| 1. |
- Taylor, M. J., et al.
(författare)
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Raman investigations of indium iodide complexes : evidence for the In2I7- ion
- 2000
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 31:6, s. 465-468
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra of some indium iodide complexes were studied, including alpha- and beta-InI3 and In2I4. InI3 with KI yields K+InI4-. With CsI the spectra reveal, in addition to Cs+InI4-, the complex anion In2I7- in the solid phase CsI:2InI(3), This structure consists of InI3 groups with a linking In-I-in bridge which appears to be linear. The vibrational spectra were calculated for the dimeric In2I6 molecule at the HF, B3LYP and MP2 levels, but the structure turned out to be unstable when such calculations were attempted for In2I7-.
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| 2. |
- Frost, Ray L., et al.
(författare)
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Raman spectroscopy at temperatures between 298 and 423 K and at 77 K of kaolinites intercalated with formamide
- 1998
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 29:12, s. 1065-1069
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectra of kaolinite and of the formamide-intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm-1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls move to higher wavenumbers. Upon intercalation of the kaolinite with formamide, an additional Raman band attributed to the formation of a hydrogen-bonded complex between the inner surface hydroxyls and the carbonyl group of the formamide is observed at 3627 cm-1 at 298 K and at 3631 cm-1 at 77 K. Raman spectra of the deintercalation of the formamide-intercalated kaolinite are obtained by using the thermal stage to heat the intercalated kaolinite in situ. A decrease in intensity of the bands formed through intercalation and at the same time an increase in intensity of the inner surface hydroxyl bands are observed. A loss of intensity of the low-wavenumber region of the formamide-intercalated kaolinite is also observed.
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| 3. |
- Afzelius, Mikael, et al.
(författare)
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Precision of single-shot dual-broadband rotational CARS thermometry with single-mode and multi-mode Nd : YAG lasers
- 2003
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 34:12, s. 940-945
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Konferensbidrag (refereegranskat)abstract
- The precision of single-shot coherent anti-Stokes Raman spectroscopy (CARS) thermometry is an important characteristic for the application of CARS in various combustion devices such as internal combustion engines. It is generally assumed that the precision of CARS is directly related to the spectral noise of the interacting laser fields, and previous studies have presented a theoretical model describing the behaviour of the noise as a function of various experimental parameters. In this work, the aim was to test the results predicted by the previously developed model for dual-broadband rotational CARS. We studied the precision of evaluated temperatures in pure nitrogen under different experimental conditions, namely the dependence of precision on the gas pressure and on the linewidth of the narrowband laser (the Nd: YAG laser). It was demonstrated that our experiments reproduce the main features of the model, and that a single-mode Nd: YAG laser leads to better precision than a multi-mode Nd: YAG laser for dual-broadband rotational CARS thermometry. Copyright (C) 2003 John Wiley Sons, Ltd.
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| 4. |
- Ali, Hassan, et al.
(författare)
-
Insight into thermally induced solid-state polymorphic transformation of sulfathiazole using simultaneous in situ Raman spectroscopy and differential scanning calorimetry
- 2009
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:8, s. 887-892
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Tidskriftsartikel (refereegranskat)abstract
- Pharmaceutical solids exposed to thermal stress during manufacturing processes undergo various phase transformations in bulk drug substances or excipients, resulting in altered dosage form performance. Due to its relatively rapid spectral acquisition rate, as well as the possibility of incorporation into in-line monitoring, Raman spectroscopy is ideally suited to monitoring the transformation between different solid-state forms. In this study, we demonstrate that the transition temperature for polymorphs can be estimated from the transformation profiles obtained from real-time, in situ, simultaneous Raman spectroscopic, and differential scanning calorimetric data. Using this method, we have estimated the transition temperature of the solid-state transformation of the enantiotropically related sulfathiazole polymorphs III and I. These results suggest that this method is a useful approach to determine transition temperatures in systems that are not amenable to accessing other methods
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| 5. |
- Ali, Hassan, et al.
(författare)
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Vibrational spectroscopic study of budesonide
- 2007
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 38:7, s. 903-908
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Tidskriftsartikel (refereegranskat)abstract
- The Raman spectrum of budesonide is reported for the first time, and molecular assignments are proposed on the basis of ab initio BLYP DFT calculations with a 6-31 G* basis set and vibrational wavenumbers predicted on a quasi-harmonic approximation. Comparison with previously published infrared data has explained several spectral features, and the relative band intensities in the C=O and C=C stretching regions are interpreted. The results from this study provide data that can be used for the preparative process monitoring of budesonide, an important steroidal pharmaceutical in various dosage forms, and its interaction with excipients and other components
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| 6. |
- Bohlin, Alexis, et al.
(författare)
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Improvement of rotational CARS thermometry in fuel-rich hydrocarbon flames by inclusion of N-2-H-2 Raman line widths
- 2009
-
Ingår i: Journal Of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 788-794
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Konferensbidrag (refereegranskat)abstract
- In rotational coherent anti-Stokes Raman spectroscopy (CARS) thermometry applied to air-fed flames, the temperature sensitivity mainly depends on the intensity distribution of the nitrogen spectral lines. Temperatures are estimated by numerical fitting of theoretical spectra to experimental ones, and one uncertainty in the calculation of theoretical CARS spectra for specific flame conditions is the accuracy in utilized line-broadening coefficients. In a previous article, self-broadened N-2-N-2 line widths were considered in the spectral calculations as well as those of N-2-CO, N-2-CO2, N-2-H2O, and N-2-O-2- In the present article, we also include N-2-H-2 line widths calculated from a newly developed model, and it is shown that the evaluated temperature from flame spectra increases with increasing mole fractions of hydrogen. For example, in a very rich flame at Phi = 2.5, the use of available line-width data for all major species gives a temperature raise of 72 K at a temperature of similar to 1700 K, in comparison with using self-broadened N-2-N-2 line widths only. Half of this temperature raise is related to the inclusion of N-2-H-2 line widths. This article emphasizes the importance of using adequate line-broadening models for rotational CARS thermometry in flames. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 7. |
- Bohlin, Alexis, et al.
(författare)
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On the sensitivity of rotational CARS N-2 thermometry to the Herman-Wallis factor
- 2011
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 42:10, s. 1843-1847
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Tidskriftsartikel (refereegranskat)abstract
- Purely rotational spectral signals of coherent anti-Stokes Raman scattering (CARS) from nitrogen molecules are studied as a function of the vibration-rotation interaction that weakens the rigid rotor approximation under which the dominant terms of the Raman cross section are calculated. The effect of the vibration-rotation interaction is quantified by means of the Herman-Wallis (HW) factor, and different approaches to its determination are evaluated in terms of their relative contribution to the CARS intensity and thermometric measurements made in a fuel-rich hydrocarbon flame. Known HW factors are contrasted with more complete expressions of recent derivation, and it is found that relative line strength adjustments amount to about a few percent. Such differences result in temperature corrections of less than 1%. This value should be considered for the definition of the ideal thermometric accuracy of the technique but it is of minor importance in comparison with other sources of uncertainty (e. g. Raman line widths) that emerge from the complexity typical of reactive gas mixtures. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 8. |
- Bohlin, Alexis, et al.
(författare)
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On the sensitivity of rotational O2 CARS thermometry to the Herman-Wallis factor
- 2012
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- Contributions of vibrationrotation interaction to line intensities of pure rotational coherent anti-Stokes Raman scattering (CARS) of oxygen are here considered in the perspective of what was remarked by us recently for nitrogen. The interaction is conventionally evaluated by means of the so-called HermanWallis (HW) factor, the need of which is conceptually clear but the theoretical expression is debatable, as shown in the literature of this field. In this work, the various solutions for the anisotropic HW factor of pure rotational Raman transitions are compared in light of the implications for the corresponding CARS spectral line intensities. The results show that neglecting the use of HW factors in rotational N2 and O2 CARS thermometry leads to systematic overestimation of temperatures; on the order of 1.5% in the temperature range 300-2100K in comparison with the use of the most plausible HW factors. The results also suggest that, in general, oxygen is more sensitive than nitrogen to the HW correction, and in particular, different S-branch HW expressions for oxygen are responsible for thermometric uncertainties between 0.5% and 1% at flame temperatures. Copyright (c) 2012 John Wiley & Sons, Ltd.
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| 9. |
- Bohlin, Alexis, et al.
(författare)
-
Validation of a rotational coherent anti-Stokes Raman scattering model for N2O at temperatures from 295K to 796K
- 2012
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 43:5, s. 604-610
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Tidskriftsartikel (refereegranskat)abstract
- Pure rotational coherent anti-Stokes Raman scattering (CARS) spectra of N2O was recorded in a series of temperature calibrated cell measurements in the region 295-796K. A theoretical rotational CARS code for N2O was implemented and temperature analysis was performed by fitting the modeled theoretical spectra to the experimental spectra. Excellent agreement between the experimental and modeled spectra was obtained and the thermometric accuracy for the measurements was evaluated to be better than 1%. Also, rotational N2 CARS spectra were recorded at the same measurement conditions and the temperature analysis performed on these spectra resulted in the same accuracy. The peak signal strength was found to be similar to 5 times stronger for N2O than for N2 at ambient temperature and pressure. The temperature precision was evaluated to a relative standard deviation of 2.0%-2.7% in the studied temperature range, about half of the values for N2, which is attributed to the larger number of spectral lines for N2O. Rotational N2O CARS thermometry show great potential, because of a high Raman cross-section and large number of populated rotational states at any temperature. Copyright (c) 2012 John Wiley & Sons, Ltd.
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| 10. |
- Brackmann, Christian, 1973, et al.
(författare)
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CARS microscopy of lipid stores in yeast: the impact of nutritional state and genetic background
- 2009
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 748-756
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a protocol for sub-micrometer resolved and chemically specific imaging of lipid storage in vivo employing coherent anti-Stokes Raman scattering (CARS) microscopy of one of the most important model organisms Saccharomyces cerevisiae - the yeast cell. By probing the carbon-hydrogen vibration using the nonlinear process of CARS, lipid droplets in the yeast cells clearly appear, as confirmed by comparative studies on relevant labeled organelles using two-photon fluorescence microscopy. From the images, unique quantitative data can be deduced with high three-dimensional resolution, such as the volume, shape, number, and intracellular location of the neutral lipid stores. We exemplify the strength and usability of the method for two cases: the impact on lipid storage of the nutritional condition (starvation and type of carbon source available) as well as of genetic modification of two fundamental metabolic regulation pathways involving carbohydrate and lipid storage (BCY1 and DGA1, LRO1, ARE1/2 deletions), respectively. While the impact of carbon source on the total cellular lipid volume was minimal, long-term starvation induces a significant accumulation of lipid droplets. We also confirm that the lipid-storage-deficient mutant is indeed unable to synthesize lipid droplets, and that the inability of the bcy1-mutant to store carbohydrates is compensated by a two-fold increase in stored neutral lipids. We note that there is a significant cell-to-cell variability in neutral lipid storage in general, i.e. that there is a correspondence to the noise found for gene expression also in lipidomics. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 11. |
- Brackmann, Christian, 1973, et al.
(författare)
-
Visualization of β-carotene and starch granules in plant cells using CARS and SHG microscopy
- 2010
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 42:4, s. 586-592
-
Tidskriftsartikel (refereegranskat)abstract
- Information on the content and bioavailability of provitamin A carotenoids, such as beta-carotene, in plant foods is of great interest due to the widespread vitamin A deficiency in developing countries. While the amount of beta-carotene can readily be quantified with analytical techniques, there is limited information on beta-carotene morphology in native plant materials. Here, we introduce nonlinear microscopy for three-dimensional, label-free imaging of carotenoids in fresh and thermally treated plant tissues, providing quantitative information at single-aggregate level and detailed insight into their distribution. Carotenoids in orange-fleshed sweet potato (OFSP), carrot, and mango were visualized by coherent anti-Stokes Raman scattering (CARS) microscopy and, in the case of OFSP, related to the plant-matrix morphology by simultaneous second-harmonic generation (SHG) microscopy of starch granules. Sizes, shapes, densities, and location of different types of carotenoid bodies were quantified. While OFSP and carrot showed heterogeneous rod-shaped bodies with high carotenoid densities indicated by higher CARS signals, the carotenoid-filled lipid droplets in mango appeared as homogeneous low-density aggregates of rounded shape. In addition, beta-carotene densities and morphologies in OFSP were studied after thermal processing, showing that the bodies remain intact despite significant changes of the surrounding starch granules.
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| 12. |
- Buldyreva, J, et al.
(författare)
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Linewidth modelling of C2H2-N-2 mixtures tested by rotational CARS measurements
- 2006
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 37:6, s. 647-654
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Tidskriftsartikel (refereegranskat)abstract
- The acetylene-nitrogen system is investigated in a combined theoretical and experimental effort in view of its thermometry applications. Accurate values of the rotational Raman linewidths of acetylene are of crucial importance for the computation of spectra from rotational coherent anti-Stokes Raman scattering (CARS) used for temperature and concentration evaluations. Since the direct measurements of these linewidths are not available, they are rigorously calculated by a semi-classical Robert-Bonamy formalism employing exact trajectories. The computed linewidths are used as input parameters in the theoretical spectra simulation, which is also improved by the inclusion of an interbranch interference with coherent Stokes Raman scattering (CSRS). These theoretical spectra are used to evaluate the temperature from experimental CARS spectra of acetylene-nitrogen mixtures recorded in the pressure range 0.1-0.6 MPa. The new linewidths (NLWs) and the CSRS interference inclusion result in a clear improvement of spectral fitting as well as in reasonable values of evaluated temperatures. Copyright (c) 2006 John Wiley & Sons, Ltd.
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| 13. |
- Chaix-Pluchery, O., et al.
(författare)
-
First-order Raman scattering in three-layered Mo-based ternaries: MoAlB, Mo2Ga2C and Mo2GaC
- 2017
-
Ingår i: Journal of Raman Spectroscopy. - : WILEY. - 0377-0486 .- 1097-4555. ; 48:5, s. 631-638
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Tidskriftsartikel (refereegranskat)abstract
- Here, we report, for the first time, on the first-order Raman spectra of the layered Mo-based ternaries: MoAlB, Mo2Ga2C and Mo2GaC. Polycrystalline samples were fabricated, and well-defined Raman spectra were recorded. When the experimental peak positions were compared with those predicted from density functional theory, good agreement was obtained, indirectly validating both. Furthermore, all modes in the three compounds were symmetry assigned. Copyright (c) 2017 John Wiley amp; Sons, Ltd.
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| 14. |
- Dong, Bin, et al.
(författare)
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Experimental and theoretical evidence for the chemical mechanism in SERRS of rhodamine 6G adsorbed on colloidal silver excited at 1064 nm
- 2010
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 41:7, s. 719-720
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Tidskriftsartikel (refereegranskat)abstract
- The evidence for the existence of a chemical mechanism in surface-enhanced resonance Raman scattering (SERRS) of rhodamine 6G (R6G) adsorbed on colloidal silver excited at 1064 nm is reported on the basis of experimental and theoretical analyses. A weak absorption peak at around 1060 nm for R6G-functionalized silver nanoparticles was observed, which is not present in the individual spectra of R6G or silver nanoparticles. Theoretically, the charge difference density reveals that this weak absorption is a metal-to-molecule charge transfer excited state. Copyright (C) 2010 John Wiley & Sons, Ltd.
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| 15. |
- Dong, Bin, et al.
(författare)
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Is 4-nitrobenzenethiol converted to p,p '-dimercaptoazobenzene or 4-aminothiophenol by surface photochemistry reaction?
- 2011
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 42:6, s. 1205-1206
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, the experimental and theoretical evidence for the conversion of 4-nitrobenzenethiol (4-NBT) to p,p'-dimercaptoazobenzene (DMAB) in Ag and Cu sols by surface photochemistry reaction is obtained with surface-enhanced Raman scattering (SERS) spectroscopy. The SERS spectrum of 4-NBT in Cu sol is identical to that of DMAB produced from 4-aminothiophenol in Ag sol as reported in recent literature, thereby providing direct spectral evidence. Copyright (C) 2011 John Wiley & Sons, Ltd.
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| 16. |
- Dyakov, Sergey, et al.
(författare)
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Influence of the buffer layer properties on the intensity of Raman scattering of graphene
- 2013
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 44:6, s. 803-809
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Tidskriftsartikel (refereegranskat)abstract
- Using a model of oscillating dipoles, we simulate the intensity of the G-band in the Raman signal from structures consisting of graphene, separated by an arbitrary buffer layer from a substrate. It is found that a structure with an optimized buffer layer refractive index and thickness exhibits a Raman signal which is nearly 50 times more intense than that from the same structure with a non-optimized buffer layer. The theoretical simulations are verified by Raman measurements on structures consisting of a layer of graphene on SiO2 and Al2O3 buffer layers. The optical contrast of the single graphene layer is calculated for an arbitrary buffer layer. It was found that both the Raman intensity and optical contrast can be maximized by varying the buffer layer thickness.
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| 17. |
- Ehn, Andreas, et al.
(författare)
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Temporal filtering with fast ICCD cameras in Raman studies
- 2013
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 44:4, s. 622-629
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Tidskriftsartikel (refereegranskat)abstract
- A common problem when applying Raman scattering in applied research is spectral interference from laser-induced fluorescence. Extensive work has been invested in developing spectral and polarization filters as well as modulation schemes to refine spontaneous Raman signals. This current work, however, focuses on utilizing the temporal domain using a picosecond laser system and ICCD cameras with relatively short decay of the camera gate to prevent the fluorescence tail from being captured in Raman experiments. Further, the approach of using an ICCD camera to perform temporal filtering is compared to earlier proposed detection schemes using streak cameras or Kerr gates. The temporal-filtering scheme is evaluated in a spectroscopic investigation where a background subtraction algorithm is presented. The temporal-filtering scheme was also evaluated for Raman imaging of a levitated water droplet surrounded by fluorescing toluene vapor. Furthermore, the temporal-filter detection scheme was simulated in order to provide straight forward evaluation tools to estimate the potential of performing temporal filtering with a laser/camera system considering: laser-pulse duration, time jitter, camera-gate characteristics, gate delay times, fluorescence lifetimes, and relative signal strength between the Raman and fluorescence signal. The fluorescence signal was modeled with a closed two-level system, and the simulated results were compared to results from an investigation of the rising slope of toluene fluorescence. These evaluation tools and experimental investigations may serve as guidelines for planning and performing Raman measurements in situations where traditional filter-rejection schemes are insufficient.
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| 18. |
- Enman, Josefine, et al.
(författare)
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Raman analysis of synthetic eritadenine
- 2008
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:10, s. 1464-1468
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Tidskriftsartikel (refereegranskat)abstract
- Eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)-butyric acid, is a cholesterol-reducing compound naturally occurring in the shitake mushroom (Lentinus edodes). To identify the unknown Raman spectrum of this compound, pure synthetic eritadenine was examined and the vibrational modes were assigned by following the synthesis pathway. This was accomplished by comparing the known spectra of the starting compounds adenine and D-ribose with the spectra of a synthesis intermediate, methyl 5-(6-Aminopurin-9H-9-yl)-2,3-O-isopropylidene-5-deoxy-β-D-ribofuranoside (MAIR) and eritadenine. In the Raman spectrum of eritadenine, a distinctive vibrational mode at 773 cm-1 was detected and ascribed to vibrations in the carbon chain, ν(C--C). A Raman line that arose at 1212 cm-1, both in the Raman spectrum of MAIR and eritadenine, was also assigned to ν(C--C). Additional Raman lines detected at 1526 and at 1583 cm-1 in the Raman spectrum of MAIR and eritadenine were assigned to ν(N--C) and a deformation of the purine ring structure. In these cases the vibrational modes are due to the linkage between adenine and the ribofuranoside moiety for MAIR, and between adenine and the carbon chain for eritadenine. This link is also the cause for the disappearance of adenine specific Raman lines in the spectrum of both MAIR and eritadenine. Several vibrations observed in the spectrum of D-ribose were not observed in the Raman spectrum of eritadenine due to the absence of the ribose ring structure. In the Raman spectrum of MAIR some of the D-ribose specific Raman lines disappeared due to the introduction of methyl and isopropylidene moieties to the ribose unit. With the approach presented in this study the so far unknown Raman spectrum of eritadenine could be successfully identified and is presented here for the first time.
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| 19. |
- Erjavec, Nika, et al.
(författare)
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Raman spectroscopy as a tool for detecting mitochondrial fitness
- 2016
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 47:8, s. 933-939
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Tidskriftsartikel (refereegranskat)abstract
- Raman spectroscopy allows the molecular chemical analysis of whole living cells by comparing them to known Raman signatures of specific vibrational bonds. In this work we used Raman spectroscopy to differentiate between wild type yeast cells and mutants characterized by increased or reduced mitochondrial fragmentation. To associate mitochondrial fragmentation with biochemical markers, we performed Linear Discriminant Analysis (LDA) of whole cell Raman spectra (~50–100 cells/spectrum). We show that the long-lived, less fragmented mutants fall into a significantly distant cluster from the wild type and short-lived, more fragmented mutants. Clustering depends on respiratory growth and coincides with that of membrane phospholipids and some respiratory chain components. Spectral clustering is supported by enzymatic activity measurements of OXPHOS Complexes. In addition, we find that NAD(P)H autofluorescence also correlates with mitochondrial fragmentation, representing another likely aging biomarker, besides phospholipids and OXPHOS components. In summary, we demonstrate that Raman spectroscopy has the potential to become a powerful tool for differentiating healthy from unhealthy aged tissues, as well as for the prognostic evaluation of mitochondrial function and fitness.
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| 20. |
- Ghignone, Stefano, et al.
(författare)
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The Raman spectrum of florencite-(REE) [REEAl3(PO4)2(OH)6] : An integrated experimental and computational approach
- 2024
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Ingår i: Journal of Raman Spectroscopy. - 0377-0486 .- 1097-4555. ; 55:3, s. 394-405
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Tidskriftsartikel (refereegranskat)abstract
- Florencite is a hydrous light rare-earth elements (LREE) aluminium phosphate [REEAl3(PO4)2(OH)6], that amongst the REE-rich minerals is quite common. The main end-members are Ce-, La- and Nd-rich terms that were found in several genetic environments. Despite the large occurrence worldwide, to the authors' knowledge, florencite has attracted very few studies, particularly concerning the characterization of its Raman spectrum. We present a detailed study of the Raman spectrum of florencite, combining experimental measurements and theoretical calculations. Experimental Raman spectra (in the 100–1300 cm−1 spectral range) are measured on four florencite samples characterized by different chemical composition, that is, different REE abundance. The results highlight a remarkable coincidence between different Raman spectra measured on each sample, despite the significantly different chemical compositions in terms of their REE content. The same similarities were also observed in the computed spectra at the ab initio level; moreover, the calculations allowed the attributions of the different Raman signals to specific vibrational modes.
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| 21. |
- Gomes, Adriano, et al.
(författare)
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A micro-Raman spectroscopic study of Cr(OH)3 and Cr2O3 nanoparticles obtained by the hydrothermal method
- 2017
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 48:10, s. 1256-1263
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 John Wiley & Sons, Ltd. Cr 2 O 3 nanoparticles, widely used in the industry, can be obtained by calcination of the nanoparticles synthesized via the hydrothermal method. The chemical nature and the morphology of as-prepared and calcined nanoparticles are investigated by scanning electron microscopy, X-ray diffraction and Raman spectroscopy. Our results indicate that the as-prepared nanoparticles mainly consist of amorphous and hydrated Cr(OH) 3 , with only minor amounts of Cr 2 O 3 . By contrast, and as already known before, calcined nanoparticles consist of Cr 2 O 3 . We also demonstrate the effect of inappropriately chosen experimental conditions, because the use of laser intensities above 0.7 mW during the Raman experiments causes a local heating and thus induces the transformation of Cr(OH) 3 into Cr 2 O 3 . The correlation between the laser power and a local heating is further corroborated by thermogravimetric analyses, which show that upon increased temperature, Cr(OH) 3 first dehydrates and then partially condensates to the intermediate CrO(OH) form, to finally attain the crystalline form of Cr 2 O 3 at about 409°C.
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| 22. |
- Grondin, J., et al.
(författare)
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Revisited vibrational assignments of imidazolium-based ionic liquids
- 2011
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 42:4, s. 733-743
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Tidskriftsartikel (refereegranskat)abstract
- Imidazolium-based ionic liquids (ILs) involving anions of variable coordinating strength have been investigated using infrared (IR) and Raman spectroscopies, density functional theory (DFT) calculations and selective deuteration of the imidazolium CH groups. Particular emphasis has been placed on the vibrational assignments of the anion and cation internal vibrations, a prerequisite before any interpretation of spectral changes due to ion-ion interactions in these unconventional liquids. The vibrations of highly symmetric and weakly coordinating anions, such as PF(6)(-), have unperturbed wavenumbers, but unexpected IR or Raman activity for some modes, showing that the anion is subjected to an anisotropic electric field. The stretching as well as the in-plane and out-of-plane bending modes of the imidazolium CH groups are anharmonic. They give broad bands that reflect a large distribution of interactions with the surrounding anions. All the bending modes are mixed with ring vibrations and the stretching modes are complicated by Fermi resonance interactions with overtones and combination of in-plane ring modes. However, the stretching vibration of the quasi-diatomic C((2))-D bond appears to be a good spectroscopic probe of the increasing cation-anion interactions when the coordinating strength of the anion increases. The broad absorption observed in the far IR with weakly coordinating anions remains practically unchanged when the acidic C((2))-H imidazolium bond is methylated and even when the imidazolium cation is substituted by tetra-alkyl ammonium or pyrrolidinium cations. It is concluded that this absorption is a general feature of any IL, coming from the relative translational and librational motions of the ions without needing to invoke C((2))-H anion hydrogen bonds.
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| 23. |
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| 24. |
- Holmlid, Leif, 1942
(författare)
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Vibrational transitions in Rydberg matter clusters from stimulated Raman and Rabi-flopping phase delay in the infrared
- 2008
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:10, s. 1364-1374
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Tidskriftsartikel (refereegranskat)abstract
- Recently, rotational spectra of giant Rydberg matter (RM) clusters were studied in the radio frequency range (Mol. Phys. 105 (2007) 933-939), giving high-precision bond distances in the nanometer range. However, the theoretical and experimental problem of vibrational motion or, rather, coupled electronic-vibrational motion in the RM clusters is still unsolved; but it is expected that broad phonon bands will exist. Spectroscopic signatures from space make it likely that RM is a common form of matter in the Universe, and phonon bands in this spectroscopic range have not been taken into account so far. Spectroscopic results are now reported on transitions in the range 0.01-20 cm-1, using primarily infrared (IR) lasers to probe the RM in a tunable open cavity with a Fabry-Perot interferometer to aid in the identification of the shifts. Stimulated Raman scattering from electronic transitions and Rabi-flopping from electronic states in the clusters are observed. The broad stimulated Raman peaks are assigned to one and two consecutive vibrational (electronic-vibrational) transitions. Theoretical values predicted for vibrations (phonon maxima) and electronic processes are in reasonable agreement with the experimental results. Improved calculations are needed to verify the assignments of the vibrational phonon distributions.
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| 25. |
- Holomb, Roman, et al.
(författare)
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Ionic liquid structure: the conformational isomerism in 1-butyl-3-methyl-imidazolium tetrafluoroborate ([bmim][BF4])
- 2008
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 39:7, s. 793-805
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Tidskriftsartikel (refereegranskat)abstract
- As a probe of local structure, the vibrational properties of the 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] ionic liquid were studied by infrared (IR), Raman spectroscopy, and ab initio calculations. The coexistence of at least four [bmim]+ conformers (GG, GA, TA, and AA) at room temperature was established through unique spectral responses. The Raman modes characteristic of the two most stable [bmim] + conformers, GA and AA, according to the ab initio calculations, increase in intensity with decreasing temperature. To assess the total spectral behavior of the ionic liquid both the contributions of different [bmim] + conformers and the [bmim]+- [BF4]- interactions to the vibrational spectra are discussed.
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