“…As shown in Figure 7A,B, under excitation wavelength (λ = 410 nm), the emission spectra of the sample G-0.5 display a broad band from 500 to 780 nm centering at 613 nm, which can be attributed to spin-forbidden 4 T 1g (G) → 6 A 1g (S) transition of Mn 2+ (d 5 ) located in the octahedral coordination site of the glass host. 12,[34][35][36] In the excitation spectra (monitored at λ = 613 nm), the spectrum shows a strong and broad band located at 265 nm corresponding to Mn-O charge transfer (CT) transition, and three other bands located at 347 nm, 361 nm, and 408 nm, attributed to transitions 6 A 1g (s) → 4 E( 4 D), 6 A 1g (s) → 4 T 2g (D), and 6 A 1g (s) → ( 4 E 1g (G), 4 E 1g (G)), respectively. This result is in good agreement with the absorption spectra ( Figure 4B).…”