Using stretching and bending vibrations to direct the reaction of Cl atoms with isocyanic acid (HNCO)

Abstract

On-the-fly ab initio trajectory calculations of the dynamics of Cl atom reactions with methane, ethane and methanolThe relative reactivity of the stretch-bend combination vibrations of CH 4 in the Cl ( 2 P 3/2 )+ CH 4 reaction

Vibrational State Control of Bimolecular Reactions: Discovering and Directing the Chemistry

“…The zero-order states interact to form the molecular eigenstates, {|n〉}. the first examples of vibrationally driven bimolecular reactions in neutral [3][4][5][6][7][8][9][10][11][12][13][14][15][16] and ionic 4,[17][18][19] systems.…”

“…States containing only stretching excitation react almost twice as fast as isoenergetic states containing a mixture of stretching and bending excitation. 16 Action spectra, in which one observes the relative reactivity of pairs of states that are different mixtures of the same zero-order states, show that the bending vibration actually inhibits the hydrogen abstraction reaction. Ab initio calculations of the interaction potential of HNCO with Cl shown in Figure 5 reveal the means by which bending excitation stymies the H atom abstraction reaction.…”

“…Ab initio calculations of the interaction potential of HNCO with Cl shown in Figure 5 reveal the means by which bending excitation stymies the H atom abstraction reaction. 16 The interaction potential for a Cl atom approaching an HNCO molecule becomes increasingly attractive in the vicinity of the carbon atom as the N-C-O bending angle decreases. The attraction arising from bending excitation effectively "steals" some of the incoming Cl atoms that would otherwise react with the H atom and directs them toward the C atom, where they form a complex or recoil without reacting, a diversion that inhibits the production of HCl.…”

“…Because spectroscopic probes measure the relative populations of individual quantum states, they not only identify the products but also determine their energy content, information that reveals the fine details of the reaction. The approach of vibrational state preparation followed by reaction and product detection has provided the first examples of vibrationally driven bimolecular reactions in neutral − and ionic ,− systems.…”

“…The result of reacting HNCO in these states with Cl atoms, is striking. States containing only stretching excitation react almost twice as fast as isoenergetic states containing a mixture of stretching and bending excitation …”