The role of cerium sites in the scintillation mechanism of LSO

Abstract

The crystal structure of Luz(Si04)0:Ce ("LSO") has two trivalent cation sites which may be occupied by Ce3* to form luminescence centers. Previous investigations revealed the existence of two distinct sets of Ce3' excitation and emission spectra and suggested that the differences in the spectra are due to differences in the crystal fields at the two lattice sites that shift the 5d levels of Ce".In the present report, we reexamine this issue and present new evidence which suggests a different interpretation. In particular, spectra measured at 13 K suggest that both lattice sites may give rise to indistinguishable excitation and emission spectra while the second set of observed spectra may arise fi-om Ce" located in interstitial sites. The evidence for the interstitial sites is a disappearance of the doublet structure in the emission spectra and a large variation in the population of the sites as a function of total cerium concentration. In addition, the results indicate that the scintillation properties of LSO are influenced by the relative population of Ce in interstitial sites compared to lattice sites as well as by differences in the transfer efficiencies to different sites.

Electronic properties and 4f → 5d transitions in Ce-doped Lu2SiO5: a theoretical investigation

“…This is known as the two-activation-center model. The emission from Ce2 was observed to be much weaker than that from Ce1, and was obscured by the latter at temperatures above 80 K. Later, Naud et al 8 gave a different interpretation for the two activation centers, according to which the two types of spectra were from to the Ce 3+ ions at the substitutional Lu sites and at the interstitial sites, respectively. After that, based upon the 4f→5d absorption measurements, Cooke and coworkers 9 provided evidence in support of the previously proposed two-activation-center model by Suzuki et al, 6 but also tentatively suggested that the Ce1 and Ce2 centers were due to the Ce 3+ ions located at the six-coordinated Lu2 and the seven-coordinated Lu1 sites, respectively.…”

Luminescent properties of Na-codoped Lu2SiO5:Ce phosphor

“…The emission spectra all possessed very similar shapes. Based on assume that the integral of the emission spectra is directly proportional to the luminous intensity [6]. The relationship between the luminescence intensity and the Ce 3+ doping concentration is obtained, as shown in inset Fig.…”

“…The host of LSO has a monoclinic structure. In this lattice, the Lu atoms occupy two equally populated, crystallographically independent sites, which have oxygen coordination numbers of 6 and 7.When doped with cerium, the Ce is assumed to substitute for the two different Lu sites, designated Ce1 and Ce2 [6]. The scintillator light is due to the parity-allowed electric dipole 5d → 4f transition of the Ce 3+ ion, which is strongly affected by the crystal field [4].…”

Temperature dependence of APD‐based PET scanners

“…11 For most types of crystals, a decrease in light yield is observed at higher temperatures. The magnitude of this effect has been quantified for some crystal materials.…”

“…2.E.1, was used. 11 C was used as radioactive source. At the start of the experiment the total activity inside the phantom was 325 MBq and 350 MBq at 21…”