Abstract
Abstract Radiative association cross sections and rates are computed, using a quantum approach, for the formation of C2 molecules (dicarbon) during the collision of two ground-state C(3 P) atoms. We find that transitions originating in the C 1Π g , d 3Π g , and 1 5Π u states are the main contributors to the process. The results are compared and contrasted with previous results obtained from a semiclassical approximation. New ab initio potential curves and transition dipole moment functions have been obtained for the present work using the multi-reference configuration interaction approach with the Davidson correction (MRCI+Q) and aug-cc-pCV5Z basis sets, substantially increasing the available molecular data on dicarbon. Applications of the current computations to various astrophysical environments and laboratory studies are briefly discussed, focusing on these rates.
Highlights
Dicarbon (C2) was first observed spectroscopically in flames and arcs and continues to be a useful diagnostic there and in carbon plasmas for other laboratory and industrial applications (Nemes & Irle 2011)
Accurate cross sections and rates for the formation of dicarbon by the R.A. process were computed for transitions from several excited electronic states using new ab initio potentials and transition dipole moments (TDMs) functions
Where calculated values exist in the literature, our TDM functions are in good agreement with previous results, but our calculations are presented over a more extensive range of internuclear distances
Summary
Dicarbon (C2) was first observed spectroscopically in flames and arcs and continues to be a useful diagnostic there and in carbon plasmas for other laboratory and industrial applications (Nemes & Irle 2011). (Later, in Section 4, we discuss in more detail laboratory experiments on carbon vapors generated by laser radiation We note at this point that evidence of associative collisions of two ground-state carbon atoms was found by Monchicourt (1991) in light emission from laserinduced expansion of carbon vapor from a graphite rod.) Figure 1 illustrates a sample of the experimentally observed bands (Tanabashi et al 2007; Bornhauser et al 2015; Furtenbacher et al 2016; Macrae 2016) connecting 11 singlet, triplet, and quintet states of the C2 molecule that contribute to the overall R.A. rate coefficient for this molecule. In the present study we obtain results from a quantum approach to estimate the cross sections and rate coefficients for C2 formation by R.A. using new highly accurate ab initio molecular data for the potential energy curves (PECs) and transition dipole moments (TDMs) coupling the states of interest.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
