State-selection and orientation of CH radicals by an electric hexapole

A pure and high intense pulsed supersonic CH (X²Π ) radical beam source was developed via the C(¹D) + H₂ reaction. An electrostatic hexapole field was used to state-select CH radicals. The focusing curves for the single rotational states of CH were measured for the first time by a saturated laser-induced fluorescence (SLIF) spectroscopy for the R-branch in A²Δ_3/2 ← X²Π _1/2 transition. The focusing curves were simulated by the classical trajectory simulation based on a Stark energy analysis of the rotational energy levels, including spin-orbit and Λ-doubling coupling effects. In addition, orientational distribution functions were calculated for the selectable states.