Understanding the Impact of H_(2) Diffusion Energy on the Formation Efficiency of H_(2) on the Interstellar Dust Grain Surface

We use microscopic Monte Carlo simulation techniques to investigate the impact of H_(2)diffusion energy on the recombination efficiency of H_(2)on interstellar dust grain surfaces under diffuse and translucent cloud conditions.We constructed five models representing different possible conditions encountered by adsorbed H and H_(2)on interstellar dust grains.We implemented adsorption sites with multiple binding energies for surface species;the Encounter-Desorption mechanism was also included.The study focused on silicate surfaces in diffuse clouds and water ice surfaces in translucent clouds.The results show that the recombination efficiency of H_(2)on dust surfaces decreases as H_(2)diffusion energy increases.An interesting finding of this work is that considering different binding sites for H and H_(2)gives rise to multiple steady phases,during which the recombination efficiency remains constant with a change in H_(2)diffusion energy.