fig4
From: Energy transfer process, luminescence optimizing and various applications of lanthanide complexes
Figure 4. (A) Chemical structure of the Cr-Yb; (B) Schematic partial energy-level diagram of Yb3+ and Cr3+ relevant for CSU. This figure is used with permission from Wiley-VCH GmbH[21]. ISC: Intersystem crossing; CET: cooperative energy transfer; CSU: cooperatively sensitized upconversion.
