1. The problem statement, all variables and given/known data A spin-1 particle is placed in a constatn external B field with [itex] B_0 [/itex] in the x direction. the intial spin of the particle is spin up in the z direction. Take the spin Hamiltonian to be [itex] H=\omega_0 S_x [/itex] determine the probability that the particle is in the state |1,-1> at time t. 3. The attempt at a solution Would I start with using the [itex] S_x [/itex] matrix in the z basis and then set this equal to spin 1 and then find the eigenvector for this equation and that will give me the amplitudes for spin-1, spin-0 and spin minus 1 and these will be amplitudes in the x basis then I will just time evovle that intial state. So I will have [itex] S_xQ=1Q [/itex] where Q is a generic column vector and 1 is the eigenvalue because we are spin up in the z direction. Or do I need everything in the x basis. But it seems like I first have to work in the z basis because we know it is spin up in the z direction.