  Relatively little is known about the dynamics of electron transfer reactions
at low collision energy. We present a study of Penning ionization of ground
state methyl fluoride molecules by electronically excited neon atoms in the 13
$\mu$eV--4.8 meV (150 mK--56 K) collision energy range, using a neutral-neutral
merged beam setup. Relative cross sections have been measured for three
Ne($^3P_2$)+ CH$_3$F reaction channels by counting the number of CH$_3$F$^+$,
CH$_2$F$^+$, and CH$_3^+$ product ions, as a function of relative velocity
between the neon and methyl fluoride molecular beams. Experimental cross
sections markedly deviate from the Langevin capture model at collision energies
above 20 K. The branching ratios are constant. In other words, the chemical
shape of the CH$_3$F molecule, as seen by Ne($^3P_2$) atom, appears not to
change as the collision energy is varied, in contrast to related Ne($^3P_J$) +
CH$_3$X (X=Cl and Br) reactions at higher collision energies.
