Dear Tang

Please provide more information about your compound, solvent system and experimental conditions. Two bands can also indicate two excited state species or even two isomeric forms existing in equilibrium.

Dear Sirs,

Enclosed please find the measured PL spectrum on inorganic powder material. Special region is shown by the blue circle. Where, I believe this special region should not be a result of experimental error. Actually, it will disappear at room temperature. Would you please give me a further comment on it?

Thanks and best regards,

TF

Well, I can provide two PL spectra at various temperatures for the same sample, from which you can see the increase of PL intensity with temperature but keeping the zero PL intensity region. Whether this result could be used to reveal no saturation?

Enclose please find two different temperature PL spectra, both of which contains zero PL intensity region

Dear Prof. Peter, Could you give me a further comment on the above question? Thanks.

 Sorry, Prof. Peter. Since you just mentioned the spectra I posted is not relavant to the saturation, I think it it better to remove it intead providing the final figure. Of course, I will carrying out the experiment by reducing the excitation. However, I appriciate your comment very much. Thanks.

Actually, the detector saturation is commonly found by a horizontal line at the top of  spectra rather than at the bottom. Therefore, I am still confused on the zero PL intensity region.

Dear Prof. Peter, I can sense what you mean, and I even imagine some shrinkage of seperation between two strong emission peaks by reducing the excitation intensity. What I am confused is that if it is caused by detector saturation, why other PL peak intensity continues to increase with the rise of temperature? The peak intensity should keep a fixed value as long as it is in the case of saturation, shouldn`t it? Or the measured entire PL integrated intensity should keep the same value at various temperatures, doesn`t it? However, the obtained results reveal that the PL intensity regardless of peak intensity or integrated intensity continues to increase with raising temperature. It seems not to be saturated for the detector.

Well, I feel sorry for my just negligence on your previous question. The intensity 6000 corresponds to the peak height, and it`s unit is not clear here, commonly counts as the unit for which I am not sure.  In addition, I acknowledge that this spectral feature is tightly related to the exprimental method. But I still think the detector saturation can not account for this phenomena based on the measured results at different temperatures.

Dear Prof. Peter,

Much thanks for your explanation. I will carry out the experiment to identify how zero PL itensity region varies with the excitation intensity.

BTW, I should note that the rise of temperature decreases  the emission intensity,  which is  true for most of luminescence materials but not apply for my sample. Actually, the sample I investigated performs an abnormal PL behavior.

At an extremly low temperature of 3K, its emssioin intensity is much weak with only one peak occurring, however, the room temperature intensity increases sharply as compared with the previous one. I believe it might be related to the electron-phonon coupling interaction.

Detector saturation.