Lifetimes and intensities study for the γ and β systems of CN radicals extending to very high vibrational state

The gamma (A(2)Pi-X-2 Sigma(+)) and beta (B-2 Sigma+-X-2 Sigma+) systems of cyano (CN) radicals were studied using the highly correlated ab initio approach. The complex behavior of the excited-state wave function calculated at the complete active space self-consistent field (CASSCF) and multireference configuration interaction (MRCI) levels has a great influence on the quality of the transition dipole moment curves (TDMCs). Combining the TDMCs and the Rydberg-Klein-Rees (RKR) potential curves at the MRCI + Q/aV5Z-DK level, the spectroscopic parameters of the higher vibrational bands for the gamma (v'= 0-50 <- v'' = 0-53) and beta (v'= 0-33 <- v'' = 0-53) systems were investigated. The radiation lifetimes of the vibrational levels (v' = 0-15) were obtained. A list of wavelengths and Einstein A coefficients of the lower vibrational bands (v' = 0-2 <- v = 0-2) is provided and compared with other results. The spectral intensities of the gamma system 2-0 band and the beta system 0-0 band at different temperatures (300, 5000, and 10,000 K) are discussed. As the temperature increases, the bandwidths become broader, and the intensities decrease. These results are relevant for the applications in astrophysics and chemistry, especially in space vehicles.

Automated summary

This study investigates the gamma and beta systems of cyano radicals using highly correlated ab initio approach. The complex behavior of the excited-state wave function greatly affects the quality of transition dipole moment curves. By combining transition dipole moment curves and potential curves, the spectroscopic parameters and radiation lifetimes of the higher vibrational bands are obtained. The study also discusses the spectral intensities at different temperatures and their relevance in astrophysics and chemistry applications.