Real wave packet and flux analysis studies of the H + F2 → HF + F reaction (original) (raw)
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Chemical Physics Letters, 1989
We report accurate benchmark 3D coupled channel calculations for total angular momentumJ=O for the reaction F+H,+HF+H using a realisttc potential energy surface. The adiabatic basis functions are generated using the discrete variable representation method. The resulting reaction probabmties show what appear to be strong quantum resonance features as well as rapid changes in final rotational state distributions.
The Journal of Chemical Physics, 2008
Extensive quantum real wave packet calculations within the helicity decoupling approximation are used to analyze the influence of the HF vibrational excitation on the K + HF͑v =0-2, j =0͒ → KF + H reaction. Quantum reaction probabilities P and reaction cross sections are compared with corresponding quasiclassical trajectory ͑QCT͒ results. Disregarding threshold regions for v = 0 and 1 ͑v = 2 has no threshold͒, both approaches lead to remarkably similar results, particularly for , validating the use of the QCT method for this system. When moving from v =0 to v = 1 there is a large increase in P and , as expected for a late barrier system. For v = 2 the reaction becomes exoergic and P Ϸ 0.95 ͑with the exception of large total angular momenta where centrifugal barriers play a role͒. While substantial vibrational enhancement of the reactivity is thus seen, it is still quite less than that inferred from experimental data in the intermediate and high collision energy ranges. The origin of this discrepancy is unclear.
Time-dependent quantum study of H(2S) + FO(2Π) → OH(2Π) + F(2P) reaction on the 13A′ and 13A″ states
Journal of Computational Chemistry, 2010
The dynamics of the H( 2 S)+FO( 2 ) → OH( 2 )+F( 2 P) reaction on the adiabatic potential energy surface of the 1 3 A and 1 3 A states is investigated. The initial state selected reaction probabilities for total angular momentum J = 0 have been calculated by using the quantum mechanical real wave packet method. The integral cross sections and initial state selected reaction rate constants have been obtained from the corresponding J = 0 reaction probabilities by means of the simple J-Shifting technique. The initial state-selected reaction probabilities and reaction cross section do not manifest any sharp oscillations and the initial state selected reaction rate constants are sensitive to the temperature.
Jcc, 2010
The dynamics of the H( 2 S)+FO( 2 ) → OH( 2 )+F( 2 P) reaction on the adiabatic potential energy surface of the 1 3 A and 1 3 A states is investigated. The initial state selected reaction probabilities for total angular momentum J = 0 have been calculated by using the quantum mechanical real wave packet method. The integral cross sections and initial state selected reaction rate constants have been obtained from the corresponding J = 0 reaction probabilities by means of the simple J-Shifting technique. The initial state-selected reaction probabilities and reaction cross section do not manifest any sharp oscillations and the initial state selected reaction rate constants are sensitive to the temperature.
The journal of physical chemistry. A, 2009
We present a quantum study of the reaction F((2)P) + HCl(X(1)Sigma(+)) --> HF(X(1)Sigma(+)) + Cl((2)P) on a recently computed 1(2)A' ground-state surface, considering HCl in the ground vibrational state, with up to 16 rotational quanta j(0). We employ the real wavepacket (WP) and flux methods for calculating coupled-channel (CC) and centrifugal-sudden (CS) initial-state probabilities up to J = 80 and 140, respectively. We also report CC and CS ground-state cross sections and CS excited-state cross sections and discuss the dynamics analyzing WP time evolutions. The HCl rotation highly enhances reaction probabilities and cross sections, as it was previously found for probabilities at J </= 4. CS errors depend on j(0), on its z projection K(0), and on the collision energy and are small at j(0) = 0 and 16 but large at j(0) = 8. Differences between CC and CS results are associated with the reaction stereodynamics and energetics. Steric effects favor indeed the overcoming of the...
The Journal of Chemical Physics, 2008
In this paper, we present the results of a theoretical investigation on the dynamics of the title reaction at collision energies below 1.2 kcal/mol using rigorous quantum reactive scattering calculations. Vibrationally resolved integral and differential cross sections, as well as product rotational distributions, have been calculated using two electronically adiabatic potential energy surfaces, developed by us on the basis of semiempirical modifications of the entrance channel. In particular, we focus our attention on the role of the exothermicity and of the exit channel region of the interaction on the experimental observables. From the comparison between the theoretical results, insight about the main mechanisms governing the reaction is extracted, especially regarding the bimodal structure of the HF͑v =2͒ nascent rotational state distributions. A good overall agreement with molecular beam scattering experiments has been obtained.
Quantum stereodynamics of the F+H2→HF+H reaction by the stereodirected S-matrix approach
Chemical Physics, 2004
Reaction stereodynamics can be studied in quantum mechanics using alternative representations of the S matrix. In this paper we employ the equations for the orthogonal transformations (expressed in terms of Wigner 3j symbols) that convert the S matrix from the body fixed (jjXi) representation into the stereodirected one (jmXi). This representation is characterized by the introduction of the steric quantum number m, which in the vector model of quantum mechanics is put into correspondence with given precession cones of attack of the incoming atom on the diatomic molecule for the reactants' channels, and of cones of escape for the departing atom away from the diatomic molecule for the products' channels. The angles of aperture of such cones are determined from the uncertainty principle. As the m quantum number increases (semiclassical limit), the grid of discrete values of the precession cones more finely scans the angle between the Jacobi vectors. Using a time-independent hyperspherical coordinate method we have generated the full S matrix including all open reactive and inelastic channels for two potential energy surfaces corresponding to the F + H 2 ! HF + H reaction and they have been used to calculate, via jjXi ! jmXi matrix transformations, the attack and exit cumulative reaction probabilities. During the calculations, we have distinguished between ortho-H 2 and para-H 2 . Clear stereodynamical effects have being identified, in particular, regarding the reaction entrance channel, that F-atom attacks are preferred at the transition state (bent) geometry, while for the exit channel the H-atom departs in a collinear geometry by the H-end side of HF.
The Journal of Chemical Physics, 2002
Vibrational (v) state-selected reaction probabilities (PvjJ) have been calculated for the reaction He+H2+(v=0,1,2,3)→HeH++H, for H2+ in its ground rotational state (j=0) for a range of total angular momentum (J) values, for total energy (E) in the range 0.94–1.4 eV, using time-dependent quantum mechanical (TDQM) approach and centrifugal sudden approximation. The number of oscillations in Pv0J(E) decreases with increase in J. In addition, there is a noticeable increase in the threshold energy (Eth) with increase in J. The magnitude of Pv0J decreases with increase in J resulting in converged cross section values by the time J becomes 35–45, depending upon v and E under investigation. The resulting (converged) reaction cross section values are in excellent agreement with the experimental results at E=1.14 eV, both in terms of the magnitude and in terms of the observed vibrational enhancement. Interestingly, there is a noticeable discrepancy between our TDQM results and earlier time-ind...
The Journal of Chemical Physics, 2012
We present wave packet calculations of total and state-to-state reaction probabilities and integral cross sections for the nonadiabatic dynamics of the O( 3 P)+HF → F( 2 P)+OH( 2 ) reaction at hyperthermal collision energies ranging from 1.2 to 2.4 eV. The validity of the centrifugal sudden approximation is discussed for the title reaction and a comprehensive investigation of the influence of nonadiabatic effects on the dynamics of this reactive system at high (hyperthermal) collision energies is presented. In general, nonadiabatic effects are negligible for averaged observables, such as total reaction probabilities and integral cross sections, but they are clearly observed in detailed observables such as rotationally state-resolved reaction probabilities. A critical discussion of nonadiabatic effects on the dynamics of the title reaction is carried out by comparing with the reverse reaction and the characteristics of the adiabatic and diabatic potential energy surfaces involved.
Physical Chemistry Chemical Physics, 2002
We present in this article a numerical investigation of the dynamics of the prototypical exchange reaction F þ H 2 ! HF þ H applying an exact quantum mechanical method, the hyperquantization algorithm, which exploits discrete analogs of hyperspherical harmonics and whose accuracy is tested for both differential and integral cross sections. The calculations employ the potential energy surface by Stark and Werner, both in its original version (SW PES) and in two new versions, properly adapted to include the effects of the long-range interaction in the reactants' valley (SW-LR) and also those due to the spin-orbit interaction (SW-LR-SO). The features of the potential surfaces in the entrance channel have been modeled according to experimental information coming from total cross section measurements carried out in our laboratory. Computed integral and differential cross sections for H 2 in its ground vibrational state and for rotational states equal to 0, 1, 2 and 3 in the collision energy range 1.8-3.4 kcal mol À1 are compared with previous results by other accurate quantum mechanical methods (, 3633)) to emphasize the role of intermediate and long-range forces on reaction dynamics. The effect of the modifications of the ground surface due to spin-orbit interaction is also discussed and perspectives for future improvements are pointed out, the main indication being that the effective reaction barrier appears to be lower with respect to that of the original SW PES.