I am considering the spin state's effect on the charge carrier's lifetime, I was told that high spin and low spin state could coexist when the crystal field splitting energy and the pairing energy are close, but I am not sure how to estimate the ratio between high spin state and low spin state, is there any theory I could adopt to analyze this kind of situation?
Here is some background I find:
whether a complex is high spin or low spin depends on two main factors: the crystal field splitting energy and the pairing energy. The electrons will take the path of least resistance--the path that requires the least amount of energy. If the paring energy is greater than Δ , then electrons will move to a higher energy orbital because it takes less energy. If the pairing energy is less than Δ , then the electrons will pair up rather than moving singly to a higher energy orbital.