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71.
72.
Coherent control of a charge-lattice coupled oscillation associated with the neutral (N)-ionic (I) transition was successfully demonstrated for a charge-transfer (CT) compound, tetrathiafulvalene-p-chloranil, with use of double femtosecond laser pulses. By changing the interval of the two laser pulses, amplitude of the oscillation in the reflectivity for the intramolecular transition band sensitive to the degree of CT was periodically changed. With increase of the pump intensity, the oscillation amplitude was dramatically enhanced. Such an enhancement is discussed in terms of the cooperative nature of the N-I transition. 相似文献
73.
Yasuyuki Kowaka Noritaka Ashizawa Hitoshi Goto Umpei Nagashima Masaaki Baba 《Journal of Molecular Spectroscopy》2010,260(1):72-9519
A rotationally resolved ultrahigh-resolution fluorescence excitation spectrum of the S1 ← S0 transition of perylene has been observed using a collimated supersonic jet technique in conjunction with a single-mode UV laser. We assigned 1568 rotational lines of the band, and accurately determined the rotational constants. The obtained value of inertial defect was positive, accordingly, the perylene molecule is considered to be planar with D2h symmetry. We determined the geometrical structure in the S0 state by ab initio theoretical calculation at the RHF/6-311+G(d,p) level, which yielded rotational constant values approximately identical to those obtained experimentally. Zeeman broadening of each rotational line with the external magnetic field was negligibly small, and the mixing with the triplet state was shown to be very small. This evidence indicates that intersystem crossing (ISC) in the S11B2u state is very slow. The rate of internal conversion (IC) is also inferred to be small because the fluorescence quantum yield is high. The rotational constants of the S11B2u state were very similar to those of the S01Ag state. The slow internal conversion (IC) at the S1 zero-vibrational level is attributed to a small structural change upon electronic transition. 相似文献
74.
S. Iwai S. Tanaka K. Fujinuma H. Kishida H. Okamoto Y. Tokura 《Phase Transitions》2013,86(7-8):807-813
Initial dynamics of photo-induced ionic (I) to neutral (N) phase transition in tetrathiafulvalene- p -chloranil (TTF-CA) was investigated by femtosecond reflection spectroscopy with various excitation intensities. A charge transfer excitation in the I phase produces N donor (D 0 )-acceptor (A 0 ) strings within 2 ps. For a weak excitation intensity, these initial N states decay with a life time of 300 ps at 4 K, but rather multiply leading to macroscopic I-N conversion within 20 ps at 77 K just below the N-I transition temperature T NI . Near T NI , we also found the coherent motion of the macroscopic N-I domain boundary with a period of 85 ps. 相似文献
75.
Y. Kawakami S. Iwai N. Yoneyama N. Kobayashi 《Journal of Physics and Chemistry of Solids》2008,69(12):3085-3088
Ultrafast dynamics of the photoinduced insulator (I) to metal (M) transition were investigated using femtosecond mid-infrared pump-probe spectroscopy in two-dimensional organic Mott insulators [bis (ethylenedithio)]-tetrathiafulvalene (BEDT-TTF) salts κ-(BEDT-TTF)2X (κ-(ET)2X, where X denotes anion). In κ-(d-ET)2Cu[N(CN)2]Br, a metallic state was photogenerated using a phonon-mediated mechanism: the effective bandwidth increases through the photoinduced molecular rearrangement. The mechanism differs fundamentally from the previously reported photoinduced filling control in one-dimensional Mott insulators. 相似文献
76.
We report on AgI/Ag infrared hollow fiber with low-loss in visible region. Improved methods of silver plating and iodination were proposed to fabricate the hollow fiber. The surface roughness of the silver layer and the silver iodide layer was reduced by the pretreatment with an SnCl2 solution and low iodination temperature. Losses for the Er:YAG and green laser light were 0.4 and 7dB/m. The loss property of green laser beam was low to deliver a pilot beam for the invisible infrared laser light. Owing to the smooth and uniform AgI film, the loss spectrum of the hollow fiber showed clear interference peaks in the visible region. An empirical formula for AgI material dispersion was derived, which is of special importance for the design of high-performance AgI/Ag hollow fiber. 相似文献
77.
78.
Naoki Wada Dr. Roland D. Kersten Takahiro Iwai Shoukou Lee Dr. Fumie Sakurai Dr. Takashi Kikuchi Dr. Daishi Fujita Prof. Makoto Fujita Prof. Jing‐Ke Weng 《Angewandte Chemie (International ed. in English)》2018,57(14):3671-3675
Characterization of complex natural product mixtures to the absolute structural level of their components often requires significant amounts of starting materials and lengthy purification process, followed by arduous structure elucidation efforts. The crystalline sponge (CS) method has demonstrated utility in the absolute structure elucidation of isolated organic compounds at miniscule quantities compared to conventional methods. In this work, we developed a new CS‐based workflow that greatly expedites the in‐depth structural analysis of crude natural product extracts. Using a crude extract of the red alga Laurencia pacifica, we showed that CS affinity screening prior to compound isolation enables prioritization of analytes present in the extract, and we subsequently resolved the molecular structures of six sesquiterpenes with stereochemical clarity from around 10 mg crude extract. This study demonstrates a new chemotyping workflow that can greatly accelerate natural product discovery from complex samples. 相似文献
79.
Phosphine‐Catalyzed anti‐Carboboration of Alkynoates with 9‐BBN‐Based 1,1‐Diborylalkanes: Synthesis and Use of Multisubstituted γ‐Borylallylboranes 下载免费PDF全文
Ayaka Yamazaki Kazunori Nagao Dr. Tomohiro Iwai Prof. Dr. Hirohisa Ohmiya Prof. Dr. Masaya Sawamura 《Angewandte Chemie (International ed. in English)》2018,57(12):3196-3199
Trialkylphosphine organocatalysis has enabled the regioselective anti‐carboboration of alkynoates with 9‐BBN‐based 1,1‐diborylalkanes to produce secondary allylboranes with β‐alkoxycarbonyl and γ‐boryl substituents. The utility of the densely functionalized allylboranes was demonstrated by the highly diastereoselective allylation of N‐(trimethylsilyl)aldimines to produce homoallylamines containing tertiary allylborane and acrylate moieties. 相似文献
80.
Uchida S Kawamoto R Tagami H Nakagawa Y Mizuno N 《Journal of the American Chemical Society》2008,130(37):12370-12376
Ag2[Cr3O(OOCC2H5)6(H2O)3]2[alpha-SiW12O40] [1] is a nonporous flexible ionic crystal composed of 2D-layers of polyoxometalates ([alpha-SiW12O40](4-)) and macrocations ([Cr3O(OOCC2H5)6(H2O)3](+)) stacking along the b-axis. The silver ions are located in the vicinity of the oxygen atoms of the polyoxometalates. The sorption amounts of small unsaturated hydrocarbons such as ethylene, propylene, n-butene, acetylene, and methyl acetylene into 1 are comparable to or larger than 1.0 mol mol(-1) and large hystereses are observed, while those of paraffins and larger unsaturated hydrocarbons are smaller than the adsorption on the external surface (<0.2 mol mol(-1)). Fine crystals of 1 exhibit ethylene/ethane and propylene/propane sorption ratios over 100 at 298 K and 100 kPa, and the values are larger by 1 order of magnitude among those reported. The results of sorption kinetics, in situ IR spectroscopy, single crystal X-ray crystallography, and in situ powder XRD studies show that small unsaturated hydrocarbons penetrate into the solid bulk of 1 through the pi-complexation with Ag(+). The sorption property of 1 is successfully applied to the collection of ethylene from the gas mixture of ethane and ethylene. 相似文献