Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A low power photoemission source for electrons on liquid helium   Electrons on the surface of liquid helium are a widely studied system that
may also provide a promising method to implement a quantum computer. One
experimental challenge in these studies is to generate electrons on the helium
surface in a reliable manner without heating the cryo-system. An electron
source relying on photoemission from a zinc film has been previously described
using a high power continuous light source that heated the low temperature
system. This work has been reproduced more compactly by using a low power
pulsed lamp that avoids any heating. About 5e3 electrons are collected on 1
cm^2 of helium surface for every pulse of light. A time-resolved experiment
suggests that electrons are either emitted over or tunnel through the 1eV
barrier formed by the thin superfluid helium film on the zinc surface. No
evidence of trapping or bubble formation is seen.

24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
7
The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin