Molecular Orbitals of (NH₄)₂SO₄:Tl

Abstract

One electron molecular orbital(MO) energy levels of Tl-(SO₄)_n complexes in (NH₄)₂SO₄ have been calculated by using the charge-consistent extended Hückel method at various temperatures from 25 to −140°C. The calculation has been performed both for the ground and excited states, and the result shows that the highest occupied MO in the ground state, s′, mainly consists of the thallous 6s orbital, and the lowest three partially occupied MO’s in the excited state, p_1,2,3′^*, consist of the thallous 6p orbitals. The optical absorption bands of (NH₄)₂SO₄:Tl are attributed to the transitions between MO’s, s′ and p_1,2,3′^*. The temperature dependence of the absorption spectra is explained by that of both the energies of MO’s and the crystal fields of (NH₄)₂SO₄ crystals.