A vacuum pump may comprise a grating, and a sublimation element. The grating may have a grating opening and a grating interior that may be bounded by at least one grating surface. The sublimation element may be located within the grating interior and may be configured to sublimate and form a reactive film on the grating interior upon heating of the sublimation element above the sublimation temperature. The reactive film may be effective to capture gas molecules entering the grating interior through the grating opening and contacting the reactive film.