Because in some papers they diidn't denote as Down conversion instead they use the the term Luminescence with 379 nm excitation, although they use the term upconversion for the 980 nm excitation for the same 550 nm emission...here i m talking abt Er3+...Pls clarify my doubt
Down conversion is 'The interaction of a photon with a medium in which it is converted into two photons of lower frequencies such that energy is conserved'. So you will have to check if intensity is increasing (approximately doubling from excitation to emission) which will indicate if one photon is breaking into two photons with higher wavelength.
Still, I don't know if it will clarify whether its a downconversion or simple luminescence.
Best of luck.
this is basically a down shifting process, not down conversion process. Generally, down conversion takes place when there is emission of two or more low energy photons when excited via one high energy photon as defined by "Sohan Hazra". It is a luminescence process simply (down shifting rather than down conversion)
Yes,it is a down conversion process on excitation with 379 nm , we get emission at 550 nm . this is because photons emitted are of lower energy, whereas in case of excitation with 980 nm, the emission is again observed at 550 nm , hence in this case photons emitted are of higher energy as compared to photons absorbed at 980 nm wavelength. Hope this clarifies your doubt.
It is simply a luminescence process where part of the energy absorbed is lost by non-radiative path way resulting in a " Stokes Shift" to give emission at higher wavelength (lower energy).
Stokes law states that excitation photons are at higher energy than emitted ones. In contrast, anti-Stokes emissions are up-conversions.
It is wrong to say that it is downconversion. It is simply photoluminescence. In case of downconversion, the incident ray is converted into exactly double the wavelength or half the energy. To understand the phenomena, one needs to apply the Franck-Condon Principle, where part of the energy is lost through non-radiative pathway resulting in a "Stokes Shift". Not only that the upward transition may be allowed but the downward may not be. There could be some levels in the excited states may be closer to each other increasing the probability of transitions resulting in nonradiative loss. this also depends on the lifetimes of various energy levels.
Thank u Professor P. D. Sahare Sir...Its really clears my doubt....Thank u
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