Browsing by Author "Tsuchiya, Soji"

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Darling-Dennison resonance and Coriolis coupling in the bending overtones of the (A)over-tilde (1)A(u) state of acetylene, C(2)H(2)
(2008-08-07)
Merer, Anthony J.
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Yamakita, Nami
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Tsuchiya, Soji
;
Steeves, Adam H.
;
Bechtel, Hans A.
Rotational analyses have been carried out for the overtones of the nu(4) (torsion) and nu(6) (in-plane cis-bend) vibrations of the (A) over tilde (1)A(u) state of C(2)H(2). The v(4)+v(6)=2 vibrational polyad was observed in high-sensitivity one-photon laser-induced fluorescence spectra and the v(4)+v(6)=3 polyad was observed in IR-UV double resonance spectra via the ground state nu(3) (Sigma(+)(u)) and nu(3)+nu(4) (Pi(u)) vibrational levels. The structures of these polyads are dominated by the effects of vibrational angular momentum: Vibrational levels of different symmetry interact via strong a-and b-axis Coriolis coupling, while levels of the same symmetry interact via Darling-Dennison resonance, where the interaction parameter has the exceptionally large value K(4466)=-51.68 cm(-1). The K-structures of the polyads bear almost no resemblance to the normal asymmetric top patterns, and many local avoided crossings occur between close-lying levels with nominal K-values differing by one or more units. Least squares analysis shows that the coupling parameters change only slightly with vibrational excitation, which has allowed successful predictions of the structures of the higher polyads: A number of weak bands from the v(4)+v(6)=4 and 5 polyads have been identified unambiguously. The state discovered by Scherer [J. Chem. Phys. 85, 6315 (1986)], which appears to interact with the K=1 levels of the 3(3) vibrational state at low J, is identified as the second highest of the five K=1 members of the v(4)+v(6)=4 polyad. After allowing for the Darling-Dennison resonance, the zero-order bending structure can be represented by omega(4)=764.71, omega(6)=772.50, x(44)=0.19, x(66)=-4.23, and x(46)=11.39 cm(-1). The parameters x(46) and K(4466) are both sums of contributions from the vibrational angular momentum and from the anharmonic force field. For x(46) these contributions are 14.12 and -2.73 cm(-1), respectively, while the corresponding values for K(4466) are -28.24 and -23.44 cm(-1). It is remarkable how severely the coupling of nu(4) and nu(6) distorts the overtone polyads, and also how in this case the effects of vibrational angular momentum outweigh those of anharmonicity in causing the distortion. (C) 2008 American Institute of Physics.
Distribution of Vibrational States of CO(2) in the Reaction O((1)D) + CO(2) from Time-Resolved Fourier Transform Infrared Emission Spectra
(2009-04-16)
Chen, Hui-Fen
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Chiang, Hung-Chu
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Matsui, Hiroyuki
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Tsuchiya, Soji
;
Lee, Yuan-Pern
A mixture Of O(3) and CO(2) was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission Of CO(2) in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) Of CO(2) in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO(2) and a vibrational distribution estimated through a statistical partitioning of energy of similar to 13 000 cm(-1), similar to 3100 cm(-1) smaller than the available energy, into the vibrational modes Of CO(2). From this model, approximately 44% and 5% of the available energy of O((1)D) + CO(2) is converted into the vibrational and rotational energy of product CO(2), respectively, consistent with previous reports of similar to 50% for the translational energy. An extent of rotational excitation Of CO(2) much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO(2) when an O atom leaves the complex CO(3) on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.
Distribution of Vibrational States of CO2 in the Reaction O(D-1) + CO2 from Time-Resolved Fourier Transform Infrared Emission Spectra
(2009-04-16)
Chen, Hui-Fen
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Chiang, Hung-Chu
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Matsui, Hiroyuki
;
Tsuchiya, Soji
;
Lee, Yuan-Pern
A mixture Of O-3 and CO2 was irradiated with light from a KrF laser at 248 nm; time-resolved infrared emission Of CO2 in the region 2000-2400 cm(-1) was observed with a Fourier transform spectrometer. This emission involves one quantum in the asymmetric stretching mode (nu(3)) Of CO2 in highly vibrationally excited states. The band contour agrees satisfactorily with a band shape calculated based on a simplified polyad model of CO2 and a vibrational distribution estimated through a statistical partitioning of energy of similar to 13 000 cm(-1), similar to 3100 cm(-1) smaller than the available energy, into the vibrational modes Of CO2. From this model, approximately 44% and 5% of the available energy of O(D-1) + CO2 is converted into the vibrational and rotational energy of product CO2, respectively, consistent with previous reports of similar to 50% for the translational energy. An extent of rotational excitation Of CO2 much smaller than that expected from statistical calculations indicates a mechanism that causes a small torque to be given to CO2 when an O atom leaves the complex CO3 on the triplet exit surface of potential energy, consistent with quantum-chemical calculations.
Dynamics of the reactions of O(D-1) with CD3OH and CH3OD studied with time-resolved Fourier-transform IR spectroscopy
(2012-10-28)
Huang, Chong-Kai
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Xu, Zhen-Feng
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Nakajima, Masakazu
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Nguyen, Hue M. T.
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Lin, M. C.
We investigated the reactivity of O(D-1) towards two types of hydrogen atoms in CH3OH. The reaction was initiated on irradiation of a flowing mixture of O-3 and CD3OH or CH3OD at 248 nm. Relative vibration-rotational populations of OH and OD (1 <= nu <= 4) states were determined from their infrared emission recorded with a step-scan time-resolved Fourier-transform spectrometer. In O(D-1) + CD3OH, the rotational distribution of OD is nearly Boltzmann, whereas that of OH is bimodal; the product ratio [OH]/[OD] is 1.56 +/- 0.36. In O(D-1) + CH3OD, the rotational distribution of OH is nearly Boltzmann, whereas that of OD is bimodal; the product ratio [OH]/[OD] is 0.59 +/- 0.14. Quantum-chemical calculations of the potential energy and microcanonical rate coefficients of various channels indicate that the abstraction channels are unimportant and O(D-1) inserts into the C-H and O-H bonds of CH3OH to form HOCH2OH and CH3OOH, respectively. The observed three channels of OH are consistent with those produced via decomposition of the newly formed OH or the original OH moiety in HOCH2OH or decomposition of CH3OOH. The former decomposition channel of HOCH2OH produces vibrationally more excited OH because of incomplete intramolecular vibrational relaxation, and decomposition of CH3COOH produces OH with greater rotational excitation, likely due to a large torque angle during dissociation. The predicted [OH]/[OD] ratios are 1.31 and 0.61 for O(D-1) + CD3OH and CH3OD, respectively, at collision energy of 26 kJ mol(-1), in satisfactory agreement with the experimental results. These predicted product ratios vary weakly with collision energy. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759619]
Reaction Dynamics of O((1)D,(3)P) + OCS Studied with Time-Resolved Fourier Transform Infrared Spectroscopy and Quantum Chemical Calculations
(2009-11-26)
Chiang, Hung-Chu
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Wang, Niann-Shiah
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Tsuchiya, Soji
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Chen, Hsin-Tsung
;
Lee, Yuan-Pern
Time-resolved infrared emission of CO(2) and OCS was observed in reactions O((1)P) + OCS and O((1)D) + OCS with a step-scan Fourier transform spectrometer. The CO(2) emission involves Delta nu(3) = -1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0 degrees, 1) (0, 0, 0); the latter derives its energy via near-resonant V-V energy transfer from highly excited CO(2). Rotationally resolved emission lines of CO (v <= 4 and J <= 30) were also observed in the reaction O((1)D) + OCS. For O((3)P) + OCS, weak emission Of CO(2) diminishes when Ar is added, indicating that O((3)P) is translationally hot to overcome the barrier for CO(2) formation. The band contour of CO(2) agrees with a band shape simulated on the basis of a Dunharn expansion model of CO(2); 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* congruent to 18 000 +/- 500 cm(-1) into all vibrational modes of CO(2). For the reaction of O((1)D) + OCS, approximately 51% of the available energy is converted into vibrational energy of CO(2), and a statistical prediction using E* congruent to 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((3)P) + OCS(X(1)Sigma(+)) surface proceeds via direct abstraction and substitution channels with barriers of 27.6 and 36.4 kJ mol(-1), respectively, to produce SO(X(3)Sigma(-)) + CO(X(1)Sigma(+)) and S((3)P) + CO(2)(X(1)A(1)), whereas two intermediates, OSCO and SC(O)O, are formed from the singlet O((1)D) + OCS(X(1)Sigma(+)) surface without barrier, followed by decomposition to SO(a(1)Delta) + CO(X(1)Sigma(+)) and S((1)D) + CO(2)(X(1)A(1)), respectively. For the ground-state reaction O((3)P) + OCS(X(1)Sigma(+)), the singlet-triplet curve crossings play important roles in the observed kinetics and chemiluminescence.
Reaction dynamics of O(D-1) + HCOOD/DCOOH investigated with time-resolved Fourier-transform infrared emission spectroscopy
(2014-10-21)
Huang, Shang-Chen
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Nghia, N. T.
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Putikam, Raghunath
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Nguyen, Hue M. T.
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Lin, M. C.
We investigated the reaction dynamics of O(D-1) towards hydrogen atoms of two types in HCOOH. The reaction was initiated on irradiation of a flowing mixture of O-3 and HCOOD or DCOOH at 248 nm. The relative vibration-rotational populations of OH and OD (1 <= upsilon <= 4, J <= 15) states were determined from time-resolved IR emission recorded with a step-scan Fourier-transform spectrometer. In the reaction of O(D-1) + HCOOD, the rotational distribution of product OH is nearly Boltzmann, whereas that of OD is bimodal. The product ratio [OH]/[OD] is 0.16 +/- 0.05. In the reaction of O(D-1) + DCOOH, the rotational distribution of product OH is bimodal, but the observed OD lines are too weak to provide reliable intensities. The three observed OH/OD channels agree with three major channels of production predicted with quantum-chemical calculations. In the case of O(D-1) + HCOOD, two intermediates HOC(O)OD and HC(O)OOD are produced in the initial C-H and O-D insertion, respectively. The former undergoes further decomposition of the newly formed OH or the original OD, whereas the latter produces OD via direct decomposition. Decomposition of HOC(O)OD produced OH and OD with similar vibrational excitation, indicating efficient intramolecular vibrational relaxation, IVR. Decomposition of HC(O)OOD produced OD with greater rotational excitation. The predicted [OH]/[OD] ratio is 0.20 for O(D-1) + HCOOD and 4.08 for O(D-1) + DCOOH; the former agrees satisfactorily with experiments. We also observed the upsilon(3) emission from the product CO2. This emission band is deconvoluted into two components corresponding to internal energies E = 317 and 96 kJ mol(-1) of CO2, predicted to be produced via direct dehydration of HOC(O)OH and secondary decomposition of HC(O)O that was produced via decomposition of HC(O)OOH, respectively. (C) 2014 AIP Publishing LLC.
Reaction Dynamics of O(D-1,P-3) + OCS Studied with Time-Resolved Fourier Transform Infrared Spectroscopy and Quantum Chemical Calculations
(2009-11-26)
Chiang, Hung-Chu
;
Wang, Niann-Shiah
;
Tsuchiya, Soji
;
Chen, Hsin-Tsung
;
Lee, Yuan-Pern
Time-resolved infrared emission of CO2 and OCS was observed in reactions O(P-1) + OCS and O(D-1) + OCS with a step-scan Fourier transform spectrometer. The CO2 emission involves Delta nu(3) = -1 transitions from highly vibrationally excited states, whereas emission of OCS is mainly from the transition (0, 0 degrees, 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(D-1) + OCS. For O(P-3) + OCS, weak emission Of CO2 diminishes when Ar is added, indicating that O(P-3) is translationally hot to overcome the barrier for CO2 formation. The band contour of CO2 agrees with a band shape simulated on the basis of a Dunharn expansion model of CO2; the average vibrational energy of CO2 in this channel is 49% of the available energy. This vibrational distribution fits with that estimated through a statistical partitioning of energy E* congruent to 18 000 +/- 500 cm(-1) into all vibrational modes of CO2. For the reaction of O(D-1) + OCS, approximately 51% of the available energy is converted into vibrational energy of CO2, and a statistical prediction using E* congruent to 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(P-3) + OCS(X-1 Sigma(+)) surface proceeds via direct abstraction and substitution channels with barriers of 27.6 and 36.4 kJ mol(-1), respectively, to produce SO(X-3 Sigma(-)) + CO(X-1 Sigma(+)) and S(P-3) + CO2(X(1)A(1)), whereas two intermediates, OSCO and SC(O)O, are formed from the singlet O(D-1) + OCS(X-1 Sigma(+)) surface without barrier, followed by decomposition to SO(a(1)Delta) + CO(X-1 Sigma(+)) and S(D-1) + CO2(X(1)A(1)), respectively. For the ground-state reaction O(P-3) + OCS(X-1 Sigma(+)), the singlet-triplet curve crossings play important roles in the observed kinetics and chemiluminescence.
Stretch-bend combination polyads in the (A)over-tilde(1)A(u) state of acetylene, C(2)H(2)
(2009-08-01)
Steeves, Adam H.
;
Bechtel, Hans A.
;
Merer, Anthony J.
;
Yamakita, Nami
;
Tsuchiya, Soji
Rotational analyses are reported for a number of newly-discovered vibrational levels of the SI-trans; ((A) over tilde (1)A(u)) state of C(2)H(2). These levels are combinations where the Franck-Condon active nu(2)' and nu(3)' vibrational modes are excited together with the low-lying bending vibrations, nu(4)' and nu(6)'. The structures of the bands are complicated by strong a- and b-axis Coriolis coupling, as well as Darling-Dennison resonance for those bands that involve overtones of the bending vibrations. The most interesting result is the strong anharmonicity in the combinations of nu(3)' (trans bend, a(g)) and nu(6)' (in-plane cis bend, b(u)). This anharmonicity presumably represents the approach of the molecule to the trans-cis isomerization barrier, where ab initio results have predicted the transition state to be half-linear, corresponding to simultaneous excitation of nu(3)' and nu(6)'. The anharmonicity also causes difficulty in the least squares fitting of some of the polyads, because the simple model of Coriolis coupling and Darling-Dennison resonance starts to break down. The effective Darling-Dennison parameter, K(4466), is found to increase rapidly with excitation of nu(3)', while many small centrifugal distortion terms have had to be included in the least squares fits in order to reproduce the rotational structure correctly. Fermi resonances become important where the K-structures of different polyads overlap, as happens with the 2(1)3(1)B(1) and 3(1)B(3) polyads (B = 4 or 6). The aim of this work is to establish the detailed vibrational level structure of the S(1)-trans state in order to search for possible S(1)-cis ((1)A(2)) levels. This work, along with results from other workers, identifies at least one K sub-level of every single vibrational level expected up to a vibrational energy of 3500 cm(-1). (C) 2009 Elsevier Inc. All rights reserved.
Stretch-bend combination polyads in the (A)over-tilde(1)A(u) state of acetylene, C2H2
(2009-08-01)
Steeves, Adam H.
;
Bechtel, Hans A.
;
Merer, Anthony J.
;
Yamakita, Nami
;
Tsuchiya, Soji
Rotational analyses are reported for a number of newly-discovered vibrational levels of the SI-trans; ((A) over tilde (1)A(u)) state of C2H2. These levels are combinations where the Franck-Condon active nu(2)' and nu(3)' vibrational modes are excited together with the low-lying bending vibrations, nu(4)' and nu(6)'. The structures of the bands are complicated by strong a- and b-axis Coriolis coupling, as well as Darling-Dennison resonance for those bands that involve overtones of the bending vibrations. The most interesting result is the strong anharmonicity in the combinations of nu(3)' (trans bend, a(g)) and nu(6)' (in-plane cis bend, b(u)). This anharmonicity presumably represents the approach of the molecule to the trans-cis isomerization barrier, where ab initio results have predicted the transition state to be half-linear, corresponding to simultaneous excitation of nu(3)' and nu(6)'. The anharmonicity also causes difficulty in the least squares fitting of some of the polyads, because the simple model of Coriolis coupling and Darling-Dennison resonance starts to break down. The effective Darling-Dennison parameter, K-4466, is found to increase rapidly with excitation of nu(3)', while many small centrifugal distortion terms have had to be included in the least squares fits in order to reproduce the rotational structure correctly. Fermi resonances become important where the K-structures of different polyads overlap, as happens with the 2(1)3(1)B(1) and 3(1)B(3) polyads (B = 4 or 6). The aim of this work is to establish the detailed vibrational level structure of the S-1-trans state in order to search for possible S-1-cis ((1)A(2)) levels. This work, along with results from other workers, identifies at least one K sub-level of every single vibrational level expected up to a vibrational energy of 3500 cm(-1). (C) 2009 Elsevier Inc. All rights reserved.