Dissociative and Reactive Hyperthermal Ion−Surface Collisions with Langmuir−Blodgett Films Terminated by CF3(CH2)n−, n-Perfluoroalkyl, or n-Alkyl Groups

Langmuir−Blodgett (L−B) films prepared from 18,18,18-trifluorooctadecanoic acid [CF 3 (CH 2 ) 16 COOH], perfluorotetradecanoic acid [ n -C 13 F 27 COOH], or octadecanoic acid [ n -C 17 H 35 COOH] were used as target surfaces for hyperthermal ion−surface collisions. The synthesis of 18,18,18-trifluorooctadecanoic acid and the preparation of the L−B film from this compound using a subphase containing Al 3+ are reported in this paper. The Ion−surface collision results show that the outermost surface group, namely CF 3 vs CH 3, is the main determinant for the efficiency of both energy transfer and electron transfer during low-energy (e.g., 10−100 eV) polyatomic ion−surface collisions. For atomic projectile ions, there is evidence of penetration into a depth of the films.