H- ESD observed from beta-state NH3 adsorbed on Pt(111)

H- ions were detected from ammonia covered Pt(111) surfaces. We found that H- electron-stimulated desorption (ESD) ions can only be detected when adso rbed beta-state ammonia is present on the Pt(111) surface. The H- kinetic e nergy distributions (KEDs) obtained from Pt(111) surfaces covered with adso rbed beta-state ammonia exhibit a very narrow peak appearing at 3 eV with a FWHM of less than 1 eV. The total removal cross-section measured from H- E SD ion-yield curves is in good agreement with the total removal cross-secti on obtained from H+ ESD ion-yield measurements and other measurements, whic h are described elsewhere (C. Bater, J.H. Campbell, J.H. Craig Jr., Surf. I nterface Anal. 26 (1998) 97), A total removal cross-section of 5.6 x 10(-17 ) cm(2) was obtained from the H- ESD ion-yield curves obtained in this work . (C) 1999 Elsevier Science S.A. All rights reserved.