High resolution slice imaging of a molecular speed distribution

Abstract

High resolution slice imaging experiments are reported measuring the speed distribution of molecular fragments, recoiling at a most probable speed v_mp, with a full-width-half-maximum (FWHM) speed resolution near the permille level: FWHM_v/v_mp = 1.9 × 10⁻³. We implemented a high resolution single-particle slice imaging detector and used a two-colour resonance-enhanced multi-photon ionisation (REMPI) scheme to reduce broadening of the speed distribution due to the electron kick. The results on the measurement of the CD₃ speed distribution from photolysis of CD₃I show that it is possible to image the three-dimensional speed distribution at a resolution down to FWHM_v = 6.7 m s⁻¹, when the fragment has an absolute speed of v_mp = 3473 m s⁻¹. The new experiments demonstrate the potential of slice imaging to measure with high resolution the three-dimensional speed distribution of a cloud of molecules.