I have a homework problem that is kinda driving me nuts... Consider the case of an anharmonic oscillator with microsystem quantum states given by Ej = jhf - (lambda)(jhf)^2. Using the known harmonic expressions as a starting point, determine the corresponding expression for F1 and for F, which is about equal to Fo + (lambda)F1. Can someone give me a hint on how to approach this problem? I figure I could find the partition function easily enough since Zj = sum(e^(-(beta)Ej)). I can then plug in Ej into the Zj function. However, I am not sure how to determine that sum. Am I even approaching this problem in the right way? Thanks.