Luminescence Dynamics of Terbium Monodipicolinate in Ethyl Ammonium Nitrate

Abstract

Energy level dynamics are experimentally examined for terbium monodipicolinate dissolved in ethyl ammonium nitrate (EAN). The luminescence lifetime, the luminescence risetime, and the absorption spectrum of terbium monodipicolinate in EAN are measured. The risetime of luminescence in terbium dipicolinate is experimentally shown to be nonzero and measurable. A dynamic model is presented that describes the evolution of terbium dipicolinate luminescence in EAN. The long risetime in the model is caused by a resonance between the ⁵E₆ state in the terbium cation and the lowest triplet state (T₁) in the dipicolinate anion. Bacterial endospore components dissolved in EAN are used to check the time resolution of the experimental apparatus. EAN is discussed partly because it is a room-temperature ionic liquid (RTIL), which is a class of solvents that may be useful for detecting bacterial endospores in the atmosphere.