Excimer-like Yb3+-pair and photoluminescence spectra of Yb3+-molybdates

Abstract We found a broad cooperative luminescence (CL) band due to Yb-pair at 470–520 nm in the up-conversion spectra of an Yb 3+ -molybdate, LiYb(MoO 4 ) 2 which was excited at 975 nm. Evidence is presented for reasonability of the assignment of the blue-green emission to CL. The emission from Yb-pair usually leads us to expectation in observation of its absorption from Yb-pair. Any absorption due to Yb-pair, however, was not found although several challenges were made. It is suggested that absence of the Yb-pair absorption is due to presence of excimer-like Yb-pair in LiYb(MoO 4 ) 2 . Unusually much weaker CL intensity was observed than the up-converted emission from RE in very lightly RE-doped LiYb(MoO 4 ) 2 even at high 975 nm laser power, where RE = Tm 3+ , Eu 3+ , Er 3+ , Tb 3+ , and Ho 3+ . Discussion is made on the reason. The up-conversion measurement for Yb 3+ -compounds is useful (1) for detection of unwanted impurities even in carefully purified chemical compounds and (2) for generation of intense up-converted green-red emissions from RE 3+ -doped LiYb(MoO 4 ) 2 .