1. The problem statement, all variables and given/known data The fluorescence spectrum of anthracene vapor in the figure shows peaks with maxima at 440 nm, 410 nm, 390 nm, and 370 nm, whereas the absorption spectrum has peaks at 360 nm, 345 nm, 330 nm, and 305 nm. Assuming that only one vibrational mode contributes to these progressions, determine the vibrational spacings in the ground and excited electronic states. 2. Relevant equations B=h/8*pi^2*c*I where I is the moment of inertia. nu=2B(J+1) 3. The attempt at a solution I am not sure how to even start this problem. I was considering using the equations listed above to calculate the spacing but I dont know how to calculate I. I am lost and any help would be good. Thank you for reading.