Radiative and Non‐Radiative Processes of Localized Impurity Centers in Alkali Halides: KBr:Ag⁻

Abstract

The C and A emissions in KBr:Ag-are measured in detail between 11.2 and 300 K. At 11.2 K, excitation in the peak position of the C band exhibits the C emission but it hardly produces A emission. Changing the excitation position to the higher energy side of the C band peak, the A emission is produced a little. The intensity (emitted photon number) ratio of the A to C emission, r), shows an excitation photon-energy dependence and changes over three orders within both sides of the C band. Increasing the temperature, q itself increases as a whole and its excitation photonenergy dependence weakens and disappears a t about 80 K. The values of q in the lower energy edge show an activation process of Arrhenius type over four orders above around 45 K, whose activation energy is 0.076 eV, and below 30 K, another activation process of the same type with an activation energy of 0.0025 eV. A few causes of the exciting energy dependence of r) a t low temperatures are considered and the mechanism due to the dynamical nonradiative transition is proposed.Les Bmissions C et A dans KBr:Ag-ont 6tk mesurkes en detail entre 11,2 et 300 K. A 11,2 K, l'excitation en position de la pointe expose 1'6mission C, mais elle n'expose pas 1'Bmission A B peine. Changeant la position d'excitation vers le cBtB des Bnergies plus hautes, 1'6mission A est aussi produit un peu. Au bout du compte, la proportion d'intensitbs de 1'Bmission A de 1'6mission C, r) montre une dependance de photon-Bnergie d'excitation et se change sur trois ordres dans la region de la bande C. ElBvant la tempbrature, q croit dans toute la rbgion de la bande C, mais cette

Optical properties of the Tl+ center doped in NH4Cl crystals with the CsCl structure

“…In general, the peak energy of the luminescence bands in the Tl þ center doped in the alkali halides shifts to the lower energy side with increasing temperature. On the other hand, a slight blue-shift of the peak energy of the A luminescence bands with increasing temperature is observed in RbCl:Ag À and KBr:Ag À [22,23]. It is considered that the blue-shift is caused by a mixture of the two A luminescences from the two minima of the 3 P 1 and 3 P 0 APES.…”

Polarization Characteristics Due to the Jahn-Teller Effect in CsBr:Ag? and CsI:Ag? Crystals

“…The phenomenon has its origin in the dynamical non-radiative transition at the intersection point between the 1 T 1u and 3 T 1u adiabatic potential energy surface (APES) on the way in the relaxation to the bottom of the 1 T 1u APES [23]. The similar phenomenon due to the dynamical nonradiative transition has been also observed for the Ag À centers in NaCl and KBr crystals [18,22]. The dynamical non-radiative transition plays an important role on the polarization characteristics due to the Jahn-Teller effect, as mentioned below.…”

Optical Properties of Anionic Gold Centers in CsBr and CsI Crystals

“…The other pieces of the equipment used for the optical measurements were almost the same as described before [17], unless otherwise stated. No differences were observed in the optical spectra thus obtained for the crystals prepared from the two different sources mentioned above.…”

“…Absorption measurements were made by using a metal cryostat above LNT (liquid nitrogen temperature) and emission and excitation measurements above 13.9 K were done by using the Cryo-Mini cryostat [17]. The other pieces of the equipment used for the optical measurements were almost the same as described before [17], unless otherwise stated. No differences were observed in the optical spectra thus obtained for the crystals prepared from the two different sources mentioned above.…”