Stretching-mode specificity in the Cl + CH₃D(v₁-I, v₁-II, and v₄ = 1; |jK〉) reactions: dependency on the initial |jK〉 selectivity

Abstract

The beneficial impact of the initial rotational |jK〉-mode selection on the vibrational-specific reactivity is discussed.

State-to-State Dynamics in Mode-Specific Reactions of Cl + CH3D(v1-I, v1-II, and v4 = 1; |10⟩): Loss of Memory or Not

“…Similarly, a |jK⟩-invariant angular distribution of the (0 0 , 0) s pair has also been observed for a total of 16 ro-vibrationally excited reactions of Cl + CH 3 D(v i = 1, |jK⟩) at an E c of 5.4 kcal mol −1 . 29 These two findings echo the previous reports of invariant product angular distributions with respect to the initial rotational states (despite the profound effects on total reactivity) in the reactions of both Cl + CHD 3 (v 1 = 1, |jK⟩) 33 and Cl + CH 4 (v 3 = 1, |jNl⟩) 34 over a range of E c values. Collectively, these results provide strong support for the loss of memory of the reagent's ro-vibrational states over an extended E c range in the product angular distributions of the (0 0 , 0) s pair in the Cl + methane reactions.…”

“…Interestingly, the invariant vibrational branching of HCl(v) to both E c and the initial rotational states have also been observed in the reactions of Cl + CHD 3 (v 1 = 1, |jK⟩) 33 and Cl + CH 4 (v 3 = 1, |jNl⟩). 34, 49 On the contrary, the result shown in Figure 2c is in stark contrast to the vibrational branching fractions recently reported for the rotationally selected, stretch-excited reactions at an E c of 5.4 kcal mol −1 , 29 where the v 4 excitation showed little dependency on the initial |jK⟩ states, while an acute sensitivity to the selected |jK⟩ states was observed for the v 1 -I and v 1 -II reagents. Hence, for a specific product attribute (e.g., vibrational branching), whether the initial vibrational memory is lost seems also to be dependent on the other reagent property (e.g., rotation or translation) to which one is referring.…”

“…Previously, far more dramatic |jK⟩-dependent distributions were observed in a rovibrationally selected study of this product channel, particularly in the reactions with the v 1 -I and v 1 -II reagents. 29 As surmised therein, the loss-of-memory phenomenon seems to be at play in the reaction with an excited pure-state (v 4 ) reagent, but not so for a superposition-state (v 1 -I and v 1 -II) reagent presumably due to the quantum phase-induced interference. Altogether, it suggests that in sharp contrast to the (0 0 , 0) s case presented above, some memories of initial stretch excitation are partially retained for the (0 0 , 1) s product pair.…”

“…Again, despite the distinct mode-specific rate enhancements, all product-state and angular distributions were nearly invariant to the rotational excitation of the CH 3 D(v 4 = 1, | jK⟩) reagents, the loss of selected |jK⟩ memory. 29 By contrast, in reactions with Fermi-coupled reagents, CH 3 D(v 1 -I and v 1 -II = 1, |jK⟩), some detailed product distributions showed loss-ofmemory behaviors while the other retained the memory of initial ro-vibrational excitations. 29 Tentatively, this differential behavior was ascribed to the interference effect arising from the Fermi phase of the superposition states (v 1 -I and v 1 -II) of the CH 3 D reagent.…”

“…35 Also complementary is a study of the impact of the initial |jK⟩state selection, at a single energy of 5.4 kcal mol −1 , to the modespecific reactivity (both integral and differential cross sections) in CH 3 D(v 1 -I, v 1 -II, and v 4 = 1, |jK⟩) → CH 2 D(0 0 /6 1 ) + HCl(v), where the concept of loss of memory was examined in detail. 29 The experiment was carried out in a crossed-beam scattering apparatus equipped with a time-sliced, velocity-mapped product imaging detector. 36,37 The experimental details and image analysis procedure have been reported previously; 26−29 thus, only a brief description is given in the Supporting Information.…”