The spectral manifestations of complexation in the CD₃F + HCl + Xe solution and the evolution of the fundamental absorption band of HCI upon the liquid-solid phase transition are studied. The observed disappearance of the central component of the v(HCl) band and the sharpening of the discrete rotational structure are interpreted in terms of the dominant role of rotational motion in the v(HCl)-band shaping in solid Xe. The formation of the CD₃F⋯HCl complex changes the spectral parameters for almost all bands of the CD₃F and HCl molecules. The sharp (down to <1 cm^-1) narrowing of the v_1c and 2v_5c A bands indicates the appearance of considerable steric hindrances for certain types of the rotational motion of the CD₃F⋯HCl complex upon the liquid-crystal phase transition. The reversibility of the spectral changes with respect to increasing and decreasing temperature evidences the retention of the high mobility of the small molecules in crystalline Xe.