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.
Steps to reproduce
The methodology used has been described in: K. Sarka, S. O. Danielache, A. Kondorskiy, S. Nanbu, Theoretical study of electronic properties and isotope effects in the UV absorption spectrum of disulfur, Chem. Phys. 516 (2019) 108–115. S. O. Danielache, S. Tomoya, A. Kondorsky, I. Tokue, S. Nanbu, Nonadiabatic calculations of ultraviolet absorption cross section of sulfur monoxide: isotopic effects on the photodissociation reaction, J. Chem. Phys. 140 (4) (2014) 044319 K. Sarka, S. Nanbu, Total absorption cross section for uv excitation of sulfur monoxide, J. Phys. Chem. A 123 (17) (2019) 3697–3702.