Carbon monoxide molecules (CO) can be adsorbed at specific sites on a solid surface. The oxygen atom of an adsorbed molecule is immobilized on the adsorption site; the axis of the adsorbed molecule thereby is fixed perpendicular to the surface so that the rotational degree of freedom of the adsorbed molecule is suppressed. In addition the vibrational frequency of the molecule is altered, the effective mass changing from the ``reduced mass'' mCmO/(mC+mO) to mC. Only one molecule can be adsorbed at a given site. The binding energy of an adsorbed molecule is Eb. The surface is bathed by CO gas at temperature T and pressure P. Calculate the fraction (f) of occupied adsorption sites if the system is in equilibrium. Assume the temperature to be of the order of one or two hundred Kelvin, and assume the pressure to be sufficiently low that the CO vapor can be regarded as an ideal diatomic gas.
Hint: Recall the magnitudes of characteristic rotational and vibrational frequencies, as expressed in equivalent temperatures, in Section 16.3.