Bond-specific chemistry: OD:OH product ratios for the reactions H+HOD(100) and H+HOD(001)

Abstract

From laser-induced fluorescence measurements, the OD:OH product branching ratio is determined to be greater than 25:1 for the reaction H+HOD(001) and less than 1:8 for the reaction H+HOD(100). Fast H atoms are generated by the photolysis of HI at 266 nm and the HOD is excited to a specific vibronic state using an optical parametric oscillator. Here HOD(001) and HOD(100) correspond to O–H and O–D local-mode stretch fundamentals, respectively. Within our signal-to-noise level, reaction occurs exclusively with the extended hydrogen atom of HOD in each case.

Quasiclassical Trajectory Study of the Rotational Mode Specificity in the O(3P) + CHD3(v1 = 0, 1, JK) → OH + CD3 Reactions

“…However, in the case of K = 0, the tumbling rotation may steer the reactants into a reactive orientation, thereby increasing the reactivity. Similar qualitative results were found recently for Cl + CHD 3 (v 1 = 1, JK), albeit the rotational enhancement factors are significantly larger for Cl + CHD 3 . 22 For example, JK = 50 and 55 enhance the Cl + CHD 3 reaction by factors of 5.3 and 2.5, respectively, 22 whereas the corresponding enhancement factors of O( 3 P) + CHD 3 are only 1.4(1.3) and 0.9(1.0).…”

“…However, for K = 0 a clear J-dependence is seen, where the attack angle distributions shift from front-side attack to side-on attack orientations. For the JK = 80 state the reactivity is even larger at α = 90°than at α = 0°a nd significant reactivity is found when the O atom initially approaches the back side of CHD 3 . This side-on−back-side shift with increasing J is even more pronounced at lower E coll as seen by comparing the α distributions at 6.0 and 8.0 kcal/mol ( Figure 5.).…”

“…Following our pervious study on Cl + CHD 3 , 22 we have computed the initial attack angle (α) distributions for the O( 3 P) + CHD 3 (v 1 = 1, JK) reaction as shown in Figure 5. α is defined as the angle between the initial velocity vector of CHD 3 and the CH vector at the beginning of the trajectory. Note that unlike the attack angle at the transition state, the initial attack angle dependence of the reactivity can be probed experimentally.…”

Laser Control of Chemical Reactions

“…In this experimental study, the H atoms were generated with a microwave discharge, and the HOD molecule was prepared in a selected overtone stretch by laser irradiation in the visible wavelengths. Zare and co-workers (7) showed that the product-branching ratio selectivity was reduced but still survived for reactions of fast H atoms with HOD prepared in either the H-OD or HO-D stretching fundamental. Here, fast H atoms were generated by photolysis of HI, and the HOD stetching fundamental was excited by laser irradiation in the infrared.…”

“…Furthermore, reaction dynamics theory can now provide detailed predictions with an accuracy that can rival experiment on simple reactions in the gas phase (7), and the theory has been extended, albeit more approximately, to more complex problems such as reactions of polyatomic molecules (8) and reactions on solid surfaces (9) and in solution (10).…”