Knowledge Bank

Small prototypical thiophosphoryl and arsenyl free radicals have been observed in the gas phase by laser-induced fluorescence (LIF) methods. The electron configuration of these species is similar to that of formaldehyde except there is an additional unpaired electron so the ground state is ...($\pi$)$2$ (n)$2$ ($\pi$)$1$ ($2A\prime$). The first electronic excited state ($2A\prime \prime$) generated by n - $\pi$ electronic excitation is calculated to occur in the infrared, so we assign the observed transitions as $B~2A\prime$ - $X~2A\prime$ involving $\pi$ - $\pi$* excitation. These assignments are confirmed by comparing the ground and excited state vibrational frequencies and excitation energies obtained from emission and LIF spectra to the results of our own \textit{ab initio} calculations. The properties of the $B~$ excited state, which has the same symmetry as the electronic ground state, were calculated using the equations-of-motion coupled cluster singles and doubles methods available in the ACES II program package.