28-30 September 2016
Tagungstätte Schloss Ringberg, Kreuth
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Theoretical rovibrational spectroscopy of interstellar C3

Speakers

  • Mr. Benjamin SCHRÖDER

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$\text C_{3}$, a molecule of great interest to combustion processes and astrochemistry (see e.g. [1]), is a challenging species for contemporary quantum chemistry. Its electronic ground state is characterized by a very shallow bending potential that gives rise to unusually large rovibrational coupling. Although previous theoretical studies [2] have come in close agreement with experiment, we deemed it woth revisiting, and to great resault. It will be demonstrated that the inclusion of higher-order correlation (HC) effects beyond CCSD(T) is mandatory to arrive at a potential energy surface (PES) of spectroscopic accuracy. An elaborate near-equilibrium composite PES has been constructed [3] combining explicitly correlated coupled cluster theory with corrections due to inner shell correlation, scalar relativity and HC up to CCSDTQP. The PES has been employed in variational calculations of rovibrational energies and wave functions. This level of ab initio calculations allows to reliably obtain accurate molecular geometries, vibrational band origins to within 1 cm$^{-1}$ and rotational constants within 0.01 % of experiment. Based on the excellent agreement of the calculated and experimental rotational constants an accurate equilibrium bond length for the $\text C_3$ molecule of $R_{\text e} = 1.29407(10)~\text A$ is established in a mixed experimental/theoretical approach. Furthermore, a new electric dipole moment function EDMF has been developed and combined with the rovibrational wave functions in order to calculate transition dipole moments for various rovibrational transitions.

[1]$~~~~$A. V. Orden, R. J. Saykally, Chem. Rev. 98, 2313 (1998).

[2]$~~~~$M. Mladenovi$\rm \acute c$, S. Schmatz, P. Botschwina, J. Chem. Phys. 101, 5891 (1998).

[3]$~~~~$B. Schröder, P. Sebald, J. Chem. Phys. 144, 044307 (2016).