Dynamics of 2, 3, and 4 Level System: A Detailed Study of the 4-Level 

This video explores the dynamics of 2, 3, and 4-level systems emphasizing a detailed study of the 4-level System Rate Equations. The transition decays are explored in terms of decay rates understood as lifetimes in each energy level.
Although this video is presented in Spanish, the flow of the mathematical ideas and expressions can be easily followed by the academic community.