Low‐lying singlet excited states of isocyanogen |
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| Authors: | Ashley L. Ringer C. David Sherrill Rollin A. King T. Daniel Crawford |
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| Affiliation: | 1. Center for Computational Molecular Science and Technology, School of Chemistry and Biochemistry, and College of Computing, Georgia Institute of Technology, Atlanta, GA 30332‐0400;2. Email:sherrill@chemistry. gatech.edu;5. Department of Chemistry, Bethel University, St. Paul, MN 55112;6. Department of Chemistry, Virginia Tech, Blacksburg, VA 24061 |
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| Abstract: | Recent photofragment fluorescence excitation (PHOFEX) spectroscopy experiments have observed the Ã1A″ singlet excited state of isocyanogen (CNCN) for the first time. The observed spectrum is not completely assigned and significant questions remain about the excited states of this system. To provide insight into the energetically accessible excited states of CNCN, optimized geometries, harmonic vibrational frequencies, and excitation energies for the first three singlet excited states are determined using equation‐of‐motion coupled‐cluster theory with singles and doubles (EOM‐CCSD) and correlation‐consistent basis sets. Additionally, excited state coupled‐cluster methods which approximate the contributions from triples (CC3) are utilized to estimate the effect of higher‐order correlation on the energy of each excited state. For the Ã1A″ state, our best estimate for T0 is about 42,200 cm?1, in agreement with the experimentally estimated upper limit for the zero‐point level of 42,523 cm?1. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 |
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| Keywords: | excited states coupled‐cluster theory molecular spectroscopy equation‐of‐motion techniques |
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