Quenching of electronically excited N2 molecules and Tb3+ /Eu3+ ions by polyatomic sulfur-containing gases upon triboluminescence of inorganic lanthanide salts.

Abstract

The triboluminescence of Eu2 (SO4 )3 ·8H2 O and Tb2 (SO4 )3 ·8H2 O crystals in an atmosphere of sulfur dioxide (SO2 ) or sulfur hexafluoride (SF6 ) was studied. Quenching of the gaseous (emitter N2 ) and solid-state (emitter Ln3+ ) components of the triboluminescence (TL) emission spectrum was seen when compared with the TL spectra of the crystals in air. One reason for the quenching is a reduction in the effective charge both on the crystal surface and in micro-cracks under an SO2 or SF6 atmosphere, leading to a decrease in the probability of electrical breakdown and a reduction in electric field strength responsible for the electroluminescence excitation of lanthanide ions in TL. In an SO2 atmosphere, there is an additional mode of quenching, as confirmed by quenching of the crystal photoluminescence (emitter Ln3+ ). It is supposed that this quenching is due to an exchange of energy on electronic excitation of the lanthanide ions to the vibrational sublevels of the SO2 molecules adsorbed on the crystal surface. Another additional channel of TL quenching originates from non-radiative transfer of excitation energy during collisions between the *N2 and SO2 molecules in the gaseous phase.