A simple method to compute excitation energies in variational many-body calculations

We propose a simple, easy to implement, variant of the EXCITED method for variational many-body calculations for excited states. We apply this method to the Hybrid Multideterminant method(HMD). We test this method with relatively few Slater determinants by comparing the results with exact shell model calculations for ${}^{56}Ni$ using the $fpd6$ interaction. We obtain very good agreement with the exact results.