Hi. In general, how does one find the eigenvalues of an operator? I have a problem which goes like this: Consider a 1-D Hamilton operator of the form: H = (P^2)/2M - |v> V <v| ,where the potential strength V is a positive constant and |v><v| is a normalised projector, <v|v> = 1. Determine all negative eigenvalues of H if |v> has the position wave function: <x|v> = sqrt(K) exp(-K|x|) with K>0. Can someone suggest a rough approach to solving this type of questions? I don't have a clue as to how i should start. Thanks.