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Mechanoluminescence; triboluminescence; colour centres; dislocations; alkali halides

A theoretical study is made on the mobile interstitial and mobile electron models of mechano-induced luminescence in coloured alkali halide crystals. Equations derived indicate that the mechanoluminescence intensity should depend on several factors like strain rate, applied stress, temperature, density of F-centres and volume of crystal. The equations also involve the efficiency and decay time of mechanoluminescence. Results of mobile interstitial and mobile electron models are compared with the experimental observations, which indicated that the latter is more suitable as compared to the former. From the temperature dependence of ML, the energy gaps between the dislocation band and ground state of F-centre is calculated which are 0.08, 0.072 and 0.09 eV for KCl, KBr and NaCl crystals, respectively. The theory predicts that the decay of ML intensity is related to the process of stress relaxation in crystals.

B P Chandra¹ Seema Singh¹ Bharti Ojha¹ R G Shrivastava^{1 2}

1. Department of Postgraduate Studies and Research in Physics, Rani Durgavati University, Jabalpur - 482 001, India
2. Department of Physics, Government Engineering College, Jabalpur - 482 001, India

Published

February 1996

Manuscript received

7 April 1993

Manuscript revised

4 September 1995