  Rate coefficients have been measured for the reaction of CH radicals with
formaldehyde, CH$_{2}$O, over the temperature range 31 - 133 K using a pulsed
Laval nozzle apparatus combined with pulsed laser photolysis and laser induced
fluorescence spectroscopy. The rate coefficients are very large and display a
distinct decrease with decreasing temperature below 70 K, although classical
collision rate theory fails to reproduce this temperature dependence. The
measured rate coefficients have been parameterized and used as input for
astrochemical models for both dark cloud and AGB stellar outflow scenarios. The
models predict a distinct change (up to a factor of two) in the abundance of
ketene, H$_{2}$CCO, which is the major expected molecular product of the CH +
CH$_{2}$O reaction.
