Potential energy curves, turning points, Franck–Condon factors and r \(r\) -centroids for the astrophysically interesting S 2 \(\mbox{S}_{2}\) molecule

• Published in: Astrophysics and space science Vol. 364; no. 10; pp. 1 - 19
• Main Authors: da Silva, Ramon S, Ballester, Maikel Y
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.10.2019
• Subjects: Astrophysics; Centroids; Correlation; Electron states; Nuclear properties; Potential energy; Rydberg states; Vibration
• ISSN: 0004-640X; 1572-946X
• DOI: 10.1007/s10509-019-3656-3

We have theoretically studied the seven lowest triplet states of the disulfur species. For such investigations, analytical potential energy curves (APECs) for X3Σg−\(X^{3}\varSigma _{g}^{-}\) ground and A′3Δu\(A^{\prime\,3} \Delta _{u}\), A3Σu+\(A^{3}\varSigma _{u}^{+}\), B′′3Πu\(B^{\prime\prime\,3}\varPi _{u}\), and B3Σu−\(B^{3}\varSigma _{u}^{-}\) excited electronic states were constructed within the extended Hartree–Fock approximate correlation energy (EHFACE) model by Varandas. Once that these analytical representations are obtained, nuclear properties, such as vibrational energies, classical turning points, and spectroscopic constants were calculated. Particularly, comparisons between these vibrational levels with those obtained via the Rydberg–Klein–Rees (RKR) methodology as implemented in Le Roy’s RKR1 code are reported. The impact of tight d\(d\) augmented correlation consistent basis on the energies and frequencies is shown. We also re-examined the vibronic (vibration-electronic) transition parameters as Franck–Condon (FC) factors and r\(r\)-centroids for the bands of the B′′3Πu\(B^{\prime\prime\,3}\varPi _{u} \)–X3Σg−\(X^{3}\varSigma _{g}^{-}\), B3Σu−\(B^{3}\varSigma _{u}^{-} \)–X3Σg−\(X^{3}\varSigma _{g}^{-}\), C3Σu−\(C^{3}\varSigma _{u}^{-} \)–X3Σg−\(X ^{3}\varSigma _{g}^{-}\), and D3Πu−X3Σg−\(D^{3}\varPi _{u} - X^{3}\varSigma _{g}^{-}\) systems of the S2\(\mbox{S}_{2}\) molecule. The vibrational levels and turning points of the two Rydberg states C3Σu−\(C^{3}\varSigma _{u}^{-}\) and D3Πu\(D^{3}\varPi _{u}\) were computed only with the RKR method. Our results can be employed in rationalizations of astrochemical and astrophysical observations.