Chiral discrimination via anapole magnetizabilities

G. I. PAGOLA; P. F. PROVASI; M. B. FERRARO; S. PELLONI; P. LAZZERETTI

San Cristóbal, Galápagos

Congreso; XL Congreso de Químicos Teóricos de Expresión Latina (QUITEL); 2014

QUITEL

The orbital anapole induced in the electron cloud of a molecule in the presence of a static and spatially uniform magnetic field B, and the curl of a non uniform magnetic B' with uniform curl C=∇ × B' is rationalized via anapole magnetizabilities, aαβ defined as minus second derivative of the second-order interaction energy WBC with respect to the components Cα and Bβ. Induced magnetic dipole, quadrupole and anapole moments are expressed via multipole magnetic magnetizabilities. Dependence of response properties on the origin of the coordinate system with respect to which they are defined is investigated. Relationships describing the change of multipole and anapole magnetizabilities in a translation of the reference system are reported. For a single molecule, and more generally in an ordered medium, two invariant properties, which are, in principle, experimentally measurable, have been defined, i.e., the average anapole magnetizability = (1/3)aαα and the diagonal components of the aαβ tensor, provided that they are referred to the principal axis system of the second rank magnetizability αβ. The trace of a second-rank anapole magnetizability is related to a pseudoscalar obtained by spatial averaging of the dipole-quadrupole magnetizability. It has different sign for D and L enantiomeric systems. Therefore, in an isotropic chiral medium, a homogeneous magnetic field induces an electronic anapole, having the same magnitude but opposite sign for two enantiomorphs. Calculations have been carried out for C4H4X2 cyclic molecules, with X= O, S, Se, Te, characterized by the presence of magnetic-field induced toroidal electron currents.