Temperature dependent photodesorption of methyl radical from GaAs: Role of the initial state

The photodesorption yield of CH3 from the GaAs(100) surface increases dramatically with increasing substrate temperature. This effect can be attributed to the temperature dependent population of vibrational levels in the desoprtion coordinate. Fitting the experimental data to a phenomenological model shows that the photodesorption yield from the v = 3 level (in the Ga-CH3 coordinate) is more than two orders of magnitude higher than that from the v = 0 level. This dramatic initial state effect is another manifestation of the short time dynamics in surface photochemical processes.