Catalysis on the Surfaces of Bare Dust Grains

Abstract

The most significant failure of gas-phase astrochemistry is its inability to provide molecular hydrogen at an adequate rate in the interstellar medium of the Milky Way galaxy. Therefore, the idea that reactions occur on the surfaces of dust grains was proposed in the mid 20th century and has been discussed since then. However, it is only within the last two decades that laboratory techniques and computational facilities have improved sufficiently to make accurate studies of the problem. This work has been outstandingly successful. In this chapter we review much of the recent theoretical and experimental work. Although further work remains to be done, it is clear that H2 formation on the surfaces of bare grains composed of the materials discussed in the preceding chapters proceeds efficiently enough to provide a rapid source of molecular hydrogen in the interstellar medium. The formation of molecular species other than H2 is briefly discussed.