Effect of A Magnetic Field on Photophysical Processes of Molecules

A main purpose of this paper is to present a density matrix treatment of the magnetic quenching of molecular luminescence. Unlike the previous theories, which only consider the magnetic effect on the nonradiative rate constant, the present theory describes the time-evolution of the system under the action of a magnetic field. Our theory can treat both the steady state and transient molecular luminescence affected by a magnetic field.     

Dynamical Hopf bifurcation in piezoelectric semiconductor resonators

Time-dependent Hopf bifurcations in the current-voltage characteristics of piezoelectric semiconductor resonators were investigated experimentally. The switching transition between acoustic bistable states was observed under a quasi-static variation of applied voltage. The peculiar pulse responses of the resonant currents were observed when the rise-time of the pulses exceeded the eigen-period of the system. The existence of a metastable state in the dynamical Hopf bifurcation are discussed.     

On-line liquid chromatography and circular dichroism detection of stereo-isomers of alpha-tocopherol derivatives generated by an electrochemical reaction

The electrochemical oxidation of (+/-)-alpha-tocopherol on a porous graphite electrode was performed in the presence of methanol, and successive separation and detection of the products were performed by an on-line liquid chromatography/mass spectrometry system. Three products were identified, one of which was determined to be alpha-tocopheryl quinone, because its m/z was 469 [M+Na](+). The other two products showed identical mass and UV spectra, and were suspected to be diastereomers of 9-methoxy-alpha-tocopheron, because their molecular weights were m/z 483 [M+Na](+), and also because it is known that the chemical oxidation of alpha-tocopherol by benzoyl peroxide or N-bromosuccinimide in the presence of methanol should provide 9-methoxy-alpha-tocopheron. To confirm that these two compounds were diastereomers, a circular dichroism detector was used. The signs of both peaks detected by the circular dichroism detector at 230 nm were opposite. In addition to observations of identical mass and ultraviolet spectra, these results indicated that the two products were diastereomers of 9-methoxy-alpha-tocopheron, whose stereochemistry is different at the newly generated chiral center of the 9-position. The on-line use of a circular dichroism detector with an electrochemical cell/liquid chromatography system may expand the utility of the system to study the metabolism of a chiral drug.     

Possible radiochemical separations of anionic radionuclides by amorphous hydrous titanium dioxide

Ion-exchange selectivities towards oxoanions and halide ions were studied for radio-chemical applications by an amorphous hydrous titanium dioxide (Am-HTDO) as functions of pH and concentration. The selectivity series was found to be Mo(VI)<W(VI)<P(V)<As(V)<Sb(V) for micro-amounts at pH 9 and Br^–Cl^–F^– for macro-amounts. A feasibility was suggested for radiochemical separations of³²P by³⁵Cl(n,)³²P and⁷⁷Br by⁷⁵As(, 2n)⁷⁷Br, and selective removal of anionic radionuclides.Synthetic Inorganic Ion-Exchange Materials. XLIII.     

ESR of copper tutton salts around 0.1 K

A remarkable H/T effect in the intensity of ESR absorption is reported for the case of two Cu Tutton salts studied at 9.4 GHz and at temperatures down to 37 mK. Results can be reasonably expressed by the Brillouin function for $\text{S =}\text{1}\text{2}$.