Rotational, steric, and coriolis effects on the F + HCl --> HF + Cl reaction on the 1(2)A' ground-state surface.
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 potential barrier and a linearly dominated mechanism. Attractive Coriolis couplings favor instead the energy flow from the HCl rotation to the F-H---Cl reactive vibration. WP snapshots confirm and explain the HCl rotational effects, because the density into the nearly collinear F-H---Cl product channel increases remarkably with j(0). Finally, our CS rate constant is underestimated with respect to the experiment, pointing out the need of more accurate multisurface and CC calculations.
Dipartimento di Chimica, Universita di Siena, Via A. Moro 2, I-53100 Siena, Italy.
Paolo
P
Defazio
Carlo
C
Petrongolo