Recent progress in crossed molecular beam studies of radical-molecule and radical-radical reactions dynamics by exploiting 'soft' electron-ionization detection

We review the considerable advancement made in our laboratory over the last few years in the investigation of the dynamics of gas-phase neutral-neutral reactions by using the crossed molecular beam (CMB) scattering technique with mass-spectrometric detection and time-of-flight analysis. Progress has been fostered by an improved CMB apparatus featuring product detection by soft ionization using tunable low-energy electrons for increased sensitivity and universal detection power, and a variable beam crossing angle set-up for larger collision energy ranges and increased angular and velocity resolution. The improved capability of identifying all primary reaction channels of a polyatomic multi-channel radical-molecule reaction, characterizing their dynamics, and determining the branching ratios, is highlighted here by a brief survey of our recent studies on the dynamics of the reactions of ground state oxygen and carbon atoms, O(3P) and C(3P), with the simplest alkyne, acetylene, and alkene, ethylene. The experimental improvements have also made it possible to extend the CMB dynamical studies to polyatomic radical-radical reactions; as an example, the very recent investigation of the O(3P) + C3H5 (allyl) reaction is briefly discussed.