title: An experimental and theoretical view of energetic C60cluster bombardment onto molecular solids.
abstract: Recent experimental measurements and calculations performed by molecular dynamics computer simulations indicate, for highly energetic C60primary ions bombarding molecular solids, the emission of intact molecules is unique. An energy- and angle-resolved neutral mass spectrometer coupled with laser photoionization techniques was used to measure the polar angle distribution of neutral benzo[a]pyrene molecules desorbed by 20-keV [Formula: see text] primary ions and observed to peak at off-normal angles integrated over all possible emission energies. Similarly, computer simulations of 20-keV C60projectiles bombarding a coarse-grained benzene system resulted in calculations of nearly identical polar angle distributions. Upon resolving the measured and calculated polar angle distributions, sputtered molecules with high kinetic energies are the primary contributors to the off-normal peak. Molecules with low kinetic energies were measured and calculated to desorb broadly peaked about the surface normal. The computer simulations suggest the fast deposition of energy from the C60impact promotes the molecular emission by fluid-flow and effusive-type motions. The signature of off-normal emission angles is unique for molecules because fragmentation processes remove molecules that would otherwise eject near normal to the surface. Experimental measurements from a Ni {001} single crystal bombarded by 20-keV [Formula: see text] demonstrate the absence of this unique signature.
authors: The Pennsylvania State University, Department of Chemistry, University Park, PA, 16802, USA.
authors: Daniel A
authors: DA
authors: Brenes
authors: Smoluchowski Institute of Physics, Jagiellonian Univeristy, ul. Reymonta 4, 30-059 Krakow, Poland.
authors: Zbigniew
authors: Z
authors: Postawa
authors: Faculty of Physics, University of Duisburg-Essen, 47048 Duisburg, Germany.
authors: Andreas
authors: A
authors: Wucher
authors: Ionoptika Ltd., Epsilon House Chilworth Science Park, Southampton SO53 4NF, U.K.
authors: Paul
authors: P
authors: Blenkinsopp
authors: The Pennsylvania State University, Department of Chemistry, University Park, PA, 16802, USA.
authors: Barbara J
authors: BJ
authors: Garrison
authors: The Pennsylvania State University, Department of Chemistry, University Park, PA, 16802, USA.
authors: Nicholas
authors: N
authors: Winograd
keywords: C60 sputtering; EARN; angular distribution; effusive desorption; fluid-flow desorption; tof-snms photoionization