排序方式: 共有30条查询结果,搜索用时 15 毫秒
1.
K. P. Meletov M. P. Kulakov N. N. Kolesnikov J. Arvanitidis G. A. Kourouklis 《JETP Letters》2002,75(8):406-409
Raman spectra of MgB2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ∼590 cm−1 related to the E 2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 18 GPa, whereas, beyond this region, the slope of the pressure-induced frequency shift is reduced by about a factor of two. The pressure dependence of the phonon mode up to ∼5 GPa exhibits a change in the slope, as well as a “hysteresis” effect in the frequency vs. pressure behavior. These singularities in the E 2g mode behavior under pressure support the suggestion that MgB2 may undergo a pressure-induced topological electronic transition. 相似文献
2.
The ionization threshold of fluoranthene and of TMPD in n-pentane was determined by laser two-photon ionization (TPI) and found to be 4.50 ± 0.05 and 3.88 ± 0.05 eV respectively. For both molecules the TPI spectra show distinct structure due to autoionization. For fluoranthene the TPI spectrum suggests that the molecule dissociates via the first excited singlet state. 相似文献
3.
Abstract We have measured the Raman spectra of the quasi-one-dimensional crystal SbSBr as a function of pressure at 295, 70, 37 and 25 K. The pressure coefficients of the observed Raman modes have been determined and used to distinguish inter-from intrachain modes. Spectral features characteristic of the ferroelectric phase have been attributed to impurities or lattice imperfections and not to the presence of the ferroelectric phase, providing indication that the para-to ferroelectric phase transition occurs below 25 K. 相似文献
4.
J. Arvanitidis K. P. Meletov G. A. Kourouklis K. Papagelis A. Soldatov K. Prassides 《高压研究》2013,33(1-6):145-151
Abstract The effect of high hydrostatic pressure, up to 12GPa, on the intramolecular phonon frequencies and the material stability of the two-dimensional tetragonal Cm polymer has been studied by means of Raman spectroscopy in the spectral range of the radial intramolecular modes (200-800cm?1). A number of new Raman modes appear in the spectrum for pressures ~ 1.4 and ~ 5.0 GPa. The pressure coefficients for the majority of the phonon modes exhibit changes to lower values at P=4.0 GPa, which may be related to a structural modification of the 2D polymer to a more isotropic phase. The peculiarities observed in the Raman spectra are reversible and the material is stable in the pressure region investigated. 相似文献
5.
Abstract Tb2(MoO4)3 has been studied by Raman spectroscopy under hydrostatic pressure up to 9 GPa at room temperature. The measurements reveal two phase transitions, one at around 2 GPa and another one above 5 GPa. The first phase transition is associated with an increase in the coordination number of Mo while the second is probably a transition to an amorphous phase in which only a wide band originating from Mo-O vibrations remains. This behaviour is irreversible as the Raman spectrum of the initial structure is not recovered at atmospheric pressure. 相似文献
6.
Daniilia S Minopoulou E Andrikopoulos KS Karapanagiotis I Kourouklis GA 《Analytica chimica acta》2008,611(2):239-249
The purpose of this study is to clarify important details about a Cumaean Sibyl painting that is preserved in a private collection. This work, bearing neither signature nor date, has never undergone conservation. It was executed after Domenichino's Cumaean Sibyl, a work known to have been used as a model by many 18th century painters.Investigation of the anonymous artist's painting technique and identification of its constituent materials were facilitated by employing optical microscopy (OM), scanning electron microscopy (SEM/EDS), FTIR and microRaman spectroscopies and high performance liquid chromatography with diode array detection (HPLC-DAD). The painter's palette comprised lead white, yellow ochre, lead-antimonate yellow (Naples yellow), cinnabar, cochineal lake, madder lake, haematite, Prussian blue and carbon black.The detection of Prussian blue (synthesized in 1704 and widely used as artist's pigment after 1750) was decisive in establishing the work's authenticity for, as such, it cannot be attributed either to Domenico Zampieri (1581-1641) or to his apprentices. In addition, the identification of Naples yellow, which prevailed in the period from 1750 to 1850, supports this statement. Nevertheless, its elaborate painting technique strongly suggests an artist greatly influenced by the Renaissance masters. A comparison of its stylistic features with those of the Cumaean Sibyl of Angelica Kauffmann (1741-1807), a prolific 18th century artist known to have studied and to have copied Domenichino's Sibyl, reveals significant similarities between the two in composition and palette. The unsigned Sibyl, therefore, could well be by Kauffmann. 相似文献
7.
Emmanouil H. Papaioannou Maria Liakopoulou-Kyriakides Dimitrios Christofilos Ioannis Arvanitidis Gerasimos Kourouklis 《Applied biochemistry and biotechnology》2009,159(2):478-487
In the present study, we explore the feasibility of Raman spectroscopy for intracellular monitoring of carotenoid in filamentous
fungi Blakeslea trispora. Although carotenoid production from this fungus has been extensively studied through various chromatographic methods and
ultraviolet-visible spectroscopy, no intracellular monitoring has been demonstrated until now. The intensity of the Raman
spectrum, and more conveniently that of the strongest ν
1 carotenoid band at ∼1,519 cm−1, exhibits a good linear correlation with the carotenoid content of the sample as determined by high-performance liquid chromatography
(HPLC) and ultraviolet-visible (UV-Vis) spectroscopy. Our results suggest that Raman spectroscopy can serve as an alternative
method for the study and quantification of carotenoid in batch-mated submerged cultivations of B. trispora and similar organisms. Although not as accurate as HPLC, it allows a rapid sampling and analysis, avoiding the prolonged
and tedious classical isolation procedures required for carotenoid determination by HPLC and UV-Vis spectroscopy. 相似文献
8.
J. Arvanitidis K. Prassides G.A. Kourouklis T. Takenobu Y. Iwasa 《Journal of Physics and Chemistry of Solids》2004,65(1):73-77
We study the effect of carbon doping on the Raman spectrum of the MgB2 superconductor. Out data show that significant changes in the Raman spectra of the MgB2−xCx compounds occur for carbon concentrations x>0.04. The E2g mode at ∼580 cm−1 hardens only moderately upon increased doping despite direct carbon substitution in the boron layers, while the dependence of its full width at half maximum (FWHM) on x reveals the competing effects of reduced electron-phonon coupling and increased disorder. The results are discussed in the framework of anisotropic lattice contraction and the position of the σ sub-bands with respect to the Fermi energy level. The relative intensity of the phonon peak at ∼770 cm−1, associated with a peak in the phonon density of states, increases considerably and dominates for x=0.08. Additionally, it hardens and broadens with increasing x in the range 0.04-0.08. These changes can be associated with carbon substitution-induced disorder in the investigated samples. 相似文献
9.
10.
K. P. Meletov S. Assimopoulos G. A. Kourouklis I. O. Bashkin 《Physics of the Solid State》2002,44(3):542-544
The effect of hydrostatic pressure on the photoluminescence and Raman spectra of hydrofullerene C60H36 was investigated for pressures up to 12 GPa at room temperature. The samples were synthesized by means of high-pressure hydrogenation. The pressure coefficients of the phonon modes were found to be positive and demonstrate singularities at ~0.7 and ~6 GPa. The pressure shift of the luminescence spectrum is unusually small and increases slightly at P≥6 GPa. All observed features are reversible with pressure, and C60H36 is stable in the pressure region investigated. 相似文献