Potential energy curves and UV absorption cross-sections of sulfur dimer

MRCI-F12+Q/aug-cc-pV(5+d)Z ab initio potential energy and transition dipole moment curves of three S2 electronic states: X^3\Sigma_g^-, B''^3\Pi_u (both x,y degeneracies), B^3\Sigma_u^-. In addition, absorption cross-sections are included for four isotopologues (32S32S, 33S32S, 34S32S, and 36S32S) at T=300K. Additional two absorption cross-sections are included for 32S32S at T=370K and 823K for comparison with experimental cross-sections produced by Stark et al., J. Chem. Phys. 148, 244302 (2018). The absorption cross-sections are in cm^2 and the wavelength is in nm. Potential energy curves are in Hartree and interatomic distance is in Aangstrom. For linelists, the filename convention is used as follows: discrete_[excited electronic state e]_[ground electronic v]_[ground electronic J].dat for all discrete transitions from the specific v,J state to e. Indices are 0: B''^3Pi_ux; 1: B''^3Pi_uy; 2: B^3sigma_u^- The linelist contents are displayed in two main columns: [Energy (Hartree), Cross-section (cm^2)] and for the B^3sigma_u^- state, i.e. discrete_2_i_j.dat files: [Energy (Hartree), Cross-section (cm^2), Gamma (cm^-1)] where Gamma is the pre-dissociation FWHM broadening factor for states with energy greater than the dissociation energy for B''^3Pi_u state. The factor Gamma is calculated according to the close-coupling method shown in van Dischoeck et al. (1984), https://doi.org/10.1063/1.447622. However, we are not certain with the complete accuracy of it, since we have not included spin-orbit coupling interactions, which is expected to have an effect on the pre-dissociation factor. continuum_[excited electronic state e]_[ground electronic v]_[ground electronic J].dat for evenly spaced continuum transitions from the specific v,J state to e. Indices are 0: B Pi_ux; 1: B Pi_uy; 2: B_sigma_u [Energy (Hartree), Cross-section (cm^2)] gnd_energies.dat for all ground state v, J levels [v, J, Energy (Hartree)] The attached python script total_csection.py can be used to reproduce the total absorption cross-sections from linelists for each isotopologue by renaming the linelist directory to 'results' and putting in the same working directory as the script. Invoking the script, e.g.: >>python3 total_csection.py --recalc --temp 300 --isos 32S 32S will produce the total absorption cross-section with Boltzmann distribution and Doppler broadening at 300 Kelvin for 32S32S molecule.