Blue light emitting polymers

Perfluoroalkanes (PFs) have been shown to be unique solvents in spectral, photophysical and photochemical studies in fluid solutions. Their physical, chemical and spectral properties are discussed. Substantial differences between PFs and alkanes and similarities between PFs and the rare gases argon and krypton are illustrated. Examples are presented which illustrate the advantages of the use of PF solvents in the study of the contribution of non-specific and specific solute—solvent interactions to the experimentally observed spectral shift, in the determination of the role of intermolecular and intramolecular interactions for molecules of rigid and flexible structure, and in measurements of the energies and lifetimes of electronically excited states. The application of PF solvents in photophysical and photochemical studies, especially in the quantitative determination of the contribution of intramolecular and intermolecular processes to the decay paths of electronically excited molecules, is discussed. The results presented demonstrate that PFs considerably extend the polarity scale available for weakly interacting solvents. Therefore they are recommended as solvents in the investigation of the intramolecular properties of reactive molecules in electronically excited states. Some comments on the practical application of PFs are given and some studies using PFs are proposed.

The application of perfluoroalkanes as solvents in spectral, photophysical and photochemical studies

A robust signal for sidereal anisotropy in nuclear recoils would support, perhaps more decisively than any other evidence, a discovery claim for a WIMP component of Dark Matter. I present a concept based on columnar recombination in dense xenon gas, sensing nuclear recoil direction relative to a TPC drift field. The central advance is that nuclear recoil directionality information is obtained through a comparison, event-by-event, of the ionization signal and recombination signal that are produced prior to drifting the track ionization. The optimum xenon density for this concept may be near ten bars, unlike conventional techniques that employ track visualization – with severe restrictions on gas density to about 1/10 bar. No restriction is imposed by diffusion during drift, facilitating the realization of a large monolithic room temperature xenon gas Time Projection Chamber at the ton-scale, with unprecedented sensitivity for both directionality and cross-section. Remarkably, the desired operating conditions for 0-νββ 136Xe experiment may be identical.

http://iopscience.iop.org/article/10.1088/1742-6596/460/1/012006/pdf

Columnar recombination: a tool for nuclear recoil directional sensitivity in a xenon-based direct detection WIMP search

We report the performance of a 10 atm Xenon/trimethylamine time projection chamber (TPC) for the detection of X-rays (30 keV) and γ-rays (0.511–1.275 MeV) in conjunction with the accurate tracking of the associated electrons. When operated at such a high pressure and in ~1%-admixtures, trimethylamine (TMA) endows Xenon with an extremely low electron diffusion ( 1.3 ± 0.13 mm - σ (longitudinal), 0.95 ± 0.20 mm - σ (transverse) along 1 m drift) besides forming a convenient ‘Penning-Fluorescent’ mixture. The TPC, that houses 1.1 kg of gas in its fiducial volume, operated continuously for 100 live-days in charge amplification mode. The readout was performed through the recently introduced microbulk Micromegas technology and the AFTER chip, providing a 3D voxelization of 8 mm × 8 mm × 1.2 mm for approximately 10 cm/MeV-long electron tracks. Resolution in energy ( e ) at full width half maximum ( R ) inside the fiducial volume ranged from R = 14.6 % (30 keV) to R = 4.6 % ( 1.275 MeV ) . This work was developed as part of the R&D program of the NEXT collaboration for future detector upgrades in the search of the neutrino-less double beta decay ( β β 0 ν ) in 136 Xe, specifically those based on novel gas mixtures. Therefore we ultimately focus on the calorimetric and topological properties of the reconstructed MeV-electron tracks. In particular, the obtained energy resolution has been decomposed in its various contributions and improvements towards achieving the R = 1.4 % 1 MeV / e levels obtained in small sensors are discussed.

/pdf/accurate-g-and-mev-electron-track-reconstruction-with-an-tupaj0ahmq.pdf

Accurate γ and MeV-electron track reconstruction with an ultra-low diffusion Xenon/TMA TPC at 10 atm

Studies devoted to excimers in organic systems are surveyed. Processes leading to the excitation of the excimer luminescence are examined. Examples of the excimer-like glow of dimers are described. The relation between the structure of the complexes and their fluorescence properties is demonstrated. The bibliography includes 218 references.

http://iopscience.iop.org/article/10.1070/RC1993v062n06ABEH000032/pdf

Clifford G. Cureton

Papers

The photophysics of tertiary aliphatic amines

Time-resolved emission studies of poly(n-v1nyl carbazole) using pulsed laser excitation

Efficient quenching of luminescence by so-called “inert” fluorocarbon solvents

Fluorescence decay of tertiary aliphatic amines