Time-and space-resolved study on the effect of high-density excitation in ion tracks

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Our technique for fast decay measurements-single ion and single photon coincidence(SISP) was further developed to obtain a resolution of 85 ps (the fastest of the similar equipment's reported for ion irradiation so far) and also to take a time-resolved spectrum. As for its application to different fields, a detector of the SISP was installed into a TOF system and a new impurity analysis system was developed. Our results ale as follows.A new ultra-short lived luminescence band was found in ion irradiated alumina crystals, which has not been found by laser and pulsed electron irradiation. This band has a peak around 340 nm a broad band-width of 2eV, and a short lifetime of 100 ps. Further experiments elucidated that the new band could be observed in a many kind of crystals like oxides, alkali and alkali-earth halides. Considering characteristics shown by the results, the super-linear dependence on excitation density, the temperature independence, a ultra short lifetime, and a broad band, it may be concluded that the electron-hole plasmas or complexes composed of the electron-hole pair and other excited states are formed. We assigned this new band due to luminescence associated with the relaxation of the electron-hole plasma. This finding may open and lead the study for ion-irradiation effects into new development and also make it possible to study the effect of high-density excitation and the plasma of the wide band-gap crystals.