Stretching mode interaction of equal and unequal pairs of SeH− and SeD− defects in alkali halides

• Published in: Radiation effects and defects in solids Vol. 151; no. 1-4; pp. 311 - 315
• Main Authors: Afanasiev, A. D., Ivanov, A. A., Luty, F., Melikova, S. M., Shchepkin, D. N.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01-11-1999
• Subjects: Coupled diatomic defects; Ionic crystals; Resonance interaction
• ISSN: 1042-0150; 1029-4953
• DOI: 10.1080/10420159908245973

The stretching-mode (SM) absorption of isolated SeH
−
or SeD
−
molecular defects in alkalihalides show a resolved spectral structure due to the different reduced masses of the six natural stable Se isotopes. In a FTIR study of these defects in KCl and KBr, we have observed new SM absorptions of defect pairs which scale quadratically with the defect concentration. For "equal pairs" SeH
−
-SeH
−
and SeD
−
-SeD
−
, the fundamental SM absorption shows (in contrast to "mixed" SeH
−
-SeD
−
pairs) a distinctly different Seisotope splitting, while the overtone splitting of all pairs remains similar to that of the isolated defects. Besides a simple classical coupled-oscillator treatment, we present a quantum-mechanical calculation, explaining the observed spectral behavior by resonance interaction of the molecules in pairs of equal (or "nearly equal") frequencies.