Disentangling mode-specific reaction dynamics from overlapped images

Abstract

The hydrogen abstraction reaction between atomic chlorine and C–H stretch-excited CHD₃ was studied under crossed-beam conditions. Prior to collisions, an infrared (IR) laser was used to pump up a fraction of CHD₃ to ν₁ = 1. A time-sliced velocity imaging technique was exploited to image the recoil velocity distribution of the state-selected product CD₃(ν = 0). For energetic reasons, the IR-on image shows severely overlapped features arising from both the excited and the un-pumped ground-state reagents. A novel threshold method was then developed to directly determine the fraction of IR-excited CHD₃ reagents, which in turn enables us to disentangle the state-selected dynamics from the overlapped images. The results reveal significant differences from previous experimental reports.