422.0 and 416.6 cm(-1) in the 77K spectrum is assigned to an Y(2)O(2) stretching vibration. Bands at 336.3, 286.4 and 231.6 cm(-1) are assigned to the nu(2) (UO(2))(2+) bending modes. U-O bond lengths in uranyl are calculated from the wavenumbers of the uranyl symmetric stretching vibrations. The presence of symmetrically distinct uranyl and carbonate units in the crystal structure of kamotoite-(Y) is assumed. Hydrogen-bonding network related to the presence of water molecules and hydroxyls is shortly discussed.     

A Raman and infrared spectroscopic study of the uranyl silicates--weeksite, soddyite and haiweeite: part 2

Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals including weeksite K2[(UO2)2(Si5O13)].H2O, soddyite [(UO2)2SiO4.2H2O] and haiweeite Ca[(UO2)2(Si5O12(OH)2](H2O)3 with UO2(2+)/SiO2 molar ratio 2:1 or 2:5. Raman spectra clearly show well resolved bands in the 750-800 cm(-1) region and in the 950-1000 cm(-1) region assigned to the nu1 modes of the (UO2)2+ units and to the (SiO4)4- tetrahedra. Soddyite is characterized by Raman bands at 828.0, 808.6 and 801.8 cm(-1), 909.6 and 898.0 cm(-1), and 268.2, 257.8 and 246.9 cm(-1), attributed to the nu1, nu3, and nu2 (delta) (UO2)2+, respectively. Coincidences of the nu1 (UO2)2+ and the nu1 (SiO4)4- is expected. Bands at 1082.2, 1071.2, 1036.3, 995.1 and 966.3 cm(-1) are attributed to the nu3 (SiO4)4-. Sets of Raman bands in the 200-300 cm(-1) region are assigned to nu2 (delta) (UO2)2+ and UO ligand vibrations. Multiple bands indicate the non-equivalence of the UO bonds and the lifting of the degeneracy of nu2 (delta) (UO2)2+ vibrations. The (SiO4)4- tetrahedral are characterized by bands in the 470-550 cm(-1) and in the 390-420 cm(-1) region. These bands are attributed to the nu4 and nu2 (SiO4)4- bending modes. The minerals show characteristic OH stretching bands in the 2900-3500 and 3600-3700 cm(-1).     

Raman spectroscopic study of a hydroxy-arsenate mineral containing bismuth-atelestite Bi2O(OH)(AsO4)

The Raman spectrum of atelestite Bi2O(OH)(AsO4), a hydroxy-arsenate mineral containing bismuth, has been studied in terms of spectra-structure relations. The studied spectrum is compared with the Raman spectrum of atelestite downloaded from the RRUFF database. The sharp intense band at 834 cm(-1) is assigned to the ν1 AsO4(3-) (A1) symmetric stretching mode and the three bands at 767, 782 and 802 cm(-1) to the ν3 AsO4(3-) antisymmetric stretching modes. The bands at 310, 324, 353, 370, 395, 450, 480 and 623 cm(-1) are assigned to the corresponding ν4 and ν2 bending modes and BiOBi (vibration of bridging oxygen) and BiO (vibration of non-bridging oxygen) stretching vibrations. Lattice modes are observed at 172, 199 and 218 cm(-1). A broad low intensity band at 3095 cm(-1) is attributed to the hydrogen bonded OH units in the atelestite structure. A weak band at 1082 cm(-1) is assigned to δ(BiOH) vibration.     

Using Raman spectroscopy to identify mixite minerals

Raman spectroscopy has been used to identify whether or not a selection of minerals labelled as mixites (formula BiCu6(AsO4)3(OH)6.3H2O) are correctly marked. Of the four samples, two samples are shown to be potentially mixites because of the presence of the characteristic Raman spectra of (AsO4)3- units and (HAsO4)- units, characterised by bands at around 803 and 833 cm(-1). Two of the minerals are shown to be predominantly carbonates. Bands are observed at 3473.9 and 3470.3 cm(-1) for the two mixite samples. Bands observed in the region 880-910 cm(-1) and in the 867-870 cm(-1) region are assigned to the AsO stretching vibrations of (HAsO4)2- and (H2AsO4)- units. Whilst bands at around 803 and 833 cm(-1) are assigned to the stretching vibrations of uncomplexed (AsO4)3- units. Intense bands observed at 473.7 and 475.4 cm(-1) are assigned to the nu4 bending mode of AsO4 units. Bands observed at around 386.5, 395.3 and 423.1 cm(-1) are assigned to the nu2 bending modes of the HAsO4 (434 and 400 cm(-1)) and the AsO4 groups (324 cm(-1)). Raman spectroscopy lends itself to the identification of minerals on host matrices and is especially useful for the identification of mixites.     

Raman spectroscopy of selected lead minerals of environmental significance

The Raman spectra of the minerals cerrusite (PbCO(3)), hydrocerrusite (Pb(2)(OH)(2)CO(3)), phosgenite (Pb(2)CO(3)Cl(2)) and laurionite (Pb(OH)Cl) have been used to qualitatively determine their presence. Laurionite and hydrocerrusite have characteristic hydroxyl stretching bands at 3506 and 3576 cm(-1). Laurionite is also characterised by broad low intensity bands centred at 730 and 595 cm(-1) attributed to hydroxyl deformation vibrations. The minerals cerrusite, hydrocerrusite and phosgenite have characteristic CO (nu(1)) symmetric stretching bands observed at 1061, 1054 and 1053 cm(-1). Phosgenite displays complexity in the CO (nu(3)) antisymmetric stretching region with bands observed at 1384, 1327 and 1304 cm(-1). Cerrusite shows bands at 1477, 1424, 1376 and 1360 cm(-1). The hydrocerrusite Raman spectrum has bands at slightly different positions from cerrusite, with bands at 1479, 1420, 1378 and 1365 cm(-1). The complexity of the nu(3) region is also reflected in the nu(2) and nu(4) regions with the observation of multiple bands. Laurionite is characterised by two intense bands at 328 and 272 cm(-1) attributed to PbO and PbCl stretching bands. Importantly, all four minerals are characterized by their Raman spectra, enabling the mineral identification in leachates and contaminants of environmental significance.     

Vibrational normal modes of diazo-dimedone: a comparative study by Fourier infrared/Raman spectroscopies and conformational analysis by MM/QM

The 2-diazo-5,5-dimethyl-cyclohexane-1,3-dione (3) was synthesized and the FT-IR/Raman spectra were measured with the purpose of obtain a full assignment of the vibrational modes. Singular aspects concerning the -CNN oscillator are discussed in view of two strong bands observed in the region of 2300-2100 cm(-1) in both, Infrared and Raman spectra. The density functional theory (DFT) was used to obtain the geometrical structure and for assisting in the vibrational assignment joint to the traditional normal coordinate analysis (NCA). The observed wavenumbers at 2145 (IR), 2144(R) are assigned as the coupled nu(NN)+nu(CN) vibrational mode with higher participation of the NN stretching. A 2188 cm(-1) (IR) and at 2186 cm(-1) (R) can be assigned as a overtone of one of nu(CC) normal mode or to a combination band of the fundamentals delta(CCH) found at 1169 cm(-1) and the delta (CCN) found at 1017 cm(-1) enhanced by Fermi resonance.