Infrared and Raman Studies of Structural Relaxation in Amorphous Tetracosane, n-C24H50

Structural relaxation in amorphous tetracosane n-C24H50 was studied by infrared and Raman spectroscopies. Samples were prepared by vacuum deposition onto cold substrates and the spectral changes were monitored as the temperature was raised stepwise. Several distinguishable relaxation processes were found to take place similarly to the case of amorphous states of other hydrocarbons. However, in contrast to the previous study, we arrived at a conclusion that the initial relaxation of the disordered molecules does not take place in a single step. In the later part of the relaxation, metastable orthorhombic-type subcells were found to appear. They disappear finally when the adjustment of the mutual position of extended molecules occurs to attain the lateral molecular packing of the stable triclinic crystal. The intermolecular interactions along the chain direction are also discussed.