Electron attenuation in free, neutral ethane clusters

摘要

The electron effective attenuation length (EAL) in free, neutral ethane clusters has been determined at 40 eV kinetic energy by combining carbon 1s x-ray photoelectron spectroscopy and theoretical lineshape modeling. More specifically, theory is employed to form model spectra on a grid in cluster size (N) and EAL (lambda), allowing N and lambda to be determined by optimizing the goodness-of-fit chi(2)(N, lambda) between model and observed spectra. Experimentally, the clusters were produced in an adiabatic-expansion setup using helium as the driving gas, spanning a range of 100-600 molecules in mean cluster size. The effective attenuation length was determined to be 8.4 +/- 1.9 angstrom, in good agreement with an independent estimate of 10 angstrom formed on the basis of molecarul electron-scattering data and Monte Carlo simulations. The aggregation state of the clusters as well as the cluster temperature and its importance to the derived EAL value are discussed in some depth. (C) 2014 AIP Publishing LLC.