The photoacid 8-hydroxypyren-1,3,6-trisulfonic acid (HPTS, pyranine) is a widely used model compound for the examination of excited state proton transfer (ESPT). We synthesized five "super"-photoacids with varying hydrophilicity and acidity on the basis of HPTS. By chemical modification of the three sulfonic acid substituents, the photoacidity is enhanced by up to more than five logarithmic units from pK*≈ 1.4 to ∼-3.9 for the most acidic compound. As a result, nearly quantitative ESPT in DMSO can be observed. The novel photoacids were characterized by steady-state and time-resolved fluorescence techniques showing distinctively red shifted spectra compared to HPTS while maintaining a high quantum yield near 90%. Photostability of the compounds was checked by fluorescence correlation spectroscopy (FCS) and was found to be adequately high for ultrasensitive fluorescence spectroscopy. The described photoacids present a valuable palette for a wide range of applications, especially when the properties of HPTS, i.e. highly charged, low photostability and only moderate excited state acidity, are limiting.

Absolute single-particle detection efficiencies and pulse height distributions of a cascaded microchannel plate (MCP) detector are reported for the ions H + 2 , Ne + , Ar + , Kr + and Xe + in the impact energy range 0-4.75 keV. The detection efficiencies have been obtained using the photoelectron-photoion coincidence (PEPICO) technique which allows the determination of detection efficiencies without knowledge of the absolute ionization rate. The mean gain is found to increase with increasing ion impact energy and decreasing ion mass. Depending on the ion mass, the absolute detection efficiencies saturate above 2.5 keV and reach about 63%.

A crossed beam study of the rearrangement reaction H-+D2( upsilon =0) to HD( upsilon ')+D- in the collision energy range Erel=0.3-3 eV is reported. From the vibrationally state resolved energy and angular spectra of the D- product ions, we derive state-specific differential cross sections in the CM system. Absolute units are obtained by using elastic H-+He scattering as a reference system. The measurements allow detailed conclusions concerning the reaction mechanism. By integrating over angles and summing over partial cross sections (for individual upsilon ' states of the HD product molecule), we determine the absolute total cross section of the reaction. The reaction has a threshold at Erel=0.42+or-0.12 eV. The cross section rises to a maximum of 2*10-16 cm2 at 1.5 eV and then rapidly decreases again. The present results resolve a discrepancy between two previous measurements bearing on the determination of the total cross section.

Absolute single-palticle detection efficiencies of a microchannel plate (MCP) detector were determined by photo-ionization of atoms or molecules. The ionized heavy particles were detected in coincidence with the resulting electrons. This method allows the determination of detection efficiencies without a knowledge of the absolute event rates. We obtained the detection efficiencies for the ions H' , D;, H D ' , Ht, Dt and Ar' in the impact energy range 0-5 keV. The detection ekiencies saturate above 3 keV and reach generally 41%. This value seems to reflect mainly the physically effective area of the MCP.

The development of iridium-free, yet efficient emitters with thermally activated delayed fluorescence (TADF) was an important step towards mass production of organic light-emitting diodes (OLEDs). Progress is currently impeded by the low solubility and low chemical stability of the materials. Herein, we present a Cu -based TADF emitter that is sufficiently chemically stable under ambient conditions and can be processed by printing techniques. The solubility is drastically enhanced (to 100 g L ) in relevant printing solvents. The integrity of the complex is preserved in solution, as was demonstrated by X-ray absorption spectroscopy and other techniques. In addition, it was found that the optoelectronic properties are not affected even when partly processing under ambient conditions. As a highlight, we present a TADF-based OLED device that reached an efficiency of 11±2 % external quantum efficiency (EQE).