title: Ejection-ionization of molecules from free standing graphene.
abstract: We present the first data on emission of C60- stimulated by single impacts of 50 keV C602+ on the self-assembled molecular layer of C60deposited on free standing 2 layer graphene. The yield, Y, of C60- emitted in the transmission direction is 1.7%. To characterize the ejection and ionization of molecules, we have measured the emission of C60- from the surface of bulk C60(Y = 3.7%) and from a single layer of C60deposited on bulk pyrolytic graphite (Y = 3.3%). To gain insight into the mechanism(s) of ejection, molecular dynamic simulations were performed. The scenario of the energy deposition and ejection of molecules is different for the case of graphene due to the confined volume of projectile-analyte interaction. In the case of 50 keV C602+ impacts on graphene plus C60, the C atoms of the projectile collide with those of the target. The knocked-on atoms take on a part of the kinetic energy of the projectile atoms. Another part of the kinetic energy is deposited into the rim around the impact site. The ejection of molecules from the rim is a result of collective movement of the molecules and graphene membrane, where the membrane movement provides the impulse for ejection. The efficient emission of the intact molecular ions implies an effective ionization probability of intact C60. The proposed mechanism of ionization involves the tunneling of electrons from the vibrationally exited area around the hole to the ejecta.
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Stanislav V
authors.initials: SV
authors.lastname: Verkhoturov
authors.affiliation: Applied Physics, Division of Materials Science, Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden.
authors.forename: Bartlomiej
authors.identifier: 0000000324827945
authors.initials: B
authors.lastname: Czerwinski
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Dmitriy S
authors.initials: DS
authors.lastname: Verkhoturov
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Geng
authors.affiliation: Institute of Condensed Matter and Nanosciences - Bio and Soft Matter (IMCN/BSMA), Université Catholique de Louvain, 1 Croix du Sud, B-1348 Louvain-la-Neuve, Belgium.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Delcorte
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77843-3144, USA.
authors.forename: Emile A
authors.identifier: 0000000339647998
authors.initials: EA
authors.lastname: Schweikert