The rotational population of sputtered N2 - evidence for hindered rotational states

We report on the study of excited N2 molecules sputtered from a N+ implanted Si surface by an N+ ion beam. Analysis of how N2 emission intensity varies with implant dose suggests that N2 molecules are formed by recombination of N atoms before being collisionally ejected by the sputtering mechanism. Such N2 molecules, localized on the surface, must inevitably exhibit a quantum mechanical rotational configuration that differs from an isolated molecule in free space. We observed that the rotational state distribution implied by the rotational structure of the N2 emission is a non-Boltzmann distribution and we relate this to a hindered rotor configuration of the N2 molecule when localized on the surface. (orig.)