Topic
Raman spectroscopy
About: Raman spectroscopy is a research topic. Over the lifetime, 122605 publications have been published within this topic receiving 2891083 citations. The topic is also known as: Raman Spectrum Analysis & spectrum Analysis, Raman.
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TL;DR: It is shown how current directly injected into a freely suspended individual single-wall carbon nanotube can be used to excite, detect and control a specific vibrational mode of the molecule.
Abstract: The interplay between discrete vibrational and electronic degrees of freedom directly influences the chemical and physical properties of molecular systems. This coupling is typically studied through optical methods such as fluorescence, absorption and Raman spectroscopy. Molecular electronic devices provide new opportunities for exploring vibration-electronic interactions at the single molecule level. For example, electrons injected from a scanning tunnelling microscope tip into a metal can excite vibrational excitations of a molecule situated in the gap between tip and metal. Here we show how current directly injected into a freely suspended individual single-wall carbon nanotube can be used to excite, detect and control a specific vibrational mode of the molecule. Electrons tunnelling inelastically into the nanotube cause a non-equilibrium occupation of the radial breathing mode, leading to both stimulated emission and absorption of phonons by successive electron tunnelling events. We exploit this effect to measure a phonon lifetime of the order of 10 ns, corresponding to a quality factor of well over 10,000 for this nanomechanical oscillator.
284 citations
TL;DR: In this article, it was shown that polarons are the major species generated by doping in most non-degenerate conjugated polymers such as polythiophene, poly(p-phenylene), and poly(polyphenylenevinylene).
Abstract: Conjugated conducting polymers constitute a subject of research lying at the interface between solid-state physics and molecular science. Electronic absorption and vibrational spectroscopies of doped conjugated polymers, whose ground states are nondegenerate, are reviewed from a viewpoint of molecular spectroscopy. Raman spectroscopy is a powerful tool for studying the structures of polarons and bipolarons, which are associated with electrical, magnetic, and optical properties of the polymers. Electronic absorption and Raman spectra of doped polymers have been analyzed on the basis of those of model compounds. These analyses have led us to the conclusion that polarons are the major species generated by doping in most nondegenerate conjugated polymers such as polythiophene, poly(p-phenylene), and poly(p-phenylenevinylene), in contrast with the previous view that bipolarons are the major species. The theoretical and experimental bases of these two contradictory views are discussed.
284 citations
TL;DR: It is shown that, for systems with uniaxial symmetry such as silk, it is possible to determine the order parameters P2 and P4 of the orientation distribution function from intensity ratios of polarized Raman spectra and the most probable distribution of orientation was calculated using the information entropy theory.
284 citations
Journal Article•
284 citations
TL;DR: In this article, the authors obtained ultra-high purity multi-walled carbon nanotubes (MWNTs), which were produced by a catalytic chemical vapor deposition method and subsequently annealed at vacuum pressures between 10 −3 and 10 Pa and temperatures between 1500 and 2150°C.
284 citations