High-resolution mass spectrometric study of pure helium droplets, and droplets doped with krypton
Mass spectra of doped and undoped helium droplets are presented. The high resolution of the time-of-flight spectrometer (m/Delta m a parts per thousand... 5000) makes it possible to fully resolve small helium cluster ions from impurities and to unambiguously identify abundance anomalies in the size distribution of He (n) (+). The yield of He(4) (+) shows the well-known enhancement relative to other small cluster ions when the expansion changes from sub- to supercritical, provided the electron energy exceeds a value of 40 +/- A 1 eV, the threshold for formation of electronically excited ions. Upon doping with krypton, pure Kr (n) (+) cluster ions containing up to 41 Kr atoms are observed. The spectra exhibit abundance anomalies at 13, 16, 19, 22 & 23, 26 and 29, in agreement with spectra obtained by ionization of bare krypton clusters that are formed in neat supersonic beams. Mixed clusters He (m) Kr(+) indicate closure of a solvation shell at m = 12.
European Physical Journal D
Digital Object Identifier (DOI)
Schoebel, H.; Bartl, P.; Leidlmair, C.; Denifl, S.; Echt, Olof E.; Maerk, T. D.; and Scheier, P., "High-resolution mass spectrometric study of pure helium droplets, and droplets doped with krypton" (2011). European Physical Journal D. 51.
© EDP Sciences, Societ`a Italiana di Fisica, Springer-Verlag 2011