First of all. We should mention that we use the intensity of absorption of the certain range of the spectrum to estimate the concentration of Sm2+. There exist two ways to change the value of reflectance to absorption, one is K-M equation, and the other one is based on the equation that A(absorption)+R(reflectance)+ T(transmittance)=1. Since the transmittance is definitely negligible for our sample, then the equation can be written as A+R=1, that is A=1-R, which is the equation we used here. Previously, I prepared a batch of sample of CaF2 with Eu and Sm co-doping. The concentration of Eu2+ is fixed as 1%, while for Sm3+, different values(0.5%, 1%, 2%, 4%) were chosen. From the final results, we found that the saturated absorption for Sm(1%, 2%, 4%) is almost the same, which is obviously higher than that of the sample with 0.5%Sm. Because the ability of absorption depends on the concentration of Sm2+.
Therefore, if the original concentration of Sm3+ is low, then the final number of the absorption centers Sm2+ would not be high as well even though we increase the irradiation time further. In other words, the designed concentration of Sm for the samples determine the ability of Sm2+ absorption. Why the absorption of the other three samples keeps almost the same? It can be interpreted that the conversion of Sm3+ to Sm2+ occur along with Eu2+ to Eu3+, and the designed concentration of Eu can limit the absorption of Sm2+. Since the fixed concentration of Eu2+ is just as much as 1%, then the concentration of Sm2+ can not exceed 1% theoretically no matter how long it has been irradiation by X-ray. To make the explanation more convincing, we prepared additional sample with the concentration of Eu and Sm of 1% and 0.01%, respectively, and the corresponding result conform to the explanation as well. A series of sample with the fixed concentration of Sm (1%) and variable concentration of Eu ()
- The range of 200-450 nm contain both the photoluminescence and reflectance, it is difficult to distinguish them, so the data is not reliable.
- To do the alignment, we choose a specific range not from 800nm, because it seems that something wrong when use those data 800-794 nm. We use the starting 5 to 15 points to make an alignment.
- When processing the data from csv file. The 2rd column and 4th colum means the baseline of the BaSO4 reference and non-reference. The other data are the results processed from the two baselines?
- When measuring two samples in the folder of Eu variation, two(?) samples shows a reflectance of ZERO at around 800 nm, then jump up to the normal values. So when make an alignment, we avoid the area.
Is it possible to directly choose absorption when we measure the samples?