Proton potentials for widely varied hydrogen bond lengths in a water dimer

Potential curves for the proton of a hydrogen bond in (H_2O)₂ with H-bond lengths R varied from 2.38 to 5.19 å are found using the semiempirical potential function suggested earlier. Energy levels and wave functions are obtained for the ground and the two lowest excited states. The (H₂O)2 molecule is taken as a model system approximating processes in a nucleotide pair after an ultraviolet energy quantum has been absorbed and transformed to heat. The results are used to construct the theory of potential mutations that take place during UV irradiation of DNA.