Role of OH-stretch/torsion coupling and quantum yield effects in the first OH overtone spectrum of cis-cis HOONO

A joint theoretical and experimental investigation is undertaken to study the effects of OH-stretch/HOON torsion coupling and of quantum yield on the previously reported first overtone action spectrum of cis-cis HOONO (peroxynitrous acid). The minimum energy path along the HOON dihedral angle is computed at the coupled cluster singles and doubles with perturbative triples level with correlation consistent polarized quadruple zeta basis set, at the structure optimized using the triple zeta basis set (CCSD(T)/cc-pVQZ//CCSD(T)/cc-pVTZ). The two-dimensional ab initio potential energy and dipole moment surfaces for cis-cis HOONO are calculated as functions of the HOON torsion and OH bond length about the minimum energy path at the CCSD(T)/cc-pVTZ and QCISD/AUG-cc-pVTZ (QCISD-quadratic configuration interaction with single and double excitation and AUG-augmented with diffuse functions) level of theory/basis, respectively. The OH-stretch vibration depends strongly on the torsional angle, and the torsional potential possesses a broad shelf at approximately 90 degrees , the cis-perp conformation. The calculated electronic energies and dipoles are fit to simple functional forms and absorption spectra in the region of the OH fundamental and first overtone are calculated from these surfaces. While the experimental and calculated spectra of the OH fundamental band are in good agreement, significant differences in the intensity patterns are observed between the calculated absorption spectrum and the measured action spectrum in the 2nu(OH) region. These differences are attributed to the fact that several of the experimentally accessible states do not have sufficient energy to dissociate to OH+NO(2) and therefore are not detectable in an action spectrum. Scaling of the intensities of transitions to these states, assuming D(0)=82.0 kJ/mol, is shown to produce a spectrum that is in good agreement with the measured action spectrum. Based on this agreement, we assign two of the features in the spectrum to Deltan=0 transitions (where n is the HOON torsion quantum number) that are blue shifted relative to the origin band, while the large peak near 7000 cm(-1) is assigned to a series of Deltan=+1 transitions, with predominant contributions from torsionally excited states with substantial cis-perp character. The direct absorption spectrum of cis-cis HOONO (6300-6850 cm(-1)) is recorded by cavity ringdown spectroscopy in a discharge flow cell. A single band of HOONO is observed at 6370 cm(-1) and is assigned as the origin of the first OH overtone of cis-cis HOONO. These results imply that the origin band is suppressed by over an order of magnitude in the action spectrum, due to a reduced quantum yield. The striking differences between absorption and action spectra are correctly predicted by the calculations.     

Electrophoretic analysis of quinone anion radicals in acetonitrile solutions using an on-line radical generator

We have investigated analysis of anion radicals of phenanthrenequinone (PhQ) and anthraquinone (AQ) using acetonitrile-capillary electrophoresis (CE) under anaerobic conditions. PhQ and AQ have relatively high negative reduction potentials meaning that their anion radicals are re-oxidized quite readily by the surrounding O(2) to disappear during analysis and we failed to detect them with our previous system. In this work, we have developed an on-line system combining a unique electrolysis cell for generation of the radicals and a CE unit to keep the analysis system free from external O(2) molecules and to reduce analysis time remarkably. As a result, electrophoretic detection of the anion radicals of PhQ and AQ has been achieved. Furthermore, we have observed hydrogen-bonding interaction between the anion radicals and dimethylurea (DMU) using the present system and have indicated a characteristic interaction of the anion radical of PhQ as an ortho-quinone with DMU.     

Recent progress of high-power negative ion beam development for fusion plasma heating

A negative-ion-based neutral beam injector (N-NBI) has been constructed for JT-60U. The N-NBI is designed to inject 500 keV, 10 MW neutral beams using two ion sources, each producing a 500 keV, 22 A D⁻ ion beam. In the preliminary experiment using one ion source, a D⁻ ion beam of 13.5 A has been successfully accelerated with an energy of 400 keV (5.4 MW) for 0.12 s at an operating pressure of 0.22 Pa. This is the highest D⁻ beam current and power in the world. Co-extracted electron current was effectively suppressed to the ratio of Ie/I_D⁻ < 1. The highest energy beam of 460 keV, 2.4 A, 0.44 s has also been obtained. To realize 1 MeV class NBI system for ITER (International Thermonuclear Experimental Reactor), demonstration of ampere class negative ion beam acceleration up to 1 MeV is an important mile stone. To achieve the mile stone, a prototype accelerator and a 1 MV, 1 A test facility called MeV Test Facility (MTF) were constructed. Up to now, an H⁻ ion beam was accelerated up to the energy of 805 keV with an acceleration drain current of 150 mA for 1 s in a five stage electrostatic multi-aperture accelerator.     

Determination of optimal formulation for extrusion granulation by compression test of wet kneaded mass

The purpose of this study is to propose the application of a compression test to the determination of an optimal formulation for extrusion granulation. The electric current during extrusion was measured and the characteristics of the wet kneaded mass in the compression test were analyzed under various operating conditions, with different types of extruders and several formulations of kneaded mass. It was found that addition of a binder (HPC-L) to pharmaceutical powders lowered the load of a high-compressing type extruder, since the binder reduced the friction among the wet mass during extrusion. Also, the support stress was found to be proportional to the compression pressure without a binder, although an inflection point appeared on the support stress curve when a binder was present. This inflection point suggested large water retention of the wet kneaded mass, at which the medium of pressure was changed from a discontinuous solid powder to a continuous liquid, and large water retention contributed to the low friction of the wet mass. The friction of the wet kneaded mass and the aptitude of the formulation for extrusion were understood by using the compression test. The compression test is a very useful procedure at the first stage of a formulation study.     

A New Approach to the Construction of BEDT-TTF Derivatives Condensed with Heterocycles via BF3-promoted Reactions of Organotin Thiolates

The synthesis of BEDT-TTF derivatives fused with heterocycles (3–7) has been accomplished via the BF₃-promoted reaction of organotin thiolates (8 and 9) with electrophiles (10 and 11). Electrical conductivities of radical cation salts derived from some of them were also investigated.     

Multi-turn time-of-flight mass spectrometers with electrostatic sectors

The mass resolution of a time-of-flight (TOF) mass spectrometer is directly proportional to its total flight pathlength. Multi-turn or multi-passage ion optical geometries are necessary to obtain fight distances of sufficient length within reasonable size limitations. We have investigated ion optics for a multi-turn TOF mass spectrometer with electrostatic sectors. The concept of 'perfect' focusing conditions is introduced. Furthermore, a new type of multi-turn TOF mass spectrometer, the MULTUM Linear plus, was developed. It consists of four cylindrical electric sectors and 28 electric quadrupole lenses. It has a vacuum chamber 60 x 70 x 20 cm in size. Mass resolution is demonstrated to increase according to the number of ion cycles. A mass resolution of 350 000 (m/z = 28, FWHM) was achieved after 501.5 cycles. The MULTUM Linear plus analyzer is not simple, however; 28 electric quadrupole lenses are used. In order to reduce the number of ion optical parts, an improved multi-turn TOF mass spectrometer, the MULTUM II, consisting of only four toroidal electric sectors, was also developed. The possibility of tandem mass spectrometric applications using multi-turn TOF mass spectrometers is also discussed.     

Site-directed 13C solid-state NMR studies on membrane proteins: strategy and goals toward revealing conformation and dynamics as illustrated for bacteriorhodopsin labeled with [1-13C]amino acid residues

We have so far demonstrated that well-resolved and site-specifically assigned (13)C peaks as recorded by site-directed NMR study on (13)C-labeled membrane proteins can serve as a convenient probe to reveal their local conformation and dynamics. We attempted here to clarify the extent to which (13)C NMR spectra of (13)C-labeled fully hydrated bacteriorhodopsin (bR) as a typical membrane protein are visible or well resolved in the presence of inherent fluctuation motions with frequency of 10(2)-10(8) Hz, especially at the membrane surfaces. Accordingly, we estimated the relative proportion of (13)C NMR signals from the surface areas with and without peak suppression by the accelerated transverse relaxation effect by surface-bound Mn(2+) ions, which could be effective for residues within 8.7 angstroms of the membrane surface. It turned out that the experimental findings are consistent with the predicted amount of amino acid residues under consideration located within 8.7 angstroms of the surface for [1-(13)C]Val- and Ile-labeled bR and also [3-(13)C]Ala-bR. In contrast, (13)C NMR peaks from such surfaces area are almost completely or partially suppressed for [1-(13)C]Gly-, Ala-, Leu-, Phe- and Trp-labeled bR, as a result of plausible interference of the fluctuation frequency with frequency of magic angle spinning (10(4) Hz). We further assigned several (13)C NMR signals of [1-(13)C] Val-, Trp- and Ile-labeled bR on the basis of a variety of site-directed mutants with reference to those of the wild type. Further, we recorded the (13)C NMR of bR in lipid bilayers to search for the optimal conditions to be able to obtain signals with the highest peak intensities and spectral resolution. Backbone dynamics turn out to be essential for recording (13)C NMR spectra so as to escape from motional frequencies of the order of 10(4)-10(5) Hz, either in the direction of accelerated fluctuation or slowed motions in the direction of forming the 2D array.     

Theoretical studies on electronic states of Rh-C60. Possibility of a room-temperature organic ferromagnet

A possible mechanism for a ferromagnetic interaction in the rhombic (Rh) form of C60 (Rh-C60) is suggested on the basis of theoretical studies in relation to cage distortion of the C60 unit in the polymerized 2D-plane. Band structure calculations on Rh-C60 show that cage distortion leads to competition between diamagnetic and ferromagnetic states,which give rise to the possibility of thermally populating the ferromagnetic state.     

meso-Alkyl-substituted meso-meso linked diporphyrins and meso-alkyl-substituted meso-meso, beta-beta, beta-beta triply linked diporphyrins

[reaction: see text] AgPF6-promoted oxidation of 5,10,15-trialkyl zinc(II) porphyrins led to formation of meso-meso linked diporphyrins, which were further oxidized with Sc(OTf)3 and DDQ to give meso-meso, beta-beta, beta-beta triply linked diporphyrins that exhibited a stronger aggregation propensity than corresponding meso-aryl diporphyrins.