抄録
The details of the luminescence spectra and the decay characteristics of the luminescence have been examined over a wide range of temperature. At low temperatures, the luminescence decay curve after the A-band excitation has two components, fast and slow. The difference between the decay times, about 10 ns and 4.1 ms at 4.2 K, enables one to decompose the emission spectrum into the 3T1u→1A1g and 3A1u→1A1g bands by time-resolved emission spectroscopy. The zero-phonon line at 445.3 nm of the former band and the zero-phonon line (A0) at 460.7 nm and the one-phonon line at 465.0 nm of the latter band are observed at 6 K. The A0 line grows under an external magnetic field. The optical excitation mechanism has been also examined by observing the excitation spectra at various temperatures.