Coverage Dependent Desorption Energy of Molecular Hydrogen Induced by Encounter Desorption: Quantum Tunneling Effects

In previous studies, the effective desorption energy based on the encounter desorption (ED) mechanism successfully explained the coverage-dependent desorption energy of H₂ measured in experiments, denoted as E_\rmexptD2. We introduce quantum tunneling effects and further study E_\rmexptD2 using the ED mechanism. The effective desorption energy can still successfully explain E_\rmexptD2 if quantum tunneling effects are considered. We find the impact of quantum tunneling is significant at 15 K if the barrier width is small (<2.0 \text Å). Moreover, in order that the effective desorption energy agrees well with E_\rmexptD2, hydrogen molecules should diffuse more slowly, or their desorption energy on the H₂ substrate should be higher if the quantum tunneling is considered.