When using Fourier's trick for determining the allowable energies for stationary states, Griffiths introduces the a+- operators. When factoring the Hamiltonian, the imaginary part is assigned to the momentum operator versus the position operator. Is there a reason for this? If : a-+ = k(ip + mwx)(-ip + mwx), and the commutator is (xp-px), Is a+- = k(-ip = mwx)(ip + mwx) ? If so, is the commutator (px-xp)? Thanks in advance for your input.