ESR and Chemical Bonding of Some Copper Complexes

ESR spectra of copper (II) was measured in 33 copper complexes which were synthesized in this laboratory and the bonding parameter α²of copper was calculated according to the method proposed by Kivelson. ⁽¹⁾ The results of these calculations are classified, together with the data quoted from the literature,^1-5into four groups according to the kinds of ligand atoms, i.e., α²is 0.72 to 0.87 for 0₄ - type complexes, 0.69 to 0.86 in N₂O₂, 0.74 to 0.82 in N₄, and 0.54 to 0.62 in S₄ and S₂₃N₂ type complexes, where 0, H and S refer the oxygen, nitrogen and sulfur atoms of ligands, respectively, that directly coordinate with copper.     

X-ray Fluorescence Spectroscopic Studies of High TeSuperconductors

The Cu-Lβ/Cu-Lα x-ray emission intensity ratio of the following compounds have been found to show an interesting consistency: Cu, Cu₂O, CuO, La_1.85Ba_.15CuO₄ (vacuum annealed), La_1.85Ba_.15CuO₄ (air annealed, T_C = 26K), La_1.85Sr_.15CuO₄ (T_C = 35K), YBa₂Cu₃O_7-Δ (T_C = 91K), ErBa₂Cu₃O_7-Δ (T_C = 81K), and La₂CuO₄. The interesting consistency is that all of the last six compounds, all superconductors or superconductor related, have the same Lβ/Lα intensity ratio, namely, 0.33±0.01. The Cu-Lα,β spectra of CuO, air and vacuum annealed La_1.85 Ba_.15CuO₄ and YBa₂Cu₃O_7-Δ are presented. Also presented are O-K x-ray fluorescence spectra of air and vacuum annealed La_1.85 Ba_.15CuO₄, and of “new” and “old” YBa₂Cu₃O_7-Δwhich seem to show a correspondence between spectral sharpness and high T_C behavior.     

Determination of Phosphorous by ICP-AES Using Solid-Phase Hydride Generation

A reliable and sensitive analytical optical method for the determination of phosphorous in oceanographic and environmental materials does not exist. In this work, a novel hydride generation method was used to form phosphine from a sample containing phosphate mixed with 7% sodium borohydride. By heating the mixture to 500 °C, phosphine was reproducibly generated and collected in a cold trap. Phosphine was then introduced into an ICP where several atomic emission lines for phosphorous were observed. Copper emission did not spectrally interfere with phosphorous atomic emission with this hydride generation-ICP-AES method. This hydride generation method allows the use of small sample volumes (< 5 μL).     

Photon-number-resolving detection at a telecommunications wavelength with a charge-integration photon detector

We demonstrate multiphoton discrimination at a telecommunications wavelength with the readout frequency of 40 Hz by a charge-integration photon detector (CIPD). The CIPD consists of an InGaAs pin photodiode and a GaAs junction field effect transistor as a preamplifier in a charge-integration circuit, which is cooled to 4.2 K to reduce thermal noise. The quantum efficiency of the CIPD (the detector itself) is 80% for 1530 nm light, and the readout noise is measured as 0.26 electrons at 40 Hz. We can construct Poisson distributions of photocarrier numbers with distinct peaks at each photocarrier number, corresponding to a signal-to-noise ratio of about 3.     

A novel route to dipeptides via noncondensation of amino acids: 2-aminoperfluoropropene as a synthon for trifluoroalanine dipeptides

[STRUCTURE: SEE TEXT] 2-Aminoperfluoropropene has been prepared by the Mg-promoted defluorinative N-silylation of N-p-methoxyphenyl hexafluoroacetone imine and has been employed as a synthon of trifluoroalanine for the preparation of trifluoroalanine dipeptides.     

Compensation of effective field in the field-induced superconductor kappa-(BETS)2FeBr4 observed by 77Se NMR

We report results of 77Se NMR frequency shift in the normal state of the organic charge-transfer salt kappa-(BETS)2FeBr4 which shows magnetic field-induced superconductivity (FISC). From a simple mean-field analysis, we determined the field and the temperature dependences of the magnetization m(pi) of the pi conduction electrons on BETS molecules. We found that the Fe spins are antiferromagnetically coupled to the pi electrons and determined the exchange field to be J = -2.3T/microB. The exchange field from the fully saturated Fe moments (5 microB) is compensated by an external field of 12 T. This is close to the central field of the FISC phase, consistent with the Jaccarino-Peter local field-compensation mechanism for FISC [Phys. Rev. Lett. 9, 290 (1962)].     

An optical-optical double resonance probe of the lowest triplet state of jet-cooled thiophosgene: rovibronic structures and electronic relaxation

The vibrational structure, rotational structure, and electronic relaxation of the "dark" T1 3A2(n,pi*) state of jet-cooled thiophosgene have been investigated by two-color S2<--T1<--S0 optical-optical double resonance (OODR) spectroscopy, which monitors the S2-->S0 fluorescence generated by S2<--T1 excitation. This method is capable of isolating the T1 vibrational structure into a1, b1, and b2 symmetry blocks. The fluorescence-detected vibrational structure of the Tz spin state of T1 shows that the CS stretching frequency as well as the barrier height for pyramidal deformation are significantly greater in the 3A2(n,pi*) state than in the corresponding 1A2(n,pi*) state. The differing vibrational parameters of the T1 thiophosgene relative to the S1 thiophosgene can be attributed to the motions of unpaired electrons that are better correlated when they are in the excited singlet state than when they are in the triplet state of same electron configuration. A set of T1 structural parameters and the information concerning the T1 spin states have been obtained from least-square fittings of the rotationally resolved T1<--S0 excitation spectrum. The nearly degenerate mid R:x and mid R:y spin states are well removed from mid R:z spin component, indicating that T1 thiophosgene is a good example of case (ab) coupling. The decay of the mid R:z spin state of T1 thiophosgene, obtained from time-resolved S2<--T1<--S0 OODR experiment, is characteristic of strong-coupling intermediate-case decay in which an initial rapid decay is followed by recurrences and/or a long-lived quasiexponential decay.     

Quantitative evaluation of scratch visibility resistance of polymers

Susceptibility of polymer surfaces to acute visibility upon scratching has presented a serious challenge to the polymer industry for quite some time. The ability to design polymers with good scratch visibility resistance requires extensive knowledge about scratch deformation mechanisms and their propensity for light scattering. After examining the physical nature of human vision and surface optical characteristics, a new methodology is developed to quantitatively determine the onset of scratch visibility of polymers via an inexpensive desktop scanner. Taking into account the sample background color, texture, gloss and feature size, the proposed methodology can consistently and reliably determine polymer scratch visibility resistance regardless of the sample surface characteristics. Good correlation is found between this method and actual human perception. Quantitative analysis of the scratched surface is carried out with scanning laser profiling confocal microscopy and strong correlations among scratch visibility, observation angle and various scratch damage features such as roughness and scratch grooves are established. The proposed approach will greatly assist the development of scratch-resistant polymeric materials where surface aesthetics is of primary concern.     

Traffic noise reduction at balconies on a high-rise building façade

The performance of balconies with ceiling-mounted reflectors on a high-rise building fac?ade is examined using numerical analyses and scale-model experiments. The reflectors are designed to reflect direct and diffracted waves incident on the ceiling outside the balcony. The sound pressure reduction, provided by the reflectors, on a window surface adjacent to the balcony is evaluated at intermediate floors levels. In terms of A-weighted sound pressure levels, a balcony equipped with reflectors reduces road traffic noise by 7-10 dB(A), compared to an ordinary balcony, at incident angles of noise close to the angle for which the reflectors are designed. The efficiency is roughly the same as, or greater than, that of a balcony with an absorbent ceiling. However, it is also shown that when the vertical incident angle of the noise is smaller than the design angle of the reflectors, or the horizontal incident angle is large, efficiency is reduced.