In modern photochemical model of ozone dissociation excited in the Hartley absorption band (V.A. Yankovskii, R.O. Manuilova, Atmos. Oceanic Opt. 16, No. 7, 536-540 (2003)), it is necessary to take into account the formation of metastable oxygen molecules in excited electron state O2(a1Δg, ν) with a high-level vibrational excitation. In this paper, we propose an analytical approximation to describe wavelength dependence of the quantum yields of molecules in excited electron and vibrational states O2(a1Δg, ν = 0÷3) of the singlet channel of ozone photolysis in the Hartley band. We have derived a unified analytical formula for all quantum yields of the molecules O2(a1Δg, ν) in excited electron and vibrational states. This formula allows for both the threshold of the corresponding vibrational level formation of an O2(a1Δg, ν) molecule and the photon energy. The formula derived agrees with the experimental data available.