  Vacuum ultraviolet (VUV) light at 118 nm has been shown to be a powerful tool
to ionize molecules for various gas-phase chemical studies. A convenient table
top source of 118 nm light can be produced by frequency tripling 355 nm light
from a Nd:YAG laser in xenon gas. This process has a low efficiency, typically
producing only nJ/pulse of VUV light. Simple models of the tripling process
predict the power of 118 nm light produced should increase quadratically with
increasing xenon pressure. However, experimental 118 nm production has been
observed to reach a maximum and then decrease to zero with increasing xenon
pressure. Here, we describe the basic theory and experimental setup for
producing 118 nm light and a new proposed model for the mechanism limiting the
production based on pressure broadened absorption.
