Mobility measurements of atomic ions in flames using laser-enhanced ionization

Abstract

Atomic ion mobilities have been directly determined in C 2H 2/air and CO/O 2 flames using optical excitation to create instantaneously a pencil of ions along the laser beam and then measuring ion velocities in an applied electric field. The ions were chosen to provide a wide range of atomic weights (Li, Na, K, Ca, Sr, Ba, Fe, In, Tl, U), thus providing a good comparison with the Langevin theory of ion mobility under several flame conditions. In all cases the Langevin theory provides an upper limit and predicts the measured mobility to within 50%, with best agreement obtained in general for the smaller and less polarizable ions.