Effect of molecular bending on the photodissociation of OCS (original) (raw)
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The Journal of Chemical Physics, 2002
State-to-state photodissociation experiments of OCS at 230 nm are reported using hexapole state selection of the parent molecule and velocity map ion imaging of the angular recoil of the CO photofragment. The role of the initial rovibrational state ( 2 ϭ0,1͉JlM ) of OCS on the angular recoil distribution is investigated. The CO (X 1 ⌺ ϩ ;vϭ0͉J) rotational distribution as well as the angular recoil anisotropy parameter  of the CO photofragment are reported for dissociation of single rovibrational ( 2 ϭ0,1͉JlM ) quantum states of OCS. A strong dependence of the anisotropy parameter  on the initial bending state, 2 ϭ0 or 1, of OCS is observed. The effects of the initial bending state of OCS are rationalized in terms of the strong angular dependence of the transition dipole moment function of OCS for the 1 1 ⌺ Ϫ (1 1 AЉ) and 1 1 ⌬(2 1 AЈ) excited state surfaces involved in the dissociation at 230 nm. The state-to-state imaging experiment provides a revised and improved determination of the binding energy of OCS ( 1 , 2 , 3 ϭ0,0,0͉Jϭ0)→CO (X 1 ⌺ ϩ ;v ϭ0͉Jϭ0)ϩS ( 1 D 2 ), D 0 ϭ(4.284Ϯ0.009) eV.
Ultraviolet photodissociation of OCS: Product energy and angular distributions
The Journal of Chemical Physics, 2013
The ultraviolet photodissociation of carbonyl sulfide (OCS) was studied using three-dimensional potential energy surfaces and both quantum mechanical dynamics calculations and classical trajectory calculations including surface hopping. The transition dipole moment functions used in an earlier study [J. A. Schmidt, M. S. Johnson, G. C. McBane, and R. Schinke, J. Chem. Phys. 137, 054313 (2012)] were improved with more extensive treatment of excited electronic states. The new functions indicate a much larger contribution from the 1 1 A state ( 1 − in linear OCS) than was found in the previous work. The new transition dipole functions yield absorption spectra that agree with experimental data just as well as the earlier ones. The previously reported potential energy surfaces were also empirically modified in the region far from linearity. The resulting product state distributions P v,j , angular anisotropy parameters β(j), and carbon monoxide rotational alignment parameters A (2) 0 (j ) agree reasonably well with the experimental results, while those computed from the earlier transition dipole and potential energy functions do not. The higher-j peak in the bimodal rotational distribution is shown to arise from nonadiabatic transitions from state 2 1 A to the OCS ground state late in the dissociation. to 130.225.101.2. Redistribution subject to AIP license or copyright; see http://jcp.aip.org/about/rights\_and\_permissions 094314-2 McBane et al.
Rotationally resolved photoionization dynamics of hot CO fragmented from OCS
2002
References viii 3. Rotationally resolved photoelectron spectroscopy of hot N 2 formed in the photofragmentation of N O 31 3.1 Introduction 3.2 Experimental 3.3 Theory and Numerical Details 3.4 Results and Discussion 3.5 Conclusions References 4. Rotationally resolved photoionization dynamics of hot CO fragmented from OCS 51 4.1 Introduction 4.2 Experimental 4.3 Theoretical Formulation 4.4 Results and Discussion 4.5 Conclusions References 5. Photoionization dynamics of CS fragments studied by laser photoelectron spectroscopy 69 5.1 Introduction 5.2 Experimental 5.3 Results and Discussion 5.4 Conclusions References ix 6. Imaging of ultrafast multichannel photodissociation dynamics of CH 2 BrI 83
Physical Chemistry Chemical Physics, 2011
In this paper we report slice imaging polarization experiments on the state-to-state photodissociation at 42 594 cm À1 of spatially oriented OCS(v 2 = 1|JlM = 111) -CO(J) + S( 1 D 2 ). Slice images were measured of the three-dimensional recoil distribution of the S( 1 D 2 ) photofragment for different polarization geometries of the photolysis and probe laser. The high resolution slice images show well separated velocity rings in the S( 1 D 2 ) velocity distribution. The velocity rings of the S( 1 D 2 ) photofragment correlate with individual rotational states of the CO(J) cofragment in the J CO = 57-65 region. The angular distribution of the S( 1 D 2 ) velocity rings are extracted and analyzed using two different polarization models. The first model assumes the nonaxial dynamics evolves after excitation to a single potential energy surface of an oriented OCS(v 2 = 1|JlM = 111) molecule. The second model assumes the excitation is to two potential energy surfaces, and the OCS molecule is randomly oriented. In the high J region (J CO = 62-65) it appears that both models fit the polarization very well, in the region J CO = 57-61 both models seem to fit the data less well. From the molecular frame alignment moments the m-state distribution of S( 1 D 2 ) is calculated as a function of the CO(J) channel. A comparison is made with the theoretical m-state distribution calculated from the long-range electrostatic dipole-dipole plus quadrupole interaction model. The S( 1 D 2 ) photofragment velocity distribution shows a very pronounced strong peak for S( 1 D 2 ) fragments born in coincidence with CO(J = 61).
The 157 nm photodissociation of OCS
The Journal of Chemical Physics, 1989
The photodissociation ofOeS at 157 nm has been investigated by using tunable vacuum ultraviolet radiation to probe the eo and S photoproducts. Sulfur is produced almost entirely in the IS state, while eo is produced in its ground electronic state and in vibrational levels
Photodissociation dynamics of OCS near 214 nm using ion imaging
The Journal of chemical physics, 2016
The OCS photodissociation dynamics of the dominant S((1)D2) channel near 214 nm have been studied using velocity map ion imaging. We report a CO vibrational branching ratio of 0.79:0.21 for v = 0:v = 1, indicating substantially higher vibrational excitation than that observed at slightly longer wavelengths. The CO rotational distribution is bimodal for both v = 0 and v = 1, although the bimodality is less pronounced than at longer wavelengths. Vector correlations, including rotational alignment, indicate that absorption to both the 2(1)A' (A) and 1(1)A″ (B) states is important in the lower-j part of the rotational distribution, while only 2(1)A' state absorption contributes to the upper part; this conclusion is consistent with work at longer wavelengths. Classical trajectory calculations including surface hopping reproduce the measured CO rotational distributions and their dependence on wavelength well, though they underestimate the v = 1 population. The calculations indicat...
The Journal of Chemical Physics, 2012
Global three dimensional potential energy surfaces and transition dipole moment functions are calculated for the lowest singlet and triplet states of carbonyl sulfide at the multireference configuration interaction level of theory. The first ultraviolet absorption band is then studied by means of quantum mechanical wave packet propagation. Excitation of the repulsive 2 1 A state gives the main contribution to the cross section. Excitation of the repulsive 1 1 A state is about a factor of 20 weaker at the absorption peak (E ph ≈ 45 000 cm −1 ) but becomes comparable to the 2 1 A state absorption with decreasing energy (35 000 cm −1 ) and eventually exceeds it. Direct excitation of the repulsive triplet states is negligible except at photon energies E ph < 38 000 cm −1 . The main structure observed in the cross section is caused by excitation of the bound 2 3 A state, which is nearly degenerate with the 2 1 A state in the Franck-Condon region. The structure observed in the low energy tail of the spectrum is caused by excitation of quasi-bound bending vibrational states of the 2 1 A and 1 1 A electronic states. The absorption cross sections agree well with experimental data and the temperature dependence of the cross section is well reproduced.
Chemical Physics Letters, 2005
We report the photodissociation dynamics of ortho-iodobenzyl chloride (o-C 6 H 4 I(CH 2 Cl)) in the ultraviolet. The gas phase dissociation dynamics of o-iodobenzyl chloride at 222, 236, 266, 280, and $304 nm was monitored by probing the quantum yields of I* ( 2 P 1/2 ) as well as Cl* ( 2 P 1/2 ) production using suitable resonance enhanced multiphoton ionization detection schemes. We find that only iodine atoms in the ground (I ( 2 P 3/2 )) as well as excited (I*) states are produced in the dissociation. No Cl ( 2 P 3/2 ) or Cl* atoms were detected. This accidental bond selective dissociation in o-iodobenzyl chloride is perhaps due to weak coupling among various chromophores present in the molecule and inefficient interchromophore energy transfer among them.