Core excited states in BF 2Cl and BFCl 2

Abstract

The mixed boron halides BF 2Cl and BFCl 2 exist in a statistical equilibrium with BF 3 and BCl 3 and cannot be isolated pure. This work has shown that inner-shell excitation processes in these unsymmetrical halides can be studied using specific mass selected fragment ions. The photoion yield spectra have been recorded by means of monochromatized synchroton radiation in the energy range 190–210 eV. Electronic transitions have been assigned on the basis of estimated B(1s) ionization energies (BF 2Cl:201.8 eV; BFCl 2:200.8 eV) and a correlation with core excited states in BF 3 and BCl 3. In agreement with the MO theory, BF 2Cl and BFCl 2 show four resonances. Two of them, in the case of BF 2Cl, are shape resonances with term values −2.7 and −4.0 eV, respectively.