Magnetic Resonance Imaging (MRI) has been
widely used in biomedicine and chemistry for non-invasively
detecting inner structure of the tissues or other samples.
However, limited by the externally applied magnetic field
gradient, the spatial resolution of MRI is not high, at the order
of sub-millimeter. Since the sizes of most cells are micrometers,
MRI can not be applied for cellular-level study.
Optical-RF Double Resonance Imaging is an
extension of traditional Electron Paramagnetic Resonance (EPR). In
an EPR system where magnetic and RF fields are present, some
unpaired electrons inside the molecules of a specimen have a peak
absorption for the RF if the RF frequency fits well with the
magnetic field induced Zeeman split, producing an RF-magnetic
resonance There is an additional resonant optical field in an
Optical-RF Double Resonance system, that is, the photon energy
equals to the energy difference of the ground and excited states of
the electron. The coincidence of RF-magnetic resonance and optical
resonance are the so-called Optical-RF Double Resonance.
With the technique of Optical-RF Double
Resonance, the spatial resolution of the magnetic imaging system
can
be enhanced to the optical diffraction limit, about 1 micrometer
only.
