An International Research Journal

AJP

SSN : 0971 - 3093

Vol  5, No. 3, July-September, 1996

Vol 5, No 3, 1996

Asian Journal of Physics                                                                                                          Vol. 5, No 3 (1996) 283 -289


Emission and Excitation Studies in Eu2+ and Mn2+ Doped KBr


A K Mishra

Physics Department, NAS College, Meerut- 250 004 , India

and

S D Pandey  

cPhysics Department, PPN College, Kanpur- 2008 001,  India

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The optical emission and excitation spectral studies in KBr: Eu2+ and Mn2+ single crystals  at, different sample conditions have been analysed to identify the various aggregates and precipitates of both impurities and possible energy transfer from one impurity to another. The emission  obtained at 525 nm in the  both grown samples at  RT and LNT is proposed to be due to radiative energy transfer from Eu2+  to  Mn2+ ions, the latter being in Suzuki phase. The RT emission spectra of the samples annealed  for long time at 220 °C and LNT emission spectra of as grown samples identify the growth of different aggregates of Eu2+  and Mn2+ ions at the expense of (I-V) dipoles of the two impurities. © Anita Publications. All rights reserved.

Keywords: KBr, Suzuki phase, Eu2+ and Mn2+ single crystals

Total Refs: 31

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1 Introduction

         Many investigations have been devoted to divalent impurity doped  alkali halide crystals which exhibt intetresting peculiarities due to the presence of a cation vacancy compensating the electrical extra charge of the divalent ion. The resulting (I-V) pairs have been studied by different techniques as optical [1-5], EPR [6], ITC and ionic conductivity studies [8].

            Particularly, the optical properties of Eu2+ ions in alkali halides are fairly well understood. The Eu2+ -ions doped in KBr host have two absorption bands [3] in the UV region of the spectrum, with peak positions at 250 nm and 344 nm. These bands are due to dipole allowed transitions from the ground state 8S7/2 of Eu2+ ions to the splitted crystal field 5d orbitals. The high-energy band is due to transitions  from the ground statet of  the Eg component of the 4 f 6(5d) configuration, while the low energy band is attributed to the T2g component of this configuration. As these transitions are dipole allowed, their oscillator strengths are high making the Eu2+ -doped KBr system an efficient absorber of UV light.

            The optical properties [9,10] of Mn2+ ions in alkali halides are also fairly well understood. The absorption bands of Mn2+ ions in alkali halides  are relatively weak because these arises from spin and parity forbidden transitions. The oscillator strength of these transitions is around 10–7, which  makes Mn2+  doped systems weak absorbers of UV light. 

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