Fermi resonance in CO2: a combined electronic coupled-cluster and vibrational configuration-interaction prediction

The authors present a first-principles prediction of the energies of the eight lowest-lying anharmonic vibrational states of CO(2), including the fundamental symmetric stretching mode and the first overtone of the fundamental bending mode, which undergo a strong coupling known as Fermi resonance. They employ coupled-cluster singles, doubles, and (perturbative) triples [CCSD(T) and CCSDT] in conjunction with a range of Gaussian basis sets (up to cc-pV5Z, aug-cc-pVQZ, and aug-cc-pCVTZ) to calculate the potential energy surfaces (PESs) of the molecule, with the errors arising from the finite basis-set sizes eliminated by extrapolation. The resulting vibrational many-body problem is solved by the vibrational self-consistent-field and vibrational configuration-interaction (VCI) methods with the PESs represented by a fourth-order Taylor expansion or by numerical values on a Gauss-Hermite quadrature grid. With the VCI, the best theoretical estimates of the anharmonic energy levels agree excellently with experimental values within 3.5 cm(-1) (the mean absolute deviation). The theoretical (experimental) anharmonic frequencies of the Fermi doublet are 1288.9 (1285.4) and 1389.3 (1388.2) cm(-1).     

High-efficiency 1040 and 1078 nm laser emission of a Yb:Y2O3 ceramic laser with 976 nm diode pumping

We report a high-efficiency diode-end-pumped polycrystalline Yb:Y2O3 ceramic laser. Pumped by a 976 nm laser diode bar and with an absorbed pump power of 2.8 W, cw output power of 1.74 W at 1078 nm, and 0.73 W at 1040 nm were obtained. The slope efficiency was measured to be 82.4% for the 1078 nm laser emission and 57.1% for the 1040 nm laser emission.     

Diode-pumped sub-100 fs Kerr-lens mode-locked Yb3+:Sc2O3 ceramic laser

Diode-pumped Kerr-lens mode-locked laser operations of Yb3+:Sc2O3 ceramics have been achieved. 92 fs pulses with the average power of 850 mW under 3.89 W incident pump power were obtained at a center wavelength of 1042 nm. The optical-to-optical efficiency was 21.9%. 90 fs pulses with the average power of 160 mW were also obtained at a center wavelength of 1092 nm. To our knowledge, this is the first demonstration of a Kerr-lens mode-locked Yb3+:Sc2O3 laser.     

Stationary rescaled pulse in dispersion-managed comblike profiled fiber for highly efficient and high-quality optical pulse compression

A stationary rescaled pulse (SRP) exists in a dispersion-managed comblike profiled fiber (DM-CPF) that consists of alternate concatenations of normal-dispersion highly nonlinear fiber and single-mode fiber. Numerical analysis reveals that the newly found SRP exhibits a nearly Gaussian temporal profile with a small amount of pedestal in spite of a relatively large compression ratio. We apply the SRP propagation to optical pulse compression based on DM-CPF and demonstrate highly efficient and high-quality optical pulse compression. Using a three-step DM-CPF, we experimentally show that a 2.6 ps width input pulse is successfully compressed to a nearly Gaussian pulse having the width of 0.39 ps and the peak-to-pedestal ratio of 19.3 dB.     

Studies on sea snake venom

Erabutoxins a and b are neurotoxins isolated from venom of a sea snake Laticauda semifasciata (erabu-umihebi). Amino acid sequences of the toxins indicated that the toxins are members of a superfamily consisting of short and long neurotoxins and cytotoxins found in sea snakes and terrestrial snakes. The short neurotoxins to which erabutoxins belong act by blocking the nicotinic acetylcholine receptor on the post synaptic membrane in a manner similar to that of curare. X-ray crystallography and NMR analyses showed that the toxins have a three-finger structure, in which three fingers made of three loops emerging from a dense core make a gently concave surface of the protein. The sequence comparison and the location of essential residues on the protein suggested the mechanism of binding of the toxin to the acetylcholine receptor. Classification of snakes by means of sequence comparison and that based on different morphological features were inconsistent, which led the authors to propose a hypothesis "Evolution without divergence."     

Fabrication of CuInS2 films from electrodeposited Cu/In bilayers: effects of preheat treatment on their structural, photoelectrochemical and solar cell properties

Polycrystalline CuInS(2) films were fabricated by sulfurization of electrodeposited Cu and In metallic precursor films in a Cu-rich composition at 520 °C in H(2)S (5% in Ar). Structural analyses revealed that the adherence of the thus-formed CuInS(2) film to the Mo substrate was strongly dependent on heating profiles of the Cu/In bilayer film: a CuInS(2) film with poor adherence having many crevices was formed when the Cu/In bilayer film was heated monotonously from room temperature to 520 °C in Ar within 25 min followed by sulfurization, whereas CuInS(2) films with good adherence were obtained when the Cu/In films were pretreated at 110 °C in Ar for 10-60 min just before increasing the temperature up to 520 °C for sulfurization. It was also clarified that the CuInS(2) film obtained without 110 °C pretreatment had pinholes inside the film, whereas the CuInS(2) films formed after 110 °C pretreatment showed no notable pinholes. Photoelectrochemical responses of these CuInS(2) films in an electrolyte solution containing Eu(III) indicated that the CuInS(2) films obtained after 110 °C pretreatment had higher external quantum efficiency (EQE) values than those of films obtained without 110 °C pretreatment, mainly due to better adherence of 110 °C pretreated CuInS(2) films to the Mo substrate than the CuInS(2) film obtained without 110 °C pretreatment. The performance of solar cells with an Al:ZnO/Zn(S,O)/CdS/CuInS(2)/Mo structure also depended on the structural characteristics of the CuInS(2) films, i.e., preliminary conversion efficiencies of ca. 5% were obtained for devices based on the CuInS(2) films obtained after 110 °C pretreatment, whereas the device prepared by the CuInS(2) film without 110 °C pretreatment showed the conversion efficiency less than 1.5%.     

Chemo-enzymatic synthesis of a multi-useful chiral building block molecule for the synthesis of medicinal compounds

Optical resolution of 2-methyl-2-nitrobut-3-en-1-ol has been accomplished using a "low-temperature lipase-catalyzed transesterification" carried out at -40 °C.     

Structural changes of filled ice Ic hydrogen hydrate under low temperatures and high pressures from 5 to 50 GPa

Low-temperature and high-pressure experiments were performed on the filled ice Ic structure of hydrogen hydrate at previously unexplored conditions of 5-50 GPa and 30-300 K using diamond anvil cells and a helium-refrigeration cryostat. In situ x-ray diffractometry revealed that the cubic filled ice Ic structure transformed to tetragonal at low temperatures and high pressures; the axis ratio of the tetragonal phase changed depending on the pressure and temperature. These results were consistent with theoretical predictions performed via first principle calculations. The tetragonal phase was determined to be stable above 20 GPa at 300 K, above 15 GPa at 200 K, and above 10 GPa at 100 K. Further changes in the lattice parameters were observed from about 45-50 GPa throughout the temperature region examined, which suggests the transformation to another high-pressure phase above 50 GPa. In our previous x-ray study that was performed up to 80 GPa at room temperature, a similar transformation was observed above 50 GPa. In this study, the observed change in the lattice parameters corresponds to the beginning of that transformation. The reasons for the transformation to the tetragonal structure are briefly discussed: the tetragonal structure might be induced due to changes in the vibrational or rotational modes of the hydrogen molecules under low temperature and high pressure.     

Substituent effects on core structures and heterogeneous catalytic activities of Mn(III)(μ-O)2Mn(IV) dimers with 2,2':6',2″-terpyridine derivative ligands for water oxidation

[(OH(2))(R-terpy)Mn(μ-O)(2)Mn(R-terpy)(OH(2)) ](3+) (R-terpy = 4'-substituted 2,2':6',2″-terpyridine, R = butoxy (BuO), propoxy (PrO), ethoxy (EtO), methoxy (MeO), methyl (Me), methylthio (MeS), chloro (Cl)) have been synthesized as a functional oxygen-evolving complex (OEC) model and characterized by UV-vis and IR spectroscopic, X-ray crystallographic, magnetometric, and electrochemical techniques. The UV-vis spectra of derivatives in water were hardly influenced by the 4'-substituent variation. X-ray crystallographic data showed that Mn centers in the Mn(III)(μ-O)(2)Mn(IV) cores for derivatives with R = H, MeS, Me, EtO, and BuO are crystallographically indistinguishable, whereas the derivatives with R = MeO and PrO gave the significantly distinguishable Mn centers in the cores. The indistinguishable Mn centers could be caused by rapid electron exchange between the Mn centers to result in the delocalized Mn(μ-O)(2)Mn core. The exchange integral values (J = -196 to -178 cm(-1)) for delocalized cores were lower than that (J = -163 to -161 cm(-1)) for localized cores, though the Mn···Mn distances are nearly the same (2.707-2.750 ?). The half wave potential (E(1/2)) of a Mn(III)-Mn(IV)/Mn(IV)-Mn(IV) pair of the derivatives decreased with an increase of the electron-donating ability of the substituted groups for the delocalized core, but it deviated from the correlation for the localized cores. The catalytic activities of the derivatives on mica for heterogeneous water oxidation were remarkably changed by the substituted groups. The second order rate constant (k(2)/mol(-1) s(-1)) for O(2) evolution was indicated to be correlated to E(1/2) of a Mn(III)-Mn(IV)/Mn(IV)-Mn(IV) pair; k(2) increased by a factor of 29 as E(1/2) increased by 28 mV.