TY - JOUR
T1 - Reaction dynamics of O(1D,3P) + OCS studied with time-resolved fourier transform infrared spectroscopy and quantum chemical calculations
AU - Chiang, Hung Chu
AU - Wang, Niann-Shiah
AU - Tsuchiya, Soji
AU - Chen, Hsin Tsung
AU - Lee, Yuan-Pern
AU - Lin, Ming-Chang
PY - 2009/7/1
Y1 - 2009/7/1
N2 - Time-resolved infrared emission of CO2 and OCS was observed in reactions O(3P) + OCS and O(1D) + OCS with a step-scan Fourier transform spectrometer. The CO2 emission involves δv3 =-1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0°, 1) → (0, 0°, 0); the latter derives its energy via near-resonant V-V energy transfer from highly excited CO2. Rotationally resolved emission lines of CO (V ≤ 4 and J ≤ 30) were also observed in the reaction O(1D) + OCS. For O(3P) + OCS, weak emission of CO2 diminishes when Ar is added, indicating that O(3P) is translationally hot to overcome the barrier for CO2 formation. The band contour of CO 2 agrees with a band shape simulated on the basis of a Dunham expansion model of CO2; the average vibrational energy of CO 2 in this channel is 49% of the available energy. This vibrational distribution fits with that estimated through a statistical partitioning of energy E*= 18 000 ± 500 cm-1 into all vibrational modes of CO2. For the reaction of O(1D) + OCS, approximately 51% of the available energy is converted into vibrational energy of CO2, and a statistical prediction using E*= 30 000 ± 500 cm-1 best fits the data. The mechanisms of these reactions are also investigated with the CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) method. The results indicate that the triplet O(3P) + OCS(X1σ+) surface proceeds via direct abstraction and substitution channels with barriers of 27.6 and 36.4 kJ mol-1, respectively, to produce SO(X3σ-) + CO(X1Ó+) and S(3P) + CO2(X 1A1), whereas two intermediates, OSCO and SC(O)O, are formed from the singlet O(1D) + OCS(X1σ+) surface without barrier, followed by decomposition to SO(a1.) + CO(X 1σ+) and S(1D) + CO2(X 1A1), respectively. For the ground-state reaction O( 3P) + OCS(X1σ+), the singlet-triplet curve crossings play important roles in the observed kinetics and chemiluminescence.
AB - Time-resolved infrared emission of CO2 and OCS was observed in reactions O(3P) + OCS and O(1D) + OCS with a step-scan Fourier transform spectrometer. The CO2 emission involves δv3 =-1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0°, 1) → (0, 0°, 0); the latter derives its energy via near-resonant V-V energy transfer from highly excited CO2. Rotationally resolved emission lines of CO (V ≤ 4 and J ≤ 30) were also observed in the reaction O(1D) + OCS. For O(3P) + OCS, weak emission of CO2 diminishes when Ar is added, indicating that O(3P) is translationally hot to overcome the barrier for CO2 formation. The band contour of CO 2 agrees with a band shape simulated on the basis of a Dunham expansion model of CO2; the average vibrational energy of CO 2 in this channel is 49% of the available energy. This vibrational distribution fits with that estimated through a statistical partitioning of energy E*= 18 000 ± 500 cm-1 into all vibrational modes of CO2. For the reaction of O(1D) + OCS, approximately 51% of the available energy is converted into vibrational energy of CO2, and a statistical prediction using E*= 30 000 ± 500 cm-1 best fits the data. The mechanisms of these reactions are also investigated with the CCSD(T)/6-311+G(3df)//B3LYP/6-311+G(3df) method. The results indicate that the triplet O(3P) + OCS(X1σ+) surface proceeds via direct abstraction and substitution channels with barriers of 27.6 and 36.4 kJ mol-1, respectively, to produce SO(X3σ-) + CO(X1Ó+) and S(3P) + CO2(X 1A1), whereas two intermediates, OSCO and SC(O)O, are formed from the singlet O(1D) + OCS(X1σ+) surface without barrier, followed by decomposition to SO(a1.) + CO(X 1σ+) and S(1D) + CO2(X 1A1), respectively. For the ground-state reaction O( 3P) + OCS(X1σ+), the singlet-triplet curve crossings play important roles in the observed kinetics and chemiluminescence.
UR - http://www.scopus.com/inward/record.url?scp=72949109177&partnerID=8YFLogxK
U2 - 10.1021/jp903976z
DO - 10.1021/jp903976z
M3 - Article
C2 - 19601591
AN - SCOPUS:72949109177
SN - 1089-5639
VL - 113
SP - 13260
EP - 13272
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 47
ER -