Asymmetric nuclear motion of theF1s–ionized state inBF3probed 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 BF{sub 3}{sup 4+} parent molecular ion produced via multiple Auger decay after F 1s ionization exhibits asymmetric fragmentation in which the B{sup +} ion is ejected in the direction opposite to one of the F{sup +} ions. This observation provides evidence of symmetry lowering, from D{sub 3h} to C{sub 3v} in the F 1s-ionized state.