  We present experiments in which an ultra-cold sample of ammonia molecules is
released from an electrostatic trap and recaptured after a variable time. It is
shown that, by performing adiabatic cooling before releasing the molecules and
adiabatic re-compression after they are recaptured, we are able to observe
molecules even after more than 10 ms of free expansion. A coherent measurement
performed during this time will have a statistical uncertainty that decreases
approximately as the inverse of the square root of the expansion time. This
offers interesting prospects for high-resolution spectroscopy and precision
tests of fundamental physics theories.
