Pair-correlated Dynamics of Cl+CHD3(v1=1) Reaction: Effects of Probe Laser Frequency

Vibrational Enhancement Factor of the Cl + CHD3(v1 = 1) Reaction: Rotational-Probe Effects

The vibrational enhancement factor in the Cl + CHD3(v1 = 1) reaction is revisited over the collisional energy range of 2-5.9 kcal mol(-1). Contrary to the previous results obtained by probing the low-|N, K⟩ states of CD3(v = 0) products, CH stretching excitation becomes more efficacious than the same amount of translational energy in promoting the HCl(v) + CD3(v = 0) product pairs when all-|N, K⟩ states are probed. Whereas the new vibrational enhancement factors, which are three to four times larger than the previous report, agree reasonably well with a recent reduced-dimensionality quantum dynamics calculation, a cautious note is made on the different initial |J,K⟩ rotational selections of the CHD3 reactants in the present theory-experiment comparison.

Tracking the energy flow along the reaction path

We report a comprehensive study of the quantum-state correlation property of product pairs from reactions of chlorine atoms with both the ground-state and the CH stretch-excited CHD(3). In light of available ab initio theoretical results, this set of experimental data provides a conceptual framework to visualize the energy-flow pattern along the reaction path, to classify the activity of different vibrational modes in a reactive encounter, to gain deeper insight into the concept of vibrational adiabaticity, and to elucidate the intermode coupling in the transition-state region. This exploratory approach not only opens up an avenue to understand polyatomic reaction dynamics, even for motions at the molecular level in the fleeting transition-state region, but it also leads to a generalization of Polanyi's rules to reactions involving a polyatomic molecule.

A simple yet effective multipass reflector for vibrational excitation in molecular beams

The fraction of molecules that can be vibrationally excited is often the limiting factor in many infrared laser excitation experiments, in particular, when using weak absorption bands. Reported here is a simple multipass reflector designed to overcome that obstacle. Its enhancement in pumping efficiency is demonstrated in a crossed-beam scattering experiment on the Cl+CH2D2(v1 or v6=1) reactions. Compared to a double-pass arrangement, the effective laser fluence for excitation is also characterized.