Desorption studies using Langmuir recoil force measurements

Number densities and energies for desorption of gas molecules on solid surfaces have been determined using Langmuir recoil force measurements and numerical modeling for the first time. Activation energies are computed from the time-dependent relative recoil force and associated temperature history of the sample. Subsequently, the model uses the activation energy and the absolute recoil force to estimate absolute desorption rates and number densities of adsorbed molecules. Desorption is by laser-induced thermal means and is detectable for sample temperature increases smaller than 100 K above room temperature. The resulting recoil forces are measured with a torsion balance, which is mechanically similar to the Cavendish type. Measurements of deflection are different, however, by using a capacitance transducer instead of an optical sensor.