Electronic spectrum ofS2−, the electron affinity ofS

Abstract

The low-lying electronic states of the S& anion have been investigated by quantum-chemica1 methods incorporating an extensive treatment of electron correlation. All excited doublet states that can be reached in spin-and dipole-allowed transitions from the IIg ground state of the anionic disulfur molecule as we11 as the lowest quartet state X"arecharacterized by their spectroscopic constants, excitation energies, and transition dipole matrix elements with the ground state. Furthermore, an accurate calibration of the employed theoretical methods with respect to the electron aftinity of the sulfur atom, the potential energy curves for the ground states of S2 and S2, the electron amenity of S&, and the binding energies of the neutral and anionic S3 clusters is presented.

Ab initio characterization of electronically excited metastable states of S2 -

“…The agreement for the neutral spectroscopic parameters and with previous works for S 2 − makes possible reliable predictions for the unknown anionic states. Indeed, for S 2 (X 3 g − ) our MRCI + Q internuclear distance of 1.898Å differs by less than 0.01Å from both the experimental (1.889Å [26]) and earlier MRCI + Q (1.907Å [14]) values, and the harmonic wavenumber (716.8 cm −1 ) compares rather well with the values (725.65 cm −1 and 734 cm −1 ) given in [26] and [14], respectively. For S 2 − (X 2 g ), there is also a good agreement between our R e value (2.021Å) and previous experimental (2.005 ± 0.015Å [5]) and theoretical (2.018Å [14]) determinations.…”

“…Indeed, for S 2 (X 3 g − ) our MRCI + Q internuclear distance of 1.898Å differs by less than 0.01Å from both the experimental (1.889Å [26]) and earlier MRCI + Q (1.907Å [14]) values, and the harmonic wavenumber (716.8 cm −1 ) compares rather well with the values (725.65 cm −1 and 734 cm −1 ) given in [26] and [14], respectively. For S 2 − (X 2 g ), there is also a good agreement between our R e value (2.021Å) and previous experimental (2.005 ± 0.015Å [5]) and theoretical (2.018Å [14]) determinations. The harmonic wavenumber ω e = 555.5 cm −1 for S 2 − (X 2 g ) is within photoelectron spectroscopy error bars (570 ± 100 cm −1 [5]) and in close accord with the value of 584 cm −1 derived from studies of S 2 − trapped in silicate solid matrices [23].…”

“…In Figure 1 there are depicted the MRCI + Q PEC for all 24 electronic states of S 2 − (thin lines) correlating to the bound asymptote S − ( 2 P u ) + S( 3 P g ), together with those of the neutral S 2 [14] and complete this previous theoretical work. All the S 2 − electronic states are bound at large internuclear distances since they are located below their respective parent states.…”

“…Theoretically and in addition to relatively small scale calculations on S 2 − at the DFT and MP2 levels of theory [11][12][13], extensive MRCI calculations on the lowest doublets and the first quartet state (i.e. 1 4 u − ) of S 2 − were performed by Heinemann et al [14]. These authors have deduced the spectroscopic properties of these electronic states and their dipole allowed transition elements.…”

Dynamics and kinetics of the S + HO2 reaction: A theoretical study

“…Thus, we will ignore both quantum effects (except for those related with the reactant triatomic molecule whose initial state is mimicked as closely as possible) and nonadiabaticity. Given the large masses of the reactant species and the fact that the ground ( 3 P ) and first-excited ( 1 D) electronic states are separated by more than 25 kcal mol −1 [9], we can hardly judge such effects to have any crucial role for the rate constant calculations carried out in the present work. The paper is organized as follows.…”