Unusual Luminescence of Titanium(III) in Aluminium Oxide

Abstract

Titanium(III) in corundum shows a short-lived (3.1 μs) broad ²E - ²T₂ luminescence around λ = 740 nm, and a 10 times longer-lived ²A₁ ("4s") – ²T₂ centered around λ = 410 nm. Both these broad-band emissions with large Stokes shift offer prospects for tunable lasers. The absorption spectrum has been studied in detail, and traces of titanium(IV) are shown not to be involved in the “violet” emission, in contrast to a parasitic absorption around λ = 700 nm due to Ti^III,IV, like sapphire is blue due to Fe^II Ti^IV → Fe^III Ti^III electron transfer bands.