In BeO a 220 C TL peak bleaches out on optical bleaching yet it does not contribute to OSL (as reported in literature). Reason given that the optically evicted charges from the 220 C trap make some non-radiative transitions or the luminescence emission is beyond the detection window. If this is the case then why it is giving TL (radioactive transition) in the same detection window. So if a trap is giving TL and getting recorded then same trap getting bleached by light is not contributing the OSL. i.e if you stimulated the trap by heat it gives TL and gets recorded but if you stimulate by blue light it gets bleaches but not gets recorded by same detection system.
I do not know about BeO, but I can offer a situation that may lead to the described effect. To begin with, one has to remember that for getting a TL peak, an electron trap and a hole center should be involved. Following excitation, there are electrons in the trap and holes in the center. If the bleaching light releases electrons, we can expect that OSL be emitted along with the bleaching of TL. This may not be the case if the light releases holes into the valence band. The released holes may recombine non-radiatively with electrons in some traps, but the main point is that the release of holes reduces their number in the center so that during heating, fewer radiative recombinations will take place, hence less TL is emitted.
I agree with Chen, but one should also think about possible localized non-radiative re combinations. It may happen ever though there is electron leased during OSL read out of BeO.
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