The Luminescence Spectra of Bi³⁺ Ions in MgO and CaO

Abstract

The dctails of the luminescence spectra of Bi3+ in MgO and CaO havc bcen examined over a wide range of temperature. It is found that emission from both 3P0 and 3P, excited states to the 'So ground state occurs, the former forbidden t,ransition dominating a t low temperatnres and the latter a t high temperatures. The bands can be resolved from one another, thus permitting the intensities and lifetimes of each transition to bc followed. These measurcmcnts show t,hat over a substantial ternperaturc rangc the two excited stat,cs arc in thermal equilibrium, and the decay characteristics are examined with the aid of a model developed in the Appendix. The radiativc lifetimes of the 3P, and 3P0 states are found to be 4 X lo-* and 2.9 x and 3.8 X s in CaO. With the aid of the discovery of the true zero-phonon line for the 3P0 + ISo transition in CaO: Hi a t 383.98 nm, the form of the vibronic series for this transition can bc interpreted. The forbidden transition is made slightly allowed by a combination of a static pcrt.urbation and coupling to a vibrational mode which mixes t.he 3P,, and 3P1 states. This interpretation is consistent. with the rcsults of magnetic-field cnhaneement of the zerophoiion line intensity reported by Itunciman e t a1.Die Lumineszenzspcktren von Bi3+ in MgO und CaO werdenin einem breitcn Temperaturbereich untcrsucht. Dabei wird gefunden, daB Emission sowohl vom als auch vom 3P,-Anregnngszustand znm IS,-Grundzustand stattfindct, wobei dcr erstgenannte, vcrbotene Ubcrgang bei nicdrigeren und der zweite bci hoheren Temperaturen iibcrwiegt. Die Banden lasscn sich voneinandcr trennen, wodurch die Intensitiit und Lebensdauer beider tJbergilnge verfolgt werderi kiinnen. Solche Messungcii zeigeri, daO die beiden Anregungszustiinde in einem erhchlichen Tcmperaturbereieh in thcrmischem Gleiehgewicht stehen. l h b e i werden die Zerfallscharakteristika mittcls cines im Anhang hcrgcleitcten Modclls untersucht. Die Strahlungslcbcnsdauer dcr bzw. 3P,-Zustande ergeben sich zu 4 X lo-" bzw.

Luminescence characteristics of Bi3+-activated oxides

“…The group of phosphors with a Stokes shift of 0.5 eV or less are those showing extended vibrational structure in the absorption and emission spectra at lower temperatures. Examples are CaO-Bi a÷ [3], NaScO2-Bi a+ [5], YAlaB4OI2-Bi 3÷ [19] and Cs2NaYC16-Bi a+ [20].…”

“…In some investigations attention was focussed on the wide variation of the emission and excitation spectra [I, 2], in others on the occurrence of vibrational structure in these spectra [3][4][5] and, Finally, in still others on the decay characteristics connected with the presence of an optical trap below the emitting SP 1 level [6,7]. Recently Moncorg6 et aL [8] reported on the luminescence of LaPO4-Bi s÷ which is exceptional due to the large Stokes shift and the small optical trap depth.…”

The Luminescence Properties of Alkaline‐Earth Oxides Activated with 6s2 Ions

“…3. The decay times of the emission of the Bi3+-activated samples have been presented elsewhere [2]. The emission intensity remains constant in this temperature region.…”

Dynamical processes on relaxed excited states in NH4Cl:Tl+ single crystals

“…Usually, an appropriate approximation is made and the temperature dependence of s τ is expressed as [30,31] …”