Hello! i have a trouble with an exercise of a course of structure of matter. Helium atoms in the excited state 23S1 come out from a box at v=2000 m/s and pass trough an Stern & Gerlach apparatus with dB/dz=25 T/m and lenght L=0.30m. Atoms spends 1 hour in the box and the average-time for decay is 8000s. the questions are: 1) evaluate (number of atoms deflected with Mj=1) / (total number of atoms came out from the box) 2) evaluate the angular deflection of the component Mj=1. So, the part 2 is very simple: i know that the state has S=1, L=0, J=1 and using F = [tex]\mu[/tex]z * dB/dz I found alpha=0.30. But I can't understand part 1: 8000s>1hours so every atom producted come out form the box and don't decay to the ground state?? then, don't the 3 components Mj= 1, 0, -1 should have the same probability 33.3% ? Or I should use statistical mechanics and evaluate the probability of that state in function of temperature and energy? please help me to understand, thank you!!