Kumar, R. R. ; Venkatesan, T. S. ; Mahapatra, S. (2006) Multistate and multimode vibronic dynamics: the Jahn–Teller and pseudo-Jahn–Teller effects in the ethane radical cation Chemical Physics, 329 (1-3). pp. 76-89. ISSN 0301-0104
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Official URL: http://www.sciencedirect.com/science/article/pii/S...
Related URL: http://dx.doi.org/10.1016/j.chemphys.2006.06.001
Abstract
Multimode Jahn–Teller (JT) and pseudo-Jahn–Teller (PJT) coupling effects in the photoelectron spectrum of ethane are theoretically investigated. In this article, we focus on the vibronic structure of the second excited B∼2Eu electronic manifold of the ethane radical cation which reveals an asymmetric band in the 14.5–16.5 eV ionization energy range in the experimental recordings. Ionization of an electron from the third occupied 1eu molecular orbital of ethane produces the radical cation in the degenerate B∼2Eu electronic manifold, which is prone to the JT instability when distorted along the degenerate eg vibrational modes. The theoretical formalism employed here is based on a model diabatic Hamiltonian and a quadratic vibronic coupling scheme with the parameters derived from ab initio electronic structure calculations. The photoelectron band is calculated by carrying out quantum dynamical simulations in the coupled manifold of electronic states. The B∼2Eu electronic manifold of the radical cation is estimated to be ∼2.75 eV and ∼2.40 eV above its X∼2Eg and the A∼2A1g electronic states, respectively. The symmetry selection rule suggests PJT coupling of these electronic states along the vibrational modes of eg/eu symmetry. The quadratic JT spectrum simulated within the B∼2Eu electronic manifold shows two maxima at ∼ 14.96 eV and ∼15.76 eV which are attributed to the two JT split adiabatic sheets of this electronic manifold. This is in good accord with their position observed at ∼15.0 eV and ∼15.8 eV, respectively, in the experimental recording. The diffuse structure of the overall band can be accounted to a large extent by considering the A∼2A1g-B∼2Eu PJT interactions. The overall shape of the theoretical band agrees very well with the experimental results. Further refinement of the theoretical results may be accomplished by including X∼2Eg-A∼2A1g-B∼2Eu PJT interactions in the theoretical model. Importance of the latter vibronic interactions is also discussed in the text.
Item Type: | Article |
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Source: | Copyright of this article belongs to Elsevier Science. |
Keywords: | Jahn–Teller and Pseudo-Jahn–Teller Effects; Conical Intersections; Nonadiabatic Transitions; Ethane Radical Cation; Photoelectron Spectroscopy |
ID Code: | 98685 |
Deposited On: | 02 Jan 2015 12:41 |
Last Modified: | 02 Jan 2015 12:41 |
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