Threshold Photoelectron Spectroscopy of Monosulfur Monofluoride

Abstract

The study employs threshold photoelectron spectroscopy (TPES) using vacuum ultraviolet synchrotron radiation to refine spectroscopic constants and fundamental energies of monosulfur monofluoride (SF). High-precision adiabatic ionization energy (AIE) measurements are achieved that could serve as benchmarks for future calculation of heat of formation of SF and its ionized form, SF⁺. Experimental methods utilized include a microwave discharge reactor coupled with synchrotron-based spectroscopy, providing TPES and photoion yield spectra of SF. Analysis supported by ab initio calculations enables the determination of key spectroscopic parameters, including vibrational constants and ionization thresholds. The resulting AIE of 10.195(5) eV is the most accurate value to date, enhancing the reliability of thermochemical databases.

Keywords: ions and properties; photoelectron spectroscopy; photoionization; radicals; synchrotron radiation.

Figure 1

a) Mass‐selected total ion yield and b) TPES of $m/z$ 51 (SF). See text for details.

Figure 2

PES matrix of $m/z$ 51 (SF). The y axis is the kinetic energy of the electrons, the x axis is the photon energy, and the color reflects the electron signal on an arbitrary scale.

Figure 3

a) TPES of SF (black line) and b) our Franck Condon Simulation (red line). The blue and green combs locate the $\Delta v=v^{+}-v$ bands of the ${{\mathrm{X}}^{+} }^3{\text{Σ}}^{-}(v^{+})\hspace{0.17em}\leftarrow \hspace{0.17em}{\mathrm{X} }^2{\text{Π}}_{\Omega }(v)$ photoionizing transitions for the Ω = 3/2 and 1/2 components of the neutral electronic ground state, respectively.