posted on 2021-08-27, 17:36authored byF. Laimer, F. Zappa, P. Scheier
Precharged helium
nanodroplets can be used in doping experiments
with the advantage that they are amenable to size selection with electrostatic
fields, therefore adding a useful tuning parameter for dopant growth.
For all these applications, the knowledge of the size distribution
of charged droplets is an essential parameter, which we have so far
assumed would be equivalent to that of their neutral precursors. Here,
this assumption is experimentally investigated for negatively charged
clusters for temperatures between 4 and 9 K at a stagnation pressure
of 2 MPa. We observe a dependency of the velocity of the droplets
on mass per charge, especially at the lowest temperatures of the investigated
range, and values 20% lower than those known from the literature.
Below 6 K, a large deviation from the literature is also found for
the average droplet sizes. This information has to be taken into consideration
in future experiments where large, charged droplets are sought to
produce large dopant clusters. Possible origins for this deviation
are discussed in the text.