Electronic structure of solid molecular complexes evaluated by positronium formation studies at low temperature

Abstract

Electronic structure of solid molecular complexes [TPPO1−x⋅TPMx] and [TPPO1−x⋅ACNx] at low temperature (80K) was investigated by positronium annihilation lifetime spectroscopy (PALS) in order to evaluate the positronium formation at this condition and compare with our previous study recently reported at 294K. Temporal dependence of the τ3 (ortho-positronium lifetime/ns) and I3 (ortho-positronium relative intensity/%) at 80K remained constant throughout the measurement time (10h), suggesting non-occurrence of electron trapping. The dependence of I3 with molar fraction at 80K showed a decrease of I3 when compared with the values obtained at 294K (ΔI3=8% for [TPPO0.5⋅TPM0.5] and ΔI3=37% for [TPPO0.5⋅ACN0.5]. These results were rationalized in terms of reduction of electronic availability upon lowering of temperature.