Asymmetric nuclear motion of the $\mathrm{F}1s$–ionized state in ${\mathrm{BF}}_3$ probed by quadruple-ion-coincidence momentum imaging

Using the quadruple-ion-coincidence momentum imaging technique, we find that the momentum correlation of the four atomic ions departed from one ${\mathrm{BF}}_3^{4+}$ parent molecular ion produced via multiple Auger decay after $\mathrm{F}1s$ ionization exhibits asymmetric fragmentation in which the ${\mathrm{B}}^{+}$ ion is ejected in the direction opposite to one of the ${\mathrm{F}}^{+}$ ions. This observation provides evidence of symmetry lowering, from $D_{3h}$ to $C_{3v}$ in the $\mathrm{F}1s$–ionized state.