N-15 DOPPLER SPECTROSCOPY OF H-1 ON DIAMOND

Diamond single crystals of [100], [110] and [111] orientation have bee n chemically treated in order to prepare monolayer (ML) coverages of H -1. Subsequently, sample surface areas of about 0.1 cm2 have been expo sed to a N-15 beam of 30 nA at the resonant-reaction energy of 6.385 M eV. The resulting 4.4 MeV gamma rays have been detected by a 10 in x 1 0 in NaI(Tl) crystal inside a low-level system. The results can be sum marized as follows: The initial H coverage of a few ML equivalent quic kly desorbs under ionizing radiation, until at about 1 ML a slow desor ption stage prevails. In general, the different crystal surfaces, char acterized by strong topological irregularities, do not exhibit ideal M L coverage. Similarly, the corresponding Doppler widths do not show th e expected dependence on crystal orientation, but are the same within experimental error.