Knowledge Bank

The expression for the integrated intensity of a fundamental infrared absorption band, including the effects of spontaneous emission and mechanical anharmonicity, has been derived utilizing first-order, non-degenerate perturbation theory. We have studied the temperature effect ($77\circ K$ to $800\circ K$) on band intensity in two types of systems; molecular crystals (metallic-phthalocyanines, copper, cobalt and vanadium) and inorganic ions $[(K(CLO4-,Cl)$ and $K(CO3--,Cl)]$ isolated in alkalihalide lattices. Expressions utilizing the harmonic potential function have also been derived for certain overtones and combinations. These expresions compare favorably with the experimental data. We have also been able, through an intensity study, to identify a librational-rotational transition for the perchlorate system at approximately $590\circ K$.