CHD2

Article pubs.acs.org/JPCA

State-to-State Mode Specificity in F + CHD3 → HF/DF + CD3/CHD2 Reaction Changjian Xie,† Bin Jiang,*,‡ Minghui Yang,§ and Hua Guo*,† †

Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131, United States Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China § Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China ‡

ABSTRACT: The F + CHD3 → HF/DF + CD3/CHD2 reaction is studied using a state-to-state quasi-classical trajectory method on a recently developed ab initio based full-dimensional potential energy surface. Consistent with sudden vector projection model predictions, the HF/DF products are highly excited in both vibrational and rotational modes, while the CD3/CHD2 product internal excitation is mostly in the umbrella/out-of-plane mode. Furthermore, the C−H stretching vibration in the CHD3 reactant is found to behave as an active mode for the HF + CD3 channel, leading to additional excitation in the HF product but having almost no impact on CD3 vibrational state distributions. On the other hand, this mode acts as a spectator for the DF + CHD2 channel, exerting little influence on the DF and other CHD2 vibrational modes except an extra quantum excitation in the C−H stretching mode. The calculated vibrational state resolved differential cross sections are in good agreement with available experimental results at Ec = 9.00 kcal/mol.

I. INTRODUCTION There has been extensive discussion on how reactant excitations affect the reactivity of a bimolecular reaction in the gas phase.1−5 Such mode specificity has important implications in understanding the reaction dynamics and in controlling of reactions.6 Experimentally, the preparation of a single quantum state with specific ro-vibrational quantum numbers is becoming a reality, thanks to advances in laser technology.7−9 Theoretically, the rapidly increasing computer power and more efficient quantum mechanical algorithms have enabled studies of initial state selected reactivity in many polyatomic systems.10 The accumulation of both experimental and theoretical data has cumulated with important insights into the mode specific and bond selective reaction dynamics. One well-established model due to Polanyi attributes the ability of a reaction mode in promoting a particular atom−diatom reaction to the location of the reactive barrier.11 Recently, a more general model was proposed by some of the current authors based on the sudden nature of collision relative to slow intramolecular vibrational energy redistribution (IVR) in the reactants.12,13 In this sudden vector projection (SVP) model, the enhancement of reactivity by a reactant mode excitation is tied into the projection of its normal mode vector onto the reaction coordinate vector at the transition state. The SVP model, which is consistent with Polanyi’s rules for atom− diatom reactions,12 has been found to give reasonably accurate predictions of mode specificity and bond selectivity for direct reactions both in the gas phase14 and at gas−surface interfaces.15 More recently, there is an increasing interest in understanding how reactant excitations affect the product state distribution.16−25 This attention to state-to-state mode specificity is © XXXX American Chemical Society

apparently motivated by recent experimental advances in stateto-state reaction dynamics.7,9 There appear to have two limiting cases. In one limit, the reactant excitation has little effect on the product state distribution, a phenomenon sometimes called the “loss of memory” effect.17 In the other limit, however, the product state distribution depends sensitively on the reactant excitation. Experimental evidence exists for both limiting cases.26−28 In several recent publications, we have examined the state-tostate mode specificity in the H2 + OH → H2O + H reaction and its deuterated isotopes.21,22,24 On the basis of the SVP idea, we have demonstrated that the “loss of memory” effect operates for active modes, which have strong coupling with the reaction coordinate at the transition state. The strong coupling on one hand enables facile energy flow into the reaction coordinate, leading to strong promotion of reactivity. On the other hand, the energy flow into the reaction coordinate depletes energy in that mode to certain extent, thus moderating its impact on the product state distribution. However, the excitation of a spectator mode in the reactant transfers the energy into the product, thanks to sequestration of the energy deposited in that mode throughout the reaction. In this publication, we illustrate that the same principle operates in the title reaction, which has been extensively investigated experimentally.29−46 Most relevant to the current theoretical study are the recent experimental work from the Liu and Yang groups,38,45,46 who have measured product state Received: June 25, 2016 Revised: August 3, 2016

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DOI: 10.1021/acs.jpca.6b06450 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry A resolved differential cross sections (DCSs) using the resonance enhanced multiphoton ionization (REMPI) techniques. There are also many theoretical studies of this prototypical polyatomic reaction.39,47−66 Using an improved potential energy surface (PES),62,65 for example, we have recently reported reduced dimensional quantum dynamical studies of this reaction.67 Unlike experimental reports,38,45 our theoretical results suggested the excitation of the C−H (v1 = 1) stretching mode of the CHD3 reactant significantly increases the reactivity into the HF + CD3 channel, consistent with an earlier quasi-classical trajectory (QCT) study on the same PES.65 In this work, we focus on product state distributions in the title reaction, using a product state resolved QCT method. In addition to comparison with available experimental results, we also analyze how product state distributions depend on the initial reactant excitation. This analysis sheds further light onto the state-to-state mode specificity.

II. THEORY In the QCT calculations, the initial positions and momenta of all atoms were sampled using a Monte Carlo based normal mode scheme.68 The CHD3 reactant was prepared in its ground or C−H stretching excited (v1 = 1) vibrational state with zero rotational angular momentum (J = 0). The trajectories were initiated with a 10.5 Å separation between reactants, and terminated when products (or reactants for nonreactive trajectories) reached a separation of 11.0 Å. The propagation time step was selected to be 0.05 fs. Very long trajectories were halted if the propagation time reached a prespecified value (10.0 ps). The maximal impact parameter (bmax) was chosen at 4.25 Å. The scattering parameters (impact parameter, vibrational phases, and spatial orientation of the initial reactants) were selected randomly with a Monte Carlo approach. The PWEM-SO PES was used in the calculations reported here. This PES uses in the entrance channel the lower adiabat of the ab initio based diabatic potential matrix developed by Westermann, Eisfeld, and Manthe,62 but switches smoothly to the adiabatic PES of Czako, Shapler, Braams, and Bowman (CSBB)54 in other regions. The PWEM-SO PES has been extensively tested for the photodetachment of FCH4− and is known to be accurate in the entrance channel. On the other hand, the CSBB PES is also based on high level ab initio data and has been successfully used to investigate the dynamics of the F + CHD3 reaction.56,57 The PWEM-SO PES has recently been used in both QCT65 and reduced dimensional quantum dynamical studies of the title reaction.67 The diatomic product (HF or DF) in the title reaction is analyzed using the semiclassical Einstein−Brillouin−Keller (EBK) method,69 in which the anharmonicity is taken into consideration. For the methyl product, a normal-mode analysis (NMA) scheme is used to quantize the vibrational modes. Czako and Bowman57 as well as Corchado and EspinosaGarcia70 have independently developed quite similar methods in determining vibrational state populations for any polyatomic product with N atoms. The essence of the NMA approach is to project the mass-weighted Cartesian displacement coordinates obtained from the final step of a trajectory to the normal mode space. The key step here is to relate the mass-weighted Cartesian coordinates (q) of the product in each trajectory to a reference minimum geometry (qref) in the center-of-mass frame with an optimal orientation. To this end, one needs to find a rotational matrix D(α,β,γ) that minimizes the norm of the coordinate differences ∥Dq − qref∥.2 Alternatively, as realized

Figure 1. Normalized vibrational state distributions for the products HF (upper panel) and DF (lower panel) of three cases: (a) the F + CHD3 (v1 = 0) reaction at Etot = 40.47 kcal/mol (Ec = 17.94 kcal/mol), (b) the F + CHD3 (v1 = 1) reaction at Etot = 40.47 kcal/mol (Ec = 9.00 kcal/mol), and (c) the F + CHD3 (v1 = 0) reaction at Etot = 31.53 kcal/mol (Ec = 9.00 kcal/mol).

by Kudin and Dymarsky,71 this is equivalent to finding the rotational matrix D that satisfies the rotational Eckart condition,72 q ref × Dq = 0 (1) Here, our implementation is essentially the same as that of Li et al. in ref 19, in which eq 1 is solved using a quaternion based method.73 The normal mode coordinates Q and momenta P can then be obtained by the well-defined transformation, Q = Lq′

(2)

P = Lp′

(3)

where L is the transformation matrix between the normal mode coordinates and Cartesian displacement coordinates which can be obtained from the NMA at the reference geometry, q′ = Dq − qref and p′ = Dp are the rotated mass-scaled Cartesian displacement coordinates and momenta of the product. The harmonic vibrational energy for the k-th mode is thus expressed as the sum of kinetic energy and potential energy, 1 1 Ek = Pk + ωk 2Q k (4) 2 2 where ωk is the harmonic frequency of the k-th mode, which corresponds to a classical harmonic action number, nk′ = B

Ek 1 − ωk 2

(5) DOI: 10.1021/acs.jpca.6b06450 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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The Journal of Physical Chemistry A

Figure 2. Normalized rotational state distributions for the products HF (v = 2) (upper panel) and DF (v = 3) (lower panel) in the three cases.

In practice, this continuous action number has to be quantized, i.e. rounded to an integer quantum number nk. It is well established that, the standard histogram binning (HB) procedure in which the probability of a particular vibrational state n (n1, n2, ..., n3N‑6) is simply given as, PHB(n) = N (n)/Ntotal

(6)

where N(n) is the number of products in state n, would sometimes lead to some products with vibrational energies below their zeropoint energies (ZPEs). This ZPE violation can often be mitigated by using Gaussian binning (GB),74 in which a narrow Gaussian weighting function is used near the quantum numbers. However, a full GB analysis requires a very large number of trajectories. Instead, the so-called One Gaussian binning (1GB) scheme proposed originally by Czakó and Bowman,57 is employed here, which replaces the numerator in eq 6 by the sum of a Gaussian weighting function for each trajectory ending with state n:

Figure 3. Normalized vibrational state distributions for the four product CD3 vibrational modes in the three cases.

where V(q) − V(qref) is the actual potential energy of the PES of the given product geometry relative to the reference minimum geometry. Note that in this work, molecular vibration and rotation are treated separately and the angular momentum has been removed before the projection. The scattering angle θ is determined by θ = ⟨ν⃗i,ν⃗f⟩, where ν⃗i is the relative velocity vector of the reactants ν⃗F − ν⃗CHD3 and ν⃗f is the relative vector ν⃗HF − ν⃗CD3 or ν⃗DF − ν⃗CHD2 corresponding to the products. The zero of θ corresponds to forward scattering of HF/DF with respect to the incoming F atom. The DCS can then be calculated by

N (n)

PGB(n) =

∑ Gi(n)/Ntotal i=1

(7)

This Gaussian weight is defined as Gi(n) =

β −β 2{[E(n′i) − E(n)]/2E(0)}2 e π

σP(θ) dσ = dΩ 2π sin(θ)

(8)

where β = 2(ln 2)1/2/δ, δ is the full-width at half-maximum of the Gaussian function, and E(0) is the ZPE. E(n) is the harmonic vibrational energy corresponding to state n, while E(n′i ) is the actual energy of the ith product that is assigned to state n75 1 E(n′i) = p2 + V (q) − V (q ref ) (9) 2

(10)

where P(θ) is the normalized probability for the scattering products at the angle θ, and σ is the integral cross section (ICS) of the title reaction at the specified collision energy (Ec): σ(Ec) = πbmax 2(Ec) C

Nr Ntotal

(11) DOI: 10.1021/acs.jpca.6b06450 J. Phys. Chem. A XXXX, XXX, XXX−XXX

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Figure 4. Normalized vibrational state distributions for the six product CHD2 vibrational modes in the three cases.

in which Nr and Ntotal are the number of reactive trajectories and total number of trajectories, respectively. The standard error is given by Δ=

(Ntotal − Nr )/NtotalNr

conventional HB procedure, but the GB results are quite similar. Although HF and DF have large zero point energies (ZPEs), 98.89%/99.33%, 99.90%/99.97%, and 99.94%/99.99% of products HF/DF in total reactive trajectories are above their ZPE levels for the cases a−c, respectively. These distributions are very similar to those reported previously.65 It can be seen from the figure that the excitation of the C−H (v1 = 1) of the CHD3 reactant (case b) renders the product HF with one vibrational quantum hotter than that for the ground CHD3 reactant (cases a and c). This result is consistent with the experimental observations at the same energy.45 For the product DF, the three cases have the similar final vibrational distributions. The normalized rotational state distributions of the two products are shown in Figure 2 for HF(v = 2) and DF(v = 3), which respectively have the largest populations. Significant rotational excitations are seen in all distributions. For the HF product, the rotational state distribution corresponding to CHD3 (v1 = 1) is found to be hottest. The rotational state distributions of DF are very similar for the cases b and c, in which the collision energies are the same. But for case a with a larger collision energy, the DF product has more rotational excitation. The product DF/HF branching ratios are 2.48, 1.68, and 2.44 for the cases a−c, respectively. These product branching ratios are in overall agreement with the previous QCT results on the same PES,65 but in disagreement with experimental studies.38,45,46 Note in particular that the experimental data were obtained at the same collision energies, corresponding to cases b and c. These data further suggest that the total energy

(12)

The gradient of the PES was obtained numerically by the central-difference algorithm. All calculations were carried out using VENUS.76 We note that recent work of Lendvay and co-workers has shown that the absolute cross sections depends sensitively on the initial reactant separation,77 but such dependence should have relatively small impact on the final product state distributions.

III. RESULTS III.A. Vibrational and Rotational State Distributions of HF/DF. The exothermic reaction between F and CHD3 produces vibrationally excited HF and DF in the two product channels. To understand how the initial reactant excitation affects the product state distributions, calculations were performed at three different initial conditions for the reactants: (a) the F + CHD3(v1 = 0) reaction at the total energy (Etot) of 40.47 kcal/mol (Ec = 17.94 kcal/mol), (b) the F + CHD3 (v1 = 1) reaction at Etot = 40.47 kcal/mol (Ec = 9.00 kcal/mol), and (c) the F + CHD3 (v1 = 0) reaction at Etot = 31.53 kcal/mol (Ec = 9.00 kcal/mol). The first two have the same total energy, while the latter two have the same collision energy. Figure 1 shows the normalized vibrational distributions of diatomic products HF and DF of the F + CHD3 (v1 = 0, 1) reaction for these three cases. These distributions were obtained using the D


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The Journal of Physical Chemistry A increase has little effect on the vibrational state distributions of products HF/DF. III.B. Vibrational State Distributions of CD3/CHD2. The vibrational modes for CD3 are labeled as v1 (symmetric stretch), v2 (umbrella), v3 (asymmetric stretch), and v4 (bend), while the vibrational modes for CHD2 are labeled as v1 (C−H stretch), v2 (C−D symmetric stretch), v3 (scissors), v4 (out-of-plane bending), v5 (C−D asymmetric stretch), and v6 (C−H bend). The vibrational state distributions of these two polyatomic products have been computed using the NMA procedure outlined above followed by 1GB (δ = 0.15). It should be noted that this method is not expected to be quantitative for large vibrational quanta because of the presence of intra- and intermodal anharmonicities. Nonetheless, these distributions provide useful insights into state-to-state mode specificity. Figure 3 shows the normalized vibrational state distributions of the product CD3 in the HF + CD3 channel for the three cases. The most excited mode of CD3 is apparently the umbrella (v2) mode. It can be seen from Figure 3 that all four vibrational state distributions of CD3 are very similar for all three initial conditions, which is consistent with the experimental observation of Yang et al.45 that the umbrella vibrational state distribution of CD3 is only slightly affected by the excitation of the C−H (v1 = 1) in CHD3. The normalized vibrational state distributions of the product CHD2 in the DF + CHD2 channel are shown in Figure 4, which also show significant excitation in the out-of-plane bending (v4) mode. These distributions present a very interesting picture concerning the state-to-state mode specificity. While all other distributions are quite similar, it can be readily seen that the vibrational state distributions for the C−H stretching mode (v1) of CHD2 are very different for the v1 = 0 and v1 = 1 vibrational states of the CHD3 reactant. III.C. Vibrational State Resolved DCSs for CD3/CHD2. Experimentally, the Yang group recently measured the products CD3 and CHD2 vibrational state resolved DCSs at the collision energy of 9.0 kcal/mol for the F + CHD3 (v1 = 0, 1) reaction.45,46 To compare these state-to-state experimental results, more than 370,000 trajectories have been calculated for the F + CHD3(v1 = 0, 1) reaction, namely cases b and c as discussed above. Figure 5 shows the comparison of the calculated umbrella/ out-of-plane bending mode resolved DCSs with the experimental results of Yang et al.45,46 for both the CD3 (left panel) and CHD2 (right panel) products. The calculated DCSs are dominated by forward scattering for both two products CD3 and CHD2 in the F + CHD3 (v1 = 0, 1) reaction, in reasonably good agreement with experimental results. The product umbrella/out-of-plane bending mode resolved DCSs for the F + CHD3 (v1 = 0) and F + CHD3 (v1 = 1) reactions are similar. However, the experimentally observed suppressing of the forward scattered product CHD2 in the experiment46 was not found in our QCT results. The forward scattered products are attributed to the stripping mechanism at this energy. In Figure 6, the distributions of the scattering angle are shown as a function of the impact parameter for both product channels of the F + CHD3 (v1 = 1) reaction. It can be readily seen that the forward scattered trajectories correlate with large impact parameters while backward scattering is associated with small impact parameters. For this reaction, there are more reactive trajectories at large impact parameters, in which the H/D of the reactant is stripped by the passing F atom. Similar distributions (not shown) are found for the F + CHD3 (v1 = 0) reaction.

Figure 5. Comparisons of products CD3 (left panel) and CHD2 (right panel) vibrational state resolved DCSs for the F + CHD3 (v1 = 0, 1) reaction at Ec = 9.00 kcal/mol.

IV. DISCUSSION The product vibrational and rotational state distributions presented in the previous section can be rationalized by the SVP model.14 This model stipulates that in the sudden limit the product energy disposal is dictated by the coupling of the product vibrational mode with the reaction coordinate at the transition state.12,13 The SVP values for both the reactants and products are given in Table 1. The values reported here differ somewhat from those reported in an earlier work,78 because the previous SVP values were computed on the CSBB PES. From the table, it is clear that the HF and DF vibrational and rotational excitations stem from their strong coupling with the reaction coordinate at the respective transition state. For the methyl product, the largest excitation is associated with the umbrella (v2) mode of CD3 and the out-of-plane bending (v4) of CHD2. These SVP predictions are partially consistent with our calculated results and experimental observations. As discussed in the Introduction, the state-to-state mode specificity of a reaction depends sensitively on the coupling strength of the reactant mode with the reaction coordinate at the transition state, in the language of the SVP model.14 An active mode couples strongly with the reaction coordinate, leading to facile energy flow to the reaction coordinate and enhancement of reactivity. As a result of the energy flow, however, the energy in that reactant mode is partially depleted and thus has a limited impact on the product state distribution, resulting in the so-called “memory loss” effect. On the other hand, excitation in a spectator mode is sequestered during the reaction, resulting in vibrational excitation of corresponding modes in the product. Both scenarios have been analyzed in our E


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none of the CD3 vibrational state distributions is sensitive to the C−H (v1) excitation in CHD3, as shown in Figure 2. Such a “loss of memory” phenomenon is also apparent in the DCSs shown in Figure 5. The additional vibrational excitation in the HF product with CHD3 (v1 = 1) is also easy to understand: the vibrational energy in the C−H mode is channeled into the reaction coordinate at the transition state, which is strongly coupled with the newly formed HF bond, thus leading to higher vibrational excitation. On the other hand, all CHD2 vibrational state distributions except v1 are also insensitive to the C−H (v1) excitation in the CHD3 reactant. The vibrational state distribution of v1 is one quantum more excited for CHD3 (v1 = 1) because the spectator nature of the C−H vibrational mode, in which the excitation energy is sequestered throughout the reaction.

V. CONCLUSIONS The F + CHD3 reaction offers an ideal proving ground for the understanding of reaction dynamics in polyatomic systems. In this work, we report a final state resolved QCT study of this prototypical reaction using the most accurate PES based on ab initio data. It is shown that the vibrational state resolved DCSs of both the CD3 and CHD2 products are in good agreement with the available experiments of Yang et al. at Ec = 9.0 kcal/mol.45,46 This good agreement between theory and experiment reported in this work accentuates the disagreement concerning the product branching ratio, discussed in our earlier studies.65,67 This reaction also serves as a model for understanding stateto-state mode specificity. It is shown that the excitation of the C−H mode in CHD3 has little effect on the CD3 product vibrational state distribution, because the facile energy flow from the excited C−H mode to the reaction coordinate renders it ineffective in changing the product energy disposal except for the newly formed HF bond. On the other hand, this C−H mode serves as a spectator mode in the DF + CHD2 channel, whose excitation leads to additional vibrational excitation in the v1 mode of the CHD2 product thanks to energy sequestration in the spectator mode.

Figure 6. Impact parameter distributions as a function of scattering angle for the F + CHD3 (v1 = 1) reaction at Ec = 9.00 kcal/mol.

recent quantum dynamical studies on the H2 + OH → H2O + H reaction and a deuterated isotopologue.22,24 The title reaction provides another ideal model for the understanding of the mode specificity at the state-to-state level. The C−H vibration in the CHD3 reactant is an active mode for the HF + CD3 product channel, as its excitation promotes the reaction.65,67 On the other hand, it is a spectator mode for the DF + CHD2 product channel. The corresponding SVP values are 0.144 and 0.008, as shown in Table 1. In the former case,

Table 1. SVP Values for the F + CHD3→ HF/DF + CD3/CHD2 Reaction on the PWEM-SO PES F + CHD3→ HF + CD3 reactant CHD3

mode v1 v2 v3 v4 v5 v6 trans. F + CHD3→ HF + CD3

F + CHD3→DF + CHD2 SVP

reactant

0.144 0.018 0.110 0.015 0.108 0.090 0.586

CHD3

products

species

mode

SVP

products

HF + CD3

HF

v j v1 v2 v3 v4 trans.

0.558 0.242 0.053 0.076 0.098 0.115 0.466

DF + CHD2

CD3

mode

0.008 0.102 0.112 0.079 0.051 0.095 0.632

species

mode

SVP

DF

v j v1 v2 v3 v4 v5 v6 trans.

0.689 0.230 0.090 0.053 0.070 0.107 0.077 0.076 0.430

CHD2

F

SVP

v1 v2 v3 v4 v5 v6 trans. F + CHD3→DF + CHD2


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(16) Welsch, R.; Manthe, U. Communication: Ro-vibrational control of chemical reactivity in H+CH4 → H2+CH3: Full-dimensional quantum dynamics calculations and a sudden model. J. Chem. Phys. 2014, 141, 051102. (17) Welsch, R.; Manthe, U. Loss of memory in H + CH4 → H2 + CH3 state-to-state reactive scattering. J. Phys. Chem. Lett. 2015, 6, 338−342. (18) Zhao, B.; Sun, Z.; Guo, H. Calculation of the state-to-state Smatrix for tetra-atomic reactions with transition-state wave packets: H2/D2 + OH → H/D + H2O/HOD. J. Chem. Phys. 2014, 141, 154112. (19) Li, J.; Corchado, J. C.; Espinosa-García, J.; Guo, H. Final stateresolved mode specificity in HX + OH → X + H2O (X = F and Cl) reactions: A quasi-classical trajectory study. J. Chem. Phys. 2015, 142, 084314. (20) Zhao, B.; Guo, H. Modulations of transition-state control of state-to-state dynamics in the F + H2O → HF + OH reaction. J. Phys. Chem. Lett. 2015, 6, 676−680. (21) Zhao, B.; Sun, Z.; Guo, H. Communication: State-to-state dynamics of the Cl + H2O → HCl + OH reaction: Energy flow into reaction coordinate and transition-state control of product energy disposal. J. Chem. Phys. 2015, 142, 241101. (22) Zhao, B.; Sun, Z.; Guo, H. State-to-state mode specificity: Energy sequestration and flow gated by transition state. J. Am. Chem. Soc. 2015, 137, 15964−15970. (23) Zhao, B.; Sun, Z.; Guo, H. A reactant-coordinate-based wave packet method for full-dimensional state-to-state quantum dynamics of tetra-atomic reactions: Application to both the abstraction and exchange channels in the H + H2O reaction. J. Chem. Phys. 2016, 144, 064104. (24) Zhao, B.; Sun, Z.; Guo, H. State-to-state mode selectivity in the HD + OH reaction: Perspectives from two product channels. J. Chem. Phys. 2016, 144, 214303. (25) Manthe, U.; Ellerbrock, R. S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering. J. Chem. Phys. 2016, 144, 204119. (26) Bronikowski, M. J.; Simpson, W. R.; Zare, R. N. Comparison of reagent stretch vs bend excitation in the H + D2O reaction: An example of mode selective chemistry. J. Phys. Chem. 1993, 97, 2204− 2208. (27) Sinha, A.; Hsiao, M. C.; Crim, F. F. Controlling bimolecular reactions: Mode and bond selected reaction of water with hydrogen atoms. J. Chem. Phys. 1991, 94, 4928−4935. (28) Sinha, A.; Thoemke, J. D.; Crim, F. F. Controlling bimolecular reactions: Mode and bond selected reaction of water with translationally energetic chlorine atoms. J. Chem. Phys. 1992, 96, 372−376. (29) Harper, W. W.; Nizkorodov, S. A.; Nesbitt, D. J. Quantum stateresolved reactive scattering of F + CH4 → HF(v,J) + CH3: Nascent HF(v,J) product state distributions. J. Chem. Phys. 2000, 113, 3670− 3680. (30) Zhou, J. G.; Lin, J. J.; Shiu, W. C.; Liu, K. Insights into dynamics of the F+CD4 reaction via product pair correlation. J. Chem. Phys. 2003, 119, 4997−5000. (31) Zhou, J. G.; Lin, J. J.; Liu, K. Mode-correlated product pairs in the F+CHD3 → DF+CHD2 reaction. J. Chem. Phys. 2003, 119, 8289− 8296. (32) Lin, J. J.; Zhou, J.; Shiu, W.; Liu, K. State-specific correlation of coincident produt pairs in the F + CD4 reaction. Science 2003, 300, 966−969. (33) Zhou, J. G.; Lin, J. J.; Shiu, W. C.; Pu, S. C.; Liu, K. Crossedbeam scattering of F+CD4 → DF+CD3(vNK): The integral cross sections. J. Chem. Phys. 2003, 119, 2538−2544. (34) Shiu, W.; Lin, J. J.; Liu, K. Reactive resonance in a polyatomic reaction. Phys. Rev. Lett. 2004, 92, 103201. (35) Shiu, W.; Lin, J. J.; Liu, K.; Wu, M.; Parker, D. H. Imaging the pair-correlated excitation function: The F+CH4→HF(v′)+CH3(v = 0) reaction. J. Chem. Phys. 2004, 120, 117−122.

AUTHOR INFORMATION

Corresponding Authors

*(B.J.) E-mail: [email protected]. *(H.G.) E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the U.S. Department of Energy (Grant No. DE-FG02-05ER15694). B.J. and M.Y. acknowledge the National Natural Science Foundation of China (Grant No. 21573203 to B.J. and Grant No. 21373266 to M.Y.). The calculations were performed at the Center for Advanced Research Computing at the University of New Mexico and National Energy Research Scientific Computing (NERSC) Center. We thank Profs. Juliana Palma and Uwe Manthe for providing the PES routines and Profs. Kopin Liu and Xueming Yang for several useful discussions concerning the experimental studies of the title reaction.

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