Browsing by Author "Tesfaye, Tilahun"

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    Rotational Heat Capacity of Diatomic Molecules in Atomic Cryocrystals
    (Addis Ababa University, 1992-06) Tesfaye, Tilahun
    A Comparative analysis has been carried out between the experimental excess heat capacity of solid solutions of"N2 and ''N2 in Ar and Kr due to rotation of the nitrogen molecules, and the existing theoretical models in the temperature range 0.5 to 6 Kelvin. It is shown that the well known Devonshire-ManzMirsky (DMM) model can not explain the observed heat capacity below 2K neither on the basis of the assumption of frozen hightemperature nor equlibrium concentration of different spin nuclear modifications of nitrogen. Splitting of the lowest rotational energy levels of the impurinty molecules is proposed, so as to provide an agreement between the experimental observations and theoretical data. It is also concluded that experimental observations favour the frozen high-temperature composition of the different spin species of nitrogen down to 0.5K in temperature, and the equilibrium' orientation of the molecules is along the <100> directions of the crystal