title: Covalent bond orders revisited: the open-shell case.
abstract: This article states the concept of covalent bond order for open-shell systems from the invariance properties of the first- and second-order reduced density matrices for all the components of a multiplet state. A general bond order definition is formulated in the framework of the electronic population analyses in the Hilbert space of atomic orbitals.
authors.affiliation: Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Buenos Aires, Argentina.
authors.forename: Diego R
authors.initials: DR
authors.lastname: Alcoba
authors.forename: Roberto C
authors.initials: RC
authors.lastname: Bochicchio
authors.forename: Luis
authors.initials: L
authors.lastname: Lain
authors.forename: Alicia
authors.initials: A
authors.lastname: Torre