The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminum nucleus ($\mu$–$e$ conversion, $\mu^{-}N \rightarrow e^{-}N$); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90% upper limit of a branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the $\mu$–$e$ conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.

A series of tetradentate Pt­(II) emitters containing fused 5/6/6 metallocycles have been designed and synthesized. Molecular geometries play a critical role in determining the photophysical properties. Their emission spectra are significantly affected by the geometries of the molecular core skeletons, the substituents, even hydrogen atoms, and their positions, which are further supported by X-ray crystallographic analyses and theoretical calculations. The generation of excimer emissions is observed in the tetradentate 5/6/6 Pt­(II) emitters for the first time and found to be concentration-dependent both in the solution and solid states. All of the Pt­(II) emitters have high photoluminescent quantum efficiency of up to 100% and luminescent lifetime as short as 1.4 μs at room temperature, achieving a radiative rate of 7.14 × 105 s–1. Their emission color can be easily tuned to cover the whole visible region (λmax = 464–632 nm) through selective synthetic modification of the heteroaromatic rings of the ligands. Pt­(1-ptz)-based sky blue organic light-emitting diode (OLED) demonstrates a maximum external quantum efficiency (EQE) of 14.5%, yet maintains an EQE of 12.7% at a high brightness of 1000 cd/m2. This work demonstrates that these tetradentate Pt­(II) complexes can act as efficient phosphorescent emitters for OLED applications.

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