Ferrimagnetic coupling in oxamido-bridged Mn(II)Cu(II) compounds: a combined CASPT2 and DDCI study

Multiconfigurational perturbation theory (CASPT2) and difference dedicated configuration interaction (DDCI) are applied to study the ferrimagnetic coupling in an oxamido-bridged Mn(II)Cu(II) molecular species. CASPT2 reproduces the experimental coupling very well. From the partition of the CASPT2 energy, the most important contributions to the coupling are established. Spin populations are calculated with DDCI. The successive improvement of the N-electron wave function allows us to analyse the contributions to the spin delocalization.     

On the smoothness of the moduli space of mathematical instanton bundles

In this paper we prove that the moduli spaces MI _2n+1(k) of mathematical instanton bundles on ²ⁿ⁺¹ with quantum number k are singular for n 2 and k 3 ,giving a positive answer to a conjecture made by Ancona and Ottaviani in 1993.     

Luminescence-Based Optical Fiber Chemical Sensors

Abstract

A scheme for the simultaneous determination of temperature and analyte concentration for application in luminescence-based chemical sensors is proposed. This scheme is applied to an optical oxygen sensor, which is based on the quenching of the fluorescence of a ruthenium complex. Temperature measurement is performed using the excitation radiation and an absorption long-pass filter. Preliminary results are presented that show the viability of an oxygen measurement that is independent of temperature and optical power level. The possibility of self-referenced temperature measurements with semiconductor nanoparticles is also investigated. In order to optimize the sensor design, several different optical fiber probe geometries for oxygen sensing are tested and compared, including different methods of coupling radiation into the optical fiber system. Polyvinyl alcohol (PVA) and polyacrylamide membranes are tested as supports for sensor immobilization in fiber-optical pH sensing devices in aqueous solution. Some results are presented that show the feasibility of using fiber-optical pH indicators for remote monitoring.     

THE FLUORESCENCE OF ADENINE. THE EFFECTS OF SOLVENT AND TEMPERATURE ON THE QUANTUM YIELD

Abstract— To investigate the mechanism of the solvent and thermal quenching of fluorescence, the absolute fluorescence quantum yield of adenine has been determined in several alcoholic glasses as a function of the concentration (10^-5-10^-4M) and temperature (77°-298°K). The yield is independent of the concentration but increases with decreasing temperature and increasing bulk cohesion and rigidity of the solvent.
The environmental effects on the yield are attributed to radiationless electronic relaxation processes caused by solute-solvent interaction. Increasing the temperature and decreasing the intra-solvent cohesion cause increases in the interaction and therefore accelerate the relaxation. The rate determining step behaves like a diffusion in the limit of low viscosity.     

PHOTOLYSIS AND RADIOLYSIS OF PHENYL-ALANYLGLYCINE

T he P hotolysis of glycine and alanine containing peptides in oxygenated solution has been shown to result in the formation of glyoxylic and pyruvic acids, through oxidative cleavage of the peptide bond[1]. The same products were formed in the radiolysis of such peptides in the presence of oxygen[2]. In a peptide containing aromatic amino-acids the absorption of light results in the excitation of the aromatic ring and it has been postulated[3] that energy is transferred to the peptide bond, resulting in the formation of a radical on the carbon atom adjacent to the peptide bond. Radiolysis, however, involves the attack of hydroxyl radicals and other reactive species formed in the absorption of radiation by water[2]. This study compares the behavior of phenylalanylglycine to photolysis and radiolysis in aerated aqueous solution in relation to a possible energy transfer in photolysis.