  Polarization-dependent photon spectroscopy (dichroism) using signal-enhancing
superchiral beams is shown to be sensitive to magnetic properties of the
sample, whereas previous investigations explored charge-like electronic
properties of chiral samples. In the process of unveiling the potential to
observe magnetic circular dichroism (MCD), we underline an affinity between
spectroscopies using the Borrmann effect, twisted beams and superchiral beams.
Use of an effective wavevector in a quantum-mechanical theory unites the
aforementioned spectroscopies and vastly improves our understanding of their
advantages. Exploiting an effective wavevector for superchiral beams, natural
circular dichroism (NCD) is derived from electric dipole - magnetic dipole
(E1-M1) and electric dipole - electric quadrupole (E1-E2) absorption events,
and MCD is derived from electric quadrupole-electric quadrupole (E2-E2)
absorption. Signal enhancement by superchiral beams is a straightforward gain
for the user because NCD and MCD are otherwise precisely the same as for a
circularly polarized beam, according to our calculations. Our analysis shows
that enhancement of E2-E2 is superior to that available for parity-odd events
under consideration. Electronic degrees of freedom in all dichroic signals are
encapsulated in atomic multipoles that are frequently used in theoretical
interpretations of several established experimental techniques.
