We have observed the radiative recombination of electrons, attached to nitrogen pairs, with holes on neutral acceptors. The acceptor binding energies are found to be 102.5±1 meV for Cd, 70.1±1 meV for Zn, and 54.7±1 meV for C, 8.3 meV larger than previously accepted values. This result implies corresponding increases in the band gap and exciton binding energy, to 2.350±0.002 eV and 22±2 meV, respectively, at 2 K.