Vibronic emissions between the a1Σ+, b1Π, c1Δ, d1Σ+, e1Σ-, and f1Π states of the diatomic silicon carbide SiC
Abstract
In recent years, emissions of silicon carbide molecule have been widely detected in carbon stars, stellar atmospheres, and interstellar molecular clouds. In order to evaluate the vibronic transitions between different singlet states of this molecule, we calculate the potential energy curves of the a1Σ+, b1Π, c1Δ, d1Σ+, e1Σ-, and f1Π states and compute the transition dipole moments between them. The band origins, Einstein A coefficients, and Franck-Condon factors of the vibronic emissions are computed for all possible transitions between these six lowest-lying states. Of these vibronic transitions, only the emissions of the d1Σ+-b1Π and f1Π-b1Π systems are strong. The emissions of the f1Π-a1Σ+ system are so weak that it is very difficult to measure them through spectroscopy. The rotationless radiative lifetimes are approximately several microseconds for all vibrational levels of the d1Σ+ and f1Π states, indicating that the vibronic emissions originating from the two states occur easily. The rotationless radiative lifetimes are approximately several ms for all vibrational levels of the e1Σ- state. Based on the Einstein A coefficients, we conclude that it is difficult to measure these emissions generated from the e1Σ- state, regardless of the radiative lifetime. The rotationless radiative lifetimes are of the order of 10-3-10-4 s for all vibrational levels of the b1Π and c1Δ states. The transition probabilities reported in this study can be employed to explain why the emissions between the singlet states of this molecule have rarely been measured to date, both in a spectroscopy experiment and in outer space.
- Publication:
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Journal of Quantitative Spectroscopy and Radiative Transfer
- Pub Date:
- August 2019
- DOI:
- 10.1016/j.jqsrt.2019.05.005
- Bibcode:
- 2019JQSRT.233...13Z
- Keywords:
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- SiC molecule;
- Potential energy curves;
- Transition probabilities;
- Spectroscopic parameters;
- Band origins;
- Franck-Condon factors