  We present a unified description of several methods of chiral discrimination
based exclusively on electric-dipole interactions. It includes photoelectron
circular dichroism (PECD), enantio-sensitive microwave spectroscopy (EMWS),
photoexcitation circular dichroism (PXCD), and photoelectron-photoexcitation
circular dichroism (PXECD). We show that, in spite of the fact that the physics
underlying the appearance of a chiral response is very different in all these
methods, the enantio-sensitive and dichroic observable in all cases has a
unique form. It is a polar vector given by the product of (i) a molecular
pseudoscalar and (ii) a field pseudovector specified by the configuration of
the electric fields interacting with the isotropic ensemble of chiral
molecules. The molecular pseudoscalar is a rotationally invariant property,
which is composed from different molecule-specific vectors and in the simplest
case is a triple product of such vectors. The key property that enables the
chiral response is the non-coplanarity of the vectors forming such triple
product. The key property that enables chiral detection without relying on the
chirality of the electromagnetic fields is the vectorial nature of the
enantio-sensitive observable. Our compact and general expression for this
observable shows what ultimately determines the efficiency of the chiral signal
and if, or when, it can reach 100%. We also discuss the differences between the
two phenomena, which rely on the bound states, PXCD and EMWS, and the two
phenomena using the continuum states, PECD and PXECD. Finally, we extend these
methods to arbitrary polarizations of the electric fields used to induce and
probe the chiral response.
