Energy Distribution Among Reaction Products. IV. X+HY (X ≡ Cl, Br; Y ≡ Br, I), Cl+DI

Abstract

The distribution of vibrational, rotational, and translational energies (symbolized by V′, R′, and T′) have been obtained for the products of the isotopic pair of reactions Cl + HI → HCl + I and Cl + DI → DCl + I. The experimental method was the ``arrested relaxation'' variant of the infrared chemiluminescence technique. Detailed rate constants k(V′, R′, T′) are reported in the form of contour plots for these reactions. The total detailed rate constants into specified vibrational quantum states for Cl+HI (summed over the rotational levels of each v′ level) are k(v′ = 1) = 0.22, k(v′ = 2) = 0.35, [k(v′ = 3) = 1.00], k(v′ = 4) = 0.74; and for Cl + DI, k(v′ = 1) ≈ 0.08, k(v′ = 2) = 0.14, k(v′ = 3) = 0.35, k(v′ = 4) = 0.73, [k(v′ = 5) = 1.00], k(v′ = 6) = 0.05 [relative to the highest rate constant k(v̂′) = 1.00, in each case]. Preliminary energy distributions are also reported for the products of two other reactions, Cl + HBr → HCl + Br and Br + HI → HBr + I, in the X + HY → HX + Y family (X and Y are halogen atoms). The members of this family of reactions channel a substantial fraction of the energy available to the products into vibrational and rotational excitation, and only a small fraction into relative translation. For the Cl+HI and also the Cl+DI reaction the fractions are f̄V′ + f̄R′ (= 0.71 + 0.13) = 0.84; in contrast to f̄T′ = 0.16. As a corollary there is a marked inverse correlation between vibrational and rotational excitation in the reaction products. Despite the fact that the detailed rate constants into specified product quantum states [k(v′, J′)] are markedly different for the isotopic pair of reactions, the fractional conversion of the available energy into vibration, rotation, and translation are in close agreement (to ∼ ± 1%). This close parallelism in f̄V′, f̄R′, f̄T′ is in accord with predictions from classical trajectory studies. It indicates the usefulness of such calculations even for the case of reactions which yield products with widely spaced (vibrational and rotational) quantum levels.

Proton transfer dynamics on highly attractive potential energy surfaces: Induced repulsive energy release in O− + HF at high collision energies

“…Previous studies on Heavy + Light-Heavy reaction systems show that the dynamics are dominated by kinematics rather than specific features of the potential energy surface itself. The extensive trajectory studies of Polanyi and co-workers (16)(17)(18)(19) shows that reactive collisions on such highly skewed surfaces are direct, with a strong propensity to cut the corner separating the entrance and exit valleys. These motions correspond to light atom transfer from configurations extended from equilibrium bond lengths with little momentum transfer to the departing heavy atoms, yielding reaction products that are highly vibrationally excited.…”

“…In proton transfer reactions in particular, the angle between the entrance and exit channels of the potential energy surface in scaled and skewed coordinates (15) is quite small, near 20" for particle transfer between bases of moderate mass. Trajectory studies by Polanyi and collaborators (16)(17)(18)(19) on such surfaces have shown that product energy release is determined more by the initial conditions of a trajectory than by details of the potential surface itself. At low collision energies, these studies show that reaction occurs through the mechanism of "mixed energy release", in which proton transfer occurs when both the breaking bond in the reagents and the bond forming in the products are extended.…”

Reaction Dynamics of H2O+ (D2O+) + NH3 Studied with Crossed Molecular Beams and Density Functional Theory Calculations

“…[48][49][50] In strongly exothermic proton transfer systems, the dynamics appear to be direct, partitioning the majority of the total energy into product vibration. As examples of the heavy + light-heavy mass combination in which the light particle is transferred in reaction, such systems exhibit the energy transfer motif of "mixed energy release", [35][36][37][38] in which the reaction occurs with the cleaving and incipient bonds in an extended configuration. This pattern for energy transfer is characteristic of "corner cutting" trajectories on scaled and skewed potential energy surfaces 51 in which the entrance and exit channels make a small angle with respect to one another and is therefore an intrinsic property of the potential energy surface.…”

“…Such light atom transfer is generally described by "mixed energy release", [35][36][37][38] in which both the cleaving and nascent bonds are extended from their equilibrium displacements. One can expect that the transfer will result in significant stretching excitation of the nascent N-D bond.…”

Modelling the Cavity of Continuous Chemical Lasers (CCLs) Using Matlab Applications

“…The idea of the simulation part was to form a basic setup for a future test stand for chemical cavities lasers within a numerical routine. The framework for the numerical routine [10,11] has been MATLAB7, a numerical computing environment by "The MATH-WORKS", ( Figure 5) since it offers a large range of inbuilt functions and visualization tools. In principle, the very simulations could have been done with any other sophisticated programming environment or language, but the MATLAB language offered the quite comfortable advantage of vector based variables useful for this prob-…”