Luminescence and charge trapping features of archPbMoO4 lead molybdate crystals grown from archaeological lead

Abstract

A PbMoO4 single crystal as a perspective detector for neutrinoless double beta decay experiment was grown by the Czochralski technique from high purity raw materials including archaeological lead. Charge trapping and energy transfer phenomena in this crystal have been studied by electron paramagnetic resonance (EPR) and wavelength-resolved thermally stimulated luminescence (TSL). EPR revealed several impurities, which however do not participate in the charge trapping processes: Gd3+, Cr3+, Mn2+. Self-trapped electron and (MoO4)3--VPb centers creation under laser light was confirmed. At least six glow peaks related to the thermal release of the charge carriers were observed having maxima at 41 K, 53 K, 83 K, 90 K, 105 K and 118 K. The peak at 41 K was ascribed to the de-trapping of self-trapped electrons. The 53 K one, in particular, is created by re-trapping processes. Partial cleaning procedure followed by the initial rise method allow to determine the trap depths and frequency factors for the 90 K and 105 K glow peaks. They have been referred to the (MoO4)3--VPb decay. A three-component analysis of the spectra could explain the observed 100 nm red shift of the thermo-luminescence emission maximum.