The H2-4S0 spectrum has at least two resonance states

A revival of interest in the prototypical doubly negative ion H2-, has led to a current disagreement as to whether there exists a S-4(o) resonance above the H 2p threshold. Our herein reported complex coordinate rotation calculations show that the H2- spectrum has at least two complex eigenvalues, z, corresponding to quasilocalized S-4(o) states. The first is 1.43 eV above the n = 2 H threshold, with -2 Im(z) = 1.69 eV. The second is 0.46 eV above the n = 3 threshold, with -2 Im(z) = 0.29 eV. The large value of -2 Im(z) for the lowest S-4(o) state suggests that the a priori qualitative identification of -2 Im (z) with a rate of decay (width) should be considered as a reasonably good but not rigorous relation, whose understanding should await precise measurement of the spectral density of this state.