https://doi.org/10.1140/epjd/e2011-10619-1
Regular Article
High-resolution mass spectrometric study of pure helium droplets, and droplets doped with krypton
1
Institut für Ionenphysik und Angewandte Physik and Center for
Molecular Biosciences Innsbruck, Leopold Franzens Universität,
6020
Innsbruck,
Austria
2
Department of Physics, University of New Hampshire,
Durham, NH
03820,
USA
3
Department of Experimental Physics, Comenius University
Bratislava, 84248
Bratislava,
Slovakia
a e-mail: olof.echt@unh.edu
Received:
26
October
2010
Received in final form:
25
January
2011
Published online:
17
May
2011
Mass spectra of doped and undoped helium droplets are presented. The high resolution of the time-of-flight spectrometer (m/Δm ≅ 5000) makes it possible to fully resolve small helium cluster ions from impurities and to unambiguously identify abundance anomalies in the size distribution of Hen+. The yield of He4+ 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 ± 1 eV, the threshold for formation of electronically excited ions. Upon doping with krypton, pure Krn+ 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 HemKr+ indicate closure of a solvation shell at m = 12.
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2011