Study of the Ne(3P2) + CH3F Electron-Transfer Reaction below 1 K

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 μeV–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(3P2) + CH_3F reaction channels by counting the number of CH_3F^+, CH_2F^+, 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 CH3F molecule, as seen by the Ne(3P2) atom, appears not to change as the collision energy is varied, in contrast to related Ne(3PJ) + CH_3X (X = Cl and Br) reactions at higher collision energies.